Maintaining Large FLA stationary battery

[Thermo1223]

Ya so running the fire pump on an exercise cycle I noticed it was cranking slower than usual.

I never did trust this old maintainer and thought it was always suspect.

I like this one from Grainger since I can maintain both separately. I can also get extensions to keep it neat plus I have a 110V outlet right there.

https://www.grainger.com/product/BATTERY-TENDER-Battery-Charger-Charging-Maintaining-10W828

Batteries in question;

You can see it only maintains one as well which is also an issue. It is a 12V system so they are not connected together at all. I haven't multimeter it yet but I don't even think both are charged at the same time while the engine is running.

 

[mk378]

On a 12 volt system they should be connected in parallel all the time. The two plus wires and the two minus wires should go to the same places on the machine, i.e. minus to ground and plus to the starter solenoid. Two batteries in parallel make twice as much current available to the starter. As far as charging and maintaining they are treated as one battery.

 

[Thermo1223]

On a 12 volt system they should be connected in parallel all the time. The two plus wires and the two minus wires should go to the same places on the machine, i.e. minus to ground and plus to the starter solenoid. Two batteries in parallel make twice as much current available to the starter. As far as charging and maintaining they are treated as one battery.

That's not how it is setup. It is a dual battery system hence Batt 1 & Batt 2 with separate connections and contactors to start. If one battery fails it automatically tries the other.

However the ancient trickle charger isn't setup that way.

 

[ripcord]

You should use a specific gravity tester to make sure they are both charged fully and all the cells are nearly equal. If you have some weak cells, then do an equalization charge. The battery manufacturer should have instructions on the voltage to use. It will typically be in the ballpark of 16.2V. Unscrew the caps as the cells will bubble and gas during the equalization charge. When doing an equalization charge you want to stop after the specific gravity in all the cells has stopped rising for a couple of hours.

An inexpensive lab power supply with adjustable voltage and current is perfect for this kind of thing.

 

[JHZR2]

You should use a specific gravity tester to make sure they are both charged fully and all the cells are nearly equal. If you have some weak cells, then do an equalization charge. The battery manufacturer should have instructions on the voltage to use. It will typically be in the ballpark of 16.2V. Unscrew the caps as the cells will bubble and gas during the equalization charge. When doing an equalization charge you want to stop after the specific gravity in all the cells has stopped rising for a couple of hours.

An inexpensive lab power supply with adjustable voltage and current is perfect for this kind of thing.

For playing lab experiment, or babysitting it, sure.

Based upon how op described it I’d get a two battery charger, or better, two one battery chargers plugged into two different circuits.

 

[ripcord]

For playing lab experiment, or babysitting it, sure.

Based upon how op described it I’d get a two battery charger, or better, two one battery chargers plugged into two different circuits.

Equalization charges aren't an everyday thing, but something you do rarely to prolong the life of neglected, expensive batteries.