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Im looking for some official information source about maximum current for Panasonic Eneloop BK-3MCC rechargeable batteries.

All I found is single page data sheet, there is just 1 table (nothing about maximum discharge current), charge and discharge characteristics.

UPDATE LINK: Datasheet BK-3HCC

/ edited - I fixed my mistake, I meant 6A not 8A /

There is discharge characteristic for 6000mA discharge. So... I can safely draw 6A from that AA cell?

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  • \$\begingroup\$ The highest curve I see on that datasheet is 6000mA, so 6A is the maximum rated discharge rate (not to say this is the maximum safe operating rate; that could be higher but I wouldn't count on it being significantly higher). \$\endgroup\$ Aug 1, 2014 at 21:43

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I think you mean 6000mA discharge. I don't see an 8000mA discharge curve there. If the ambient temperature is 25C then yes, you should be able to pull at least 6000mA from it.

I think that the safety factor would be highly dependent upon ambient temperature and how fast you're pulling the heat away from it. Otherwise, I've never heard of NiMH having issues with fast discharge current unlike lithium ion batteries.

I used to have a remote control plane that would suck the NiMH batteries dry in about 10 minutes so that would make them capable of at least 6C discharge. That was probably 10 years ago. I can't imagine batteries getting worse with time.

At 6A current draw, that's only 3C, so my guess would be that you have some room to play with. Anything beyond 6A should be experimentally tested as the datasheet doesn't show anything beyond that.

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  • \$\begingroup\$ Thats 6A indeed. I edited my post. \$\endgroup\$
    – Kamil
    Aug 1, 2014 at 22:35
  • \$\begingroup\$ "I can't imagine batteries getting worse with time." Well, these are eneloop with 2100 cycles... I know they are diffrent from regular NiMH, so I can't expect they are better in everything. \$\endgroup\$
    – Kamil
    Aug 1, 2014 at 22:37
  • \$\begingroup\$ @Kamil The faster you drain them, the more chance there is that you won't get the advertised 2100 cycles. You also aren't going to get the full rated capacity as you can see from plots as well. Even OEM's will run their own tests on components before putting something into their design. Your design work shouldn't be any different. Trusting graphs on datasheets isn't a game experienced EE's will play. \$\endgroup\$
    – horta
    Aug 2, 2014 at 23:24
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No you cannot safely draw 8A from a battery rated at 6000mA.

New battery EsR is 25mΩ at 1V. Internal dissipation at 6A is then 36*25mΩ=0.9W

8A is then 64*25mΩ=1.6W which means temperature rise is almost double.

Worse yet cell voltage on plateau drops 50mV for each 2A curve difference, power output drops 100mW for each 2A step. Thus total Wh capacity is diminished more than Ah capacity.

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  • \$\begingroup\$ 8A was my mistake. I meant 6A from discharge curve. However answer is interesting (power on internal resistance approach) \$\endgroup\$
    – Kamil
    Aug 1, 2014 at 22:41
  • \$\begingroup\$ There is a way to calculate max safe current from Ah capacity and ESA for each chemistry type based on W/Ah but this does not give optimal life. Reducing depth of discharge, cell temp. rise and C ratio of charge/discharge affect specified recharge lifespan. There is no free lunch. \$\endgroup\$ Aug 6, 2014 at 4:50

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