Two fuses blew in a row. What can cause current to spike?

[CGameProgrammer]

After getting a new motor, I've had two fuses blow each within about two miles of riding. I'm using only components I've used reliably before, except for the motor which is new. The fuses are 50A, the controller is rated for 48V 40A and I'm using four 12V 12AH SLA batteries along with a new rear 5303.

After the first one blew, I used the one backup I had and went for another ride. Acceleration and top speed were perfectly optimal so nothing was damaged as far as a brief ride could ascertain.

I bought 60A fuses from AutoZone so I hope continuing to ride with 50+ amp spikes won't hurt anything. What can cause this? What can be done about it? Is there any harm in it?

 

[knoxie]

Hello

There is something wrong either motor or controller, you should not be blowing a 40A fuse with that setup let alone a 50 or 60A fuse, I would say there must be a problem with the motor of some sort, the xlyte controllers are sensitive but if they blow the controller would blow the fuse as soon as you turn on the controller.

I have not blown a main 40A battery fuse in over a year running the same controller with NIMH batteries, something is up, im guessing the motor has an issue, I am sure somebody will disagree they always do, good luck.

Knoxie

 

[CGameProgrammer]

How annoying; I had just spent $50 shipping it back to get repaired, and now there's yet another problem with it. I just put on a 60A fuse and it too blew within a quarter of a mile from my house. I was going 10 mph and accelerating very gently, and pop.

In all cases, it happened when accelerating gently, though not usually immediately.

 

[NickF23]

what kind of fuses are you using and where are they. You might want to invest in an amp hour meter like the drainbrain or add an ammeter and voltmeter to your bike. can be pretty useful to work out whats going on. Are the fuses blowing normally or is the fuse holder melting? I've had problems with cheap badly fitted fuse holders in the past. tell us a bit more about your setup.

 

[knoxie]

Hi

Sorry to hear that! also these problems are always hard to diagnose as well, it still may be the controller also, as the fet screws can intermittently short to the case through the rubber washers which would cause quite a problem.

If you have a DVM set it to ohms and check for continuity between the motor phases and the case of the controller, do the same between the motor plus lead from the controller and the case, if there is a high impedance or a short then you are going to have problems and it is the controller that is failing.

The latest batch of xlyte controllers have been shockingly bad, I dont know if its the fets, or the fet insulation but a few things combined have made these controllers highly unreliable, I would not want to be a distributor for them.

Do those tests and let me know the results

Cheers

Knoxie

 

[CGameProgrammer]

The fuse holder, in fact, is a bit problematic. I have always had problems with it, because one of the contact plates stuck out too much (see photo; the one on the right side is the bad one) and made poor contact with the fuse, causing a whole lot of pretty blue arcs. It also eventually melted the fuse, making it look like a half-eaten lollipop.

I eventually tried pressing on it with a narrow object to try to push them down. I wasn't able to seat them correctly, but it made them a bit closer together, and I haven't noticed any problems with arcs since. However, the fuses have now started blowing often. But since I also just bought that motor, I wasn't sure which was the problem. Could it be the fuseholder?

EDIT: Knoxie, after the first fuse blew and I put on a replacement, I was still able to hit 35 mph (on 48V) perfectly fine. Surely performance would be severely affected if the controller short-circuited? Throttle response has been perfectly normal as well.

 

[Instant Karma]

Hi

Sorry to hear that! also these problems are always hard to diagnose as well, it still may be the controller also, as the fet screws can intermittently short to the case through the rubber washers which would cause quite a problem.

If you have a DVM set it to ohms and check for continuity between the motor phases and the case of the controller, do the same between the motor plus lead from the controller and the case, if there is a high impedance or a short then you are going to have problems and it is the controller that is failing.

The latest batch of xlyte controllers have been shockingly bad, I dont know if its the fets, or the fet insulation but a few things combined have made these controllers highly unreliable, I would not want to be a distributor for them.

Do those tests and let me know the results

Cheers

Knoxie

I got 2 backup xlyte controllers last year just in case, so far the original controller is still good so haven't had to try the 2 backup ones, lucky me.
Hopefully a few will adapt hub motors to the Sevcon controller, the one that Randy was promoting in another thread, I'd like to see if it is bulletproof but apparently there's a 48V limit on them.

 

[knoxie]

Hi

Thanks for the pictures, its clear your fuseholder is the problem here, you must replace it, you would be better off cutting it out and putting in a minature circuit breaker! thats bad, thats the problem for sure, those fuse holders are only rated for 32V but should still be ok at 48V, get a moulded one in there and put a smear of vaseline on the blades of the fuse before you put it in the holder.

As to the other poster, yes the older xlyte controllers seem to be fine even at 72V but the newer ones are a little more hit and miss shall we say and yes Randys controller is an option if you dont want to go over 48V, my modified controller is looking good so far at up to 120V time will tell.

Knoxie

 

[NickF23]

lol, I've got a few similar looking fuses myself and I'm only runnning 26 amps, basically caused by shit connections heating the fuse up. Get good fuse holders something lke these

http://tinyurl.com/3ytxwr

- thick cable and a good connection and you won't have the problem. If you want to be 100% sure then get maxi fuses with good quality fuse holders.

 

[knightmb]

Yeah, judging by the picture, it's the fuse holder, not the fuse. Otherwise the center would have blown instead of melting. Looks like the fuse holder can't handle the current, so it heats up and melts the fuse (which will eventually cause failure).

As others have suggested, you're going to need a more heavy duty fuse holder (try the 32 volt ones instead of the 12 volt automobile fuse holders)

 

[CGameProgrammer]

Yeah, judging by the picture, it's the fuse holder, not the fuse. Otherwise the center would have blown instead of melting. Looks like the fuse holder can't handle the current, so it heats up and melts the fuse (which will eventually cause failure).

