BAC Forum
General Boards => Technical Support => Topic started by: Walt Pocock on May 22, 2015, 12:46:57 AM
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Hello, Thank you all for sharing your expertise on these complicated rigs.
My current problem is my chassis batteries will go dead from a full charge in about 48 hours. When the coach is unplugged from shore power, main switch off and Echo Charger disconnected the batteries will go from 12.8V to 5V in 48 hours. I don't know what is still hot after the main switches are off so I don't know where to start looking for the fault.
Thank you for any suggestions.
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Walt, better minds than mine will no doubt help.
Let me suggest that you post the age of the batteries, type (wet or gel), fluid level and condition of connections.
This will help others help you.
Also, by main switch are you refering to the switches in the battery compartment or the one by the entry door?
Keith
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Kieth, Thanks for the head's up.
The batteries are wet and about two years old. The connections are great. The switch is the main in the battery compartment. I should have noted that the batteries will stay charged if I disconnect them.
Thanks
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Guys ...
I, too, am interested in the answer as my coach chassis batteries on a couple of occasions have died. One of the posters suggested in another string that the Delco radio may be drawing from the chassis battery. My batteries were new last fall. Like Walt, if I turn off the switch in the battery compartment there is no problem.
Larry
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Walt,
The ECM (engine control module) for the C12 on your coach is wired to the chassis batteries before the cutoff switch, and it has nearly a 2 amp constant draw for the keep alive memory. To solve this problem, the coach needs a charging source (either solar or shore power) or a heavy duty marine style disconnect directly at the chassis batteries.
If the batteries are disconnected from the ECM, the keep alive memory is lost, but it will be rewritten in about a minute after power is restored.
Gerald
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Walt, Gerald is 100 percent correct on your battery drain. This is one area that many people have
problem with ( power to the ECM. ) The connection is direct to the ECM from the battery's that has
a inline fuse. another problem that follows dead batteries is incorrect voltage from ECM to sensor's,
engine will not start until correct voltage to sensor's is present. Dave Atherton
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Walt,
The ECM (engine control module) for the C12 on your coach is wired to the chassis batteries before the cutoff switch, and it has nearly a 2 amp constant draw for the keep alive memory. To solve this problem, the coach needs a charging source (either solar or shore power) or a heavy duty marine style disconnect directly at the chassis batteries.
If the batteries are disconnected from the ECM, the keep alive memory is lost, but it will be rewritten in about a minute after power is restored.
Gerald
All,
They may have done something different between the 1999 and 2000 year Marquis. I store my 1999 a month at a time, with only the disconnects switches off for both House and Chassis, and I've not run down the chassis batteries yet. The lowest I've seen them is at 11.7V after a month away, and I store undercover at a storage facility. I had read about the batteries running down on this forum, so at first I returned after each week to check and run the generator, then 2, then 3, then a whole month. So, must be a different approach pre 2000 year.
Any other 1999 Marquis owners notice this on theirs? Sorry a bit off topic, but I find the difference interesting and wonder why the 2000s would drain so quickly (48 hrs?).
Thanks, Mike
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All,
After reading the posts about chassic battery discharge on the C12, I am also interested in learning about the marine switch to eliminate battery drain. I believe our coach was always stored with shore power on, and therefore never experienced the referenced battery drain.
What should I look for to determine if this is applicable to our coach as we plan to store it without shore power?
Thank you in advance!
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Mike,
12V batteries are essentially dead at 12.2V so I am not sure how your batteries will hold up if they end up at 11.7V repeatedly. Normally you would not be able to start the engine without using the switch to tie the house bank in at those voltage levels.
If you can go a month and start the coach normally without the back up battery bank involved it could also be that someone has modified the wiring and moved the ECU voltage source to turn off with the coach switches.
Later Ed
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Mike,
If you have a DC amp meter capable of measuring 5 to 10 amps, you would remove the chassis + main lead that goes to the coach from the starting battery bank and put the meter in series with it. You should have all known loads like lights turned off. If you see between 1 to 2 amps you are powering the ECU. If you see .25 amps or less you are probably not powering anything but minor electronic memory items like in the dash radio. If you see the normal ECU load between 1 and 2 amps and you were leaving the coach unplugged to a 120V source for an extended period of time beyond several days, you would disconnect the main plus battery lead and leave it disconnected until you return.
Later Ed
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Mike,
12V batteries are essentially dead at 12.2V so I am not sure how your batteries will hold up if they end up at 11.7V repeatedly. Normally you would not be able to start the engine without using the switch to tie the house bank in at those voltage levels.
If you can go a month and start the coach normally without the back up battery bank involved it could also be that someone has modified the wiring and moved the ECU voltage source to turn off with the coach switches.
Later Ed
Ed,
I will admit to never having tried to start it after a month without first starting the generator. The generator has always started even at 11.7V, so that's been my bridge - not the house batteries. Doesn't take long, after the generator has been running to start the coach. I'll be going down in a couple of weeks (that will be over 1 month) and I'll see what happens.
