Fuse Keeps Blowing...

[gtd2000]

I was given a faulty bike that wouldn't run properly which turned out to be due to duff or failing batteries (lead acid).

I redid the battery using a mixture of NP12-12 units and some narrower Yuasa security system units.

The bike (looks like an unbranded Windsor Powacycle) worked perfectly but range was somewhat limited. Possibly a total of 3/4 miles assisted. If anybody can identify it, I'm all ears!

Here's a pic of the offending bike:



I was thinking about buying some new NP12-12 batteries to get it back up to original performance but decided to try to give the batteries a good charge by using a motorcycle smart charger on the individual batteries. (I'd done this before I got the bike running properly)

The charged Genesys NP12's were showing around 12.8v after charging and the Yuasa showing 13.1v

Total voltage at the battery box terminals is showing 37.Xv

I used 2 x Genesys and 1 x Yuasa (which I've used previously) but each time I turn on the bike, the fuse pops...

The base discharge connector on the battery box has seen better days but it doesn't look like there's any chance of shorting.

Any clues as to what to look for to resolve the blown fuse as soon as the key is turned to activate the system? It only blows when connected to the bike, turning the key when out of the bike is fine.

Logic would suggest something at the bike connector but nothing has been changed or adjusted at that end....

 

[Deleted member 25121]

What's the current rating of the fuse?

 

[gtd2000]

What's the current rating of the fuse?

The original was 20A .

I've been through about 4 of those yesterday, then today I tried a 25A and a 30A.

Battery turns on fine with no load but as soon as it's on the bike and the switch is turned you can hear the fuse blow.

 

[Nealh]

I would suspect cross polarity may be the issue, double & triple check this.

 

[gtd2000]

I would think cross polarity may be the issue, double & triple check this.

I've not checked yet but I'm suspicious that one of the terminals on the bike end might be grounding onto the frame or suchlike.

The battery box has been checked and rechecked multiple times and the wiring arrangement is pretty fool proof internally.

I'll see if I can get some photos in the morning when I pull the bike out of the shed.

 

[Deleted member 25121]

Are you able to disconnect the motor to see if the fuse still blows?

 

[vfr400]

You've used the wrong type of batteries. You must use ones that are for electric vehicles. the ones for security systems cannot provide enough current.

 

[Deleted member 25121]

You've used the wrong type of batteries. You must use ones that are for electric vehicles. the ones for security systems cannot provide enough current.

Why would the fuse keep blowing if the batteries aren't providing enough current for the motor?

 

[gtd2000]

Are you able to disconnect the motor to see if the fuse still blows?

I can try this in the morning.

Would that just be a case of disconnecting the cables from the controller wiring?

It's just somewhat strange it was all working fine, then the fuse keeps blowing.

 

[gtd2000]

You've used the wrong type of batteries. You must use ones that are for electric vehicles. the ones for security systems cannot provide enough current.

The (Yuasa) security batteries were just being used for test purposes.

The system is 3 x 12 (12-12 batteries) and one was goosed at 8.9v, the Yuasa 12v batteries are the same length but narrower - using 2 x 12-12's and 1 x Yuasa battery gave around 3/4 miles of assisted range which wasn't too bad.

I was only doing this to see if the bike worked properly, then I'll either source a full set of 3 x 12-12's or perhaps see if I can build a Lithium Ion battery pack out of the original case but this may well be beyond my knowledge level for now.

 

[gtd2000]

Here's some other photos I took of the bike earlier in the year when I was still scratching my head! I was told the battery was good and it measured "good" when not under load

 

[Deleted member 25121]

I can try this in the morning.

Would that just be a case of disconnecting the cables from the controller wiring?

It's just somewhat strange it was all working fine, then the fuse keeps blowing.

If you can then disconnect the wires going to the motor.

When did you last see the bike working fine?

 

[vfr400]

Security system batteries are completely unsuitable. Even if the fuse didn't blow, you'd be lucky to get to the paper shop.

If the fuse keeps blowing, there's obviously a short somewhere. It could be a blown mosfet in the controller if you can't find a short anywhere else. Brushed motor controllers are not as reliable as brushless ones. Their mosfets often pop, especially if you go too slow.

12.8v means knackered batteries. They should charge to around 13.5V or more.

You can test the motor with a car battery charger directly to the two wires with the wheel off the ground, or you can use one of your knackered batteries direct to the motor wires.

 

[gtd2000]

If you can then disconnect the wires going to the motor.

When did you last see the bike working fine?

It was working fine on Monday.

Just tried to give the old batteries a final "revive" before deciding on buying new replacements.

Then the problem with the fuse blowing.

 

[gtd2000]

Security system batteries are completely unsuitable. Even if the fuse didn't blow, you'd be lucky to get to the paper shop.

If the fuse keeps blowing, there's obviously a short somewhere. It could be a blown mosfet in the controller if you can't find a short anywhere else. Brushed motor controllers are not as reliable as brushless ones. Their mosfets often pop, especially if you go too slow.

12.8v means knackered batteries. They should charge to around 13.5V or more.

You can test the motor with a car battery charger directly to the two wires with the wheel off the ground, or you can use one of your knackered batteries direct to the motor wires.

I've done a start to tearing down the bike end of the connection.

Here's the wiring that comes from the hub motor.



Which two wires do you think will be the ones?

 

[gtd2000]

Start of the strip down, discharge connector soldering looks pretty suspect...









Live terminal is only hanging on with a few strands of cable.



I'm absolutely crap at soldering but I'll give it a shot!

 

[vfr400]

It's a brushless motor and controller. I couldn't see all those wires in the other picture. It looks like one of your batteries leaked. The acid is not only very corrosive but also highly conductive. A good clean around all those terminals might be a good idea.

Was that blob on the red wire touching anything? It must have been close to the controller case.

What's that bare bullet connector for on the purple wire?

Try it now with everything out when there's no danger of that red wire shorting, but make sure you stick that connector in the battery the right way round, and make sure you reassemble it the right way round.

 

[gtd2000]

Well, glad to report back with success!

I firstly re-soldered the discharge positive connector cable...and put some insulating tape around the terminals, more on that later...



Put in a fresh fuse and used 2 x 12-12's and 1 x Yuasa battery.







Now all taped up and re-installed back into the frame, I think we can see what the problem was...



From my point of view, I think the controller was touching the exposed wiring of the discharge connector positive terminal.

Put it all back together and no pop of the fuse and the motor turns freely again.

Here's the battery box connector details - any idea what the name of this discharge connector type is?

 

[gtd2000]

On another note, here's the batteries that I was using.





Now that the problem has been resolved, it's time to think about upgrading the current power source.

Should I just buy three new NP12-12's and save a lot of hassle and effort or should I switch to another solution.

I've got some 18650 batteries on the way that could be used for a variety of things but is it worth trying to make a homebrew battery for this sort of ebike?

I still don't actually know what the make and model of the bike is, or the specs.

 

[wheeliepete]

I would consider buying a cheap Li-ion battery pack over new lead acid ones, as you will get much better range and reduce the weight of the bike. A silver fish case should fit were your existing pack is, although you may have to drill new fixing points to mount it.

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