amberwolf said:
flippy said:
a balance wire that breaks off is not helped by a fuse. as its considerably more likly it will fail before the fuse then after it making the whole enterprise useless.
I didn't say anything about a balance wire breaking off being helped by a fuse.
I said that balance wires breaking doesn't blow up a BMS, based on examples previously encountered here on ES.
That means a fuse in a balance wire wouldn't blow up a BMS either, as it would cause exactly the same condition.
Please show how this condition occurs, if you have seen it, with examples, etc.
putting fuses on balance wires is looking for a solution when there is no problem in the first place, and by using fuses you are creating more problems then solutions.
One possible need for a fuse on a balance wire is if the balance wires are shorted together or to other parts of the pack, etc., by a crash or other unpreventable physical damage to the pack or vehicle.
if you need to remove the bms to prevent it from draining you need to replace the bms for a better one. a bms should NEVER be removed once the battery is built.
Has nothing to do with the point I was making, and you know it.
Please respond to my previous post with examples of exactly how a BMS will be destroyed by disconnecting a balance wire (which is exactly what the fuse blowing would do).
*removed the personal shit*
i will start using smaller words, your inabillity to understand does not mean you need to make it personal.
lets start at the beginning: a the reason a balance wire disconnects or breaks is 90% at the solder joints as they are by far the most fagile connection. in a PROPER pack you only have 1 solder joint (coverd in hot glue/sillicone), on the pack itself. in a pack with fuses you suddenly have a minium of 3, 2 of them are before the fuse. so a breaking connection that shorts out is most likly to happen BEFORE the fuse, not after. its also WAY more likly to happen because solder joints are weaker then the crimped connector.
so solder joints = bad.
if you have a crimped connector wire that is iffy you need to fix it, use proper connectors, change the bms, use better crimping tool and/or better quality wire. get sillicone insulated wire whenever possible and use hot glue on the wire/connector part to stop viberations from degrading the connection. that way its basically impossible to get ANY physical problems barring shitty pack construction and not glued/taped down the wires properly.
a fuse is NOT a solution to solve shitty pack construction.
most of the bms that are out there (chinese crap) use A/D converters to measure voltages, try removing/breaking a single input. the bms generally does NOT fault out when that happens, the voltage is just lower on 1 or more groups depending on the implementation. so a fuse does not do anything to help in the most common issue. and even worse: you dont notice it because the bms does not fault out because it still measures voltages.
fun fact, a fuse does not work because the bms is not isolated, current can and will flow FROM the bms to the short so popping a fuse one one end does nothing because the current can still flow from the other end.
high end partially isolated A/D converters like the ones you see on a tinybms for example dont have this issue and will correctly report a fault BUT most of the time in the litteraly dozens of those i have used its usually the A/D converter itself that shits the bed when something shorts out the wires and instantly blows up the A/D converter bricking the bms because these things generally pop at anything above 5v on a single input. and yes, i have had serveral tinybms that failed at the converter (nice chuncks blown out of the chip) that had to be warrantied. and no, i dont keep collages of broken boards, i have a business to run.
you want a bms to fault out hard, and always trigger when something breaks. the cheap chinese ones often do not do this, they will happely continue working with missing balance wires and still register voltages on those missing lines.
if you are in a accident and you have the problem that the bms if physically separated from the rest of the pack and balance wires are ripped apart i will bet you have bigger problems at that point. a couple a fuses will not help you in any way at a point that the pack is physically destroyed. especially if the pack is inside the frame of the vechicle....
i will bet a crate of beer that anyone that is folded around a lamppost at 35mph+ is not thinking about the balance wire fusing of the bms.
in short (little pun), there is no reason to add fuses and add even more points of falliure then you already have. if you build shitty packs that tend to blow up you need to fix that instead of trying to make up solution from a problem that should never be possible in the first place. using dozens of fuses to fix bad construction habits is like the twisted logic of saying its ok to drive 150mph because the car has airbags.