Thanks,
Mike
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Ed,
Thank you for the information for checking the ECM draw and the battery work around.
Best regards,
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Thanks everyone for the comments and input on my battery draining problem. It appears all that should still be connected after the main switch is off is the ECM and possibly the clock in the radio which are minimal drains (2 amps +/-). Since my batts will go dead in 48 hours with the main switches off and the solar on I must have a situation unique to my old blue Beaver.
I will use the volt/ohm/amp meter to identify the actual draw. The only other thing I can think of is to check the switch itself and, if it's OK, continue to disconnect the positive cable when parking for short or long term.
Thanks again, Walt
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Hey, Walt.... Careful with the "Old Beaver" stuff, eh? <GRIN>
Andy
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Walt:
On my own "old Beaver" I put in a positive disconnect at the negative terminal. I found a knife switch at an RV store. Seemed like tailor made for the job. I never had that problem again.
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Walt,
I know it seems strange, but at a couple of amps of draw, my starting bank gets pretty far down charge wise over 2 to 3 days. Don't be surprised if that is all it is. I have never researched how the ECU voltage is fed from the starting bank to the ECU. It must just be a lead that comes from the unswitched side of the battery switch or from a terminal in the battery bay. If you find it and route to the switched side of the battery switch you would solve the problem. I am not a fan of the knife switches Keith is referring to if they have a plastic base. He may have found higher quality then I have seen. I would add a diesel rated marine on off switch with leads to add another on/off shut off capability if you think what you find is a bit flimsy.
Later Ed
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Walt,
The ECM on virtually all Marquis coaches of your era is powered from the battery cable terminal on the starter solenoid. The battery cable to that terminal does not run through the cut off switch because of the very high amperage demand of the starter.
Gerald
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Gerald,
Is the starter solenoid the one in the wiring basement cabinet below the driver? I have noticed under some conditions, that when starting my coach the starter makes an initial revolution (perhaps), then a short pause, then starts the engine. I always felt like this was due to a lower voltage as I've never noticed it during a restart, for example, after a rest stop. Only happens on a "cold" start. Could this be the solenoid beginning to fail?
Ok, updated question, now that it appears that the starter solenoid means the one on the starter, then what is the part called that's in the wiring cabinet under the driver and what is it for? Perhaps I need to check my connections at the starter. Maybe this wire to the ECU has been taken off since I can leave mine for such long periods of time without it running down.
Thanks, Mike
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Thanks Gerald, I did not know where the ECU tie in was.
So Walt, if you got a length of the same gauge stranded wire as what leads to the ECU from the starter post (that is the smaller wire, main positive lug connection on the starter also has the large gauge wire from the battery), remove that smaller wire from the starter post, and used a high quality butt crimp connector to connect them. Ancor makes a heat shrinkable tubing with a glue type sealer (available at West Marine) or depending on size 3M or Ancor makes smaller self sealing butt connectors with the self sealing heat shrink already incorporated.
http://www.westmarine.com/buy/ancor-marine--heat-shrink-butt-connectors--P009_275_004_003
http://www.westmarine.com/buy/ancor-marine--adhesive-lined-heat-shrink-tubing-alt--P009_275_003_003
Basically, make a weatherproof connection and tie wrap the new wire along the battery to starter cable until you are behind the battery compartment and then lead it up to the chassis switch and put a suitable size crimp lug connector that will go on the switched post. I like to crimp and then solder the wire in the connector and then use some sealing heat shrink on it....just my way of assuring I will never have a problem. So basically you are moving the connection from a battery post feed at the starter to a switched feed now at the switch.
If you add this change there will be an extra 20 seconds or so of wait time for the ECU memory to be written when the battery switch is turned on. Once the battery switch is left on, that delay will not be involved until you turn the chassis battery switch off again. Hope this helps.
Later Ed
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Walt,
One more thing, the battery lead on the starter is hot all the time so the end that is at the chassis battery will have to be disconnected from the battery post to do this job. I never know whether to assume that everyone who might do this job knows this or not...I'm guessing the do but just in case :-)
Later Ed
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There is one thing that I would like to caution everyone about here. The ECM does not like dirty power (no spikes are static), and that is one reason that the ECM was wired to the battery cable at the starter, it was the cleanest power source available. Another reason is that it was a very short wire run (the ECM is bolted to the engine just above and to the front of the engine), and this gives less of a chance of induced noise in the power supply from outside sources. Therefore, if you decide to make this modification as a last resort to prevent chassis battery depletion, be very careful with connections, wire gauge, and wire routing.
Do not confuse the problem of the ECM discharging the chassis batteries with the inability of the chassis batteries to be recharged when plugged in to shore power. If you are plugged in to shore power and your chassis batteries become discharged, you have another problem. On an SMC era or early Monaco era Beaver it is usually a malfunctioning Echo Charger caused by a bad fuse, and on a later Monaco era coach it is usually a malfunctioning "Bird" system. Therefore, determine witch system you have and address the correct problem.
