Inline fuse

[gazza19]

Hi everyone I have a 36v 250 watt electric bike I was wondering if I could put a inline fuse holder in instead of the fuse holder it has in as when the fuse blows I have to get a new holder all the time I would appreciate any help and advice given thanks in advance

 

[roadrash]

I would be looking at why the fuse is blowing rather than just making it easier to replace.

 

[the_mikey]

Which fuse are you fitting as a replacement? Assuming the motor is drawing a maximum of 250Watt no matter what condition the battery is in, and ignoring potential overheads from the control circuit , the current draw could range from 6.3A to 8.4A (given the battery won't necessarily be 36V, assuming a bank of 10x lithium ion batteries in series, it could be anything between 40V when fully charged to 30v when they are near fully discharged) , this would mean you'll need at least a 10A fuse, maybe 15A.

 

[raleighnut]

Which fuse are you fitting as a replacement? Assuming the motor is drawing a maximum of 250Watt no matter what condition the battery is in, and ignoring potential overheads from the control circuit The current draw could range from 6.3A to 8.4A (given the battery won't necessarily be 36V, assuming a bank of 10x lithium ion batteries in series, it could be anything between 40V when fully charged to 30v when they are near fully discharged) , this would mean you'll need at least a 10A fuse, maybe 15A.

Yep my 36v 250w kit has a 15 Amp fuse, never 'blown' it.

 

[CXRAndy]

If its blowing you need to monitor the current draw, ideally with a meter which has min max hold feature. Current clamp meter (read up to hundred of Amps) would be better because most digital meter have only a 10 Amp internal fuse for current protection. Ride the bike and see what the peak draw is to help locate fault.

 

[numbnuts]

Yep my 36v 250w kit has a 15 Amp fuse, never 'blown' it.

Goes off to check...........36v 250w kit has a 30 amp fuse

 

[ColinJ]

Goes off to check...........36v 250w kit has a 30 amp fuse

Hmm, sounds like your motor and/or wiring could 'blow' to protect the fuse!

 

[Tenkaykev]

It's worth looking for any other letters/numbers that might be on the fuse.

When I was working in electrical engineering we'd see occasions where the correct amperage fuse had been fitted but with an incorrect rating. For example some fuses were " quick blow" some were " slow blow"
The quick blow fuses were usually used to protect electronics, slow blow would be used when there was a high inrush current such as switching on an electric motor.
While some were dimensionaly different, some were physically alike but with ratings such as " T1", "T2", "T3" to reflect the time sensitivity.

 

[Low Gear Guy]

Have you fitted the correct replacement fuse? As well as current and voltage some fuses are designated as motor or time lag variants. They purpose of the motor fuse rating is that they do not blow with the motor start current.

 

[numbnuts]

Hmm, sounds like your motor and/or wiring could 'blow' to protect the fuse!

Been OK for the last 3 years

 

[ColinJ]

Been OK for the last 3 years

I knew someone once who used a metal nail as a fuse... seriously - he told me that he had run out of fuses!

It's OK until the moment when you actually NEED a fuse which is when it is NOT OK because the fuse (or nail!) doesn't blow...

I'm not saying that 30 A is definitely too high a rating but it does sound high by @the_mikey and my calculations.

 

[the_mikey]

I knew someone once who used a metal nail as a fuse... seriously - he told me that he had run out of fuses!

It's OK until the moment when you actually NEED a fuse which is when it is NOT OK because the fuse (or nail!) doesn't blow...

I'm not saying that 30 A is definitely too high a rating but it does sound high by @the_mikey and my calculations.

15A seems about right, maybe the battery is running lights and other things, which would need to be taken into account although at 36v, we're talking maybe 500mA of extra current, and that's being very generous.

 

[numbnuts]

15A seems about right, maybe the battery is running lights and other things, which would need to be taken into account although at 36v, we're talking maybe 500mA of extra current, and that's being very generous.

No lights and the kit bought from cyclotricity in the UK

 

[the_mikey]

It's also worth bearing in mind that not every e-bike will have a 250watt motor, there will be some with much more powerful motors limited by a control circuit, and others with smaller motors offering a little bit of assistance, and many variations, and while there are legal limits on power and speed in the UK, these may not be absolutely respected, or will be different in other countries, and won't necessarily be achieved through good design but by simply limiting more capable equipment, what you have may be capable of delivering 500 watts or more.

 

[gazza19]

i was using a ten amp fuse the wire on the fuse holder came off and touched the other wire that was connected to it i was thinking of an inline fuse holder to make it easier to change if it went again the fuse has been ok for a few years does anyone have a pic of the fuse they use does it have to be a glass one if anyone can recommend a fuse holder and fuse and have a pic or link to one would be very much appreciated