Brand New Deep Cycle Batteries Keep Dying Overnight

Clampmeter with DC amps range for $50.
https://www.amazon.com/Multimeter-BTMETER-BT-570C-APP-Resistance-Temperature/dp/B07CFWL3SY/ref=sr_1_25?keywords=dc+clamp+meter&qid=1569816381&sr=8-25

Uni-T brand for about $50.
https://www.ebay.com/itm/UNI-T-UT210E-Digital-Clamp-Meter-Multimeter-Handheld-RMS-AC-DC-Mini-Resistance/303171177473?epid=10024590837&hash=item4696690c01:g:~UcAAOSwNqRcLYXX
I have had a Uni-T brand for about the same price for years and it works perfectly.
Careful going lower in price - it may only measure AC amps. Measuring DC amps without contact requires a very special Hall Effect sensor to measure the tiny magnetic field that circulates around a current flowing in a wire.

My batteries apparently died overnight in the first year of use on a long trip. I was using the idiot lights and voltage readings to get the state of charge. The thing is the voltage on the battery is what the charging voltage was for hours so the voltage method can be overly optimistic for hours after any charging. I thought engine charging was keeping the batteries fully charged but it wasn’t. The solution is a battery monitor that counts amp-hours going in and out of the batteries to calculate the per cent of full charge.
I have a $30 one from eBay that works very well.
https://www.ebay.com/itm/DC-120V-100A-Battery-Monitor-State-of-Charge-Remaining-Capacity-AMP-Voltage-AH-/182147916411?hash=item2a68dca27b:g:gWUAAOSwyQtVz1vp

And beware, some things may be hardwired to the battery with their own fuses.

My RV was so old it did not have a built-in propane leak detector. So I installed a combo propane/CO detector - hardwired to the house battery. It has its own fuse on the wires that run to it. So pulling fuses at the converter won't find that.

Likewise I installed a cigarette lighter outlet under the kitchen table with a USB adapter in it. This is also hardwired to the house battery again with its own fuse inline. The USB adapter has a little LED on it, so it is always drawing power.

By pushing the boost button, it ties the starter battery together with the house batteries. The parasitic draw is the same and still there. The only difference is that the starter battery is now providing 1.95 amps of the drain and the house batteries are providing 0.4 amps. This is confirmation that the drain is on the house side of the system.

Like bobndot suggested, watch the current drain as you remove and reinstall each fuse in the distribution panel. If that doesn't help, there may be high amperage loads connected directly to the load side of the disconnect relay causing the drain to investigate.

Good luck

While I have a Sears clampon I would not buy one today if you can even find a open Sears store - yes I know there are some.

I recently bought a new one from Lowes while not a Fluke it's accurate and very acceptable for RV work. Be sure to buy one with AC and DC amp capability.

Remove the connection to the chassis and see what fails. Although don't let your chassis battery run flat dead either.

Need to find the leak. Divide and conquer. That is you need to isolate systems to find the issue. Pulling fuses and the clamp-on ammeter are both good methods.

sjls wrote:
The strange thing is when I press the AUX Start Button by the steering wheel the drain on the house RV batteries drops down to 0.4 amps. I know there is a bridge / link between the engine battery and the house batteries but it appears that power is being drawn upfront and the drain is not caused from something running in the Motorhome side. Any ideas or suggestions?

Just the opposite may be happening. With the solenoid engaged (which draws it's own amps) the house is now drawing some amps from the chassis battery hence reducing the house battery draw.

Much better and easier to use a clampon ammeter.

Disconnection and reconnecting a circuit may change/reduce the draw due to a reset condition and hence it's easy to be mislead about where the draw is occurring.

RVs have parasitic draws that cannot be turned off. My inverter cannot be turned off - sleep mode is not off. My salesman switch turns some items off and the Monaco battery disconnect switch turns off more items but still have a battery drain.

I have one of these CRAFTSMAN CLAMP ON DC AMP meter that comes in real handy when trying to locate amp draw...

Really comes in handy for looking for DC drains... Just clamp around any wire you want to measure...


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Roy Ken

pull each fuse in the 12v panel to see which one removes the draw then you will be able to isolate which circuit is causing the drain.

That's the way to isolate your problem. ;)

How did you measure your parasitic drain of 2.35 amps? I would measure the draw by removing the neg cable and inserting the leads from your multimeter set on 10 amps between the neg cable and neg post. Then do the same on your starting battery. What do these read? If draw is only on the house batteries, pull each fuse in the 12v panel to see which one removes the draw then you will be able to isolate which circuit is causing the drain.