Gerald
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Gerald makes a good point about keeping the power source clean and proper routing. If this was a car you would avoid being near the coil or plug wires for instance. The reason for being on a heavy gauge wire near the battery is that the 12V batteries have a very low impedance, meaning they absorb rises in voltage, like spikes and will protect electronics to a great extent. On the downside that lead sees make and break heavy acing from the starter solenoid contacts so it is not all that clean.
I discussed this issue with Caterpillar engineering and they indicated that most vehicles are wired to turn the ECU on and off with the ignition switch or with a relay. The wire to the battery chassis switch is also a pretty heavy wire so when the switch is on it will be very similar to the way it is wired now and when you turn the battery switch off the only collapsing field I can think of would be the ignition buss solenoid if the key happened to be on and that is diode protected. My opinion is that this change should work fine but as always keep good wiring practices in mind.
Later Ed
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I put a switch to kill the power from the main 12v supply power to my AC Delco stereo. My chassis batteries would go dead within 48 hrs if I didn't turn off the switch in the engine filter bay. Beaver, at least in my 2000 Patriot Thunder, did not kill the supply power to the stereo with the ign. switch. The rocker switch I put in kills the main stereo power, but not the memory. The stereo still has a pretty good draw even if it is shut off otherwise. Maybe my coach is a little different, but I too had new batteries and after I installed the switch it worked. I also have the solar, but it would still drain. My radio switch is the unmarked switch on the right. It lights up when the radio is on.
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All,
After 6 weeks absence from my coach, I returned to the "undercover" storage facility this morning, turned on the batteries, and checked the chassis battery voltage (as I promised I would). It was 11.7V so it was no lower than I have ever seen it after having been disconnected by the battery disconnect switch. Up to now I've only left it as long as a month between visits. As usual after checking the generator oil and coolant levels, I started the generator using 11.7V and it started immediately after its 5-10 second delay to heat the diesel fuel.
Obviously something was changed between the 1999 and 2000 model years and my coach doesn't suffer this drain from the ECM (I still think that 2amps is a pretty high current just to refresh a small microprocessor). My guess would be that other '99 Marquis owners won't have this issue either.
Thanks,
Mike
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Mike,
If you are down to 11.7V you do have the problem, those are essentially dead batteries and if you leave them depleted for long periods of time it will sulfate the battery lead plates more rapidly and that will diminish the battery life. Either you have a very voltage tolerant starting system on the generator or the generator starting load is actually tied to the house battery bank. You could test that by turning off the house battery switch and see if the genset will start.
I'm not saying you have to change anything if you are happy, there is no real issue if you can always start the coach and you do not mind getting a bit shorter life out of your starting battery bank. It is just that 11.7V means all that battery charge is going somewhere and that is not likely caused by small parasitic loads like a radio memory.
If anyone has been following this post and really would like to make a change to finally fix this problem, after reading my info and Gerald's concern about having a clean power source, the safest change would be to buy a diesel rated battery cut off switch and mount it in the battery compartment. The heavy positive lead that goes directly to the starter would be removed from the battery post and tied into the new switch. A new lead of the same or similar gauge would come from the switch to the battery post where the starter cable was previously tied in. In essence you have not changed any of the connection points/wiring paths in the coach wiring. If you leave the coach this extra switch will end the load issue due to the ECM power issue that we have today. This switch is marine rated, 400amps continuous, 600 amps intermittent, and 1500amps cranking and will do the job nicely for $50. NAPA and other places will usually make up cables if they do not have a suitable one that is premade.
http://www.westmarine.com/buy/marinco--pro-installer-400a-on-off-battery-switch--15798911
Later Ed
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Hi Ed,
I've already tested where the generator gets its power, and unfortunately it is tied to the chassis batteries. I say unfortunately because I'd considered installing an Automatic Generator Start (AGS) but the idea was not that appealing to me for the very reason that my coach and your coach and everybody's SMC era coach's generators start off the chassis batteries unless you rewire them to the house system.
So I was disappointed to find this out, however, the reason to choose the chassis batteries is due to their relatively "light use" when compared to the 4-6 house batteries. In today's coaches with AGS, well, that point is moot, because the generator will sense low voltage from the house batteries because that's what its tied to and then it will start automatically BEFORE the batteries get too low - so that makes sense as well.
I understand SMC's choice (no AGS included in our coaches) therefore and its the logical one - you want to split the system and be able to start the generator if the house batteries get run down while dry camping.
What nags at me is all the forum talk about this "ECM parasitic charge" even when one turns off the battery using the "disconnect switches" whose design should be to do exactly that while in storage. I believe that switch does exactly what its designed to do just like the house battery disconnect switch. There is no "EMC parasitic draw" in my SMC era coach, so I am suggesting that there might be another issue your coaches have other than the "ECM Parasitic draw" (simply because we have such similar coaches - especially the engine).
