Red Scholefield
Posts: 4980
Joined: 12/8/2001
From: Newberry,
FL, USA
Status: offline
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When we are talking DISCHARGE cut off:
The cut off voltage is set by the type of cell, not the size or capacity. Of course if you are discharging at a very high rate the cut off can be lower. But in our use, normally to determine the battery capacity in the C/5 discharge region (than this is good for discharges up to C rate) the recommended cut offs are:
Ni-Cd/Ni-MH V cut off = (N-1) X 0.9volts, where N= the number of cells. Or if you don't want to mess with the math just use 0.9 volts/cell - this is good for as many cells as we find in the hobby application.
For Lithium systems the cut off is 2.5 volts, for saftey use 3.0 volts because there is very little left between 2.5 and 3.0 anyway. CHECK THE MANUFACTURER'S SPECS - AS THIS NUMBER IS SOMEWHAT FLUID AT PRESENT, DEPENDING ON THE ACTUAL CELL DESIGN.
The CHARGE cut off for constant potential systems (Lithium) is set by the manufacturer. It is usually 4.1 volts per cell, which would give you 12.3 volts for a 3 cells (in series) Lithium system.
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Red S.
AMA 951 Leader Member
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Great Planes new DC charger/cycler - 
Great Planes new DC charger/cycler - 
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