Finished building it last night and left it outside next to my grill (thank god). Dang thing just detonated. Looks like once cell went. Then a few min later, another one blew.
These are cheap Ultrafire (what a terrible name) cells that I picked up on the cheap for learning how to spot weld, assemble etc. It was a 10s6p pack. Not sure what went wrong. I checked voltage last night and was reading ~40v.
Not sure what to think. Should I continue down this path or switch to lipos? Is this just a function of these terrible starter batteries?
Regardless… buyer beware of these cheap cells. I’ll be looking for a disposal site for them.
Ultrafire is know to resell (old and used) recycled cells in new heat shrink with some extraordinary rating (like 18650 with >5000mAh…which is just not possible with todays technology). Just google it.
Still even old batteries don’t just explode. Especially 18650 are quite robust, do you have some pictures of the pack before the detonation? E.g. with a too high setting of the spotwelder you can puncture holes into the cells…
Here’s info on my incident. First of all, let’s not underestimate my stupidity.
After thinking about it, I may be at fault. When I finished the pack last night, I checked the voltage and put it outside on my grill. This morning, one of the cells suddenly exploded followed by another about 2 min later. In one of the pictures you can see how I found the pack. Two cells completely gone. But, as you can see, the entire pack was sitting on a metal shelf on the grill. The other night, I put the pack out there while under construction but I placed it on its side. Last night, I forgot. So, for some reason the pack may have contacted the shelf and shorted out. Why it didn’t do it during the previous 12 hours, I don’t know. Maybe the pack got warm with the sun coming up and it shifted somehow.
I’m also including a pic of the spot welder. Those are the settings I found that worked for the nickel strips I am using. The strips are pure nickel and are 8mm and 0.15 thickness.
The other pic is the remnant of the pack in a cooler I had on the deck.
So, this may have been my fault. Don’t rip me too hard. Also, if you think I have the welder settings wrong, let me know. Def flying blind there. Hopefully others can learn from my mistakes.
Here’s the dumb part. Earlier this week when I was constructing,I read a post where someone said they kept their packs in their grill in case of a fire. I thought, ‘that’s smart, I’ll do that.” Then when I went to put them out there that night, I thought, “wait, there’s a metal rack in there. I don’t want to put this thing in there where it could contact the grill rack”.
Two days later, ‘whew, I’m glad I’m done building this thing, let me throw it out here on the grill shelf THATS METAL’.
Yeah that’ll do it! lmao… sorry that happened. I’m going to say it wasn’t the cells, even though Ultrafire is a bad brand. Just learn from the mistake and next time, kapton tape everything always!!!
Yeah. I had a big fat roll of kapton tape right there. Just didn’t put it on. Also, thank god my wife doesn’t know about this or else this project would be under severe scrutiny. Certainly no more battery building at the kitchen table.
Most cells have a vent valve for degazing ( happen to me often on short cut …) if not , or filled with epoxy (???) then I guess it explodes
Lipo will swell and burn , add both but it was a under voltage lipo pack so it burned slowly
I prefer degas on 18650 rather than fire on full charged lipo
To push thing father I think it is best to know and test : short cut a 18650 fully charged and see what happens ( scary but I didn’t have a problem with Samsung…)
Lipo we know enough video around
Will try to do this correctly with thermal camera on a 30q tomorrow …
I shorted a sony vtc6 once by accident. It was at 3.5V (came at that voltage from nkon) and it was fire immediately. So not all cels are save for shortcuts