The radio has been mentioned as well, but I've replaced mine, and when the battery disconnect is used, that radio is DEAD, so that's not an issue either. Besides that design has 2 leads to the radio, one for the radio (through the ignition switch) and one to keep the memory fresh (to the battery) while the ignition switch (and radio) is off. I installed my new radio with both leads tied to the battery so that I can play it while the ignition is off, but like I said, when the battery disconnect is OFF, my radio is dead, I lose all previous settings, so there's no parasitic draw there and again I don't believe my wiring is different from other SMC era coach wiring with respect to the radio.
We can disagree over whether 11.7 is a dead battery or not, but if it starts the generator after 6 full weeks in dry and covered storage, then it bridges the system so that you can start the coach after leaving it in storage for that long period of time rather than having to have an electrical connection (and you should be exercising the generator anyway). The difference between 12V and 11.7V might be the temperature outside, or, as I've been told before, the loss of voltage from the battery to the Silverleaf (yes, I've actually had people tell me that!) indicator.
Ed, now that you've eliminated the "ECM Parasitic Charge" with your wiring mod, which I assume you did because you experienced "dead batteries" after a week or so, even with batteries disconnected, have you left your coach for up to 6 weeks in dry (batteries turn off), covered (no direct sun solar assist) storage and is the chassis battery up to 12V after that time? That would convince me that SMC 2000 and later coaches have an ECM parasitic charge issue since that would be the "control" to the experiment. In my case, after 6 weeks, and without the mod I have certainly proved the opposite, that there is no draw of this nature on my '99 Marquis.
(Full disclaimer here, I haven't looked to see if either of the previous 2 owners made any sort of modification to my coach in this regard. I only say I doubt it, due to the fact that the hurricane system was maintained so poorly that I would wonder who would make this mod while at the same time allowing a critical system to decay.)
Let me state directly what I think. I think the "ECM parasitic draw" is a myth, and I've stated why I believe this to be so. I do agree that while batteries are connected, that my batteries will run down due to the ECM within a couple of days, and therefore I do use the battery disconnect for the chassis if I know I am going to be parked without power. That being said, I'd like to see if we can "mythbust" this claim that the battery disconnect doesn't prevent this draw by having someone who's "worked around" the issue, as you have, do the experiment as I have done WITHOUT doing anything in my case. I'd guess that you use your coach a bit more often than I do, so you're not going to be able to do the experiment, but I wish someone would. Here are old post references and I've read them, and I see no documentation provided -
http://beaveramb.org/forum/index.php/topic,1369.msg9210.html#msg9210
http://beaveramb.org/forum/index.php/topic,955.msg5780.html#msg5780
http://beaveramb.org/forum/index.php/topic,891.msg5961.html#msg5961
It's funny now, but based on these posts, and later ones, when I first got my coach, I made sure I bought storage with an available electrical connection (cost me more) so that when my chassis batteries ran down as I was now sure they would from reading the forum, I could charge them up. I drove 60 miles round trip once a week to storage and back just to check on the batteries, then lengthened that to every two weeks, then slipped up and skipped 3 weeks (still without a problem), then went to once a month just to see how long they would last, and now sort of accidently (forgot when I'd last gone until my wife showed me) left it parked for 6 weeks. All without a problem. Based on my experience, and that I don't see why the design would change between 1998 and 1999 (the build years for 1999 and 2000 coaches) that something would have changed. Personally, I think the parasitic draw might be in the solar charging system. It is documented that the when solar panels are not producing current they are actually drawing on the connected batteries, and I believe the solar charging system is attached to both batteries - might be wrong. In my case, being in covered storage, I may be getting a slight charging during the day because there is light bouncing around even in under the storage, and at night there's the draw. If someone keeps their coach totally inside, in the dark, then there is a continual draw which might, over time, draw down the batteries even with disconnect switches off because I think the solar is still connected, right?
Thanks,
Mike
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Mike,
When I bought my current coach, a 2002 Marquis on an SMC chassis, I parked it without being plugged in for about 3 days and I went out to start it and all I got was a click. Not sure if you went three or four days or more if you ever mentioned trying to start the main engine and if that worked with a normal cranking speed. That led me to take a look at the problem and there was already a lot of info on the forum given this is not a new issue. I have not rewired my coach or added a switch to eliminate this load because my coach is always plugged in being stored at my home.
I lifted the chassis battery main lead and measured about 1.7 amps of draw with the battery switches off using a DC current meter in series with the battery lead on my coach. In discussions with Caterpillar engineering about the ECU current draw, 1.7 amps +/- is the correct amount of current draw if left powered. It is not a myth and you can verify yours with a DC amp meter if you like. I discussed if there were any issues if we did rewire our coaches and drop the constant current source to the ECU and after some research they came back and said dropping power would not be an issue, so anyone should feel free to change this configuration if you prefer to as long as good wiring practices are used.
