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how do you charge lithium betteries

6456 Views 13 Replies 9 Participants Last post by  ElectriCar
i was hoping to find out a little more about how the charger actually charges the batteries.

is it as simple as setting the max voltage and then pumping that many volts into the battery untill the battery reaches that level.

for example if i have a lithium battery that i want to charge to 4v could i just pump 4v into the cell no matter what the voltage of the cell is. even if the cell is discharged to 3v.

or does the charge voltage need to be set at a slightly higher level then the battery voltage.
for example
cell voltage = 3v charge voltage =3.1v,
cell voltage = 3.2v charge voltage =3.3v

there are two reasons i ask. Firstly I've seen a couple of people use dc/dc converters to charge cells individually and these can't adjust the voltage. Secondly i have been pondering the idea of putting in a permanent petrol generator, which I'll rectify to DC and then use that to charge the batteries on the go.

So will a constant charge voltage damage the batteries?

thanks you for all you help:D
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My CALB SE 130AHA batteries (38 pcs.) have a charge voltage about 3.6V.
I charge them up (with a Zivan NG3) to 3.5V max (133V), so I don't "pump" them up to the max.
This should increase the lifetime and security by seriell charging.

I use a initial constant current (129V / 15A) until the "rest" of the charge the current goes sligtly down (steps between 9V and zero) and the voltage rises up to 133V at the end.

IMHO: a constant charge voltage would not damage the cells, but it might be difficult to watch the voltage not running high at the end of the charge. Less current you charge, more voltage would come out of your power supply I think. A good charger would compensate this.

But let's read what others write to your post ... :)
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