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Old 06-21-2016, 04:10 PM
bistander bistander is online now
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Join Date: Apr 2015
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Lithium cells

Quote:
Originally Posted by BroMikey View Post

hello Bitstander

Yes I agree that the C20 and C15 or the C10 rates do
not seem to apply with these Lithium ion batteries.

This is my first test ever with this kind of battery.

As Aaron mentioned, Peukert doesn't really apply to Lithium ion cells. So for a 2C, 1C, C/5 or C/20 charge or discharge, Ampere-hours will be the same. For very high rates, > 25C, that will change. But at reasonable currents, you can pretty much count on C Ah for a good fully charged cell.

And Lithium ion is nearly 100% for Coulombic efficiency; like 99.98% or thereabouts. So if your methods are good, you can count Ah in and get the same Ah out of a cell assuming you start and end at the same state of charge (SOC). And SOC can be fairly accurately determined from the cell's open circuit voltage.

I assume you were using the 18650 cells, 18mm dia 65mm long. Those are common and cheap. Here is a link to an inexpensive charger/discharger (<$20) which should be able to characterize cells for you. Take some precautions when charging Lithium as severely overcharged cells can overheat and possibly ignite.

I think these Lithium cells would make excellent subjects for your tests. They should eliminate a lot of ambiguity you find dealing with lead-acid.

bi

IMAX B6 DC Charger 5A 50W (Copy)
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