Quote:
Originally Posted by redpoint5
I'm not following the reason for the math, please explain. My battery is 4s (4 cells in series), so that should give 3.4v times 4, or 13.6 volts total.
What are you recommending for those wanting to run a LiFePO4 battery that is charged by the alternator?
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The voltage on each cell depends on the state of charge on those cells. If those are exactly equal there is no need for balancing, obviously. But if one cell gets slightly out of line you do have a problem, because that cell will peek above 4 Volt and start destroying itself while the other cells are still around 3.4 Volt just shy of being completely full.
If your alternator or charger or solar panel or whatever provides more than (3.4 *3) + 4.0 = 14.2 Volts, then you might destroy one cell in a pack of 4 LiFePO4 cells.
Because it will not shed charge by itself like LA cells do there is no self balancing. You cannot trust them to stay balanced indefinitely without some means of control.
If you stay below 14.2 Volt then an unbalanced pack will stop being charged when one of the cells is full. If the balance deteriorates there will be less and less practical charge available. Finally you may kill a cell by depleting it too much, again while the other cells are still around 3.4 Volt.
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