18650 battery pack build Kepler style

[Remus]

The rear suspension layout works well for your design.

Nice work.

 

[dingos]

Hello Kepler,

can you tell me please what material you use for supporting cells in sides of your pack. Is it some special thermal conductive folie (but not electric conductive) or what material? Where can I get this material? I have just finished my 8S6P pack from the same LG cells from Tumich, but I placed cells into tight food plastic box, that is not ideal, because I can not provide good cooling for cells. So I perforated the plastic box with drill so colling is OK now, but enclosure is no more waterproof. So I would like to make aluminium box for cells similar to your enclosure, but really do not know what material you use for suporting cells in the sides inside your box... Thank you for your aditional information. Petr

 

[Kepler]

A quick follow up on this pack build.

It is now 12 months old. Gets charge around 3 times per week so around 150 cycles so far. The pack is pulling around 800W most of the time when in use. To date, no measurable reduction in capacity. Not bad for soldered pack. Admittedly I am a spot welder convert and wouldn't solder 18650 cell any more. However, I am more then pleased with this packs performance and don't regret using the soldering method to get me into the 18650 game and away from RC LiPo. 8)

 

[steppe]

Hey Kepler, just wanted to say your pack is awesome and the way you went about building the case is amazing. I would pay top bucks for something with that kind of finish.

I was looking for ideas to use on my build and this is for sure one of the best ones.

Thanks for sharing.

 

[Hillhater]

Another follow up / hindsight tip for folks without a welder, building similar packs and specifically using Tumich's cells from those 4p, 10s packs.....or cells from laptop packs.
.. Separate the cells into parallel pairs with the welded tab still in place joining them. ( use small snips or surgical sissors)
Then use those pairs to build your packs in any configuration you preferr..(as long as the are even numbers in the parallel groups ,)..by soldering links onto the tabs mid way between the cells.
This will avoid any potential overheating of the cells , or damage to the insulating rings on the +ve ends..
....And there is only 50% of the soldered joins to make !
But if you only need 36volt pack, obviously its simpler to just make a custom case for the pack as supplied by Tumich !

 

[Kepler]

A good tip however cells are all supported in a single plastic holder on each side of the pack. It would be a very tedious job to cut up the plastic holders with the welded tabs still in place.

 

[dmwahl]

I like it, I've been debating how best to mount my similarly shaped LFP pack (40152 cells) and I think this is a winner. Really looks like it belongs there.

 

[docnjoj]

My Tumich packs 2X4Px10cells were soldered where they needed to be and have held up on my wife's trike for over a year, using the trike about 3x per week.

I do recommend this method. but I paralleled the cells on the BMS and that took a lot of work.

Next time I buy a pack already done.
otherDoc

 

[DasDouble]

Just to recap, the cells are LG 2850 mah from this thread https://endless-sphere.com/forums/viewtopic.php?f=31&t=61608

My configuration is 14S 4P which means 56 cells are required. Ended up buying 60 cells which came packaged up as per the picture below (10S 3P) x 2

Batt.jpg

First job was to break the packs down to individual cells. This required breaking off all the spot welded tabs so the plastic cell spacers could be removed. Was a bit disappointing having to break off all the spot welded tabs but unfortunately there was no other option if i was to squeeze 54 cells and a BMS into this battery box.

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Next step was to make sure 54 cells actually fitted including the BMS.

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Cells were then arranged as individual 4P 1S packs and parallel soldered using 3mm wide solder wick to bridge each cell

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Of course soldering is not the ideal method of joining the cell however this was my only option if I wanted to build an 18650 battery pack. Each cell had the spotweld remnants ground off with a Dremel tool which also gave a roughened nice clean surface for the solder to stick too. Using an 80 Watt soldering iron, each cell was tinned with only a few seconds of heat being applied. Compressed air was then immediately blown on to soldered area to ensure all heat was quickly removed. After a quick blast with compressed air, the soldered area was immediately cool to the touch. The solder wick by nature solders with very little effort so it only took a quick touch of the soldering iron to attach the solder wick link to the battery. Again the soldered area was immediately cooled with compressed air.

Cells were hot glued and linked together in manageable sections with the 3 main sections joined and linked afterwards.

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Before installing the BMS, I wanted to test out the pack and make sure it performed as expected. Also wanted to make sure the solder wick links were handling the current OK. Female 5mm bullet connectors were soldered directly to the positive and negative tabs of the pack and a 12 gauge power cable attached.

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A quick 10km ride was completed with a good mix of moderate to high power used. Pack was then removed straight off the bike and all connections checked. Also used an infrared heat gun to see if there were any hot spots. Pack was an even 25 degC across every terminal and cell voltage had stayed nicely in balance.

How much current can go through one of these nickel or copper whatever cable???

 

[EbikeAus]

Just found this thread. Very nice build.
I've been considering the best place to mount a battery on a full suspension mtb.
That looks like a great option!

Good to see someone else have a go with a soldered pack. Are you still using it. How's it going now?
Cheers

 

[Kepler]

Still running. The pack is getting tired now but it did way better then expected.