Battery not charging

Basil48192

I have had my 2021T@B 320S for about 4 months.  I have boondock camped twice and camped on shore power 3 times.   I just noticed that when I turn off my shore power (after being connected for days) my battery voltage drops to 12.35 volts.  Could my battery be bad already or is it just not charging for some reason?  All cells are full, inverter seems to be working.  Any help would be appreciated.

m_lewis

Either your convertor isn't charging at the proper voltage, your battery is bad, or (most likely) you have some load on the battery when you are checking the voltage. 
Make sure your battery has zero load on it. You should probably go so far as to disconnect it from the camper, let it sit for about an hour, then measure the voltage with a high quality voltmeter. If it then reads only 12.35, it is at a state of charge of about 70%. This could be due to insufficient charging voltage. 
While the battery is disconnected, with the camper plugged in to shore power, the convertor should be supplying about 13.2 volts. Check that is is.
If so, then I would suspect a bad battery. Before replacing it though, I would try another charger, or at least have it tested at an auto parts store.

Basil48192

Thank you m_lewis.  When plugged into shore power, my Victron Controller app shows 13.7 volts at the battery.  I'll keep an eye on it...maybe there was a draw when I checked thought I'm not sure what it could be.  I'll try disconnecting it as you suggested as well.  Thanks again for your comments!

pthomas745

Your trailer has several "parasitic drains" that carry about 4 amps a day from the battery.  Like m lewis pointed out, a battery "in use" will always read a lower state of charge, and a battery plugged in will read whatever is going to the battery to charge it.  (This is called "false capacity.")  You need to measure a "rested battery".

You can read your battery state with your Victron app, with the battery off.  Take a reading with the battery on, turn the battery off, wait a few minutes...and see the voltage reading rise.  You will get a jump pretty immediately, but if you can wait a little longer you will get a better idea of your state of charge.

Find yourself a decent "auto ranging multimeter" and learn how to use it.  Usually, this will involve simply turning a dial to the proper "function", putting the probes on the appropriate battery terminals, and reading the data. 

This is how my Victron shunt reacts when I turn the battery switch off.  Picture on the left is the trailer with the fan running.  12.09!  Picture on the right is the reading with the battery switch turned off and waiting for 10 minutes. 12.46.  This is what "rested battery" is all about.

Basil48192

Thank you pthomas745 as well.  I may have over-reacted.  With the battery disconnect open (off), I was at 12.75 and rising.  I guess it puzzled me a bit.  I did check the fuses at the battery earlier today and it seemed to get much better after that.  Maybe one was loose...or maybe it was just the battery load when I checked it earlier.  The thing that got me checking was that my battery indicator inside the unit showed 3 lights instead of all 4...which it had never done before unless I was boondocking.  I'll keep an eye on it and take your advice when checking.  Thank you again....this is quite a learning curve!

Sharon_is_SAM

@Basil48192 - the KiB battery indicator monitor that comes with the TaB is not very helpful and it tends to over estimate.

Basil48192

Thank you!  The more I investigate, the more confused I get!  I'm wondering if I have a short in my wiring or in one of the fuse holders near the battery.  I have been on shore power but my history page on the Victron app shows virtually no solar input for the past few days.  I think the extremely low voltage reading from today is when I removed the fuse to check it. 


 

Deb55

@Basil48192 I noticed in your first post that you mentioned your inverter is working. Did you turn it off after using it? My T@B 400 doesn't have an inverter, but I've learned from this forum that they draw a lot of power when on, and should only be on when in use. 

Basil48192

Thanks Deb55.  I apologize...but I used the wrong terminology.  I should have said that my con-verter is working...though I still need to check it with the battery disconnected.  I don't believe I have an inverter on my 320S either.  Thanks to you and others on this site, I am slowly being educated on this electrical system.  I still think I may have had a wiring connection or fuse connection issue that initially prevented my battery from charging.  I will check that closer this weekend.  Thank you again!