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Charger recommendation for 8 6V series-parallel system

snazawa

New Member
Joined
Sep 19, 2020
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Location
Puerto Rico
Recently purchased a farm in Puerto Rico. We plan to install solar next year, but for the time being we inherited a standby battery bank which consists of 8 6V 230AH Duracell (SLIGC115) lead acid batteries wired in series-parallel. I've attached an image of the battery bank and the charger. The charger that came with the bank is a Duralast DL-15D model with the following specs
Input Voltage: 120V AC @ 60Hz, 3.6A, Output Voltage: 6V or 12V, with Auto Voltage Detection, Output Current Rating: 2A @ 6V DC; 15A @ 12V DC

My guess is that this charger is under powered for this battery configuration and even though the batteries appear to be in decent condition (tested with a SG meter and water is at correct levels) I can't get them to charge to more than about 12.4V. Any recommendation on the type of charger I should be using. If you could include a link that would be great.

Also, the previous owner would just connect the charger to the main positive and negative terminals/posts that connect to the inverter. Will that work or do I need to be charging each battery individually. That sounds tedious, but I could do it knowing this is just for standby/emergency power. Thanks! :)
 

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Good guess.

Looks like 24V system.

6 * 8 * 230 = 460Ah @ 24V

You need to charge at 46A (10% of cap) optimal, but you can get away with a bit less.


The 40A unit is close enough. It can act as both a 3 stage charger, or it can operate in constant voltage mode, i.e., if you're not cycling the bank, you could fully charge it once and then put it on constant voltage "float" of 13.2V to store them at 100% SoC.
 
Good guess.

Looks like 24V system.

6 * 8 * 230 = 460Ah @ 24V

Thanks but I'm pretty sure it's a 12 amp system. The inverter I'm using is connected straight to the battery bank and the inverter is a 3,000 watt unit labeled with 12V20A.
 
Duh. 6V + 6V = 12V... sorry.

That puts your charge current closer to 90A.

That same company makes similarly sized chargers for 12V in their PM3 and PM4 lines. I think there is a 75A version.
 
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