Maximum safe continuous charhe current NiMH Batteries

I am busy designing a AA NiMH battery charging circuit, and basically they are being trickle charged. However to meet IEC 60950 I believe we have to test the charge current with a shorted cell and a one fault in the charging circuit. Does anybody know what the maximum charge current can be before the batteries become dangerous. My circuit currently limits the current to 300mA but I cannot find any data on what is the maximum safe continuous charge current for a rechargeable battery.

Reply to
Loading thread data ...

"and a one fault in the charging circuit"

any particular fault in mind?


Reply to
Martin Griffith

I expect he needs to pass with a SFC (Single Fault Condition). So basically any possible single fault in the charger.

But he asks for testing with a fault in the charcher AND and a shorted cell. That sounds like a double fault condition to me.

Best thing to do is to ask battery supplier.

If you can't get the circuit safe, you can also incorporate a thermal fuse in the battery pack. Depending on the application it might be even mandatory to at least have a (resettable)fuse in the pack.

Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)
Reply to

I would think about the worst case would be a short in the current regulator.

Reply to
David R Brooks

Yes, that is the worse case, having spoken to UL battery short and current regulator short counts as two shorts, so only one fault needs to be considered. It is my understanding that all rechargable batteries have to have a safety vent so they can cope with gross overcharging. However UL still want a maximum charge current which no battery manufacturer can give me, any help would be appreciated Thanks

Reply to

Try sci.chem.electrochem.battery

My suspicion is that there isn't a single number though, it will likely depend on capacity (and maybe on the definition of safe).

For Li-Ion this figure would probably be close to zero. For NiMH something like C/10 or C/20 will be considered non-damaging (which might be a reasonable proxy for 'safe') in which case you might have a limit as low as 25mA (for a 500mAH cell) or as high as 110mA (for an

1100mAH cell). Depending on how you restrict your battery supplier choices the range might be higher or lower.


Reply to
Robert Adsett

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.