Blowing Fuses

Ryan_Peters

Ryan_Peters

New Member
Hi there,

I recently blew a fuse on a brand new Spark RX from Spark bikes (I know, it’s ironic that the spark bike actually has spark issues) This bike was actually rated as the best value mid drive by electricbikereview.com but surprisingly broke down the second day riding it.

Anyways, now that I’m in the process of repairing a brand new 3000 dollar bike I was wondering if anyone could please explain how fuses on e-bikes are used and what component it’s trying to protect (battery, wiring, controller, motor, etc.) I ask because I am not able to return the bike and am stuck with it warts and all, so if there is a mismatch in components I would like to identify this early on so I can talk to the dealer about a potential recall, or if necessary replace components and void the warranty (Spark bikes voids the warranty if any parts are installed that they didn’t provide)

There is no info from the dealer about what kind of controller is in the bike but it has a 48 v 17aH battery with a 30 amp mini fuse connecting it’s output. The motor is a bafang 500w m600 mid drive limited to 32 km/h
 
I saw your other post on this topic.

https://electricbikereview.com/foru...5-with-shimano-altus-17-ah.28890/#post-207124

A comment was made about the pack possibly encountering a short circuit when you had it in your knapsack. Not knowing how the contacts are arranged, you're the best person to tell if that were possible. You would have had to have it powered on too. If that looked like a remote possibility, just replace the fuse and don't do it again.

Fuses on a battery are installed for this purpose. Accidental short circuits.
 
rich c said:
They won't help with warranty issues? What if there is a short in the battery pack? They won't send you a new one? The fuses are cheap, the dealer should have that part, get a new one and see if just the fuse was bad. This page should help with your troubleshooting. https://turbobobbicycleblog.wordpress.com/2012/02/09/electric-bike-troubleshooting-part-1/
Click to expand...

Yes I’m doing that already and they did send me a fuse, this was just a theoretical question on fuses since I wasn’t sure why it blew. Though I’m not an electrician of any sorts, I do have e a bit of science background and I’m informed enough to know now that fuses don’t only blow from short circuits or from being built defectively. They also blow when more amps are pulled through them than they’re designed for and this is done to protect other more expensive electronics within the circuit. My nagging question which I still haven’t been able to answer is why would more than 30 amps be getting pulled through the circuit and blow the fuse (yes short circuit is one possibility but unlikely on a brand new battery from a dealer with good reviews). I’m thinking more that the controller or motor possibly pulled too much amps through, but this would be a big issue because that is not something easily fixable unless a different fuse is installed that allows fluctuations in current larger than 30 amps (e.g. a 40 amp fuse). And if doing that, the question then becomes what is the risk or what other options are there besides upping the fuse to 40 or 50 amps. My guess and correct me if I’m wrong is that maybe the controller has a flux in amps that can go too high for the fuse or the wiring or the battery and so if changing the fuse to 40 a I would be risking damage to the wiring or the battery. It may be that those components are too cheap to combine with a controller that can pull more than 30 amps and long term should be upgraded if I want to stop replacing fuses indefinitely...
 
I agree with your thinking....thats why you asked if the components for your setup are suitable for each other. Drawing too much current would blow a fuse but let me ask do you know if this is a slow blow fuse? I know that my setup has a 25A controller so I know this specification. Do you have any data on your components or is the dealer not versed enough to send along this information or just doesn't have the information so you can make an intelligent evaluation of their product.
 
I was trained as a tool designer, but did mechanical engineering all my career. What you never do is assume anything. You can’t assume there is nothing wrong with the wiring harness because it’s new.
 
I'd probably just risk it and put in a higher amp rated fuse. If it can handle 30 amps, it can probably handle 39
 
Ryan_Peters said:
Yes I’m doing that already and they did send me a fuse, this was just a theoretical question on fuses since I wasn’t sure why it blew. Though I’m not an electrician of any sorts, I do have e a bit of science background and I’m informed enough to know now that fuses don’t only blow from short circuits or from being built defectively. They also blow when more amps are pulled through them than they’re designed for and this is done to protect other more expensive electronics within the circuit. My nagging question which I still haven’t been able to answer is why would more than 30 amps be getting pulled through the circuit and blow the fuse (yes short circuit is one possibility but unlikely on a brand new battery from a dealer with good reviews). I’m thinking more that the controller or motor possibly pulled too much amps through, but this would be a big issue because that is not something easily fixable unless a different fuse is installed that allows fluctuations in current larger than 30 amps (e.g. a 40 amp fuse). And if doing that, the question then becomes what is the risk or what other options are there besides upping the fuse to 40 or 50 amps. My guess and correct me if I’m wrong is that maybe the controller has a flux in amps that can go too high for the fuse or the wiring or the battery and so if changing the fuse to 40 a I would be risking damage to the wiring or the battery. It may be that those components are too cheap to combine with a controller that can pull more than 30 amps and long term should be upgraded if I want to stop replacing fuses indefinitely...
Click to expand...

Under no circumstances would I ever consider 'upping' the fuse rating from it's original 30 amps. That could prove lethal. A lithium Ion battery fire is extremely
nasty. You mentioned fuses can fail from built defectively. That opinion is extremely unlikely almost zero, but by replacing the burnt fuse with another 30amp
( I hope ) fuse, by default you'll help to test that thought.

A minor point....Unrelated to your subject. When typing a narrative as you've done, typing using paragraphs instead of a massive 'word dump' makes
for a much easier reading and thus perhaps more feedback.
 
LOL.. upping amp draw from a 10s lithium battery from 30 to 40 amps is not a big deal, if it even happens.
 
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