Eneloop XX

Tsportmat

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After being impressed with my eneloops, I decided to grab some XX versions.

I ran a 'Test' in my BC-700 (as I've done with all my cells). To my surprise they only read ~1600mAh, except one at ~1900mAh. :shakehead

Is this normal? Do they normally need more of a break in than eneloops?

I also noted that they were pretty warm while charging, although I've only just started charging at 700mA, so this may be normal?

It's worth noting that I had just tested some normal eneloops at 700mA (straight out of the packet), and got readings of ~2000-2100mAh...
 

Mr Happy

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No, I don't think it's normal. Although I don't own any XX eneloops (no need for the extra capacity), others here have bought and tested them and found them to perform to their specifications.

It could be that you have some dud cells, or it could perhaps be that they are not genuine. Low capacity and hot charging are both indications of low quality counterfeit cells.

Are you confident about the source that you purchased them from?
 

Tsportmat

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As I'm not experience in charging at higher currents, how warm would you expect a cell to get at 700mA? They were not too hot to touch - just more than I am used to.

I am fairly confident that they are genuine, they came in the blister pack and look alright - they were off Amazon (although they were from a seller on there). I also got eneloop glitters from the same seller, and they seem okay. (The seller is iCell Media).

It just seems strange that they all demonstrate the same behaviour. They are now coming up the the end of their charge, I am intending to let everything cool off and run the test again. I hope for an improvement, but it seems crazy that they should need to be refreshed straight out of the packet, especially for a quality cell such as eneloop.
 

JacobJones

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It is normal for batteries to get hot at high charge currents, At 700mA aslong as you can touch them they are ok. I also have bought eneloops from icell media and they seem to have the same performance as genuine eneloops so I assume that they are genuine. Does seem a bit strange that you got such poor results, did you do the test imediately after charging them? The xx ones arent LSD so if you left it a few weeks before testing them they would have lost a lot of their charge
 

Tsportmat

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This was my first use, I put them in and hit test; that charges them, discharges at 350mA, then charges again. It tells you the capacity at the end. If they were a little lower I wouldn't have been concerned and assumed that they needed a couple of break ins. This seems an awful lot lower though. I'll see what happens this time...
 

Mr Happy

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It is unavoidable that NiMH cells get a bit warm when being charged, this is in the physics of the charging algorithm. Warmth is not a problem, but if cells ever get too hot to touch that is too much. I don't consider 700 mA to be a high charging rate, in fact it is probably the minimum you should use for a 2500 mAh cell. At that rate the cells should get gently warm I think, but not hot. (For reference, I would consider 1500 mA or 2000 mA to be high charging rates, and then the batteries might get really hot.)

Anyhow, it seems like you should run the test again and see what happens. Also, check the voltage at the end of charging. If they are fully charged the voltage should be 1.45 V at least hot off the charger, so to speak.
 

Anonnn

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I don't consider 700 mA to be a high charging rate, in fact it is probably the minimum you should use for a 2500 mAh cell.

Mr. Happy, can you elaborate on this? I was under the impression that it's always safer to charge at lower mA rates because you don't run the risk of overheating the batteries and thereby lose precious battery liquid through evaporation. Am I misinformed?
 

hellokitty[hk]

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It's worth noting that I had just tested some normal eneloops at 700mA (straight out of the packet), and got readings of ~2000-2100mAh...
I find that strange, considering they are not fully charged by the manufacture before they are shipped.
 

Tsportmat

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I find that strange, considering they are not fully charged by the manufacture before they are shipped.

The test function charges fully, then discharges recording the mAh.

Mr. Happy, can you elaborate on this? I was under the impression that it's always safer to charge at lower mA rates because you don't run the risk of overheating the batteries and thereby lose precious battery liquid through evaporation. Am I misinformed?

Charging at lower current means you risk missing terminations (overcharging the batteries) - more so when they get a bit older. That's why people say choose a bit higher (but not too much higher...).
 

Tsportmat

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Some good news, three of them now read over 2600mAh. One is at 2100mAh, so I'll do another cycle on that cell and hopefully it will bring it up to the correct capacity.
 

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