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Voltage needed to charge batteries

1K views 2 replies 3 participants last post by  Moltenmetal 
#1 ·
So we are designing a BMS; and need a few batteries for testing and prototyping.
So our battery pack will be 16 LiFePO4 cells.
giving us a max. voltage of 58V.
My question is when charging this battery pack; what is the necessary voltage of the charger???
if the voltage of the charger is lower than that of the battery pack it won't charge, what could happen if the voltage of the charger is much higher like around 200V for example.
furthermore if I'm just using two cells for prototyping what voltage would the power source have to have in order to charge just two cells giving us a voltage of 7.2V
And lastly during charging what is the amount of current which will be passing through the batteries????
Thank you all.
 
#2 ·
It has to be higher than the finished pack voltage. A 16S finish voltage is 58.4 volts.

How much higher depends on the voltage drop of your regulator circuit and what kind of regulation you are using. If you are using a Buck converter, you can run line voltage of 240 volts or higher. If you are using a Series or Shunt type, depends on how much the forward voltage drop is of your FET has. Get the voltage to high, and the FET has to dissipate more heat. Get it to low and you may not make finish voltage.
 
#3 ·
The questions you are asking are so elementary and could be so easily answered by doing a little Google searching that I'm quite concerned about you. Why are you designing a BMS when you don't seem to know even elementary electrical/electronic theory or anything about LFP batteries?
 
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