Which Cells?

[Benjahmin]

I have one of those little 4 cell waterproof packs, the one with a usb socket and jack type output/charger socket. Cells are duff and no longer holding charge, so need 4 new ones.
Just went on to Nkon and got overwhelmed. Which cells?
I use it to power a very bright 3 led light and, occaisionally, a TomTom sat nav. Don't know the current draw of the light but it's this type:

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Any recommendations?
Thanks.

 

[Nealh]

Working current will surprisingly likely be about 2 or 3 amps to power these super bright lamps so any good cell is better then a cheap one, as you only need four price will not be to bad. NASA best cell for low amp draw is the Samsung 35E.
More mah means more running time then your current 2200mah cells.
Configuration is 2s2p.

 

[Benjahmin]

Thanks Neal. Current cells are unbranded marked only with a + and -, so almost anything will be better.

 

[Nealh]

Thanks Neal. Current cells are unbranded marked only with a + and -, so almost anything will be better.

Don't be tempted by the 9900mah Trustfires or any thing with fire in the name or any 18650 cell that claims more then 3500mah as they are excellent genuine fake cells that deliver <1000mah. Some have been opened and only contain sawdust and other loose filling .

 

[Benjahmin]

Strewth - truly not all cells are equal!
Going for some 35E's.

Having taken a closer look at the old cells I'm not surprised I was getting nowhere.
One cell measured 3.5ish, two were at 1.7ish and one was at zero. Two were showing signs of leakage. They are currently to be found outside in a sealed container pending a trip to the tip.

 

[Benjahmin]

Received 4 35E's today, semi-charged all at 3.5v. Put them in the container and put the charger on until green light (around 3 hours). I now have two cells at 4.13v and two at3.62v.
Is this evidence of rubbish circuitry in the bms or is this to be expected on first charge?

 

[soundwave]

what case did you put them in?

 

[Nealh]

All cells should fully charge if from Nkon, most likely fault is with your case/charger.

 

[soundwave]

if you have one of these dont use the wall adaptor to charge the cells in it because when 1 cell reaches 4.2ish volts it stops charging.

and it does the same when drained wen one cell reaches 3.2v it cuts off even tho the other cells will be higher.

so it dont take long for the cells to get well out of range.

i use one of these for charging

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[Benjahmin]

Yes, that's exactly the one. And that was going to be my next question. Thanks SW, for that price it's worth doing especially as I have somee AA's that I use elsewhere and only have a crappy charger that's about 20 years old - think it's done it's job!

 

[soundwave]

and make sure you put the cells in the pack the right way round as there is no short protection other than if you do put one in the wrong way it will melt the springs

 

[RossG]

I've got one of those lights Ben and god are they bright ! You can go out at night and point them at the sky and light the clouds up, scare the life out of the locals.

 

[RossG]

You could always take this route...

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[soundwave]

You could always take this route...

8.4V Bike Light Pack for sale | eBay

Find great deals on eBay for 8.4V Bike Light Pack. Shop with confidence.

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if you want the best cells for a light try these

Panasonic NCR18650B 3400mAh Li-ion Battery Flat-Top Unprotected

Panasonic NCR18650B 3400mAh Li-ion Battery Flat-Top Unprotected

bga-reworking.co.uk

 

[Benjahmin]

Well, here's a thing.
Since charging 4 days ago, the cells have been sitting in the case doing nothing. Measuring them today they are all at 3.8v. So there's some sort of balancing going on here.
I've ordered the charger thar SW linked to, think I'll wait for it to arrive before charging again. I'll monitor the cells when in the case, if it shows drain then I'll have to keep them seperate when not in use.