chassis battery

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
Joined
Nov 3, 2021
Posts
22
Location
Wales
Hello, I've got an issue with my two 85amp chassis batteries in my Damon Daybreak 95'. I left them to charge with the RV battery charger for 24hrs and both of them them seemed ok, went up to 13.25v. Next time I left them on for 48hrs to see how this will effect them and they got flat, down to 11.4v. Is there something I'm missing? It is still the original 95 charger so maybe it's faulty? Or perhaps something else is draining the chassis batteries that I'm not aware of? I don't drive my RV at all right now, not till I get the licence so I'm also searching for a way to keep the batteries in good working condition.
 

Mark_K5LXP

Well-known member
Joined
Nov 17, 2018
Posts
1,803
Location
Albuquerque, NM
Not sure what you mean by "next time I left them on" - what was left on?

It's highly probable there is a draw on the chassis batteries, commonly called a phantom load or something more specific like something being on that can draw chassis batteries down. The most direct solutions are to disconnect the batteries when not in use (either lifting a cable or using a disconnect switch) or applying a charger that can overcome those loads and keep the batteries charged. If you're so motivated you can trace through and discover what's drawing the current and mitigate that but there may be more than one, and not easy to find.

Mark B.
Albuquerque, NM
 

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
75,313
Location
At my Silver Springs FL home
Your batteries charged up but then the stored power was consumed by whatever was left on.

If the "left on" was minimal, I suspect you have at least one poor battery, i.e. it is not accepting & storing much charge, so they run down quickly.
 

Henry J Fate

Well-known member
Joined
Jun 14, 2018
Posts
1,701
Hello, I've got an issue with my two 85amp chassis batteries in my Damon Daybreak 95'. I left them to charge with the RV battery charger for 24hrs and both of them them seemed ok, went up to 13.25v. Next time I left them on for 48hrs to see how this will effect them and they got flat, down to 11.4v. Is there something I'm missing? It is still the original 95 charger so maybe it's faulty? Or perhaps something else is draining the chassis batteries that I'm not aware of? I don't drive my RV at all right now, not till I get the licence so I'm also searching for a way to keep the batteries in good working condition.

You will need to determine if the batteries are good or bad. You can bring them to your local auto store to have them tested there but first you should perform some tests, checks, charging and maintenance.

You will need a digital multimeter $30-$50.

Before charging check the water levels in the batteries. If any of the plates are exposed, add just enough water to cover them and no more. Use distilled water. Distilled water can be found at most grocery stores.

Try to read the date of manufacture on the batteries. Age is important. Anything over 3 years probably should get replaced based on the age and the assumed use up till now.

Readings at the batteries with the converter charger ON and charging should not be any less than 13 volts and should not exceed 14 volts.

After charging the batteries, fill the batteries with distilled water just up to the bottom of the vent hole.

You should have a "salesman switch" by the entry door. That switch will disconnect the batteries from the house and usually will allow charging from the converter charger. Set that switch so that no power is getting to the house and confirm that the batteries are still charging with your digital volt meter.

If you think you may have a converter charger problem, pull the batteries from the motorhome and use an axillary charger. Follow the same process and have your local auto parts store load test the batteries.
 

Kirk

Well-known member
Joined
Oct 30, 2005
Posts
1,612
Location
Full-time , Escapee
A quick way to know if the batteries are being discharged is to let them charge up again and then remove the cable from the negative batter post so that they are on an open circuit. That way nothing can discharge them and if the voltage drops more than a .1V overnight you have bad batteries. As Henry suggests, you do need to check the battery electrolyte levels and each cell should have liquid above the top of all plates, even if discharged. If you do add water, make sure that it is distilled water and not demineralized as they are not the same. When you add water be sure to leave at least 1/2 inch of space at the top to avoid overfilling.

Here is a listing of battery charge levels.
Percent -- Hydrometer -- Unloaded
charge -- -- reading -- -- voltage
100 ---- 1.265 -- -- 12.63
75 -- -- 1.210 -- -- 12.30
50 -- -- 1.160 -- -- 12.00
25 -- -- 1.120 -- - - 11.76
0 -- -- 1.100 -- -- 11.64
 
Joined
Nov 3, 2021
Posts
22
Location
Wales
Than you kindly for all the advices. I'm making notes as I write.

