Keeping chassis batteries charged up

I can't speak for Ron, but here's some reasons why I can't/won't normally respond to these kinds of questions privately:

• Most of us learn from asking questions and receiving responses/opinions from a number of people.
• We also learn from responses to questions asked by others.
• A response provided privately doesn't benefit others.
• A private response doesn't allow others to validate or challenge it.
• Private responses provided by someone else don't allow me to gather the information and put it in the library to benefit others at a later date.
• If everyone on the forum asked me questions privately, I wouldn't have time to do anything else.

Folks should never be concerned about "showing their ignorance" here; I do it daily and learn something every day from my own and others' questions and responses. We don't consider any question to be a "dumb question" either.

My reasons for asking you to ask on the forum was not to expose your self precieved ingnorance but for the same reasons Tom listed.  Here the ONLY dumb questions are the ones not asked.  I am sure there are others wondering the same thing.  Please don't hesitate to ask questions here since we all can learn from them.  Besides what if I had answered privately and in my ignorance gave you a wrong answer?  Nobody would have seen my incorrect answer and set us both straight. ;D

If after reading the links Tom provided if you still have questions please come back and ask and we will try to provide the information you desire.

Thanks for asking here.

OK, OK...I got your point.  Thanks for the tips.  I will get back to you with any follow-up questions.

Mike

Strikenmike said:

OK, OK...I got your point.  Thanks for the tips.  I will get back to you with any follow-up questions.

Mike

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Please do.

I am back.  The article Tom referred me to says, "The equalization process, which should only be done on flooded wet cell batteries, involves applying a controlled over-voltage (14-17V) to the batteries while limiting the current. "  What does "while limiting the current" mean and how is it accomplished?

Thanks again,
Mike

Mike,

The correct conditions for equalizing are usually achieved automatically by a charger or inverter with that feature built in. If you applied the overvoltage without limiting the current, it (the current) would be very high and you'd boil the batteries dry in no time.

On the PD Charge-Wizard there is a push-button that you can use to manually force the charger to  force-feed a 14 Volt+ charge, when batteries are near or fully charged.

    This facilitates an anti-sulfating process. They recommend about 15-20 minutes and then go back to normal float mode.

    The unit also does this automatically once every 21 hours ? when plugged in to 120V external power.

carson FL

Our inverter charger has this feature built in and when we activate it the higher voltage at lower current is applied to the batterys for about 8 hours then returns to normal operation automatically.  Must do a good job since my trojan 105 batteries lasted over 9.5 years.

Tom:  When I first got my motorhome, the chassis battery died in less than a week.  Repeatedly.  Finally someone at the motorhome manufacturer recommended a knife switch.  I haven't experienced a dead chassis battery since, and sometimes it hasn't been started for 5 months. 


--pat

Pat,

Same thing on the last two coaches I've owned. Both were due to parasitic loads on the batteries. To resolve the issue on our prior coach I installed a marine-style battery isolator. On our current coach I merely have to remember to turn off the battery isolator switch installed by the manufacturer.

Tom said:

A Battery Minder should work just fine.

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That's what we use for extended periods of parking.  Batteries will drain down from those items we seldom think about during storage. 

That's for sure. Unfortunately, we have no power at the storage lot where we keep our coach. I've considered solar panels, but I'm hoping to get a covered berth (aka inside storage), so solar panels wouldn't help.

rotzla said:

Hello,

My wife and I acquired our first motorhome last summer and have been going through all of the learning processes.  Most recently was the discovery that the charging unit for the house batteries does not take care of the chassis batteries.  Luckily this was discovered at home vs some remote location.

I was not sure if this was a missing feature of our motorhome or another one of the 1st year errata items for the list.  I first called the local dealer (in Oregon) to ask them about it but did not get a good answer. The next call was to the factory (Safari), which also did not result in a definitive answer.  Finally, I called the dealer I purchased the unit from in Calif. and they informed me that my unit does not have a built in "battery maintainer" circuit and that I would need to add it.

So this long winded story leads me to my question,  can anyone suggest a good battery maintainer system for keeping the chassis batteries charged up?   

BTW: the unit I have in an '07 Safari Simba Toy Hauler, it's a Freightliner FRED chassis.  I have four house batteries located in the middle bay and two chassis batteries up front.

Thanks,
Dave

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Chassis batt's are NOT normally charged by converter system. On my unit I replaced my converter with a 3-state version, added a wire through a switch to go from the house-batt to the chassis-batt. This allows me to keep both charged when I am connected to power. I put a power diode in series so the chassis batt cannot feed back into the house batt. Works just fine.

Chassis batt's are NOT normally charged by converter system.

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Are you sure?  I don't know if that's true or not, but if it is, I certainly wonder why!  After all, motorhome chassis manufacturers do wire in a number of devices (parasitic and otherwise) to the chassis batteries.  One example is the electric step.  Most chassis manufacturers wire it to the chassis batteries so they can control it from the ignition switch, which also is wired to the chassis batteries. 

So when a motorhome is parked for an extended period of time while hooked up to shore power, the chassis batteries are going to go dead rather rapidly in some cases.  How did these motorhome chassis designers expect the chassis batteries to get charged in this case when the converter/charger isn't configured to charge them?  Looks like a major design flaw to me, but maybe I'm missing something here.  I'm sure glad my motorhome doesn't have this 'feature', I park in campgrounds for weeks at a time in some cases and would hate to have to charge the chassis batteries separately when it could be easily done by the converter/charger.