The solar panels are wired to the house battery system so they are not part of the chassis battery drain issue.
Normally a pair of chassis batteries should be able to sit for a month with a few milliamps of current draw to power normal parasitic loads like radio memory and lose maybe .1 volts. A fully charged battery after using the coach would settle out at 12.6V at 100% charge level and should remain above 12.4-12.5V if not being drawn down by the load of the ECU.
Mike, as an electrical engineer, that is the analysis of this problem as best I can describe it to you and what is possible as a solutions for you and other folks on the forum. Batteries at 11.7V are essentially discharged.
One way you could examine this on your own is to have the coach charged up and your car charged up and measure the voltage day by day on the coach chassis batteries and your car battery if it is also not in use. What you would see is the voltage decay on the chassis batteries on your coach and not on your car, the difference is the ECU load on your coach. You could also with a DC current meter measure the load on your car and your coach and see the difference is in the range of 1.5amps more on the coach. If you are not concerned and what you do now works for you then that is fine, no need to fix a problem if it is not an issue with how you use and store your coach.
Later Ed
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I'm going to guess there are diodes in place in the controller to prevent electrons backfeeding through the solar cells, making them essentially LED's, Mike. The cells themselves are like LED's in reverse.
Joel
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Mike,
When I bought my current coach, a 2002 Marquis on an SMC chassis, I parked it without being plugged in for about 3 days and I went out to start it and all I got was a click. Not sure if you went three or four days or more if you ever mentioned trying to start the main engine and if that worked with a normal cranking speed. That led me to take a look at the problem and there was already a lot of info on the forum given this is not a new issue. I have not rewired my coach or added a switch to eliminate this load because my coach is always plugged in being stored at my home.
Ed,
And when I first brought mine home I only had it parked for a couple of days, and went to start it, and it wouldn't turnover, so we're saying the same thing, and I am not disagreeing that the ECM is drawing from the battery normally - i.e. without using the battery disconnect, as I am suspecting was your case as well as you didn't mention disconnecting the battery in your opening paragraph.
The difference, evidently, and when I say evidently, I mean based on the evidence, is that if your coach continues to draw that off while the disconnect switch is set in the proper way such that the chassis battery is "disconnected", then your system is simply different than mine.
An electrical engineer would certainly tell me that a 2 amp draw on my 12V battery system will certainly result in a battery being discharged way below 11.7 amps after a couple days, let alone 6 weeks. My daughter recently called us late at night and told us the Jeep wouldn't start. When I got over there the next morning it was at just over 9V, not able to crank the starter. I charged it up, and crossed my fingers, since my daughter assured me that no lights had been left on (meaning that it couldn't possibly have been discharged that way, right?). After a couple hours sitting there, waiting for it to charge, it started right up, and hasn't exhibited the same issue again.
Conclusion, obviously something was drawing current so I think she probably did leave something on but either didn't notice or was being sheepish about it. Wouldn't have taken much draw over the approximately 6 hours it had been sitting when she returned to it and tried to start it.
My point is that my coach, for one, is obviously different than these other "SMC era" coaches, and the one size fits all solution to a battery drain problem with battery disconnect set as "oh, its the ECM parasitic draw problem once again", simply shouldn't be given out as a fact. It could be other things. I know in my case it CERTAINLY would be something else, as mine, after rigorously having been tested again and again, doesn't exhibit this condition. I encourage you, Ed, since your have shore power available anyway, to disconnect your chassis battery using the rotary switch, and let it sit those 3 days in that condition and see if the battery did discharge. If you meant to say that in paragraph 1, then fine.
As an example of what else could be wrong, perhaps the disconnect switch is faulty, and not actually disconnecting but leaving open the opportunity for, example, the ECM to continue drawing its current or something else (which I believe you said in a post long ago according to the CAT engineer more on the order of 300ma).
All I can say is that because I assumed I would have a dead battery and need external help in order to start my CAT if I left it for over a week, I spent a lot of time fretting about it, when I needn't have done so. I should have thought it out and wondered, why it would take a whole week, but I am not sure anyone has been posting the 2amp draw scenario until lately because that certainly would have indicated to me that a week's time would have been way more than could possibly have been expected for the batteries to remain charged, especially if a .3 volt lost is considered to be a dead battery.
I am pretty sure my coach will start if the silverleaf is showing 11.7V but in reading the forum, it has been my understanding that while in storage, if you're not going to fully operate your coach, then you shouldn't start it up, so I haven't. But next time over there, which will be another 11 days, I will be starting it since we're going to Pacific Shores, so I'll post the results including the voltage prior to start up.
