To fuse or not to fuse?

[its_me_jason]

Does a fuse
1. Protect the controller form the battery?
or
2. Protect the battery from the controller?

 

[chroot]

Basically protected all of it when accident shorted and fuse will blown.

 

[dnmun]

i don't even get that. first you have the two spade contacts on the fuse which are crimped onto the little stranded wire inside that huge insulation, and then they double it to make sure you lose twice as much power to heat, but at least they concentrate all the heat back to back by using zip ties to hold the fuses clips together.

 

[its_me_jason]

i don't even get that. first you have the two spade contacts on the fuse which are crimped onto the little stranded wire inside that huge insulation, and then they double it to make sure you lose twice as much power to heat, but at least they concentrate all the heat back to back by using zip ties to hold the fuses clips together.

lol it was just the first photo i found... Everybody, the above photo is not how to do it! One blade fuse is enough!
On my bike its a 40amp fues like this one below. Not sure if its better or worse then a blade fuse, although with a blade fuse its easy to remove the fuse like a key for your bike.

 

[999zip999]

Jason I would put one fuse between the pos. battery and the controller. The fuse and type is the question. Tell us your battery and amp draw of your controller, plus what motor you running ?

 

[its_me_jason]

what I got.
-24v sla pack
-40A 250V fuse
-controller output current 35A
-450W external motor.

what I want to get.
-36v20A Ping
or
this battery from ebay. with a 3 yr warranty

 

[999zip999]

A 3yr. warranty means nothing as to ship it back to china is 125.00usd. and ship from china home is 125.00usd. so 250.00 in shipping for a warranty ? Plus they will change there name by then.
Ping is great as a plug and play with real support if there is a problem.

 

[ZOMGVTEK]

Most commonly, a fuse is used to protect wiring. If the controller has a fault that causes the fuse to pop, it most likely has a big problem and is toast anyways. No fuse would simply allow the fault to correct itself, typically by going up in smoke. Lets say you are using the fuse to 'protect the controller'. This would most likely mean you want to protect the controller from an overcurrent situation, since thats about all a fuse could possibly do. You would size the fuse for something around or a bit over the peak current you run. Now, lets imagine for whatever reason the controller starts drawing way more current than usual for long enough to pop the fuse. The controller is likely already drawing more current than it can reasonably tolerate, and all of a sudden the fuse pops. Now the battery is no longer connected to ballast any inductive kick. Since there likely exists some considerable enough inductance from where the fuse pops up until the controller, you will see a large inductive voltage spike on the controller, quite likely damaging it anyways. If the components are running way under the max spec, they might be fine. However, if the controller is running near its limits, it's probably going to have an issue.

For low voltage systems most standard fuses will work fine. Typically, they can actually be effective on low current systems. However, once you start talking about high voltage and high current systems, common fuses often offer very little, if any, real protection for components. Plus, most batteries with a BMS don't really need a fuse at all. I wouldn't bother running a fuse on a SLA battery unless it's a BIG pack, but thats just me. At 24 or 36V the average fuse with a reasonable current rating can provide some limited protection. It will most likely help most if you like to connect things backwards. Past that they don't help much for ebikes.

 

[its_me_jason]

Now the battery is no longer connected to ballast any inductive kick. Since there likely exists some considerable enough inductance from where the fuse pops up until the controller, you will see a large inductive voltage spike on the controller,

wow great post! lost on this part? "ballast any inductive kick" what does that mean?

Plus, most batteries with a BMS don't really need a fuse at all. It will most likely help most if you like to connect things backwards. Past that they don't help much for ebikes.

So with a 36V battery with a BMS they only reason to use a fuse, is to protect the bike from myself when I accidently short circuit it.

 

[dnmun]

no, the fuse is useless if you have a BMS.

the risk is from the positive charger lead shorting out to the battery or ground. you should use a small fuse on the charger lead to the battery. place a small fuse capable of handling the charger current in the charger lead right at the battery B+ terminal where there the charger positive lead connects.

 

[its_me_jason]

I never thought of the charger as being a danger to my battery, Thanks! I have a Surge protector between the wall and charger. But if its a cheap charger, it could potentially damage an expensive battery.

 

[migueralliart]

I got a couple of those MAXI fuse holders if you're interested pm me.

 

[dnmun]

I never thought of the charger as being a danger to my battery, Thanks! I have a Surge protector between the wall and charger. But if its a cheap charger, it could potentially damage an expensive battery.

the charger is not a danger to your battery. we tried to explain that you do not need a fuse if your battery has a BMS. that will shut off the current flow if the output of the battery is shorted.

the BMS does not shut off the red power wire, just the ground. so if your charger wire to the B+ terminal shorts to ground or lower in the battery then it will cause a fire. the entire power of the battery would be discharged through that charger lead and it will catch everything near it on fire that is combustible like a plastic battery bag. that fire can burn down your house or apartment building.

but nobody puts a fuse there, they just put the fuse on the main power output so the main controller current can melt down the fuse holder.

 

[its_me_jason]

no, the fuse is useless if you have a BMS.

the risk is from the positive charger lead shorting out to the battery or ground. you should use a small fuse on the charger lead to the battery. place a small fuse capable of handling the charger current in the charger lead right at the battery B+ terminal where there the charger positive lead connects.

I'm new here and I was wrong to assume that "positive charger lead" was the positive wire from the battery charger........

 

[dnmun]

it is. you put the fuse on the battery where the charger lead connects. but nobody ever does. they always put a fuse in the output to the controller. nobody ever puts a fuse on the charger lead.