RV Gremlins - Electrical

[B & J T]

I expect this to be a struggle as I am ignorant in all things electrical especially when it comes to RV's. Quick back story...we bought our 2020 Newmar New Aire in the fall of 2020 (our first RV). In January of 2021 it showed signs of house and chassis batteries not staying charged but it was explained away by the 30 amp service we were plugged into having a tripped breaker (we store The Beauty at the dealership). I visit every 3-4 weeks and say hello and start her up. No issues until June 2021 right before we were to depart for Colorado. Gremlin reappears and we found several dry cells in the coach battery bank and replace them along with the two chassis batteries. We think we're golden, take several trips and no problems.
Fast forward to last week. I've still be going out and starting her every 3-4 weeks. Last week they have it in the shop to do some warranty work and had to jump if off to start. Back to the 30 amp storage breaker must have flipped. They finish the work and I drive it to the house on Tuesday as we were going to do a short trip locally with grandsons (see Where are you with your Newmar today thread). On Tuesday everything seems nominal, generator runs, one AC unit running while we prep and I turn everything off for the night. The next day we barely have 8v across each sets of battery, nothing starts. Keep in mind I'm plugged into our house 110v service so I'm thinking the batteries should be getting a trickle charge. For safety reasons the inverter is shut off (?). After charging both house and chassis batteries all day I get it started early evening and let things run for a couple of hours. Everything looks great. Until the next morning (Wednesday) and we're back where we were the previous morning. The dealership sends out a tech (great guy and very knowledgeable) and we get things started. He believes everything should be fine and we should go (my wife had her car to transport grans so I'm not overly concerned about being stranded plus the RV parks is just over an hour from the house).

We return home Friday, everything seems fine as we had 50 amp service at the park (much needed with the ACs running nearly none stop!). On Sunday we're below enough juice to turn the engine (~11.2v across the chassis batteries) and put back into storage. It was plugged into our house 110. I recharge them all day and get it started Sunday evening and let things run for a couple of hours again. Everything is fine and I shut it off. Monday morning, same thing but I get it started again and back to the dealer and storage. Keep in mind all the batteries are about one year old. Also to note The Beauty has solar panels so it has the additional source to keep batteries topped off.

I know too long but any ideas or suggestions to try? The dealership is working it but I'd like to learn more to ask the right questions. Sure would like to hear your ideas.

 

[B52Bombardier1]

I'd want to know if one or more of your onboard recharge devices might have a leaky diode in its rectifier. This allows alternating current to pass through to a DC-loving battery with generally rapid and bad results for the life of the batteries.

A quick check with a good multimeter set to AC volts can reveal this problem. Hope for less than .05 volts AC measured at the battery while charging.

Rick

 

[AbdRahim]

Is your inverter also your charger? You mentioned that it was off.

 

[Gronk]

I'd want to know if one or more of your onboard recharge devices might have a leaky diode in its rectifier. This allows alternating current to pass through to a DC-loving battery with generally rapid and bad results for the life of the batteries.

A quick check with a good multimeter set to AC volts can reveal this problem. Hope for less than .05 volts AC measured at the battery while charging.

Rick

Excellent advice. That will also make any 12V appliance act screwey. The "several dry cells" is also concerning. That tells me your converter is overcharging the batteries. Running a cell dry is a great way to ruin a battery. If you have one bad battery it will kill all the rest. I had that happen with a semi I drove. Ond battery went bad and sucked the voltage out of the other three. Once I disconnected the bad one the others did fine.

 

[B & J T]

Is your inverter also your charger? You mentioned that it was off.

Yes, I understand it's also a converter and shuts off as a safety feature when the batteries get below a certain charge.

I don't understand how the batteries are not kept "topped" with a trickle charge. There must be something draining the power from them.

@Gronk yes that was concerning and on the original set of batteries. I'm wondering if what happened to them is happening again.

@B52Bombardier1 just put the multimeter on the batter posts while charging and check for AC power?

 

[Gronk]

The next step in my opinion is to get your multi-meter out and see what the voltage is coming from your converter. Depending on the state of charge in the batteries it could be as low as about 13 volts to as high as 16 volts. If you can check with the batteries hooked up and then with the batteries disconnected. The volts from theconverter should be close to 12 volts. Also check the voltage in your batteries and see where it is. Get the numbers and post them here for more assistance.
Far as the AC voltage, yes, you are correct to set your meter to AC and see what it says. It should be zero or near (very near) zero. If you are getting AC voltage then a diode is probably leaking some through.

 

[Rich W.]

Your battery charger is built in to your inverter. So turning off your inverter also turns off your battery charger. And since your coach is all electric, with the inverter on your refrigerator alone will run your battery bank down, leaving your batteries at whatever voltage is set in your energy management to cut them off to protect them. However since there are other parasitic draws, they will continue to discharge, killing them prematurely.

I don’t know why your engine start batteries are discharging, but that is something to correct. Try turning them off when you park it - that should stop that issue and tell you if you have other things drawing them down. Your engine start batteries should easily last five or six years. Mine lasted seven and were still working well when I replaced them, but I don’t have all the KIB stuff that may be draining yours.

The brochure says your coach came with AGM house batteries so while you can kill them just like conventional batteries, its hard understand how you could have dry cells. Something to ask your tech.

That coach uses a lot of electricity to keep everything going and 400 watts of solar (if you have the factory solar option ) isn't enough to keep things charged. I also have six house batteries and a residential fridge. With 1575 watts of solar, and two Victron 35/150 charge controllers, the system provides just enough power so that by the end of daylight hours, I am charged enough to get me through the night and have enough power in the morning for coffee and toast. I can’t see 400w being enough for anything and really don’t understand why they even offer that option.

Plugging in to a 120v (20 amp max) outlet probably doesnt supply enough power run your charger. I’ll test mine doing that, but that’s my guess. My feeling is that the coach systems may be working normally but you aren’t providing it enough power to keep it charged. I would ask other 35’ New Aire owners about their experiences and what they are doing. Also none of this should be a mystery to the tech so maybe its time for a different shop.

 

[Richpatty]

Not sure what is the issue here, but I do want to point out that you CAN turn off your Inverter w/o turning off the charger (Magnum). I do it all the time to save batteries when parked for storage.

I also believe that a typical 120v/15amp connection can keep the fridge running and the batteries topped off. Especially with solar.

Will be watching to see what is causing this...as it is puzzling.

 

[B & J T]

Thank you all for the tips, I'll be investigating them when I get out to where are coach is stored.

Maybe I'm being unrealistic about 110V keeping the batteries charged and still running the 'fridge?

 

[Richpatty]

Maybe I'm being unrealistic about 110V keeping the batteries charged and still running the 'fridge?

Not at all. You can adjust the Magnum charger (assuming that is what you have) to take less amps...to leave some spare for the fridge.