Attaching to 18650 Li-ions

[llama]

I've never had to deal with these before. How do you experienced guys do it, please?

I need to restuff the battery pack of my Aldi Multi-tool. There are 3x 18650s and they're attached to the charger circuit and output tabs by spot-welded strips of (probably) tinned copper. It's all very tightly packed.

Would it be safe to solder onto the ends if I cut some tin-plate strips to match the originals? Would that be dangerous to either me or the 18650?

Is a 18650 a cell or a battery?!?
TIA
Graham

[HamishBoxer]

Those 18650,s are available. They are batteries.

[snowman_al]

I believe they are single cells.
There is only one active 'structure' in each tube.
You can get them with wires bonded to them already, have a look in RS for examples.

Just found this article for info: https://batteryuniversity.com/learn/..._battery_cells

[Bazz4CQJ]

I built up a battery consisting of 3 18650 cells earlier this year and stuffed them in to a battery case which previously had 10 off Nicads (an old Bosch drill, though working perfectly after>20 years).

You can buy them with the solder tags already in place. For reasons I cannot recal, I bought ones without the tags and just used some substantial wire to connect them, soldering on to the cases. I was a bit concerned about the issue of soldering on to the case, but looked at a number of Youtube vids suggesting how this is best done (flux, a hot iron and get "in and out" quickly). That's all been working very nicely - wish I done it earlier, as the extra AH capacity, and the faster recharge are a real bonus.

Do take care with Li ion cells; they do need using with much more care than previous batteries we have all worked with due to their very high discharge capability.

B

Tagged cells are the best for this but if you need to solder directly do it quickly as mentioned above. I a) tin a lead quite well, b) sand (emery, wet and dry) the cell's surface, c) drop a bit of flux on the cell, d) get a very hot iron and squash the lead down. This can be done in less than 1/2 a second.

[Superscope]

Be aware though, that not all Li-ion Battery Packs can be easily re-celled.

It's not that it's dangerous per sa, it's just that the built in Gas Gauge as it's
often called, may not recognise the new increased or restored capacity,
meaning you might not get any increase in usage than you had with the
old Knackered Cells.

Sometimes the Gas Gauge can be re-trained over new charges, sometimes
they can't.
Depends on the Protection Circuit used.

And with that in Mind, if the pack wasn't a Li-ion before, be very careful
how you plan to re-charge a Li-ion Cell.
You don't want to overcharge one, it might end very badly.


Ian

[paulsherwin]

I generally use them in holders, which don't cost much on eBay. Obviously this is only possible if there's room.

[Glowing Bits!]

Tagged batteries are available, I could do with some for a grass trimmer but it'll most likely never happen.
The main issue in all this is balance charging and low voltage shut off.
As the OP is planning to change batteries like for like, the above statement does not come into it.
It is not worth trying to solder wires onto batteries when the correct product is available, the tags are usually spot welded to the battery before the chemistry goes inside it.

[wireman]

I recall coming across a load of videos on Youtube around a year ago showing people spot welding these for battery packs of varying configurations.

[Glowing Bits!]

Originally Posted by paulsherwin

I generally use them in holders, which don't cost much on eBay. Obviously this is only possible if there's room.

I could do with finding one of these for the intelligent bells & whistles charger, at least then I can run the charge/discharge function to wake up dormant batteries.

[Refugee]

I had one that claimed 3.8AH and it did not stay at that capacity for all that long perhaps 50 to 100 cycles.
I pulled the pack apart to see if I could re-cell it. The wires were just soldered to the ends.
The parts are on order for me to rebuild the pack in the next week or so.
18650 cells fit into 22mm copper pipe with a wire running up the side and with the spring fitted into a stop end a new battery holder can be fabricated if need be.

[paulsherwin]

But, be very, very careful about short circuits. These things can dump an awful lot of energy very quickly.

[Bazz4CQJ]

I think the term "Gas Gauge" is just an American nod to the use of Li-ion in cars, and actually means the battery management system (BMS).

While I did urge caution in working with Li ion in my first post, I think this is a situation where replacing three type 18650 cells with three 18650 cells is entirely reasonable and practicable. The multi-tool must have an appropriate charger (incorporating a BMS) with it. I would certainly do it; if you really want to be very cautious, put it somewhere safe for the first charge or two. As Paul said, just take care not to short them when working with them; but you wouldn't short a charged car battery either.

B

[Radio Wrangler]

I've come across a few yootoob videos of people making spot welders out of ex-microwave transformers for just this purpose.

They seem effective and are made from costless junk.

Looks good to me.

David

[wave solder]

Some years ago to replace a nicad battery pack I wired 3 18650 cells in series and just used 6 silicon diodes in series across each cell for crude load balancing. It has worked well for many years

[fetteler]

Originally Posted by Radio Wrangler

I've come across a few yootoob videos of people making spot welders out of ex-microwave transformers for just this purpose.

They seem effective and are made from costless junk.

Looks good to me.

David

Yes, they are pretty successful. The metal strips used as tags are nickel and readily available from ebay sellers - search nickel strip 18650

Steve.

[Bazz4CQJ]

Originally Posted by wave solder

Some years ago to replace a nicad battery pack I wired 3 18650 cells in series and just used 6 silicon diodes in series across each cell for crude load balancing. It has worked well for many years

That simple approach may well be an attractive alternative to using one of the cheap 'BMS' available on-line, which very often have pretty vague and/or confusing descriptions as to what they are supposed to do, which is to say, some of them are not true BMS.

B

[Diabolical Artificer]

I've soldered these and other batteries by scratching off the coating, in quick with a very hot iron, tin the battery then solder wire onto it again using a V hot iron & very short dwell time.

Andy.

[whiskas]

I think it might be potentially dangerous to introduce a heat source to a LI-ion battery due to risk of fire/expolsion.
It's best to buy the pre-tagged types for best safety.

[Herald1360]

Glasses, gloves and a biscuit tin or roasting tray?