NiMH AA from eBay (what was I thinking?) - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: September 07, 2017, 01:21:04 am
content: I bought some cheap not really expecting full capacity, even half would be OK for my use, but my experience is so far off the general feedback on these that I must be doing something wrong.First I measured the voltages all 1.2x, so I pop 4 into my La Cross charger and give them a 700mA charge. They charge fairly quick and take around 100mAh. I set those aside and popped in 4 more and gave them a discharge/charge cycle. I come back about 20 mins later and a couple are charged taking less than 300mAh. The rest finish off soon after under 300mAh.Maybe the smart charger is faulty so I pull out my Orion RC charger and set it up for NiMH and let it charge a cell. I get less than 100mAh, so I try another cell discharge/charge, with cutoff of 0.9V. I get less than 10mAh out and around 250mAh in. The remaining two do about the same.This seems wrong to me. Supposed to be 3000mAh cells, but how is everyone so happy with them?http://www.ebay.com/itm/6x-AA-battery-batteries-Bulk-Nickel-Hydride-Rechargeable-NI-MH-3000mAh-1-2V-Yel/272383483150

author: metrologist
author_rank: Super Contributor
timestamp: September 07, 2017, 01:26:09 am
content: After a charge I did Dave's drop test. These will make great dead-blow hammers. Hit the counter with a thunk and absolutely no bounce.

author: hendorog
author_rank: Super Contributor
timestamp: September 07, 2017, 01:28:24 am
content: Not everyone...http://budgetlightforum.com/node/9274http://www.davidhunt.ie/no-name-ebay-batteries-too-good-to-be-true-probably/http://forums.parallax.com/discussion/152959/beware-of-fake-batteries-on-ebay

author: BradC
author_rank: Super Contributor
timestamp: September 07, 2017, 01:30:32 am
content: They are probably 200/300mAh solar light Ni-Cd cells.I did the same thing when I first got back into re-chargies. Most of the batteries I bought topped out at about 3-400 mAh and had something like a 10%/day self discharge.

author: bitseeker
author_rank: Super Contributor
timestamp: September 07, 2017, 02:00:27 am
content: Seeing the title made meThose cells do sound like they're toast. However, NiMH batteries that have sat dormant for a long time can improve after several full charge/discharge cycles. If you're in the mood for it, you could try a couple more cycles to see if the capacity improves, but I wouldn't be surprised if they didn't.Even for tinkering and casual projects, it's best to get new, low self-discharge NiMH batteries.

author: metrologist
author_rank: Super Contributor
timestamp: September 07, 2017, 02:12:57 am
content: I might have been ok enough with it if they performed as well my ancient Sanyo 700mAh NiCD. I wanted to replace a dead 6-cell pack in a portable DVD player.

author: IanB
author_rank: Super Contributor
timestamp: September 07, 2017, 02:21:53 am
content: Quote from: metrologist on September 07, 2017, 01:21:04 amThere's no such thing as 3000 mAh cells. From a good manufacturer, if they really cram the electrons in, you might get 2700 mAh, but the robustness and longevity will be poor.It is really easy to screw up the manufacture of NiMH cells and really hard to make good ones. This is one item where it pays to spend more and buy quality.

author: metrologist
author_rank: Super Contributor
timestamp: September 07, 2017, 02:36:36 am
content: yeah, like I said I wasn't expecting 3Ah, but half would have been good. The "Great Power" cell pack that was in the DVD says 2100mAh, from 2006. It was working long enough to play a 90 minute movie at least, just a few years ago.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 07, 2017, 04:18:47 am
content: I got burned a few years back buying nimh aa cells from ebay. I learned since then to take the advertised capacity and drop the least significant digit and that is your true capacity.So 3000mAh is really 300mAh. You can tell just by picking them up they are nowhere near their rated capacity.I heard good things about Amazon Basics possibly being Eneloops, but made for Amazon.If you live near an Ikea, I had good success with the Ladda LSD AA and AAA cells.Eneloops are the gold standard for me and I have about 60+.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 07, 2017, 04:21:13 am
content: Quote from: metrologist on September 07, 2017, 01:21:04 amMost people have dumb chargers and probably don't pay attention to the run time. They probably stick them inside remotes, AA flashlight and other non demanding applications.They will certainly see the difference between Eneloops and generic ebay crap in a digital camera/flash or something like that.

author: BradC
author_rank: Super Contributor
timestamp: September 07, 2017, 05:37:36 am
content: Quote from: retiredcaps on September 07, 2017, 04:21:13 amThat was what initially tipped me off. I put them in some remotes which failed to work after a week/fortnight. I then did some characterizing of the cells to find they had an insane self discharge rate.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 07, 2017, 05:58:08 am
content: BTW, an eevblog member, HJK, has this great website on everything with respect to rechargeableshttp://lygte-info.dk/