Electric Bikes Conversion Kits EMTBS eRoad/Commuting What's New?

18650 cell types & recelling battery pack

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Haku

Esteemed Pedelecer
Jun 20, 2007
339
4
Gloucestershire
Couple of years ago I tried to make a capacitive discharge spot welder to help rebuild one of my old ebike battery packs, but to cut a long story short I couldn't do it and someone I knew who's an electronics engineer had moved away making it too difficult to get help from them.

So I spent months saving up the £320 for a new battery, 6 months later it showed signs of deterioation and couldn't get help from the company I bought it from. Now 1.5 years old it's almost a hinderance as on the flat I find myself pulling slightly on the brake to disengage the motor to preserve the battery for the hills (which it struggles on)

So yesterday I had a look on eBay for reputable brand 18650 cells with tabs already on and found this UK seller with a nice range of them with good pricing: http://www.ebay.co.uk/sch/m.html?_ssn=ecoluxshop&_nkw=18650+tabs

But some of them are lithium-manganese and LiNiCoMn (whatever that is). Are they a drop-in replacement for li-ions or should I avoid them?
 
D

Deleted member 4366

Guest
You need 40 of them, which will cost £250 to £320. Then you need a BMS for about £30 and a case plus about £30 for a charger. For £250, you can get get a nice 20aH 36v one with a charger from BMSBattery. Why do you want to build one?
 
H

Haku

Esteemed Pedelecer
Jun 20, 2007
339
4
Gloucestershire
I have 3 old Urban Mover 26v lithium battery packs that don't hold much charge anymore, the electronics in them are fine they just need new 18650 cells.

They're decently built packs which can be taken apart easily, and the cells are held in a specially designed plastic cage, 28 of them wired in a 4P 7S configuration.
 
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T

trex

Esteemed Pedelecer
May 15, 2011
7,703
2,671
it seems like a good source for parts. In your situation, I would be tempted to by 28 pieces of 3400mAH.
 
H

Haku

Esteemed Pedelecer
Jun 20, 2007
339
4
Gloucestershire
Those 3400mAH do look tempting but current budget constraints may mean I can only get 2600mAH or 3000mAH cells.

One thing I hope someone knows the answer to; if I buy cells that have very high continuous amp output will they maintain a relative high ampage output when they get old?

I ask because I tried one of my several year old battery packs and during acceleration on the flat using only the throttle it felt as though it was doing a better job than my 1.7 year old pack, despite the voltage dropping lower than the 1.7 year old pack doing the same acceleration on the flat.


Finding these pre-tabbed cells in this country at good prices means I can finally re-think making a lithium pack for my Urban Mover UM30

Using the BMS from another of my old packs and these neat 18650 cell holders http://www.ebay.co.uk/itm/321114233041 with the cells in packs of 4 all stacked up into a long thin pack so it'll fit inside the frame where the original D-cell pack went.
 
H

Haku

Esteemed Pedelecer
Jun 20, 2007
339
4
Gloucestershire
Just placed an order for 28x LG ABD1 3000mAh tabbed cells for about £133, good price & good continuous + peak ampage output ratings that exceed the 7A nominal 15A max controller of my UM36X.
 
H

Haku

Esteemed Pedelecer
Jun 20, 2007
339
4
Gloucestershire
Well I put the new cells in my oldest pack last weekend during the cool of the nights, night 1 cutting out the old cells and soldering in the new ones, night 2 I soldered them to the BMS and put everything back inside the shell.

Charged it up with the normal charger and all went well.

However during my rides since with the recelled pack I realise I probably should've picked different cells, sure I'm now able to go further but the voltage drop when put under full load is more than I hoped for.
Starting out at around 29.4v when charged they can drop down to 25v and below under full load which means less power to the motor which isn't nice trying to go up all the hills round where I live. I think this is due to the cell output ampage being 3A continuous and 6A short peak, and am guessing that the ones which can do 10A continuous and 15A short peak don't drop the voltage so much under high loads, but generally they're lower capacity.


I knew from the start this was going to be an experiment as I wasn't sure of the outcome, but still I call this a success because I found somewhere that sells pre-tabbed decent cells, I managed to replace the cells of an old pack and it worked, I now have more range on my ebike, and the price turned out to be about 1/3 that of a new pack.
 
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D

Deleted member 4366

Guest
It's possible that they're not genuine cells. Other people have had excess sag from ones that they bought from Ebay. If they're counterfeit, the specification is meaningless. Keep us informed how you get on with them. Where did you get them from?
 
H

Haku

Esteemed Pedelecer
Jun 20, 2007
339
4
Gloucestershire
I got the cells from the ebay seller linked in my first post, if they're counterfeit (which I don't believe) then they're very well made as when I measured the out-of-the-packaging voltages of the first batch of 10 I received the voltage difference between the highest and lowest was 0.0004v, the rest of the cells were also extremely closely matched in terms of voltage so had no worries soldering them in the parallel-series configuration for the pack.

I did some further reading up and it appears the IMR types are more suited to higher current drain than the ICR types I bought.

Still intending to buy 28 more in the future from them, likely the IMR type, to build a pack for my UM30 bike pictured above as I really haven't been able to ride it as much as I want.


edit: replaced ICR with IMR for the next 28 cells as that's what I meant to say originally
 
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