My cheapo spot welders led to consistency issues, which made learning how to establish a technique, slower and more frustrating. I was also maxing their , and the welding lipo’s ability out using 0.1copper, 0.1 nickel.plated steel sandwich.
When practicing with my cheap welder, The used ‘practice’ cells I established my technique and welder settings on, did not translate well to the cells I actually used.
When I had to roll off the unacceptably welded copper/nickel sandwich strip, I shorted the strip. It welded itself stuck, and it turned red hot in less than a second before i could break the short. Those 2 P groups were both 4.169v, when the other 8 reached 4.20 on the initial charge.
I injected those 2groups with 4.20v manually, as after 12 hours waiting on the bms to balance them seemed to be a waste of time and abusive to the other 8 groups, and they behaved surprisingly well thereafter.
I built my own fiberglass enclosure, and even once claimed my yet to be built battery will be able to ‘swim laps inside it’, yet stuffing all the wiring inside next to the battery, ate up a lot of that extra room, and I was very glad I built the enclosure way bigger than the battery.
Routing the balance leads so they do not cross over each other, I found to be frustrating.
I also resisted great advice to get a quality soldering iron, and thought my soldering skillls were pretty good, but getting 10awg into an XT90 cleanly proved far harder than anticipated.
Thankfully my soldering irons failed and I got a Miniware TS101, and can now achieve solder joints I am almost proud enough to post pics of here.
i also allowed many months pass inbetween battery buikds one, two and three.
How much pressure to use on the welding pens, and the feel of them when they sink into the strip during a proper weld, were muscle memory I had lost in the interim, and had to reestablish. The aging lipo added another variable, and its temperature played a much bigger role regarding consistency as it aged.
Get a few extra of the cells you intend to use, for the tear off testing, and in case you get a faulty cell or two. Any old cells you use to establish weld settings, will nit translate directly to thd new cells. The thickness of the nickel plating can be different, and if you ground off weld niluggets, there is no more nickel, just scratched steel, which will have different resistance.
Another regret of mine, is using inexpensive cells that just made the acceptable minimum CDR, when new. I did not want to use more expensive cells on my first battery, but somehow despite all the mistakes I made, It was a reliable battery.
But it developed way too much sag, and as it aged, got way too hot, and I had to lay off throttle, and charge much slower than I otherwise would. It has 3500 miles on it though, and still works. I just wished I spent more on quality cells.
My third battery build went much better, but my weld Lipo was losing steam, and I was having to use longer pulse durations, nearly maxxing out welder. The lipo needed to be warm, and would falk from 12.6 to 12.0 after 8 pairs of 85ms pulse welds, and the 12awg leads on lipo were too hot to touch,.and id need to recharge back.to above 12.45v after the 8 pairs of welds.
The lipo weld battery started emitting the sickly sweet smell of leaking electrolyte on the last few welds, attaching the main + and - which had 10awg and an xt90s already soldered.
Basically, I regret cheaping out, on the spot welder, weld battery, and soldering iron, and cells.
the bent tip makes it easier to sweep across multiple connections without leaving behind gobs of solder bridging pins
