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AA cells, rechargeable NiMH

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amlu View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amlu Quote  Post ReplyReply Direct Link To This Post Topic: AA cells, rechargeable NiMH
    Posted: 19 February 2012 at 9:46pm
heyah

i had an idea of building myself a battery pack using standard AA rechargeable cells, usually 2500mAh.
got nice battery analyser to charge them up.

do you have any experiences which cells currently on the market are worth buying?
there is huge selection on ebay but i dont want to end up with 40 pieces of chinese crap holding  half of stated capacity...



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davey t View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote davey t Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2012 at 11:47am
Buy the Hybrid low discharge ones, they are only 2100mAh but the normal ones will be flat in a couple months on the shelf. 

You can trickle charge the pack with a contant voltage source and current limiting resistor. trickle at <200mA (<0.1C). Lower is safer. 
Minirig portable soundsystem movement
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markie View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2012 at 12:00pm
If they're any use to you (or anyone) I have a bag full of the plastic frames that hold 8 x AA cells into a 12v pack. with snap on connectors.

Like this http://www.ebay.co.uk/itm/2x-battery-holder-box-8x-AA-square-2x2x2-transmitter-etc-/360425343570?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item53eb064a52

Just cover the postage.
If it's got wheels or tits it's gonna cost a fortune
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slaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2012 at 12:49pm
Originally posted by markie markie wrote:

If they're any use to you (or anyone) I have a bag full of the plastic frames that hold 8 x AA cells into a 12v pack. with snap on connectors.

Like this http://www.ebay.co.uk/itm/2x-battery-holder-box-8x-AA-square-2x2x2-transmitter-etc-/360425343570?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item53eb064a52

Just cover the postage.


:-) It was one of those things that got me on the slippery slope of battery-powered audio.
My first trip to the West Indies - fancied some music on the beach - had no money to spend on it ....
Well I had a spare pair of little plastic "computer" speakers - were actually some of the better ones - had 5.5mm DC barrel on the back and expected 9V DC - so I thought - hmmm ..... 8 x AA NiMH cells should do it - may not last long ....

So I took that - worked out really quite well - made myself very popular on that beach :-)
The AA cells lasted much longer than I thought. Since then got a bit addicted to bigger/better battery-powered systems .....

8 x series NiMH would probably yield more like 10V than 12V .... still could be useful for some stuff though. Might be good for stuff like small mixers etc.

Mebbe one of those would make for a OK "backup" supply for a minirig ? Would (say) 10V @ 2500mAH make for a full-ish fresh charge for a minirig ?
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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amlu View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amlu Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2012 at 2:36pm
my plan is to use 10 of them and a holder for a battery pack.
voltage on the cells drops to around 1.2v under load.

looking currently at sanyo eneloop, they should be like 1.50£ each.
makes 15 quid for  a 2ah battery pack. no so cheap but running on good cells.

another option - http://www.ebay.co.uk/itm/12V-6800mAh-Rechargeable-Battery-Pack-LED-Light-Strip-CCTV-Security-Camera-/250919245956?pt=UK_Home_Garden_PowerTools_SM&hash=item3a6bf3d884

they go for 20 quid for 6800mah, but look really chinese crappish.
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Saturnus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saturnus Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2012 at 3:36pm
 
Originally posted by amlu amlu wrote:


they go for 20 quid for 6800mah, but look really chinese crappish.

More accurately they go for £33 for 6800maH because those e-bay lithium cells don't hold anywhere near their advertised capacity. Look at the weight, then calculate how much they could hold if they're were good cells in the first place. That'd be around 60% of the advertised capacity, still assuming they good solid cells which nothing indicates they are.

Sure. They work but you should absolutely not trust them to hold the advertised capacity, maybe half at best, they won't last nearly the advertised recharge cycles, and they do not have protection circuits built-in even if they advertise they do.



Edited by Saturnus - 20 February 2012 at 3:37pm
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