Rolf,

On the flip side, the chassis batteries on our prior coach were charged from the converter which was, at best, a lousy battery charger. I used to disconnect the charging wire while we were plugged in, to prevent over-charging.

Rolf,

So when a motorhome is parked for an extended period of time while hooked up to shore power, the chassis batteries are going to go dead rather rapidly in some cases.  How did these motorhome chassis designers expect the chassis batteries to get charged in this case when the converter/charger isn't configured to charge them?  Looks like a major design flaw to me, but maybe I'm missing something here.  I'm sure glad my motorhome doesn't have this 'feature', I park in campgrounds for weeks at a time in some cases and would hate to have to charge the chassis batteries separately when it could be easily done by the converter/charger.

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I think you may have answered your own question. RVs are designed to be just that - vehicles, and not park models. In most cases, normal driving will handle the chassis battery charging quite well with no risk of overcharging, so there's no need to tie the two systems together. If put into storage or parked for extended periods, some sort of battery disconnection is recommended to help avoid parasitic or phantom loads. A battery will self-discharge over time due to internal resistance regardless. A small trickle charger may be what's needed for your style of RVing, or you could go the wire/switch/diode route, but then it would be up to you to figure out when the battery has had enough. It's hard enough for some folks to check the water every month or so; think about checking the battery voltage every day or two.  

So when a motorhome is parked for an extended period of time while hooked up to shore power, the chassis batteries are going to go dead rather rapidly in some cases.  How did these motorhome chassis designers expect the chassis batteries to get charged in this case when the converter/charger isn't configured to charge them?  Looks like a major design flaw to me, but maybe I'm missing something here.  I'm sure glad my motorhome doesn't have this 'feature', I park in campgrounds for weeks at a time in some cases and would hate to have to charge the chassis batteries separately when it could be easily done by the converter/charger.

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High end coaches usually do charge the chassis battery from the house charger but many others do not. It's a cost thing because to do it properly requires a bit more than just another pair of wires. The chassis batteries need to be isolated from the house system so that the house power consumption will not run down the chassis batteries, as would happen if they were wired in direct. To allow charging, the isolator has to work both ways, detecting when the engine is charging and the house is not, and vice versa, then closing the cross connect relay when and if needed. And opening up again when charging is complete.  A big deal and ultra expensive? No, but every extra feature adds  to the bottom line and this is a feature that is valuable only in selected usage scenarios. Most RVs get driven often enough so that chassis charging is not a concern. It's only when you stay parked for extended periods that the chassis system may drain.

Some manufacturers believe like you do and include the charge feature in nearly all their brands & models, others do it selectively and a few don't do it at all. For example, most Fleetwood coaches have it and most Winnebagos do not.

RVs are designed to be just that - vehicles, and not park models.

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OK, let me see if I understand this. 

Suppose I go out and buy a brand new, big, expensive motorhome and I pull into a campground on my maiden voyage and spend a long weekend enjoying my new motorhome while hooked up to shore power.  I try out all the new gadgets and everything goes well until Monday morning when I try to start the engine and find that the chassis battery is dead.  Hey, Karl, this isn't supposed to happen with a brand new motorhome, is it? 

Now suppose I call up the dealer where I bought the motorhome and after several hours of diagnosing the problem over the telephone, I find that there is neither nothing wrong with the engine nor with the chassis batteries.  The dealer tells me that this motorhome has no built-in provisions to charge the chassis batteries via shore power, and if I want to insure that my chassis batteries are kept charged, I should either go out and buy and install a battery minder to keep the batteries charged up or go out and buy a battery charger and charge the chassis batteries myself as needed, or buy and install a different converter/charger that charges BOTH the coach and chassis batteries at the same time. 

I say:  Are you kidding me?  What other surprises (i.e. design flaws) am I going to find with this motorhome?  Why is it that many other new, smaller, cheaper motorhomes don't have this problem?  What is my hard-earned money paying for?

For me, this would probably be a deal buster!  I'd be so mad that I would probably take the motorhome back and find myself a different motorhome manufacturer.  Obviously, this motorhome was not designed with me in mind (and many others like me if I'm correct).  How do new owners of motorhomes like this put up with this kind of oversight?

Rolf,

Hey, Karl, this isn't supposed to happen with a brand new motorhome, is it? 

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No it isn't, and the chances of that happening are quite slim. The key words in my post were "If put into storage or parked for extended periods,", and I don't think anyone considers a long weekend as an extended period. Normal setup/teardown and trying out new gadgets should not drain the chassis batteries to the point where they won't start the engine. There also should (may) be an "Aux Start" button on the dash that momentarily connects your house batteries to the chassis batteries for just such emergencies, and it works in both directions - it can be used to connect them together to provide power to start our generator in the event your house batteries are too low.

No it isn't, and the chances of that happening are quite slim.

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You don't think a new owner can rundown a chassis battery or a set of chassis batteries on a long weekend?  I do.  Especially if he's trying things out for the first time and maybe practicing things over and over (like lowering and raising the jacks) to learn the operation better.  Even accidentally leaving something powered up (headlights, fan, GPS, radio, computer - there might be a long list of possiblities) for a day or longer would almost certainly run a chassis battery down. 

I still say it's an oversight (and maybe even a gross oversight if it results in lost sales) on the part of a chassis manufacturer and therefore an oversight on the part of a motorhome manufacturer to not include the capability to charge the chassis batteries via the charger/converter.  I'd really like to hear what other people think about this.