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51 minutes ago, Pilotguy said:

I hear from a reliable source

You should be more specific on your statement rather than throwing out the generic "reliable source" statement. :)

The general rule of thumb is to charge your batteries at a 1C rate.  This means that whatever the cell size is for the batteries in series in amp hours is the charge rate.   For example, if the battery pack uses 3000mAH cells (3.0Ah) then the 1C charge rate would be 3.0 amp rate to safely charge the battery.  

Let's use the King Song 14C with a 340Wh (Watt hours) pack.  It has 16 batteries in series to get the max voltage of 67.2V (4.2v * 16).  But it also has two rows of these batteries in parallel to give it a higher capacity.  

Assuming I have all my math right, we can calculate the capacity of individual cell the pack uses with a simple formula.  Since battery packs are expressed in watt hours and a watt is equal to the volts * amps (Vamp for easy reference), we will use Vamp in the equation to get the units to work out.

Pack size  / (max voltage * cells in series * cells in parallel) = Cell capacity

340WH / (4.2V * 16 * 2) =  340 VampH / (134 V) = 2.530 ampH or 2530 maH capacity battery for each cell.  

So a 1C rate for this battery would be 2.53Amps.   

But wait...there's more!  Since we have a parallel pack, the current is divided between the two series of cells.  So you take your 1C rating and multiply it by the number of parallel cells you have (in this case 2).

So the true 1C rate for charging a King Song 14C 340Wh battery pack is 5.06Amps.  

How about a King Song 14C 680Wh battery pack?  This one, I believe has 4 cells in parallel (two 340Wh battery packs).  This means each cell is still 2530maH but the 1C charging rate is a whopping 10.12 Amps.

How about a King Song 14D 860Wh battery pack?  Again, this is 4 cells in parallel.  This means that each cell is 3200maH and the 1C charging rate can be 12.8 Amps!


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