Perhaps by now Walt has found out what actually did draw his battery down since I believe he did say he had flipped the battery disconnect in order to disconnect his battery. If he found that it was indeed the ECM, I would suggest that a change was made by Beaver between my build year and his, and perhaps we can change the "SMC era" designation to "SMC millennial" or even, hey, remember this, "SMC Y2K". :)
Thanks Ed,
Mike
PS - oh, on a 12V battery, 11.7V is a "discharged battery", I agree, I was disagreeing when you said it is "essentially dead" at 11.7V before. :)
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1996 36' Beaver Monterey. First, this is a recently purchased motorhome. It is not plugged into a 110 source. After 3-4 days, the chassis batteries are at about 10-11. I have had the batteries checked and they are not the problem. (1) If I plug into a 110 source, how long would or should it take to charge up the batteries enough to start the engine? (2) For my year and model, should I put a diesel battery kill switch in the battery compartment as discussed previously? (3) Will the battery kill switch eliminate any and all the drain on the chassis batteries?
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Rod,
I'm not sure which charging system you have for the chassis batteries that usually utilizes the main charging system in some manner. If it is a 10 amp output Echo Charger it will take a long time, probably several days. I do not know for your coach year and model if you have the ECU load issue or some other load causing your batteries to discharge. Usually the main charging system charges just the house bank. If you do not have a maintenance charger or a small coupling charger you can take a set of jumper cables and connect the positive post from the house bank that has the main wiring lead on it that powers the coach and connect the other lead to the main positive post of the chassis bank. If you have any doubts check with a voltmeter that you have +11 to 13.8V on the connection points before you connect them just to be sure that you are not connecting to a 6V post in the house bank or a ground post. That should charge the chassis bank in just a couple of hours. The grounds of the two banks are in common so you just need to use a positive jumper cable.
The battery switch will solve your problem but if there are several leads that head out into the coach wiring going to the chassis battery positive post you will need to sort out which lead has the load on it that is causing the discharge before you add the switch. If there is just one positive wire on the battery post then this is easier. If more then one lead you will need to get hold of a DC current meter that will measure up to 10 amps and put it in series with each lead and record the loads with everything in the coach chassis wise that uses 12v in the off position (like head lights etc.) You would add the switch into the wiring that is connecting the load. Hope this helps.
Later Ed
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1996 36' Beaver Monterey. First, this is a recently purchased motorhome. It is not plugged into a 110 source. After 3-4 days, the chassis batteries are at about 10-11. I have had the batteries checked and they are not the problem. (1) If I plug into a 110 source, how long would or should it take to charge up the batteries enough to start the engine? (2) For my year and model, should I put a diesel battery kill switch in the battery compartment as discussed previously? (3) Will the battery kill switch eliminate any and all the drain on the chassis batteries?
Rod,
Based on my experience with my pre-2000 Beaver, the reason your battery ran down was because the ECM does draw from the battery IF THE BATTERY DISCONNECT switch is not set to disconnect. So, as stated, your issue is the same as most SMC owners experience and the issue has been typically the parasitic drain on the battery cause by the ECM. It should take no more than a couple hours with a charger to charge the battery back up (with high charge). That being said, I think in all RVs typically you want to disconnect your battery(ies) from the rest of the coach while charging so as not to cause an issue with the coach's normal charging features. When mine ran down after a couple days of sitting the first time I experienced this issue, that's what I did.
In the future, when you know the coach will be sitting, with no shore power, my recommendation is that you do as I do now, and use the battery disconnect switch to turn off that battery connection. In my coach that has been sufficient to prevent the batteries from discharging to a worthless condition. As previously stated in this thread, even after 6 weeks of this condition, my chassis batteries are still at 11.7V as indicated on the silverleaf computer in my coach.
Of course, if you model beaver has no battery disconnect, then certainly you might add one even a simple one.
Just my opinion.
Mike
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Mike and Rod,
There is no need to disconnect anything from the coach when you are charging, there are no interference issues.
Mike, the only way you will ever know if shutting off your battery disconnect eliminates the ECU load is to actually measure it with a current meter with the switch in the on position and then again in the off position as I have mentioned before. You should also check for a smaller lead coming off of the starter solenoid post on the starter that has the large lead coming from the battery as a clue to see if a possible ECU wire is connected as Gerald eluded to.
Until you do that, telling others that just turning off the switch fixes the problem is misinformation. The fact that your battery voltage decays to 11.7V, which is basically dead leads me to believe that you have the ECU load issue like others, and if not the ECU, then some other load with the switch off. I'm not trying to be difficult here, it is just that you have to take current measurements to know the loads and what is happening before you can say that turning off the switch disconnects the ECU load. Hope this helps.
Later Ed
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Mike, the only way you will ever know if shutting off your battery disconnect eliminates the ECU load is to actually measure it with a current meter with the switch in the on position and then again in the off position as I have mentioned before. You should also check for a smaller lead coming off of the starter solenoid post on the starter that has the large lead coming from the battery as a clue to see if a possible ECU wire is connected as Gerald eluded to.
Until you do that, telling others that just turning off the switch fixes the problem is misinformation. The fact that your battery voltage decays to 11.7V, which is basically dead leads me to believe that you have the ECU load issue like others, and if not the ECU, then some other load with the switch off. I'm not trying to be difficult here, it is just that you have to take current measurements to know the loads and what is happening before you can say that turning off the switch disconnects the ECU load. Hope this helps.
