This is deceiving to noobs…
…because this is eliminating the need.
I find balance charging with a hobby charger to be a PITA and it completely wrecks most waterproof longboard designs. Specifically, the “waterproof” part. But it will work. It’s a lot easier on a lunchbox emtb.
I just don’t want anyone reading this to think that you don’t need a BMS or balance charging. 
You definitely need one of them.
100% never charge just willy nilly
Actually, charging a couple times without a BMS or balancing should be mostly fine.
You just can’t do that for every charge. You need balance charges sprinkled in.
I’ll add that in my quest for a cheap REX, I fried the BMS in the REX twice, damaged the BMS inside my Nazare in such a manner that I caused a FIRE charging it. (I fried only SOME of the transistors on the internal BMS, so the survivors split the current, got HOT doing so. The heatsink got so hot it discolored & melted / shorted my balancing harness, which started the short/fire.)
Adding an external or swappable battery can be VERY dangerous, and can end up costing far more than replacing the original pack with something bigger if you’re not careful.
My range extender life was short, and I’m never touching hoverboard packs anymore again
Was peacefully working when my dad knocks saying my board is caching fire
One of the hoverboard cases was smoking and popping, hurried it to the backyard and started with the hose on it, opened the case with a long knife, once I realized it wasn’t the cell’s themselves I started screwing out of the board in case the worst happened, the 16 screws that secured it to the deck didn’t help
For good measure I also took out the second one
Not sure what happened, there was a bit of oxidation on the connector, but the BMS should cut it in case of short right? Guess it’s also a piece of shit of a BMS, and the short current was too much for it to cut and the mosfets started popping, at least it smelled like electronics magic smoke
Funny thing is that the board has been sitting in the same place unriden since I came back from vacation 10 days ago. And also I today a few hours earlier decided to check the pack voltage after reading about @janpom loosing his pack after draining it to 0, would be too bad for me to do that a second time
@Battery_Mooch leaving this pack is a bucket of water is my best option right? Until it reads 0 V or close to it?
That pack was actually only damaged, not completely lost. I lost one P-group. I will need to replace 2-3 cells in another P-group (some are clearly self-discharging much quicker than all the other cells). The other 10 P-groups I charged to ~3V and they’ve now been happily sitting at that voltage for about 3 weeks without noticeable self-discharge so this looks promising so far. I thought it was a completely lost case since the P-groups went under 1V.
Probably no major risk there. The question is what will you do with the toxic water afterwards. It’s more ecological to discharge the cells to 0V with some load (resistor, bulb).
Ah, I haven’t finished reading yet, glad to know, I did the same thing a while ago with mine, but didn’t risk trying to revive them
Maybe, I haven’t tested but I’m 99% sure there is no voltage on the terminals since the BMS blew, not sure if I want to open it and plug directly in the cells, I can probably leave tonight on the bucket, nothing is leaking from the cells, take it out tomorrow and try to open it if it doesn’t starts heating up once out of the water
Wow…very strange to pop after so long. Just the BMS was damaged, no cells vented smoke?
Sorry, no way for me to know what the best thing to do might be as I don’t know what’s going on. If it’s only the BMS, and it’s not shorting the pack, then I would think that the water isn’t needed as nothing would be happening.
You’ll probably need to check the p-group voltages to see what is going on. Or just leave the pack out of the water and somewhere completely safe from kids and pets, on a non-flammable surface, for a couple of days and then carefully wrap up the pack and bring it to a recycler who handles li-ion cells/packs. But maybe some (all?) of the p-groups are okay as long as it was only the BMS that was damaged?
So weird that the BMS blew like that.
Could you possibly have shorted the pack doing this, damaging the BMS? Wait…that wouldn’t put the BMS on a delay until it failed though. So weird. We’re missing something here I think.
“Cheap hoverboard battery” might be the missing ingredient
But IDK, I’m not there LOL
Well, I know that in August they recalled the Hovertrax 2.0 due to the packs overheating and exploding/catching fire. Those were sold in pretty much every major store (Walmart, Target, etc). I like to think almost all hoverboards are made to the same standards and methods since I’ve opened a dozen for neighbors and they all had the same internals from varying companies.
At least it looks like no cell vented, I never had a cell vent on me but I imagine the popping sound would be way louder and more violent, it was similar with other electronics I had pop before
Yeah, exactly, it makes no sense, I have two theories, but neither are good. Keep in mind I rode this board on the beach around 2 weeks ago, didn’t touch salt water and I had run this board on the wet a bunch of times, although not with the range extenders
1: Water creeped through the wires from the external connector to the PCB and shorted, it probably wasn’t conformal coated. I had this happen before on a RC car, but it tools way longer than 2 weeks
2: The external pack has it own BMS, which is plugged directly to the main pack, let’s say that for some weird reason this this external pack had some high self discharge and the voltage dropped in relation to the main pack, and the BMS had also entered in some sleep state and the connection between packs was severed. This also doesn’t make sense because how the pack would wake up? Turning of and off my board changes nothing between the packs. For it to start popping it must have been 3 or 4 hours from when I turned the board on to check the voltages
So my roommate is a retard, picked up my box of Lishen cells and threw it around like they’re not batteries while he was moving his shit out of the garage,
Anyway I lost a single Lishen LR2170LA cell, anyone know how bad it would be to substitute a single cell with a used Molicel P42A in a 12s5p pack with the other 59 cells being Lishen LR2170LA?
From what I can tell looking at the discharge graphs I shouldn’t even notice the substitution
He must work at FedEx
There’s not a huge difference in performance between those two cells so, maybe, perhaps, possibly, it wouldn’t have a huge effect on that p-group.
We’re just not able to accurately predict what will happen. Build two p-groups, one all Lishen and the other with the P42A mixed in, and test them to see what their capacities are and how they respond to being under load.
Otherwise, build the pack and find out what happens. 
Have a good BMS though!
No one has them in stock?
They do but I want to build the pack this weekend, I’ve been waiting weeks for the fishpaper to come in and I’m getting antsy for more amps. The longer these cells spend outside of a battery pack is more opportunity for problems too. I just don’t wanna wait another week or two and pay $40 more to ship 1-2 cells. Also don’t wanna wait until my next large cell order.
Then it kind of doesn’t matter what happens if you mix in that P42A, that pack is getting built. 
I just wanted to send out the query so if something’s really wrong I can refrain and recoup.
I want this pack but what I want more is to not blow up.
