House batteries not being charged by inverter-charger

[Tic Wilson]

2005 Monterey: I have had to put a standalone charger on my house batteries while connected to shore power.  In the attached photo of the DC distribution panel, looking at the bottom bus bar, I have 13.8V on the left side connection, and reading battery voltage of 12.5 on right side by red wire.  What is the component that looks like a coil of wire?  I called BCS, but have not heard back from them.  I believe the 13.8 is coming from the inverter-charger.  The red wire appears to come from solar source.  This photo is to the right of the Big Boy battery isolator.
Thanks!

[Edward Buker]

Tic,

I think those are Class T fuses. They are high current like 200-400 amps. Their claim to fame is that by design they are very fast acting with the intent to protect things like inverter chargers. I cannot tell you that is how it is wired in your coach but if you are seeing different voltages on either side and one is battery voltage and the other is inverter voltage then that is likely what it is doing. The fuse is open (blown) if the voltage is different on eith side by more then a couple of tenths of volts. That can be confirmed by removing it and checking it with an ohm meter. I see writing on it that should have the amp rating. Hope this helps.

Source link here... http://shop.pkys.com/Class-T-Fuses_c_113.html

Later Ed

[Tic Wilson]

Thanks Ed!  BCS called and confirmed that as well.  New fuse on order.

[Edward Buker]

Tic,

Glad that you are getting the parts. Sometimes a fuse will age with stress and go open, these are large fuses and it is not so common to have one of these fail. Hopefully because you have 13.8V from the charger on one side and appropriate battery voltage on the other, this may just be just an age issue. The other possibility is a shorted battery that pulls a lot of current. You would see that using a temporary charger. A failing engine starter that is shorting might also pull high current from both the battery bank and the charging system.

Thought I would just alert you that if another fuse fails, you need to be looking for a high current demand source that is not acting properly. Might also give a once over at the batteries for a loose or corroded cable to assure good connections or a warm battery and a cell that is using more water by boiling it out. Hopefully the fuse was just getting old like we are :-)

Later Ed