Ed,
And I'll politely disagree in that I've had the coach unplugged from electrical power now for 6 weeks at a time, as I've said previously. If I had a parasitic drain from ANYTHING drawing 2 amps continuously I would have had a battery discharged way, way, way below 11.7V.
So, all I am saying, politely, is that until others with SMC era coaches actually test theirs to see if their battery disconnects actually do (as mine does) disconnect the battery from this mysterious ECM, I believe you are misinforming other owners by giving solutions to problems that may not even be problems. I was certainly misled and have been up until very recently when I found that my coach doesn't have this issue.
Why on earth would I put a meter on my battery to measure anything when I don't perceive a problem at all? Or crawl under the coach to find the starter solenoid? 11.7V may merely indicate that my batteries were not fully charged with I left the coach, who knows?
Ed, since you're an electrical engineer by trade, let's assume when I left the coach at T0, it was at 12V. What would the current draw be if T1 is 6 weeks later and its at 11.7V. That simple, I guess, calculation, would save me the trouble of attaching a meter to my battery. But as I've said in the past, it always shows about 11.7V (its never shown lower) even when looked at after 2 weeks, or 3 weeks, or a month. So I think its certain that for my specific 1999 there's not this ECM issue. And that's all that I am saying. I am not, as you and others are saying that one size fits all. I am merely giving evidence to what is actually a fact for my 1999 Beaver Marquis.
Others can try the battery disconnect as I did and see for themselves. Mine works so I'll continue to add my 2 cents worth and suggest that other owners charge their battery and use the disconnect when parking more than a couple of days, and if that still drains the battery they can then look further to find out what the issue is. That's pretty simple advice I think. I am never giving misinformation to anyone, I am merely sharing my experience as I hope everyone here is.
I must admit I was a bit disappointed by your detailed solution of rewiring the ECM circuit when you admitted you've not actually done it.
Thanks,
Mike
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Mike,
If you go to page 5 in this reference you will see that at 11.7V a lead acid battery is 100% discharged. It will not give up any significant current at that voltage level so I am not sure how rapidly the voltage continues to drop at that point but I know it will continue to drop. The next thing, the only way to know the true voltage state of the battery is to get a meter out and measure it at the posts, not the Silverleaf, given we do not know exactly where the voltage is being sensed by the Silverleaf.
http://ecee.colorado.edu/~ecen2060/materials/lecture_notes/Battery2.pdf
I believe you have a pair of group 31 batteries in parallel and if you look at this Trojan reference at 2 amps a single group 31 would have discharged in 3000 minutes, so say 6000 minutes for two in parallel as a reasonable approximation. That is 4 days. So if you are truly at 11.7V in 4 days at the battery posts that would represent about a 2 amp load. You do not know without measurements what kind of current load you have and where it is going which is the whole point.
http://www.trojanbattery.com/pdf/datasheets/31AGM_Trojan_Data_Sheets.pdf
I will try this one last time, the reason you would put a meter on the battery is to measure the voltage, or in series with a positive lead is to read the current so that you actually know what is happening load wise on your coach. You have made a bad assumption that you do not have a problem because your batteries only get down to 11.7V. That voltage represents complete discharge and the current is going somewhere with the chassis switch off. The idea that your batteries are at 11.7V because they were not fully charged to begin with is out of the range of partially charged batteries, more like 12.4V might be a rational expectation representing a 75% charge level, 12.2V is 50%.
Mike the whole issue is you do not perceive that you have a problem and my point is that if you did not have a load, ECU or otherwise, you would be able to measure the voltage at the battery and it would stay in the 12.5 or 12.6 V range for several weeks or longer, so you have an issue whether you want to do anything to understand it or not is up to you.
I understand the current loads on my batteries with the battery switches in both the on and off positions because I have measured it. I know where the current is going with the chassis switch off, it is going to the engine ECU. I know that load is 1.7amps and I have chosen to not address that issue because my coach is always plugged in. If my batteries were decaying charge wise to 11.7V in 3-4 days, I would rewire my coach in a heartbeat because at those discharge levels the plates sulfate much more rapidly and you are basically destroying the batteries.
I am very comfortable with the information I have provided about rewiring this ECU circuit because I have done the research with Caterpillar on the downsides of not powering the ECU all the time and because I have done the measurements to characterize what the loads are and what needs to be done wiring wise to eliminate this issue. This info is to help those who want to follow a path to see if they have the issue and based on how they use their coach provide a suitable path if they find they need to correct this design flaw.
I do not understand you being disappointed if I have elected not to make this change based on how I use my coach, that seems irrelevant to me, but so be it... I will be happy to answer specific questions if there are questions but I will probably end the long explanations here given this subject has been fully discussed.
