Chassis Batteries Discharging

[Jerry Pattison]

Jerry,

I think your ECU is probably not on with your battery switch off, given you have gone long periods since you have owned the coach without this issue. That is an assumption and it seems rare that these coaches do not have the ECU on all the time but yours and Mikes are similar vintages and do not seem to discharge sitting.

I think you need a way to monitor the DC current flow out of the chassis battery bank with a DC amp meter and start turning off DC breakers if they are the resettable type, pull DC fuses, and in the electrical bay below the drivers seat is a row of breakers on the left buss that you could unbolt the wire one at a time and lift it off. These are the branches of loads that could be using current. Hopefully one of those will eliminate the current load and give you a clue where your problem is.

Later Ed

Good info, Ed.  I've been studying all the factory manuals, etc., that came with the coach, and reviewing all the input from this forum.  My Saturday plan is to start diagnosis!  Thanks for your help!

[Jerry Pattison]

OK, all!!  Problem is resolved.  All your comments went a long way into my troubleshooting analyses!  Here is the scoop:  My house batteries were 5 year old (almost to the day!) Trojan T-125.  I have had those batteries before, and they lasted much more than 5 years, so I did not suspect them.  Well, how wrong I was!!  They were causing my problem!!  I went to Costco (based on comments re batteries on this Forum!) and purchased 6 new golf cart batteries, Interstate label.  Installed them, charged for a bit from the generator.  Waiting several weeks, I went back and attempted to start the generator....success!!  The chassis batteries measured 11.9 volts at the battery posts using a voltmeter prior to starting.  Before the new house batteries, that would have been impossible.  So, here are my thoughts:  The Trojan house batteries had died, and were apparently discharging the chassis batteries through the echo charger.  As for the blowing of the fuse of my ammeter during troubleshooting, the load on the chassis batteries (ECU) is likely capacitive, and the initial current surge vaporized the fuse.  The chassis batteries no longer discharge, and the only change I have made is the replacement of the house batteries.  Shame on Trojan!!!

[Gerald Farris]

Jerry,
I am glad that your problem is resolved. However, your theory about the Echo Charger discharging the chassis batteries is incorrect unless it is malfunctioning. The Echo Charger is designed to only charge the chassis batteries when it sees that the house batteries are being charged. At any time that the house batteries are not being charged, the battery banks are totally isolated from each other by the Echo Charger.

Gerald

[Edward Buker]

Jerry,

Gerald is right, the Echo Charger by design will only conduct one way, house to chassis bank to preserve the chassis set so you can always start the coach. They are in essence a current limiting one way switch. The 11.9V on the house bank os very low with the new batteries, essentially a vale that represents little or no charge. If your coach is plugged in it looks like the main house charger is not charging. This is all food for thought. If things are working properly the 11.9V value must be wrong.

Later Ed

[Keith Moffett Co-Admin]

Jerry,
I am glad that your problem is resolved. However, your theory about the Echo Charger discharging the chassis batteries is incorrect unless it is malfunctioning. The Echo Charger is designed to only charge the chassis batteries when it sees that the house batteries are being charged. At any time that the house batteries are not being charged, the battery banks are totally isolated from each other by the Echo Charger.

Gerald

Gerald and all.  My question here is, are we talking exclusively about an echo charger or anything in that catagory, regardless of brand.  We have a Magnum inverter, about 3 years old, and the Magnum battery combiner, not an echo charger.  We are having almost the identical problem except that last night we ran the gen. to where the monitor read 13.8 volt and 0 amp float charging.  Two hrs later the Magnum monitor and the CMP 20 both read 12.9 V.  This was with no inverter on, no lights on and dry camp in a field at a rally.
I had just told Carol the same thing about a reverse drain on the chassis batteries due to dead house batteries.  It sure seems that is what is happening.  We are getting new Interstates tomorrow here at the FMCA rally unless I hear differently from you all.

I ran the engine this afternoon to verify I had not lost the alternator and both the house and chassis batteries were getting 14.2  to 14.5 volts.  This seems a bit high.

Thanks,  Keith

[Edward Buker]

Keith,

The 12.9V readings do not represent battery discharging coming down from 13.8V. It represents the settling voltage that tells you the true charge state of the batteries. It takes awhile for the batteries to get to that point after 13.8V or some charge voltage has been applied. You have some status lights on the Magnum SBC and probably an external solenoid used for combining. You also have some adjustments for the combining voltage and the over and under voltage disconnect. The combine setting at 13.1V, the disconnect at 12.8V, the high voltage disconnect at 14.6V would be about right.

Without load 12.65V is 100% charge, 75% is 12.45V. 50% is 12.24V, 25% is 12.06V, and 0% is 11.89V. If you have a load (drawing amps) then these voltages would be lower.

Basically you want to know that the main charger is doing its job, that you see the disconnect light on and off at the right voltages and that if you have an external solenoid that it is opening and closing contacts as it should. I would not change batteries until I had a battery problem, 12.9V is not a battery problem.

As an aside my float voltage on my Xantrex charge system will drop as low as 12.9V while things are fully charged. I had a recent starting battery issue at a little over 5 years old and just changed those out. Keith, not sure if you are you having starting battery issues.

Later Ed

[Gerald Farris]

Keith,
Ed is right, the voltages that you listed are in the normal range. What problem are you having that makes you think that you need house and/or chassis batteries?

Gerald

[Keith Moffett Co-Admin]

Ed and Gerald
Dang, every time I think I have a handle on the right and wrong voltages I find I have missed the mark.  I believe this clairity will help our newer members too so let me explain.

