Soldering

[royfellows]

I have been thinking on this from your pictures. In the nicest possible way I have to say that with the amount of heat you have put into the cells I would seriously question the safety aspect. If you use them , consider recharging in a safe place where a fire could not be started. Back yard etc.
I am not taking the pee, but have genuine concerns.
Dedicated lithium ion chargers - management circuits will not allow an over discharged cell to recharge, but I am thinking in terms of other cell damage.

If your cells are parallel, surely it would be better to use spring loaded battery holders?
The problem with these is if they are serial, a jolt can cause a temporary disconnection causing a multi mode lamp to change modes on you. This issue would not arise with parallel cells.

Also, the shrink wrapping will not keep water out. Stenlight found this out in terms of customer complaints which is why they redesigned their batteries with sealed plastic cases. Water tends to find its way in along the cable route. Of course, if you are enclosing your battery pack in a sealed case, this caution becomes unnecessary.

I like to see people having a go, and try to help as much as possible.

 

[Ian Ball]

Actually looks pretty tidy wrapped up.  Can you charge it in a way that measure current to determine if the solder process has reduced capacity? Might be worth knowing.

The 18650 cell is two sheets of material with an insulator membrane in the middle,  65mm or wide and a metre long, then it's rolled up and fitted into a can.

https://www.youtube.com/watch?v=-KAHiCb_8-s

 

[Cantclimbtom]

Thanks Ian -- I'll compare the current for the wrapped 3 against the current load of 1 battery and check that the two numbers relate roughly as expected

Roy -- I was worrying the same thing and will charge cautiously by the back door, not under the end of some curtains and then forget about them and go out to the shops, as I heard happen to someone in a very unfortunate story.
They are in parallel and yes I'm sold on the idea of a proper battery box, this is intended for use in a duo battery box.
Please be gracious and don't point out the cost of a 2nd hand duo + custom duo insert + the cost of batteries and wrap etc etc, the time spent bodging it with soldering irons and swearing in my kitchen, fire hazard all added up --> then compare that to the cost of having just gone and bought a Dragon EX in the first place, because if you did might be right, but it wouldn't make me happy. I suppose I got an educational experience from it?

 

[Fulk]

I know next to nothing about electronics, so I've merely flicked through this thread quickly, but one question that comes to my mind with regard to batteries in parallel is  ? 'When you charge them, now do you know that they are all getting charged, and that two arem't taking most of the current and leaving one dead?'

 

[ChrisJC]

You don't!

You rely on them all being the same age from the same batch, so they will age more or less the same.

But for sure one will conk out before the rest of them.

Chris.

 

[royfellows]

This situation could only arise if a connection becomes broken, as its not normally possible because they will each take a proportion of the output current of the charger. This current will vary, hopefully slightly though, due to slightly differing internal resistances of the cells. So you will have a first to get fully charged, then second, etc. As Li Ion cells are charged at a constant voltage of 4.2V, when a cell reaches 4.2 V there is no voltage overhead so current cannot pass, but its desirable for the charge to cease and this will happen with a dedicated charger, any LED indicator will go from red to green.
To directly answer the question, charging will not cease until all cells are charged.

Issues will arise if one cell is faulty as this will discharge the other(s) in a parallel array. But likewise in a series array of cells it will shut off the whole array on discharge when it reaches about 2.7V, and will also fail to recharge to the same level as the others, in this event the battery is scrap. In reality, when this happens the others would not be far behind anyway.

Just picked up on Chris's comment, yes agreed, but I would not expect anyone to mix cells from different ages etc

 

[Fjell]

Thanks Ian -- I'll compare the current for the wrapped 3 against the current load of 1 battery and check that the two numbers relate roughly as expected

Roy -- I was worrying the same thing and will charge cautiously by the back door, not under the end of some curtains and then forget about them and go out to the shops, as I heard happen to someone in a very unfortunate story.
They are in parallel and yes I'm sold on the idea of a proper battery box, this is intended for use in a duo battery box.
Please be gracious and don't point out the cost of a 2nd hand duo + custom duo insert + the cost of batteries and wrap etc etc, the time spent bodging it with soldering irons and swearing in my kitchen, fire hazard all added up --> then compare that to the cost of having just gone and bought a Dragon EX in the first place, because if you did might be right, but it wouldn't make me happy. I suppose I got an educational experience from it?

Purely in a spirit of inquiry, do you have a BMS in there somewhere, or are those protected cells (ie it's inside)? If they are protected cells, you have put a lot of heat on the board. Might be worth checking they turn off by 2.5V (hard to check the 4.2V because the charger will do it).

 

[Steve Clark]

Commercially manufactured packs are spot-welded with short strips of nickel or nickel-plated steel strip. The current passes between two spots on the same terminal, so no current through the battery and very short duration so limited overall heat.

You can buy a 'battery spot welding pen' on ebay for about ?15-20. Works on 12v from a car battery or similar. No idea on the reliability.

The strip itself is cheap. Search 'battery spot welding strip'

We have had some quite large packs for diving/suit heating manufactured this way. 12v / 70Ah. Same energy as a car battery, but only the size and weight of 4 cans of coke. We think quite carefully about where we charge those 

 

[Cantclimbtom]

Purely in a spirit of inquiry, do you have a BMS in there somewhere, or are those protected cells (ie it's inside)? If they are protected cells, you have put a lot of heat on the board. Might be worth checking they turn off by 2.5V (hard to check the 4.2V because the charger will do it).

No, I realised that was a good idea after I bought them. However with all my cack-handed soldering, maybe that was for the best?

