I have a brand new (Chinese) electric bicycle that melts (rather than blows) the 30 amp spade fuse every time I use it. Voltage is 36v and the motor is 180 watts. A 40amp fuse is available by special order but I am reluctant to use one without specialist advice. Just to clarify; the spade fuse is the standard one used on 12v automotive systems. Any thoughts would be appreciated.
Melting fuses
Jul 24, 2007
5 Replies
Off the top of my head, a 180 watt motor is pretty underpowered for the application. Moreover, the voltage and current you list indicates power capability of close to 1000W. Check your numbers.
Bill
Errmm, that 1kw would be at the fuse rating. The actual running current would be more like 5amp once up and running. Noting the source of manufacture there can be disrepancies on name plate data and mebbe the startup current is taking the fuse or there is a fault. On the other hand 'melting' the fuse is usually overload rather than a fault. Perhaps you may be able to borrow an ammeter and check the draw of the motor ?
I assume that you mean that the plastic body of the fuse is melting? Which is usually down to a faulty fuseholder either not making good contact with the fuse or, IME more often, a bad crimp between the conductors and the fuse holder contacts. This produces a high resistance and enough heat to melt the fuseholder.
The solution is to replace the fuse-holder. I would suggest using a resettable over-current trip rather than the blade fuse. Or, at least, carry a few spares.
Thanks for your thoughts. A motor of 200/180W is pretty standard for the "electrically-assisted" bikes in the UK. My old bike has a faulty
200W motor and it goes like a train. I understand that torque is the prime requirement. Since posing the question I've found that the power display on the handlebars goes out when pressure is put on the saddle. (Weird or what!) So it looks like there is a short to the frame - somewhere. I think the answer must be that the 40amp fuse is not an option,it's back to the shop for a wiring check. Thanks again.
Or use the correct 36v fuse and not a 12v one
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