18650 batteries

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mattsccm
Posts: 3623
Joined: 28 Nov 2009, 9:44pm

18650 batteries

Postby mattsccm » 8 Nov 2020, 2:51pm

I am a bit of a fan of these. Got a couple of torches, sold as bike lights that use a single 18650 which is removeable. Easy to carry a spare etc.
At school I have scrapped some laptops (out of date/corrupt etc) with good battery packs and have extracted the 18650's from the packs. They were charged and seem fine in the torches but are there any issue I need to be aware of. I have heard of "protected" or "unprotected" versions, which I assume to be some elecwizardy which copes with charging issues, but wouldn't know if it was internal, visible or even such a thing. Any thoughts?

thelawnet
Posts: 2667
Joined: 27 Aug 2010, 12:56am

Re: 18650 batteries

Postby thelawnet » 8 Nov 2020, 3:25pm

They sell them for about 25p each here in Indonesia. Often rewrapped. Very popular. I'm sure there are issues, but main one would be damage to the cell and not having capacity. I'd only worry if I was vaping with one or something like that. And have a good charger....

alanesq
Posts: 128
Joined: 11 Dec 2011, 7:34am
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Re: 18650 batteries

Postby alanesq » 8 Nov 2020, 4:18pm

Hi,

The protected 18650 cells have a small circuit board attached on the end (you can usually tell them as they are slightly longer than a bare 18650) which cuts the power if it detects it is getting too high (e.g. if the terminals of the battery get shorted together) and also cuts the power if the voltage gets too high or low (lithium cells do not like to be over discharged).
Cells recovered from a laptop battery will not have this as there will have been a separate protection circuit board inside the battery case which handled this.

The great thing with lithium cells is they can hold a lot of energy but they also need to be treated with some respect for this same reason as if they get shorted the amount of power involved can cause them to catch fire/explode pretty spectacularly (search youtube for examples of this).
So for example if you are carrying a spare 18650 you need to make very sure it is protected from anything which can short the connections or damage the case (the whole case is the negative terminal so accidentally shorting can be easier than you might think).

So when using recovered cells from a laptop you need to be aware that there is no protection from the battery terminals being shorted and so there is the risk of fire and also they will not cut the power when the voltage drops below the recommended level and so you can end up over discharging the cell which can damage them (I don't think this is a fire risk as much as will shorten the life of the cell).

BTW - Lithium cells need to be charged in a special way so make sure whatever you use to charge them is designed for lithium cells.

You can buy protection circuits on eBay but with a single cell torch I am guessing there will not be much spare space to fit one in?
What I do is buy a 4 cell power bank case from eBay for around £2 and put the cells in this which has the protection and charging circuits built in, I then run my light from the constant 5volts supplied by the power bank.

mattsccm
Posts: 3623
Joined: 28 Nov 2009, 9:44pm

Re: 18650 batteries

Postby mattsccm » 8 Nov 2020, 4:41pm

Cheers.
Got plenty of chargers for these cells.
Not overly worried about killing them as I have an endless supply plus they can go back to work for recycling. I usually recharge after every commute so they don't fully discharge. Might try a few out in a torch.

DevonDamo
Posts: 500
Joined: 24 May 2011, 1:42am

Re: 18650 batteries

Postby DevonDamo » 8 Nov 2020, 4:54pm

mattsccm wrote:Cheers.
Got plenty of chargers for these cells.
Not overly worried about killing them as I have an endless supply plus they can go back to work for recycling. I usually recharge after every commute so they don't fully discharge. Might try a few out in a torch.


alanesq's point was more about them killing you than you killing them.




mattsccm
Posts: 3623
Joined: 28 Nov 2009, 9:44pm

Re: 18650 batteries

Postby mattsccm » 8 Nov 2020, 5:02pm

cheers
Wasn't replying to that

2_i
Posts: 78
Joined: 25 Feb 2020, 3:12am

Re: 18650 batteries

Postby 2_i » 8 Nov 2020, 5:16pm

18650 are my base standard now and AA/AAA are only used in legacy devices. To the sources of these cells you can add battery packs for power tools. Incidentally they become now rare in laptops as the latter now mostly utilize flat batteries formed to fill specific space.

The problem with the recycled and/or cheap cells is that they have a half or third of the capacity of the good contemporary ones, so you end up carrying 2x or 3x as many for the same outcome. In addition their failure rate is higher and you are more likely to end up with a dead one at the time you need it most.

All my power banks are now based on 18650. For travel, I have a huge intelligent bank with several outputs and adjustable voltage. Aside from a 65W laptop and phone, I run a soldering iron off it and even a modest power drill. I can also use it for anything that could run off a USB C or a car lighter output.

mattsccm
Posts: 3623
Joined: 28 Nov 2009, 9:44pm

Re: 18650 batteries

Postby mattsccm » 8 Nov 2020, 8:13pm

Well I now have 24 of them carefully stored in the shed awaiting a project. One torch has some form of protection built in to stop the cells going too flat. 25 more lap tops to write off! X 6 cells. Hmmm. I could run my lawn mower.