1)  The chassis batteries are 3 yr. Old but drop to match the house batteries at 12.8.  This turns the gen over but I have to use house batteries too to start the generator.
2)  The house batteries are 5 yr. Old and not great ones at that.  They were run very very dry before I bought the coach and I filled them.
3)  Last year we left shore power and went to dry camp.  Two hours later we were dead and barely got the gen started. We replaced the battery temp sensor which stabi.ized the CMP 20 readings some. 

We dont run the inverter and use only flashlights if the generator is not running.  Considering Eds numbers, this will take more investigating.
By the way, the batteries and cables and connections are all well maintained!

Thanks again and sorry to hijack this thread!

[Keith Moffett Co-Admin]

ALSO!  Welcome to the club Jerry!

[Joel Ashley]

Jerry,

Gerald is right, the Echo Charger by design will only conduct one way, house to chassis bank to preserve the chassis set so you can always start the coach. They are in essence a current limiting one way switch. The 11.9V on the house bank os very low with the new batteries, essentially a vale that represents little or no charge. If your coach is plugged in it looks like the main house charger is not charging. This is all food for thought. If things are working properly the 11.9V value must be wrong.

Later Ed

Unless I'm mistaken, Ed, I think Jerry said his chassis batteries were at 11.9, not his new house set.  And given over the years I've read of several Echo Charger issues, I'd start considering that might be what's amiss if his new Interstates are displaying a good condition off the charger. 

As experienced ones here know, and to reiterate for the newest owners here, 12v. is not a fully charged "12 volt" battery but rather only a 25% charged one - 12.7v is a full charge;  so 11.9 is hardly up to snuff on Jerry's starting set.  And if he did manage to get it going on that or with the boost switch, his alternator would be stressing for a bit.

And as an afterthought, I'm not sure about Jerry's, but on some coaches like mine you have to make the inverter, and I think the solar controller, aware of the type of batteries you install, e.g. wet cell or glass mat (AGM).  That's probably just to prevent any equalizing charge phase of an AGM, though.  Unless some previous owner switched from glass mats back to wet cells, and the settings were such that equalizing was still shut off, it probably is not a factor with Jerry's rig.

-Joel

[Jeff Wheless]

I had similar issues with our new to us Marquis.   With house (lowish voltage) and chassis  (discharged) batteries never seeming to charge when parked, even on shore power.   

A couple of compounding issues:

The (original) Echo Charger was non-functional.   The new version has a very useful diagnostic LED (when used in conjunction with the manual)
The Xantrex charger function was set to only output at the minimal 5A setting.   So it would show as charging, but with 6 6V batteries, that is a losing battle.

Replaced the Echo Charger and set the Xantrex DIP switches to an appropriate battery capacity/max charging current and now everything works like a charm, even in storage with solar keeping everything topped up nicely.  Just went 5 weeks with nothing but solar and both sets of batteries were all charged up, ready to roll.

[Joel Ashley]

Keith, as Ed and Gerald explained, your numbers are perfectly normal.  What you're seeing on your panel during charge is just that... the charging voltage, not the static voltage of a resting battery.  That at full charge should settle down to be 12.7v or slightly more.  12.9 is great - not to worry.

That said, your genset starting issue first brings to mind a poor generator ground connection situation.  But when you say that is pristine, it's head scratching time I reckon.  Yes, you may need to get new house batteries (I suggest Costco's Interstate 6v ones);  when you say your connections are well-maintained, I'd like to know that includes, though, the chassis ground points, especially the genset's.

-Joel

Jeff brings up a good point:  the inverter's charging can be tied to the settings for the Park Power source.  Make sure yours aren't set for something like 15 amp when you're actually plugged into 30 or 50, or that the charger output itself is like Jeff's was, set way too low.

[Keith Moffett Co-Admin]

Joel
you make a good point on the connections.  I like clean and shiney on the batteries.  I had the gen.  Serviced last year but that might not have included an inspection on those contacts.  It would certainly drag down the starting.

I had all our batteries checked today with both a hydrometer and a load test.  House and chassis passed with flying colors.  Later I thought perhaps it would have been better to load test with the solar covered.  I am getting about 7 amps solar on the CMP 20.
For now no new batteries.  I do take a different view of those Costco 6V Interstates.  There is no amp hr rating on them and after speaking with the manager it was determined that they are rated at 110 max amp hr. .  220 is average on descent batteries.  Some Trojans are 260.

[Joel Ashley]

Keith, the amp hour rating depends on the load it's calculated on.  The number you were given appears to be that at 75 amps.  If one uses the commonly seen 20 or 25 amp load, the minutes I've seen are closer to 240.  But if you look at the Interstate site for what is feasibly the comparable battery at Costco, the figures are even better;  so I think one needs to find out exactly which 6v deep cycle Interstate it is that Costco's selling by getting numbers off one, if nothing else.  Personally, I'm not too concerned that the results would be disappointing.

http://www.interstatebatteries.com/p/golf-car/group-number-size/group-number-size-gc2-2300s?dsNav=N~2147384911-2147384903

Now that said, take a gander at this 2011 video, keeping in mind they had made improvements in them by that time, 5 years after their predecessor battery versions were put in my coach at the factory;  and mine are into their 11th year.

https://www.bing.com/videos/search?q=costco+deep+cycle+marine+battery+reviews&view=detail&mid=A0D9A483DF2376A2DEDEA0D9A483DF2376A2DEDE&FORM=VIRE

Forum followers may find the YouTube video that follows that one of interest also.

-Joel

[Edward Buker]

Keith,

Joel's point on the ground is a possible cause of your cranking issue. Also the plus lead has a coupling block near the generator I believe. You should clean the plus contacts also. Be sure that you have disconnected 12v back at the bank before cleaning these contacts. Chassis switch may do it it check. This is a marginal design with such a long wire run that mine cranks very slow but has never failed to start. It is not too surprising that you need to use both banks at times to start it. You are compensating for voltage drop in the long wire run.

Later Ed