My look key does both (just an XT90s along the pos and neg). But I suppose one or the other does the same thing.
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Even some heat transferred over by means of the connected wire, I doubt it would seriously damage any of the cells, if at all. Maybe it would damage the BMS, but overall it should be fine.
If you get your battery pack made by a trusted vendor or take the necessary precautions in self-assembly, you should be set if you have a loop key. If you’re really paranoid, I suppose you could have two loop keys, one for the positive and one for the negative, though I still fail to see why that would be needed.
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Just use a loopkey to both turn the board off and act as a secondary means of “damage protection”, and use the fuse as the main means of protecting the pack.
I don’t think a loop key has actually saved anyone while they’re out and about riding when things start smoking… A fuse will certaintly be of more use in a situation where you’ll need to act fast to save anything.
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You just described the loop key that like 90% of DIY esk8 builders already use to disconnect their batteries.
No. As long as the circuit is broken (which is what a loop key does), nothing can happen.
You should not rely on human intervention at all to protect your stuff from electrical faults, however. You should have a fuse inline with your discharge leads so that any significant overcurrent event will be automatically disconnected.
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just bring a extinguisher ball with u all the time, if battery goes boom boom, then u can throw the ball in the fire
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What kind of fuse would you use for discharge lead? Double your batt max?
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I wouldn’t use a fuse for that, or at least make it double the amperage you’ll ever be drawing.
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Yeah I figured. It seems potentially risky. Last thing you want to do is lose power mid ride.
I was more thinking, what physical type of fuse fits the bill for this?
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Battery fire is actually extremely difficult to put out. I wouldn’t count on extinguisher ball to help much. You really want to avoid battery fire at all cost cuz it’s no fun:
In case it does happen your best bet is to move the board somewhere it can burn down in a controlled way without putting anything else on fire.
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A discharge BMS or a fuse is a must in my opinion. I try to use both if possible. Fuse rating depends on the speed. If you use a slow fuse i wouldn’t go much over your max Current or it just wont do anything. Im pretty sure 2 times max battery amps wouldn’t help you at all.
charge BMS / Balancer is even more important to prevent fire. Recently a board of a friend almost burned his flat down because he wasn’t using a charge BMS.
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i know battery fire is serious shit, it was just meant to be a jokey reply about the extinguisher ball thing 
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From my experience if a short on esc happens with a bypassed bms the huge current from the battery usually just blows up some component and thats it.
And if a battery is shorted, it usually just sparks as its a small short and eventually a p group dies and you notiece it, unless the builder really fucked it up and serious shorts happened to ignite the cells, which is quite hard when you have even the slightest amount of insulation between p groups. And a discharge bms doesnt help here as it cant do anything
So the best bet to deal with battery fire is to build your battery properly and do a slight amount of cable menagment
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That poor Davega…you can hear it crying “Someone! Please save me! HELP!”
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This. The extinguisher isn’t for the battery, its for everything around it. Once the lithium ignites its not going to go out until its done, no matter what you do.
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Did you ever track down the specific cause of the overtemp cell that led to fire?
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Unfortunately not. It’s a mystery. The only hint I have is that the Unity connector desoldered itself.
So probably something shorted out around there.
Now that I think about it, it would have been worthwhile checking the continuity between the two desoldered lead.
Here’s how everything looked inside the enclosure before the accident.
I had an XT90 parallel adapter for connecting an external battery.
Maybe something went wrong around the parallel adapter. It’s really strange though. I have done all the soldering myself and I believe my soldering skills are pretty decent.
Also, I have used this for a few hundred km both with and without the external battery before the accident happened.
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MMMMMMmmmm Well, in case of fire…
Run to the hills…Run for your life…
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hmm, what if you integrated dry gunpowder into the deck and when it catches fire, it detaches the battery part from the rest of the deck? 
#buildingforfailure
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