The batteries are most likely dead by now. I left one of them on charge on the c-tech smart charger over night, it went up from 11 to 13.6 but as soon as I unplug it the voltage started to drop, so I'm guessing they're both dead flat.

How would I come about determine the "phantom load"?

I live in my RV full-time and am plugged in constantly at the moment so a fair assumption would be that the batteries should be constantly charged but instead they get drained. I'm thinking it might be one of the appliances (everything in the RV is original 95', so old and most likely requiring replacement) or the battery converter the one with the fuse box?

How would I come about getting to the bottom of this? I don't want to get new batteries again and drained them until I figure out what's going on.
 

John From Detroit

Well-known member
Joined
Apr 12, 2005
Posts
25,627
Location
Davison Michigan
Chass batteries (Starting) that low... Toast generally
How old are they?

Deep cycle batteries that low.. MIGHT recover (no guarantee but the odds are way way way way better) That is the big advantage of GC-class batteries for the house... They can't crank the amps, but they can take a beating.
 

Rene T

Site Team
Joined
May 20, 2011
Posts
18,679
Location
Farmington NH
is there a way of telling how old a battery is? I have four batteries and none of them have the sticker on top with the year of manufacture you can peel off. Do they have a date code permanently stamped into the body someplace if they do, what would it look like?
 

Mark_K5LXP

Well-known member
Joined
Nov 17, 2018
Posts
1,803
Location
Albuquerque, NM
it went up from 11 to 13.6 but as soon as I unplug it the voltage started to drop,
That's actually normal. Charging voltage for lead acid batteries is higher than their operating voltage. So 13V+ during charge is normal, off the charger they'll drop to their "resting" voltage which corresponds to their state of charge, per Kirk's table above. It should be pointed out that a "bad" battery may have perfectly normal operating voltages and electrolyte specific gravity so using these alone is not a sufficient method for determining serviceability. For starting batteries a load test can sort things out pretty quickly but that usually involves plucking them out and taking them somewhere with a tester. You can buy a simple tester fairly inexpensively which have some degree of usefulness but in my travels if a battery isn't performing as you'd expect you generally don't need a tester to tell you that. The engine starter is the proof in the puddin' for any starting battery so it either can, or it can't.

How would I come about determine the "phantom load"?
In a perfect world you'd connect a meter to your chassis battery to measure current, then start pulling fuses or unplugging things until you find the offending device. Sometimes it really is that easy and generally there are few things that draw current when the vehicle is off. Sometimes too you find it's something that you either don't want to shut off like a carbon monoxide detector or it's not convenient, like the engine computer. So you might be faced with either rewiring something to run off the house battery, disconnecting the chassis battery or leaving a charger connected to it full time.

I live in my RV full-time and am plugged in constantly
So it would seem in your case either disconnecting the battery or connecting a maintainer full time would be the most direct solution. Do you ever start the RV? If you're parked long term the idea of leaving the battery out entirely would also be an option if you don't operate anything on the chassis side.

Mark B.
Albuquerque, NM
 

Kirk

Well-known member
Joined
Oct 30, 2005
Posts
1,612
Location
Full-time , Escapee
If you're parked long term the idea of leaving the battery out entirely would also be an option if you don't operate anything on the chassis side.
Or at least lift the cable off of the negative battery post, which will prevent anything from discharging it. If you do that with the battery fully charged and the voltage still drops quickly, the battery is no good and will have to be replaced before you drive it again, but no hurry if you are not driving it anyway.
 

Henry J Fate

Well-known member
Joined
Jun 14, 2018
Posts
1,701
If the battery on the C-tech smart charger was disconnected from the rv, a voltage drop is normal and should be monitored and left to settle for 6 hours or so. The voltage reading after letting settle for 6 hours should give you a good idea if the battery is good or bad. Letting the battery settle for 24 hours disconnected would offer more accurate info with a voltage reading. Charge and check both batteries using that technique. It is possible your batteries still have some life to them.
 
Top Bottom