Best practices for soldering 18650?

Your goal is to have the cell stay cool, not frozen and to allow the joint to cool normally.

No need to scuff the cells, you are soldering nickel to nickel. Use a good liquid flux and pre-tin your cells with a little pool of solder hitting them with a wet sponge after removing the iron. We only scuff metals that have oxidation, remember soldering is not a mechanical bond.

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And please use at least an 80 watt iron to do this. You have to get in and out quick. If you use a little smd iron you will need to let the iron dwell for much too long and the cell will get hot.

I was going to use a 85watt weller iron (450°C max. temperature). Also I am not using nickel strips but either copper desoldering braid, thick cables or welding rods. What is the sponge for? I thought rapid cooling is not ideal.

It not that rapid, it will be fine. Don’t scuff the cells, do scuff the bare copper. I wouldn’t use anything too rigid to join the cells. Something flexible is better, more resilient.

I use a Weller 85w WD-1 soldering station and it gets the job done WELL!! If you are using the WP-80 or WSP-80, you will most definitely want to get a nice fat chisel tip. retains temp well and transfers loads of heat quilckly. I use the Weller LTD 4.6mm chisel tip. http://www.ebay.com/itm/WELLER-LTD-Solder-Tip-Chisel-4-6mm-/331348517512?hash=item4d25e92288:g:eDkAAOSwNsdXRJRj Also, it should go without saying, but you gotta tin those leads up before you try to attach them to the cells. 2-3 seconds per joint max should get it done. :v:

I do my battery’s with a 200 watt soldiering iron. In and out fast, and afterward you need to test your weld by tugging on lead. I’ve made about 8 battery packs this way.

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I’m also interested for the first time of making my own 18650 battery. I plan on running dual R-Spec 190Kv motors and would a 10S3P be good enough for a 170lb rider like me? I’m looking for 10-15 miles which I’m sure will be quite tiring after that distance since you’re constantly leaning on side or the other. Anyhow, I’ve been searching and what cells are good? I mean I know LG and Samsung or Panasonic/Sanyo are the best but what specs are good? Is 10A discharge enough for this setup? I will also be soldering them since I don’t have a spot welder :frowning: Thanks in advance everybody.

You’re pretty much building a raptor, so yea, you should be able to get that mileage no problem. As for cells, Enertion uses Samsung 25R’s for their space cells. I’ve also heard good things about a123’s LiFePo4 cells if you want to go that route. Legit Panasonic and LG cells are a good choice too. You’ll probably want 50A+ continuous (rating for the VESC) at least, which means a 3P pack of 25R’s would suffice (60A continuous). Make sure you get a 85w+ iron if you’re going to solder as the less time in contact with high heat for the battery, the better.

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Thank you. I was looking at the Panasonic NCR18650PF which stated that it would have 4000 charge cycles. But it does say each cell is 10A only. Would that be OK for my setup if I built it 10S3P? Perhaps not since that would be only 30A or so continuous? I’m sorry for these dumb questions but I guess it’s never too late to learn. Thanks guys.

you’d probably want a different cell that can handle more continuous discharge. Also where did you read 4000 cycle count? That’s abnormally high for a li-ion cell.

I saw it on eBay. http://www.ebay.com/itm/100-Genuine-Panasonic-NCR18650PF-18650-2900mAh-3-7v-lithium-ion-cells-USA-seller-/162052006286?hash=item25bb0d618e:g:VcIAAOSweW5VWsHE Just exaggeration? Just wondering I was searching for the Samsung 25R and states that the cycle life is only 250? That’s very low for any Lithium Ion battery isn’t it? I mean that’s like Lithium Polymer low! Can anyone expand on that? I know I like LifePO4 since I got an eBike (Prodeco) with it. They are not as energy dense but safe all around. A little pricey but hopefully they will come down with time…as with everything else.

250 is about the right cycle count for 70%~capacity. Keep in mind this is done in a test environment discharged to 2.5v and recharged to 4.2v. This puts a lot of strain on the battery so if you treat it well it should last a good amount more than that. It doesn’t flat out die at 250 cycles, just losses a bit of capacity over time. LiFePo4’s are heavier and less dense, but provide over 2000 cycles.

Wow that I didn’t know about them testing the battery down to 2.5V! I’m still trying to absorb the 25R’s 20A continuous and 35A peak specs. It can strain my old brain! What’s a good price per battery for the people that has already built their packs? I know I should not buy those cheap fake China ones.

If you live in the states you can find 25r’s for $5 each easily.

Can someone explain to me why the most used batteries seem to be samsung 25R’s? I’ve used them for my e-cigarettes way back, but switched to LG’s 18650HG2 because the performance was way better.

They offer 500mAh more per battery, and significantly higher discharge rate.

I think its mostly the price. They are nearly double the price.

This may not make a huge difference on the few cells you need for smoking, but does on 40-70 cells.

HG2: ~5.75€ per cell → 522mAh/€ 25R: ~3.65€ per cell → 685mAh/€

Where do you get your cells?

So it’s the price… okay :slight_smile: I’ve found genuine HG2 for 6$, but couldn’t find 25R under 5$. Where did you get these prices from?