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Trojan L16H-AC 435Ah, 6V Deep Cycle Batteries troubleshooting

snoobler

Solar Honey Badger
Joined
Jul 10, 2020
Messages
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Location
HBR, AZ
@Olliewood

Issue: 12 Trojan 6 volt 435AH 4 in series, 3 banks. 5 of 12 batteries showing low voltage.

SG not checked regularly. Little to no maintenance.

Recent voltages taken a week apart:

1597370389585.png
 
If you wish to pursue diagnostics/restoration rather than just replace them, this procedure will help:

From this datasheet:


Need to confirm charges are properly setup.

Bulk/absorption should be 29.64V (7.41/battery)
Float should be 27.0V (6.75/battery)
Equalization should be at 32.40V with a 4 hour limit (8.10/battery)

You should have a temperature probe, and temperature compensation should be active with a total of -.06V/°C or -.005°C per cell.

Confirm your charger is configured accordingly (solar charger, inverter/charger).

Due to your fairly large bank, 1305Ah, you should have the ability to charge at 65-130A in normal.

Before you get started, you should reconfigure the batteries and work with the 3 strings separately:

Battery​
Volts​
5​
7.3​
8​
7.2​
1​
7.1​
4​
7.1​
6​
6.5​
9​
6.5​
12​
6.5​
7​
5.2​
2​
5​
10​
4.8​
3​
4.6​
11​
4.6​

10.3kWh is still pretty respectable and should be fine unless your power use is very high.

It is important to take specific gravity (SG) readings after a full charge.

After a full charge, record all SG readings and the 4 battery voltages. SG readings are best if you fill the hydrometer, expel it and then fill it a second time. This helps insure the electrolyte is mixed.

Conduct an equalization charge, which should last up to 4 hours, or until one of the batteries hit 110°F. At such time, terminate the equalization charge and take SG readings as soon as possible repeating the prior technique.

Note that during any charge operation, you may have to alter the total charge voltage to keep individual batteries from exceeding their limit. Given that you're working to recover them, the hard limit is 8.1V, and you need to monitor the temperature of that battery for 110°F.

Do not add water unless the plates threaten to be exposed and then add only enough water to keep the plates submerged.

If you can demonstrate an improvement in SG with an equalization charge, there may be hope for recovery. The severe voltage disparity may make this particularly challenging.
 
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