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I have a battery charger with an output rated at 8.5V DC / 1.8A - it's charging four of these:
http://www.dealextreme.com/details.dx/sku.5790
If I tried to charge them with a charger rated at 8V DC / 0.5A - what would happen ?
I assume you're charging a pair in series?
8V wouldn't be able to charge a pair in series to 100% capacity - but would come pretty close - charging voltage is normally 4.2V per cell.
The battery charger MUST be Lithium specific.
4.2V per cell is a very precise voltage. 4.1 is not enough for a full charge and 4.3 is too much. Also they don't take overcharge, so a decent charger will have a timeout facility.
There should be a balancing facility to ensure each battery has an equal voltage across it when charging. If you're making up a pack, the individual batteries should be UNPROTECTED. Then they are connected to a specific circuit tailored for the right number of cells. This circuit then provides the power limiting and voltage balance.
Its more complex than most think!
This made me laugh,
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Photo taken just before the caliper went up in smoke?
Cheers Dave - the 'other' charger is not lithium specific (came with a lead acid battery) [i]so I'll not be plugging that in :-)[/i]
Dave- they're shrink-wrapped 🙂
If they are protected cells, then you'll struggle to damage then as the protection circuitry cuts out if you try and over charge them.
The cheapo Li-ion chargers from Trustfire charge a pair in series with no balancing - they (the chargers) also seem to blow up quite frequently as well 🙁
If they are protected cells, then you'll struggle to damage then as the protection circuitry cuts out if you try and over charge them.
If you have a load in series and one is fully charged with the others at, say 75%, then the protection circuit on the first will cut in and prevent the others being fully charged. Result - reduced performance.
