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# Batteries and capacity

#1
03-23-16, 04:54 AM
Member
Join Date: Mar 2016
Location: KSA
Posts: 1
Batteries and capacity

Hi all

I have a battery charger system with charger out put of 50 amp and 125 V.
the AC input is 480 V, 3Ph

the battery bank has 60 cells. I am not sure about the battery capacity. The question is the battery capacity is ..... amp for ....... hours to a final volts of 1.75 per cell

Any help friends ?

Thanks,

#2
03-23-16, 05:42 AM
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Join Date: Mar 2003
Location: NC, USA
Posts: 18,112
You cannot tell a batteries capacity by the charger. It's like asking how big a car's fuel tank is by looking at the engine. They are two different things.

Are you certain you have 60 (sixty) cells? 125 volts would be a more appropriate charging voltage for 54 cells which would be 9 six volt (three cell) batteries.

As for final cell voltage it depends on what type of battery you have. There are charts online that will show the charged voltages for batteries depending on the temperature. Off hand I don't know any that have a fully charged voltage of 1.75. That's quite low for any battery I know about.

#3
03-23-16, 06:52 AM
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Join Date: Mar 2010
Location: USA
Posts: 3,089
You are going to have to contact thge manufacturer or someone who has a spec sheet for those batteries.

The apparent capacity (in ampere hours) can vary depending on the rate of drain (amperes). The output voltage can vary significantly depending on the amperes.

Sixty battery cells delivering 2 volts fully charged (lead acid batteries) will give you 120 volts. You might use as a starting point a draw from fully charged batteries resulting in a voltage drop of five percent (leaving 114 out of 120 volts) to be the maximum draw. You might use as a starting point a voltage of 10 percent less than full voltage (down to 108 volts out of 120) under full load as the discharged condition where you stop using the batteries and turn on the charger. Oh well, you could let the batteries under load go down 12-1/2 percent to 105 volts averaging 1.75 volts per cell and then recharge.

The cells will not necessarily discharge at the same rate. For lead acid batteries, individual cell voltages could drop precipitiously one at a time. It is hard to detect when individual cells go dead when you have many (like 60) in series but individual dead cells suffer strain in a battery still under heavy load.

Last edited by AllanJ; 03-23-16 at 07:14 AM.

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