Later Ed
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All,
I'll let everyone know on 9th of June, if my "dead chassis batteries" start my coach. If they do, then I'll have to believe in miracles. And, as Forest Gump was fond of saying, "and that's all I have to say about that". :)
Mike
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Mike,
Forest had a lot of good sayings, I did love that movie, one of Hanks best. That we can probably all agree on :-) By the time this post is all done we will probably all learn something new...that is the way things normally go. Have a good Sunday.
Later Ed
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Mike,
As a retired mechanic that has dealt with many Beaver coaches through the club and as a owner over the last 15 years, I can tell you that Ed is totally correct in every statement he made, including the one where he said that your batteries are dead (sufficiently discharged to be non-serviceable) at 11.7 volts. Even deep cycle batteries can not be discharged below 12 volts without shorting their life expectancy.
Rod,
To answer your question about recharging time, you have to tell me if your coach is equipped with an Echo Charger or not.
If you are going to store your coach without it being connected to shore power, it would probably be beneficial to you to install a battery disconnect at the negative battery cable for the chassis batteries.
Gerald
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Gerald and all,
Well, I may be starting a church soon, as there will be lots of believers when I miraculously bring my C12 to life on June 9th with dead chassis batteries. :)
"Do you believe in miracles....YES!"...that's another famous quote - Al Michaels this time. Anybody remember?
Thanks,
Mike
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All,
I'll let everyone know on 9th of June, if my "dead chassis batteries" start my coach. If they do, then I'll have to believe in miracles. And, as Forest Gump was fond of saying, "and that's all I have to say about that". :)
Mike
All,
As promised, an update on my coach's condition POST STORAGE over the last 10 days.
I store the coach under cover, and simply use the rotary switches in the battery compartment to shut off both batteries. Since I am under cover, I get only reflective sunlight I guess on the 2 rooftop 75W solar panels.
Prior to this return, on June 9th, my last visit was May 30th. I checked fluids, then turned on both battery banks via the rotary switches, and on the Silverleaf noted that chassis voltage as 11.9V. As I usually do, I turn the key on, watch the Silverleaf come on, there is some sort of system noise (chunk chunk...chunk chunk - I think its the air valves perhaps), then I turn the key off, then on again. This all according to my owner's manual.
After this I started the coach. At 11.9V, there was no hesitation, see Adam's Thread on Starter Hesitation. There may have been an initial slower starter revolution, for just a split second, but it sounded pretty normal to me. The engine started right up.
Now, as previously stated, over that 6 week period prior to May 30th, I'd left the coach stored under the same conditions an upon my return, noted the chassis voltage of 11.7V.
My conclusion, as offered previously, is that my coach, and perhaps other pre-2000 coaches DO NOT suffer from a separate circuit to the engine computer which draws a 2 amp (or even a 1 amp or even a .3amp) current in order to run this ECM computer. If it did, my batteries would have drained over this constant draw for 10 days. And I'll repeat that when the chassis batteries ARE connected, there is a huge draw, which I assume is the ECM, that will kill the batteries within a couple days if they are not supplemented - at least that's happened to myself and others.
So, while I can not "bust the myth" on 2000-2001 SMC Era coaches, I can certainly tell owners of 1999 Beaver Marquis that they can leave them stored for long periods (up to at least 6 weeks) in a "dry condition", ie not hooked to electric. Since having the electric at my storage lot is an additional $20/month I believe (the covered is $171.00 without electrical hookup) you can certainly save money.
I haven't had the opportunity to start the coach using the 11.7V which Ed and Gerald both describe as a "dead battery", however, that voltage easily starts the generator, and by running the generator (which is a good idea anyway after 6 weeks) you can charge up the battery to 11.9V and then start the engine. I am pretty sure mine would start at 11.7V as I just don't see a huge difference in 11.9V not being dead (which obviously it isn't since it started the coach) and 11.7V.
Enjoying Pacific Shores at the moment - Lot 53. Any other BAC members here? This is our first visit, so we'll be out and about. This is by far the most maintained "RV Park" I've ever visited, but as I told Margaret, it is obviously the most expensive we've visited as well, having purchased our lot and with the HOA dues. :)
Thanks,
Mike
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Mike,
Glad it started for you at 11.9V. I would guess one of the following, your ECU is not fed from before the chassis switch as you suspect, or your ECU is fed directly from the batteries but your battery banks are coupled by a change in wiring at the jump starter solenoid or a defective solenoid so you have extra battery capacity during storage. The only way you will know for sure is with measurements and a meter.
If you are happy and comfortable with your arrangement then that is all that matters. Obviously you have some charge or your C12 would not have started.
The problem is without a DC voltmeter measurement on the battery posts when you left the coach, and when you returned, it is hard to know what state of charge you started with and what it really was when you returned? Even better would be a current measurement with the switch off.
This reference has 11.9V as 0% charge. Like I say if you are happy then that is all that matters.
http://www.autoshop101.com/forms/hweb4.pdf
Later Ed