 

[Steve Clark]

Also, you can contact Strikealite and they will make custom stuff to order and/or copy other manufacturers or discontinued packs. Conveniently, they list them on the website afterwards so you can just order them if someone else has beaten you to it!

https://www.strikalite.co.uk/prodcat_type/20/ALL/0/Specialist_Battery_Packs.html

 

[Fjell]

You do need a BMS, but protected cells are not a good idea for a pack, you need an external one like this on the side of the pack. For three cells in parallel at 4V, I think you don?t really need them to be isolated from each other.

https://www.ebay.co.uk/itm/274816765248?_trkparms=ispr%3D1&hash=item3ffc5b0d40:g:hGgAAOSwH9tgtKJh&amdata=enc%3AAQAGAAACkPYe5NmHp%252B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsSlHY%252FYTip4QFVjNQrCEJt6oRXPnQUqI5GRvF9cVLkiOfD3fImX87a6XHY60%252BAZEGn90BVv7cv1jg19Qw7EbBhgFbOe3pxoeCB9%252BGYZ%252BUqbKgpTdelpP8gVJhUoJF%252BQ1BPdo3fGYnoPQB5BYgnpEomPPOMOOE2CQEfg66lF0kDY9PxYMH6v52aNk3W7Huf82hNsRyN%252FyvCHkZOgcFURh7L4fpBwAEUjR0rqyBPBGma9Jyx1I%252FnVrixzT5wMu0nJR0rRMaMG43Uf5Sr69Yi0TVd8Gzv5VoEQa53jJ8FXNrbHTzbxStv57yhR%252BNiD8Gvl%252FBPtRwbZI3vCghzrWUFF442jM92mdY4iDuvwBd689Vo4iu4bL6sXDpshLDjdQHCfFinUfODeWv2KiWabJ5O7THVqSSgzFjYmQF1UhafXsCuG0GBzOBg%252FdK96Ob%252BRhy6psDIcyvWPD7Dgxo1kdvmbHN8kuoV3BHK7MghycKSfgZWe6TeIBVkgWSh8B30ZKNHBtx1a6oxsysBkZUOMo9iKYTb5DE9SXup2Xt9J2Awoy4DQX13%252FXo7WdG30VdwgnGH2PukK8p2CKOLp%252BnJEKmucSAdL%252FYSAeZ50hsqQxISe24x9kRneeFUC%252Fa8TtLG%252BkWTXocbRRcP7QSYh3M73Ssne%252FuEMTPzwvNqYNqpaC7M1bkBs%252BcxQJmqkLArppYpNw1aCHWDH864OXroliB2kFgOwUM6SZFtFEV6G2fUk7e88ZUGkUqJrfvS8fo9cQvDiE5xwvFGZhC%252FDV4iujxA15USH74IjpXo5dURHKctrLGX%252FAg8TyrVqun%252FMgy0%252BVyXgG7ELoDN%7Cclp%3A2334524%7Ctkp%3ABFBM0OHu9Jhf

The lamp wires connect to the solder pads. You need a slightly more sophisticated one (and its more critical) for a 8V Scurion-type pack with cells in series.

 

[Cantclimbtom]

Also, you can contact Strikealite and they will make custom stuff to order and/or copy other manufacturers or discontinued packs. Conveniently, they list them on the website afterwards so you can just order them if someone else has beaten you to it!

https://www.strikalite.co.uk/prodcat_type/20/ALL/0/Specialist_Battery_Packs.html

Too late for me now, but a very useful site in future.
Thanks!

 

[Fjell]

You really must use a BMS with the Custom Duo as I don?t think there is anything in there to prevent the battery dropping below 2.5V. It is in principle designed for batteries which can go to zero. If anyone knows different I would be glad to be updated as I have several. If you go much below 2.5V or even to zero, and then try and recharge it then you may well experience interesting times - and the pack is anyway prob ruined.

The BMS prevents over and under charge plus protects against short circuit. A very techy point is maybe to make sure you get one that unlatches after a short circuit. Otherwise you have to charge it to unlatch - ie cell is unusable even if charged - a disappointing situation far underground if you got it wet or something.

 

[royfellows]

Prompted by this thread and the OPs soldering skills, no disrespect intended, I have done a bit of reading up on my material. I have a report on lab tests undertaken by Samsung on their high discharge cells which included, believe it or not, putting them in an oven at 140C.
After 20 minutes their capacity nosedived.

Well, with memories of Steven Seagal's microwave booby trap in Under Siege I am surprised that they didn't bloody explode.

I would say if anything this is a comforting thought.

 

[Cantclimbtom]

You do need a BMS, but protected cells are not a good idea for a pack, you need an external one like this on the side of the pack... ... ...

  Thanks. Ordered from ebay using link provided

 

[Cantclimbtom]

... with memories of Steven Seagal's microwave booby trap in Under Siege... ...

If I'm ever underground and come across Tommy Lee Jones leading a team of mercenaries, I can lend them my helmet/lamp

 

[Ian Ball]

I used that same BMS for my pack of 18650s.  I suspect it will be an easier soldering this time but I will say I am glad I ordered 3 so I had a spare ;-)

 

[royfellows]

... with memories of Steven Seagal's microwave booby trap in Under Siege... ...

If I'm ever underground and come across Tommy Lee Jones leading a team of mercenaries, I can lend them my helmet/lamp

 

[Stuart France]

Well folks, I'm horrified to say the least at what I've seen on this thread especially the photos.

Please take a look at the suggested method and the issues raised in the attached PDF.

If you follow this step by step then you will get a good result.

 

[royfellows]

Stuart's paper looks good to me but I think its true to say that the more you do of anything, whether its soldering, caving, or karate, the better you will get at it.