Winter Battery Maintenance With Cover in Place

Cracker

I just discovered the Victron App for my phone.  I can read it from inside my home with the T@B 400 parked 20' away outside.  I installed the PaHaQue cover about five days ago and the first thing I noticed on the Victron was that the battery voltage was dropping daily, ever so slightly.  I had not disconnected the batteries so I did so right away.  Afterwards, I was pleased to note that the voltage drop had ceased and the solar panels were putting out just enough power for the batteries to increase their voltage daily.  They're now reading about 12.50 volts.  It's my understanding that this should be enough to maintain the batteries over the winter - provided I keep snow from reducing the solar panel output any further?

Marceline

What kind of batteries do you have? What’s the voltage reading at night (when there is no light on the solar panels)?

pthomas745

What year? What batteries?  The large AGM? Or a newer lithium setup?

With the battery switch on in your trailer, the voltage readout you were getting was fluctuating as the parasitic drain of the trailer (things like the entertainment units, the Gas monitor, etc) slowly drained the battery, and then when the sun hit the trailer, the attempt by the solar panels to charge the battery.  Your voltage readouts were "lower than actual" because the battery switch was on, and the voltage readout was not accurate.  The voltage will always read "lower than actual" with the battery switch on.

The question would be: did the solar recharge the battery back to 100 percent each day while the battery switch was on.  Look at the "History" page of the app, and send us a screen shot if you want.  If you were getting enough sun, you should see the battery reaching "float" stage of charging.

If you were not getting enough sun to completely charge the battery, the history page will show that, also.  But, since the battery switch was on.....the voltage readouts will not be accurate.

With the switch off: all batteries have a "self discharge" rate.  Depending on a lot of things (type of battery, age of battery, lithium, lead acid, etc) that rate can be anywhere from 1 percent to 5 percent per month.  Once a battery reaches full charge, the solar will wait to start charging again when it senses a certain amount of voltage drop.  On a healthy battery, only discharging at 1 percent, this might take several weeks for the solar to put in the tiny amount of charge necessary to bring the battery back to 100 percent.

If the battery switch is off, a fully charged battery can hold a charge for months even with no solar input. 

The important thing, though, is unless you are absolutely sure of a decent amount of solar input, it would always be best to have the battery switch off.

Cracker

I neglected to mention that this was the twin AGM battery setup on the 2021 T@B 400 Boondock.

pthomas745

Keep checking on the battery charge level.  The kicker here is: the status of the dual 6V Harris batteries (if those are the batteries you have).  Now that they are 4-5 years old, they may be starting to fade a bit, and not be able to hold a charge as well as they should. If your voltage, with the switch off, does not hold a state of charge near or above 12.5, you could have an older battery that is beginning to fail.