Should I fuse my battery?
- Thread starter Turbotd04
- Start date
In the past, I've used maxi blade fuses for values up to 80A. They are cheap, and so are the holders. For what it's worth, I don't use a fuse protected pack at the moment, even though I built my own pack.
Determine your pack's maximum current rating, and use the next higher value fuse for short circuit protection. And carry a spare.
Determine your pack's maximum current rating, and use the next higher value fuse for short circuit protection. And carry a spare.
Rassy
1 MW
I always use a 48V DC circuit breaker at the battery. It also serves as a handy on/off switch and handles the external spark when you hook the battery up to the controller which happens as the capacitor draws a burst of current. And thus there is no need for any anti spark circuit to keep from damaging your connectors.
Does the pack have a BMS? Most BMS boards offer some protection against short circuits.
Automotive fuses made for 12v may work or they may start arcing and catch everything on fire. A "proper" 48v fuse is stupidly expensive and quite large. I like circuit breakers as you can get them designed for DC and pretty decent current ratings. I've seen people use "fuseable links" which is just a short piece of smaller gauge wire that will burn before the other wiring during a short. The fuseable link is placed somewhere that won't be a problem if the wire burns.
Automotive fuses made for 12v may work or they may start arcing and catch everything on fire. A "proper" 48v fuse is stupidly expensive and quite large. I like circuit breakers as you can get them designed for DC and pretty decent current ratings. I've seen people use "fuseable links" which is just a short piece of smaller gauge wire that will burn before the other wiring during a short. The fuseable link is placed somewhere that won't be a problem if the wire burns.
Turbotd04 said:
If you have a capable controller, you could be stuffing a lot more than 15.68a into a 750w motor. For instance, if you have a 35a controller, at wide open throttle the limiting factor will be either the battery's ability to deliver amperage, or the controller's ability. In either case, a LOT of power.
Personally, my plan is to restrict available power with the controller settings, then it's easy to pick a safe fuse size. Problem is not all controllers will have that ability.
My point is, to prevent having to constantly change that fuse, you don't want it to be the bottleneck between the motor and the battery.
Turbotd04 said:
The motor has a 750W rating, but in fact it will burn up as much wattage as the controller can stuff into it. The controller has a maximum current rating, which may or may not be printed on it. You want the fuse to be higher than that value.
Since the battery pack has a current rating, and since it's the thing being fused, it makes sense to use a fuse just higher than the pack's rating. That way it will open the circuit in a serious fault condition, but not under ordinary operating conditions.
MAXIMUM_AMPS
10 mW
- Joined
- Nov 13, 2019
- Messages
- 33
I would use a fuse, BMS or not. Under a dead short circuit, it is possible that the BMS's FETs can go into an avalanche condition, where they are stuck ON and the BMS chip's FET driver cannot turn them off.
https://www.infineon.com/dgdl/Infineon-ApplicationNote_Some_key_facts_about_avalanche-AN-v01_00-EN.pdf
https://www.infineon.com/dgdl/Infineon-ApplicationNote_Some_key_facts_about_avalanche-AN-v01_00-EN.pdf
motomech
10 MW
6 M/M bullet connectors make pretty good fuseable links w/ a 48 Volt system.
Don't ask me how I know that.
goatman
10 MW
I vapourised a xt60 once at 52v/14s and was left with a cooked bms, white flash burn on my hands under all the black soot and a bunch of black soot on the wall. a fuse is cheaper than a bms.motomech said:
I don't use a bms or a fuse on my packs, theyre wired for a bms so ill use a bms to balance if needed . I consider the xt60 the fuse. each of the packs can do 100 amp continuous though.
