My question then is: how can I tell if my charger has capacitors on its output or not? Or is it simply that if the charger is powered on before connecting there won’t be a spark?
I guess this is why it’s critical to have the fuse on the charge port.
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Oh you’re right! Thanks!!
The spark itself is not a problem. A big enough spark will oxidize contacts over many repetitions, but I don’t think this generally happens with charge ports.
Even if your charger has caps on the output and makes a spark when connected, usually it’s not a problem. I’ve not read anyone else complaining about blown parts from this. I don’t think I took particular care to make sure the charger was on first when connecting, and it wasn’t a problem for me until the smart bms. I have hundreds and hundreds of charge cycles on different setups.
With the smart bms I honestly wasn’t sure what was happening until I installed the charge port fuse and it blew. On that board I typically use a DPS PSU to charge, and I think it has output caps for transient suppression. I’m not sure that typical chargers have ouput caps, or enough to matter.
IOW I think you’re overthinking it. 
Yes, this is something I do often. It is also because I’m living on the southern tip of Africa and getting replacement parts for stuff that blows up is REALLY expensive.
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I got bad news for you. This hobby’s gonna be expensive At this point i order at least one extra of everything that I don’t want downtime with. I’m sure I’m not alone.
Maybe you can start a shop and supply parts to your brethren in the area? 
Oh this is the battery thread, so I’ll mention, I’ve started adding solid state fuses to each balance lead, right where it connects to the p-group. A Littelfuse Pico II, 3A 125VDC. They’re the size and shape of through hole resistors and pretty cheap. If batteries are expensive to get where you are, this kind of thing might be worth doing. I bought like a hundred at 3A, and a dozen or two at 5A and 7A for charge ports.
Hm looked up my order history. The 3A ones were $0.25USD when I bought them, but now they’re up to like $0.50. Part number 0251003.NRT1L. But there are different part numbers for the same item with different packaging that may still be in the 25 cent range.
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Yeah, understood. I just want to minimise expense where I can. I try to do this by making as sure as possible that I’ve learnt from the esk8 masters on this forum. Thanks all for your help.
Couple questions. Building my first pack soon.
When spot welding cell’s do you guys fully charge or discharge the cells or does it not matter as long as they are the same voltage/capacity when welded.
Also maybe alittle anal but for hot gluing the cells together, are you guys using 20/60/100W glue guns? Can hot melt adhesive get “to hot” and damage the cells?
Cells need to be same voltage.
Neutral cure silicone is the go to for gluing cells together.
@Crashby ive put a lot of dissimilar voltage cells together in parallel either by welding or other ways and not the worst thing. surprising how slow even a high power cell was to balance. they more so should have the same capacity and history if being used together.
Not to step on your toes, as minor difference in voltage is not a big deal. But making the statement of dissimilar voltages can be a little broad for this topic of discussion. When I was practicing my welding I grabbed a handful of old batteries without checking voltages from my buddy that vapes. Long story short, things got very hot and very dangerous very fast and I had to rip it all apart due to the rapid balancing creating a hazardous situation. That’s why I made the “same voltage” recommendation. As a new battery builder myself I try to supply the safest most foolproof advice.
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I shouldn’t have left it vague and as you say there’s likely limits to the votage difference possible. I’ve thrown together some pretty extreme voltages though with surprisingly little heat. I’m gunna go do a video now and see what happens. Show u in a bit
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After five minutes of a 3.98 and 3.02 cell thrown in parallel the voltages were 3.84 and 3.64. My thermometer wouldn’t get a good reading being reflective but the both got almost unnoticeable warmer. (Not recommended charging method unless u have hawk mind) (the discharging through my hot air gun …it’s rated 300 watts at 120v so per volt it’s a measly 2.5watts per volt, so this discharges maybe 8watts. Bumped up to the 1875watt hairdryer discharging 15.6watts per volt and about 50watts discharge and that was nice. No heat or fan motion comes for that low wattage )
(upload://tw3GpxqeYkO3lgxxihe18AjoIjr.jpeg)
Need to get more exciting
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Looks like some fun experimenting going on over there! For some context to my experience… my issues were experienced when welding the 5th battery in a 5p configuration. Pretty sure all the cells had varying volts. Lowest being under 3 (possible dead cell) and highest being over 4 when I tore everything apart and grabbed some readings. There was also damage to heat shrink so it is quite possible there was a short but I’m not sure of that because I’m pretty confident I was doing a full mock-up including fishpaper. So just chalked it up as uncontrolled discharge.
Don’t wear a metal ring while making a battery. I can’t believe I have had no issues until now.
Jeebers, no thought… Ouchh!
I really could have anticipated this. Any married men out there? Anticipate this from now on.
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Yeaaah I saw a post about this on the other forum, I think it was way worse than what you got. I usually remove anything from my hands when working on batteries now.
That’s a really good idea. I was thinking earlier, lessons you learn as you build batteries as things happen… and all the while I am thinking “I am safe, I take precautions”… and yet something right in front of my face that I never think about being on my hand. It wasn’t that bad. It burned for a second before I flung it to the side. Thankfully the nickel I was working on didn’t short to the previous P group. It hurt, plenty enough to teach me another valuable lesson.
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A little late on this, but you can use these boards to charge your out of balance packs. They also do discharge.
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Ive decided to scrap the battery in favor for 30Q as it seems like a dead cell int the P1 group.
They are handy little devices though, can be used on a seperate P pack to make a portable charger.
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Swap that ring out for a qalo ring(any of the rubber rings). I started wearing them for rock climbing, but they have proven to be very useful.
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