As others have suggested, you're going to need a more heavy duty fuse holder (try the 32 volt ones instead of the 12 volt automobile fuse holders)

Well the center did blow, three times in a row. That was after I played with the contacts to try to fix the arcing. I think I liked the arcs better.

By the way, I will be upgrading to 72V perhaps within the month, assuming I can get it working reliably at 48V first. So what fuseholder should I be using with that in mind? None?

 

[knoxie]

Hi

If you have problems at 48V dont upgrade to 72V until you got it sorted as the problems will be even worse, the 32V mini blade fuses dont work well at 72V, change to maxiblade fuses, they are physically bigger but handle the power better, you watch people chip in and tell me I am wrong here but the 32V fuses dont like the (vxI) power at 72V and blow, the maxi blade ones handle it much better, I know as I have tried both and the minblade ones blow frequently at 72V, the maxis are fine at 72V.

Someone will tell me I am wrong, probably someone who has made 17 posts so far and thinks they have the answers to everything!! hope you sort this as it is so frustrating isnt it! you could always attach a dust bin lid to the front of your bike that might help?

Good Luck

Knoxie

 

[CGameProgrammer]

My fuses are maxi fuses. And how do you guys 'know' the fuseholder is only rated for 32V?

 

[knoxie]

Hi

The melted fuse picture looks like a mini blade fuse? maxi blade fuses look like bigger! ok I believe you, the holder must be the issue still, change it out and I am sure it will be ok, its hard to get an idea of scale from your picture as it sure looks like a mini blade.

Cheers

Knoxie

 

[Lowell]

I've seen fuse holders melt down on Supra fuel pumps which only draw 19 amps peak. Try using car stereo fuse holders.

Ebay item # 230124293925

http://cgi.ebay.com/Directed-In-Line-Agu-Fuse-Holder-4-8-gauge-DEI_W0QQitemZ230124293925QQihZ013QQcategoryZ50551QQrdZ1QQcmdZViewItem

 

[fechter]

Your fuse holder is toast at this point, but there might still be another problem causing it to draw too much current. Usually the current limiter will do its job unless a FET blows, limiting the current to well under 60 amps.

If the contacts in the fuse holder are bad, the fuse element can be heated enough to melt, even though the amps are not enough to blow it. If it's really hot, it takes fewer amps to blow. Obviously yours was a bit warm.

It would be best if you could measure the current.

One remote possibility is if the hall or phase wires are somehow mismatched. This will cause a much higher than normal current, but again, the limiter should prevent this from exceeding the fuse rating.

I use a circuit breaker that's soldered in place.

 

[CGameProgrammer]

To give you a sense of scale, the fuse is about one inch wide. It's the fuseholder that's the problem, not the fuses themselves.

Fechter, can you post a picture or link to an appropriate circuit breaker?

 

[knightmb]

I use a circuit breaker that's soldered in place.

Yeah, those are my favorite because you can reset them

Quick question though, say someone goes down to local hardware store and buys a simple 15 AMP breaker, in theory that's 15 X 110 = 1,650 watts and anything more should trip the breaker, but I've always wondered if that means you need 110 volts and not total power (in watts) to trip the breaker.

For example, you have an e-bike on this and something goes wrong and the power spikes to 2000 watts, would this breaker trip at say 48 volts or 72 volts since it's over the power limit or would it let the power pass and your stuff would toast?

 

[Lowell]

I believe only the amperage would matter.

 

[fechter]

Right, the current rating is independent of the voltage rating. A 15 amp house breaker will still trip at 15 amps on 12 volts. 120v breakers are not really well suited to battery applications.

It's pretty hard to find good circuit breakers. The one I'm using is stock Vego, but I'm running over the rated voltage. The voltage rating of a breaker doesn't really matter until it trips. If the rating is too low, there's a chance a nasty arc will develop across the contacts when they open and cause some kind of meltdown/fire.

Fuses can be soldered directly, but then it's hard to change them.
It's also fair to put two or more in parallel. This spreads out the current over more sets of contacts. If one blows, the current will pass to the rest, and quickly blow all of them.

 

[Ypedal]

Soldering to fuses... hm. I"ve considered that but never went thru with it.

The better " Molded " fuse holders are crimp conections.. no solder. and you can't take them apart to solder them in.. I have never blown a fuse while in " Use " .. in 3 years of ebiking.

The Car audio types posted by Lowell.. i had those on my nimh packs at 72v last season. worked out well. but the Wires are held down by screws and were prone to loosening over time.

 

[Lowell]

The screws shouldn't loosen if you have the correctly sized wire for the terminal.

I just use a pair of cast-in-rubber blade fuse holders in parallel with a 40 amp fuse in each. Check the voltage drop on your wire runs at full throttle to get an idea of how much heat to expect.

 

[CGameProgrammer]

ElectricRider said they felt something must be shorting en route from batteries to controller, and suggested I look for exposed wire. Well a couple of the battery leads did have exposed wire; the heatshrink tubing had receded. And the batteries had been facing each other, so the exposed copper could have pressed against the shell of the adjacent battery. I covered them with duct tape and positioned the batteries so the leads weren't near each other, and I went for a brief 3-mile no-pedaling ride at various speeds and throttle, and it held up fine. And the other three times, the fuse blew between 1/4 and 2 miles, so I guess that's all it was.

 

[Lessss]

Might want to put some "glue" gun plastic on those leads THEN cover it with black tape.

 

[Lowell]

Electrical splicing tape is excellent where you can use a little extra thickness to protect wires. Spiral loom also works well, and wires should be protected from scrapes in the event of a crash.