Troubleshooting rapid battery discharge

DinOregon

T@G Boondock Edge, 2019 vintage (it was a good year). After coming home from a 3-day dry camp yesterday the (brand new) battery was WAY down on voltage. I do not remember that happening on previous dry camp trips.

I disconnected the wiring harness from the battery and it's on a trickle charger as I write.

Checking resistance across the wiring harness, I read 8.8 ohms. There are 5 fuses in the main panel (see pic) and two fuses in the compartment behind the television (where the TV used to be, anyway). Pulling the fuses one by one, I get an open circuit on the wiring harness if either the main panel 7.5 amp fuse (F1) or the 25 amp fuse (F4) are pulled; nothing else makes a difference. (Caveat: I didn't mess with the 30 amp battery polarity fuse.)

I don't know what devices are on which fuse circuit, and the owner's manual seems to be of no use. I can figure out most of that once I reconnect the battery just by pulling fuses and seeing what loses power. But I'd like to know for sure all the draws on each fuse circuit, so I don't miss something hidden. Like the gas line solenoid.

Anybody got that info?

I realize that phantom power draws are present. But I'd like to minimize those. We removed the video screen soon after buying the trailer (we don't even watch much at home). The sound system is never used, so it could go away too. We have an Igloo cooler instead of a thermoelectric fridge, so there's no draw from that.

We'll be hooking up a 100 W solar suitcase for our next trip (Death Valley!) and I want to be sure that we can stay charged up for the duration. If there's an unnecessarily large draw on the battery I want to know what it is and how to disconnect it before we go.

Any help is appreciated, and happy spring travels to all!

JamesDow

Turning off the battery disconnect switch should cut your power draws. If you still have the usb ports, then while the disconnect switch is on, they will have a slight draw. They are prone to failure and in that failure process, the draw may change. If yor tow vehicle battery is wired as to charge your trailer while towing, that also could be a point to investigate, especially if the tow vehicle and trailer are connected for extended periods without driving.

It sounds as if you largest draw currently would be your fan-tastic vent fan. I rarely use my overhead fan because it is a substantial draw.

The low voltage on your new battery could be a bad battery.

A trickle charger is designed to maintain the battery. I would suggest using a full charger for charging (6A -10A).

DinOregon

Thanks, Jim. I did not know that about USB ports. I may remove them, since we can charge phones with the car.

The battery disconnect switch works correctly, as the wiring harness shows open circuit when the disconnect is off. You're right, I need to check the 7-prong hookup to see that the TV is charging the battery -- this last trip was very close to home, a 15-minute drive, so not much time to charge.

I always disconnect from the TV when I make camp or park at home, so that's not it.

The circuit for the 7.5 amp fuse includes the cabin lights and the gas line solenoid, so pulling it would be a last resort.

I notice that my multimeter doesn't seem to have an ammeter setting, so I can't check the actual draw on the battery. May have to get a better one.

Bad battery? Darn, I hadn't even considered that although it's obvious. It charged to 13.41 V before the trip, and it got back to 13.42 V just now ("trickle charger" was wrong, I use a 6 amp Black & Decker, sorry about the misinformation). I'll leave the battery disconnected overnight and check again in the morning. If it's down, back to the shop it goes.

Sharon_is_SAM

@DinOregon - you can use a USB adapter in the 12V outlet to charge devices. We disabled our USB ports in the TaB. Check for LEDs on your audio system as they add to phantom drain. If you have a remote with your Fantastik Fan, it may account for some draw down. You didn’t say what kind of battery, but if it is a regular lead acid from the dealer, it may be time to replace it.

DinOregon

@JamesDow: OK, I believe my battery is sound. It's reading a stable 12.88 volts. The 13.42 volts immediately after charging was surface charge and depleted overnight. "Surface charge?" Again, stuff I did not know.

@Sharon_is_SAM: Even when "off" the radio display is activated (shows time of day), so I pulled the plug on that. I also disabled the USB port in the cabin area, just as you guys did. The battery is indeed wet lead-acid, but it's new, and seems to hold a charge at least over the time I have available to test it. (We leave on Saturday.)

Right now: the new Renology 100W solar suitcase is hooked up to the battery, the trailer's battery disconnect is ON, and I have a brand-new Igloo thermoelectric cooler running from a plugin in the galley. That's the setup we plan to use on our upcoming trip. We will see how the battery looks near sundown.

Good thing we don't need the Fan-tastic Fan 'cos we're not going anywhere hot -- oh, wait, it's Death Valley.

Test again tomorrow, but I'm hopeful the problem is licked.

DinOregon

OK, thanks Sharon and Jim, I think we've got it.

Overnight with the disconnect ON the battery lost about 0.5 volt, so there's still some draw somewhere. Not bad, though. I imagine the gas line solenoid draws a little bit. Once the sun was well up, the Solar Suitcase brought the battery back up to full charge in 90 minutes.

The Solar Suitcase holds the battery steady with the thermoelectric cooler plugged in, but that won't take it through the night. So the cooler is only for sites with shore power. Unless we do a backup battery thing, which is not now.

The solar also keeps the battery at 100% charge with the Fan-tastic Fan on full speed (no cooler), so the fan could be run during the day.

The upshot is, having the ability to recharge with the Solar Suitcase is a game changer. We now have no worries about running the battery into the ground no matter how long we stay, as long as the sun shines.

I appreciate your ideas. Somehow lead-acid batteries were a blank spot in my electrical education. Thanks again.

Sharon_is_SAM

IIRC the gas line solenoid is active when the galley hatch is open.