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Old Oct 21, 2011, 02:46 PM
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1800mAh AAA NiMH Rechargeable Batteries

Do 1800mAh AAA NiMH Rechargeable Batteries Exist?

I bought some on eBay, but they are being detected as defective by 2 separate chargers.

Thanks.

Mike
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Old Oct 21, 2011, 03:03 PM
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800 mAh is a lot for AAAs perhaps the 1 was a mistake.
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Old Oct 21, 2011, 05:14 PM
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Unfortunately, there are a multitude of sellers peddling "1800mAh" AAA NiMH cells on eBay. Nearly all are garbage and none are likely anywhere near 1800mAh in capacity.

http://www.ebay.com/sch/i.html?_nkw=...hargeable+1800

Rechargeable AAA's are a bit more finicky than rechargeable AA's so it's best to restrict purchases to those with known good performance. AAA Eneloops are the best that I have ever personally tested and use them in many devices and have yet to have one fail. The AAA Eneloops have a reported capacity of 800mAh and all that I have tested had usable capacity between 750 and 825mAh.

Mark
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Old Oct 21, 2011, 06:40 PM
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1800 AAA? Complete scam. Likely complete garbage.
Anything over 800 is a lie.
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Old Oct 21, 2011, 06:45 PM
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Thanks, guys!
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Old Oct 21, 2011, 06:52 PM
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You might be able to get close to 1800mAh with some chemistries of primary AAA cells at very low drain rates, but definitely not any NiMH rechargeable cells that I'm aware of.
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Old Oct 22, 2011, 08:32 AM
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Max AAA NiMHs I've been able to find are 1000 mAH.
Sanyo, Lenmar, DuraCell all have them.
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Old Oct 22, 2011, 07:34 PM
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eBay sided with me and issued a full refund.

I'd have done a research beforehand. Live and learn, I guess.

Thanks!
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Old Oct 27, 2011, 12:47 PM
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Just stick with 800 mAh AAA Sanyo Eneloop's and you'll have no problem.

Capacities over 2500 on AA's are generally fake.
Capacities over 1000 on AAA's are generally fake.
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Old Oct 27, 2011, 01:05 PM
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Can't you set up the batteries in parallel to make it an 1800mAh, just like you would do with lipos? or is that can only be accomplished with lipos? I've always been curious.
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Old Oct 27, 2011, 03:04 PM
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Quote:
Originally Posted by merlin703 View Post
Can't you set up the batteries in parallel to make it an 1800mAh, just like you would do with lipos?
For discharge, yes. For charging, no.

Cell counts must obviously be the same.

Mark
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Old Oct 27, 2011, 06:28 PM
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That, and usually you get AAAs because of size or weight limitations. AAs would be more effective if those weren't issues.
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Old Oct 28, 2011, 04:34 PM
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Quote:
Originally Posted by mrforsyth View Post
For discharge, yes. For charging, no.

Cell counts must obviously be the same.

Mark
Yes, that's what I mean, discharging. So for charging I assume lipos make it possible due to the balancing tabs. Good to know, thanks guys!
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Old Oct 28, 2011, 04:47 PM
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Originally Posted by merlin703 View Post
So for charging I assume lipos make it possible due to the balancing tabs.
Not related to balance taps. It's possible with lipolys (and Pb) due to charge algorithm. Lipolys charge to a specific voltage (4.2V) via CC/CV (constant current / constant voltage) charge algorithm whereas NiXX employ dV/dT (peak sense) algorithm.

Multiple lipolys can be charged in parallel independent of whether one chooses to use the balance taps. It's generally wiser to use the balance taps, but certainly not necessary.

Mark
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Old Oct 28, 2011, 09:09 PM
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NiMH cells can be parallel charged, but it isn't recommended due to their variations and their drop in voltage as they warm up near the end of their charge.

Eneloop C and D "cells" sold in other countries are actually paralleled AAA and AA cells. This isn't as much of an issue for them because they're very similar and because they'll have the same usage history.

You could reasonably safely parallel charge similarly performing NiMH cells, but it would be at such a low rate (so as to not inadvertently dangerously overcharge individual cells) that it isn't practical. (About 30 hours for 2 cell, 45 hours for 3, and so on.)
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