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Start Batteries

I have developed a problem with the chassis batteries not holding a charge.

The batteries are OK - load tested "good". I disconnected the positive lead at the battery paralleling bar and watched the voltage (after leaving the BOOST switch on for a couple of days). Initially the voltage was about 13.5; after sitting disconnected for 24 hours, the voltage was 12.8, so something is drawing them down when the BOOST switch is off and the positive lead connected, since they then show about 11.8 to 12 volts in 24 hours.

Where do I start looking for the load? Should I disconnect the inverter/charger (Freedom 25) and see what happens? If so, how much of problem is that to do?

It is snowing here, so I will have to wait for a bit better weather to get to the root cause!

Re: Start Batteries

Reply #1 –
Quote
something is drawing them down when the BOOST switch is off and the positive lead connected, since they then show about 11.8 to 12 volts in 24 hours.


Duane, If batteries are discharging under these circumstances you will have to trace out where the load is.  Connect a meter between the positive cable and the battery to get a reading of how much of a discharge you have,. then start pulling fuses to determine what circuit it is. 
good luck

Re: Start Batteries

Reply #2 –
12.8 is 100% charged
The selected media item is not currently available. Dave Head & Megan Westbrook
Titusville, FL - The Great Outdoors
'98 270 buying this month
Toad is a 2018 F150 XLT

Re: Start Batteries

Reply #3 –
It is my understanding that the nominal voltage of a fully charged lead-acid battery is 12.6 volts. Wet cells, gel, or AGM, are all lead-acid batteries. The voltage measured at the terminals will be something higher than 12.6 while the battery is being charged. However, after the charger is removed the voltage will settle to 12.6 volts with no load on the battery.

If they are at 12.6 volts after 24 hours, you are doing well. If they test good and also hold at 12.6 volts for a few days while not attached to any circuits, you are probably doing fine. If they fall to below 12 volts in 24 hours while attached, go searching for a load.

The previous owner of our coach had attached a satellite telephone to a 12VDC circuit. I took out the satellite phone and installed a small inverter and DVR to the same point. After 24 hours, I discovered that he had attached the satellite phone to the coach battery rather than the house battery. I immediately disconnected the DVR and found a 12VDC "house" circuit. We've done fine since then as long as remember to turn off the CB radio, dock lights, or any other accessory that is attached to the coach battery.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX
 

Re: Start Batteries

Reply #4 –
Quote from: J. D. Stevens –
We've done fine since then as long as remember to turn off the CB radio, dock lights, or any other accessory that is attached to the coach battery.

J.D.
            That reminds me to add to my "to do" list. I am going to change the CB over to be powered only when the ignition switch is ON and have an alternate switch to power it when ign sw is off. I keep the CB on with the squelch high only in case someone sees a problem with my coach hopefully they will let me know.
Rick