Power/Converter Issue

[Michael Hannan]

As some may recall, I am living at a RV site that suits my budget but has 30 amp service only.  The other day I was sitting inside with my front AC humming away when all of a sudden all my 110 outlets shut down & the AC kept going..  The error warning was low battery voltage. Am I correct that what is happening is that the AC was using most or all of the incoming power leaving little or no power to charge the batteries and the 110 stuff I had running drained the batteries that's when I lost my 110 outlets? I'm monitoring how and what I'm using and trying to balance AC with 110 outlet usage.  I've even considered getting a 110 volt portable AC unit and run an extension through a window from a 110 outlet on the power pole. Costco has one that also acts as a heat pump which would help in the winter.

Thanks
MJ

[Edward Buker]

Michael,

It is hard to know what happened but low voltage is probably the cause. There is a pass through relay in the inverter charger and maybe that went to a non pass through condition. Hopefully this was a temporary condition and charging is taking place now. You need to have the batteries charging properly and enough voltage and current not to damage systems in the coach. You are doing the best you can with load shedding but it appears at times not to be enough. Check and be sure that charging is taking place. While this would not be ideal, you could turn the AC breaker that feeds the inverter charger off during the day and run one air, then at night turn off the thermostats that run the air systems and turn on the inverter/charger breaker to charge batteries at night if your load shedding routine is not enough to keep things working properly. You should also be checking that the house battery fluid levels are being maintained properly.

As far as the 110 outlet on the post that is likely wired into the same inadequate grid that feeds your coach. It is the total load that is the issue and not which outlet you use so just using a different outlet will not be helpful if it is fed by the same wiring source.

Later Ed

[Michael Hannan]

Thanks Ed.  The batteries are charging just not as they were before I started using the AC during the day. At night I shut the AC down just as soon as it cools enough to open the windows and turn on the Fantastic fans to draw in that nice cool air.  The yellow charge light is on when I go to bed and it's green when I wake in the morning.  I have been checking the water level in the batteries regularly as you recommended and I bought one of those battery fillers you suggested which makes refilling them easy.  I just bought the last 3 batteries to replace the old ones which will leave me with all new coach batteries. I may see a difference with them but the old ones still seemed to be doing ok, not using too much water and not over heating.  The only other anomaly is that periodical I heard a thud (like a cupboard door being slammed) coming from the basement.  I'm not sure it's the inverter as sometimes it sounds like it maybe coming from further back.  I wouldn't think there are any electrical components over the black & grey tanks so it might just be the inverter noise transmitting through the frame.

MJ

[Edward Buker]

MJ,

Sounds like you are managing well and may have little glitches here and there when the AC supply voltage drops very low due to other peoples loads coming on together affecting the grid.

The noise in the basement, really no idea. The transfer switch relay will make a noise when it closes but that transfer of contacts closing would happen with the generator running after a minute or so. The relay in the inverter is not that big and I cannot see how that would be heard from above. The noise is one of those mysteries you will just have to figure out over time. A man needs a little mystery in his life :-)

Later Ed

[Roy Warren Co-Admin]

MJ
There is a relay near the Big Boy which makes a loud thump when it closes.  I get that periodically when the batteries get a little low, often near the end of the month just before I check my batteries.  I found out it was a loose wire connection on the batteries and when I got that fixed, the noise has stopped completely.  It was one of the smaller wires and it was where the crimp was on it.
Roy

[Michael Hannan]

Thanks Roy!  I'll check that out when I change over the batteries today. Big Boy???

MJ

[David T. Richelderfer]

Read this - quite informative I thought... especially the last paragraph.

http://beaveramb.org/forum/index.php/topic,968.msg5866.html#msg5866

[Michael Hannan]

Thanks David.  I looked at it and yes it's quite informative.  I have no idea what the BIRD nor the Big Boy thingies are.

MJ

[Joel Ashley]

MJ-

Your configuration is likely a bit different, but what you are looking for look like the devices in the photo attached.  The Big Boy is labeled as such on its case.  The BIRD (Bidirectional Isolator Relay Delay, or something like that) is mounted on the inside of the cabinet door to the right.  The Big Boy is the isolating solenoid, and the BIRD essentially is the controlling module for it.  Together they manage the charging balance and separation of the chassis battery and house battery sets.
-Joel

[David T. Richelderfer]

The Big Boy-BIRD system acts as a bi-directional system for charging all your batteries.  If your coach is on shore power or on generator power, then your inverter should be charging the COACH batteries (the 4 or 6 6v batteries).  When the main motorhome engine is running, then its alternator is charging the CHASSIS batteries (the twin 12v batteries).  When either set of batteries gets charged to 13.3v, then the Big Boy-BIRD system allows the charging current to cross-over to the other set of batteries.  Thus the bi-directional nature of the Big Boy-BIRD system.

As noted in the linked message in my prior post, the inverter needs to be programmed such that it charges the COACH batteries to at least 13.3v in order for the bi-directional cross-over function to kick in to deliver the inverter's charge current to the CHASSIS batteries.  Likewise, the main engine's alternator must get the CHASSIS batteries to at least 13.3v in order for the bi-directional cross-over function to kick in to deliver the alternator's charge current to the COACH batteries.  If either the inverter or alternator do not supply sufficient charging voltage to get to 13.3v, then the other set of batteries won't receive charging current.

Here it's important to note again that if the COACH batteries are down and the main engine is started, then the alternator will be asked to charge the COACH batteries at a high rate of charge.  That high rate of charging is too much work for the alternator and will eventually burn it up.  Thus, if the COACH batteries are down from dry-camping, then before starting the main engine you should run the generator for 30 minutes or more to get the COACH batteries up to at least 12.5v or so BEFORE starting the main engine.  Before I was aware of this I replaced one alternator to the tune of $400 more or less.