DIY Battery - First time soldering

Hi, can someone pleas evaluate if a did a good job. soldering!?
Battery pack will be a 10s3p made from Molicel P26A cells (25A cont. discharge per cell) I was doing a lot of research before I eventually did it. But I’m still not sure if its good or not. As I progressed and did more of the series connections my soldering got better, but I’m not too sure about the first few connections. Here are some pictures:


Hi there!

First of all, thank you for asking and not just hoping :call_me_hand: very smart of you.

I would pop this in the battery builders club thread and get the right opinions from the right people.


I was about to merge it but discourse throws the lucky 502 again. :man_shrugging:t2:


+1 on checking out the battery builder’s thread. First off, I can tell you that what you have done here is overkill for the current it will be carrying. Bus bars like what you’ve done here are not necessary for series connections. Many use this method for the main pos and neg termnials but for series connections it’s excessive. The way you’ve made your S connections also will not allow for any flex in your pack which can put undue stress on the solder joints and lead to breakage. Some other threads to check out are:

@Skyart makes beautiful batteries so if you’re looking for an example to to follow, the last thread I linked is a good place to look for inspiration.

Huh, Really? :confused: Well its to late now. :slight_smile:
But the cells are capable of 25A each, so 75A. Molicel even states 35A, I am using 12 AWG silicone wire. Which is rated for 70A
I manly wanted it to be safe and yeah a bit of overkill perhaps. I’m not planing on my deck flexing at all. At least not for now. Soooo…the soldering is good? I really struggled using an iron. A hand little torch saved my but.


What you have to be aware of is peak current vs continuous current. Yes your p groups may be capable of 75 amps but this would only be in short bursts. 1 x 14 awg can carry 57 amps continuous with approx double that current for short bursts. You also don’t need to solder along the entire length of thr bus bar as you’ve done. What would have been easier to solder and would’ve given your pack some ability to flex and have some resilience to the vibrations inherent in an Esk8 would be to solder your wires as so:

Notice this battery does use the bus bar method for the main terminals but not the series connections. If you’re concerned w carrying current between p groups, you’re better to use multiple wires as in this pack. For a 3p pack of 18650s tho, 1 x 14 awg is plenty. Think you may have used 12 awg? That will carry 85 amps continous and double that in bursts. For most builds, 12 awg for the main connections is more than sufficient to carry current for the whole pack.

Curling the wires like this also gives the pack some flex. You also only need to make sure the series connection is soldered in one spot as above. It’s way easier than soldering all along the bus bar and will easily carry the current. I built a 10s3p out of Murata VTC6’s which will also do 25 amps a cell and it’s running beautifully with 1 x 14 awg.

Edit: soldering looks a little touch and go in some places. What you’re looking for is smooth, shiny surfaces on the pool of solder once you’re done. If I were you, I’d reflow the joints after some practise. What kind of solder are you using?


Well, now I feel a bit stupid… but yeah. Its already done. Do you think I should trow away my serveries connection and the nickel strip and wire. It took meat least 2 days of work too. For my next battery I will def. follow your advice.

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Don’t feel stupid homie! It’s ur first pack. I made tons of mistakes the first time around including almost shorting my whole pack (cover the connections you’re not working on!!!)

I wouldn’t bin everything. You can desolder the series connections easily enough and solder as above without too much trouble. Do you have any 14awg?

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Nope. I barely got my hands on this 3 meters of 12 AWG silicone wire. I’m from Slovenia. I asked around my whole town to get some and no electric store or any such had it. I ended up ordering some other parts to offset the high cost of shipping form a e-store in Europe. Like i said. My board doesn’t really flex a lot…there is room in my enclosure to double stack my battery so I will put some 1cm armaflex foam on top and the bottom. That should provide enough protection and some buffer between the battery and the enclosure/deck confinement. I rally don’t want to desolder everything. I was mostly worried about the soldering not being on par. I mean I’m thankful for the tips but i seen so many batteries mad just from nickel strip, that is supper stiff to.

If you’re short on materials than I would just try and reflow some of the joints. Do u have a leaded solder?

Yeah I used 60/40 with rosin core. What do you mean? Melt it again and wick away some solder or what? Will it suck out the solder from between the strands enough to make it flexible?

Don’t worry about the flexibility at this point. Just try and get some smoother joints. Add flux to the area you want to improve. Clean your iron. Tin the iron’s tip. Place the iron onto your joint and feed some solder to the point where the iron and joint meet. Let the solder pool become completely liquid before removing your iron. Hold the wire in place with something (e.g. needle nose pliers) and carefully remove your iron. Count to 3 before letting the wire go. Try not to disturb the pool of solder at all once you remove your iron. Also, it’s integral to make sure you a) have your iron to at least 400C and to b) make sure your solder becomes fully liquid before you remove the iron. Also, you should be using a chisel tip to help w heat transfer for big wires like this.

Good luck!


Honestly, not bad, I’ve seen worse and better soldering

I highly doubt it would come undone on there - that being said, like others mentioned, it’s a lot haha

You’ve already done it though so might as well leave it


Hold up, we need real opinions on this situation. @AviatorEsk8er is this your cousin? :wink:


Who? Me? I don’t get the joke sorry :smiley: