Fuses- again!

[alsmith]

Is anyone using those resettable type fuses for their bike battery? They are specified for 12-24V, how would you derate them for higher voltages, say 36V (would it even need derating?) or 72V. I recall a post saying they wouldn't react quickly enough to protect your controller- can anyone expand on using this kind of breaker with examples from personal experience or real world tests?

[silviasol]

Can you post a link where you get these? I can use them for my ride.

For yours can't you just put one per 24v worth of cells? Like if you have a 36v pack put one between the 24v series link then another at the end (which would be 12v), or one in the closest middle series link and one at the end.

[Matt Gruber]

reminds me of overvolting a motor. you can get away with running a 24v motor on 36v if you are careful and lucky.
a 32 volt fuse may arc at higher voltage. i'm at 36v, and i consider the risk small. at 72v i'd guess a plastic fuse might catch fire. that is better than the whole pack on fire imo, as long as the fuse is placed where it can burn itself out. There is said to be a risk that the arc would continue for a long time. Better would be a fuse designed for hgh v. They are often filled with sand so they won't arc and catch fire.
i did blow 2, 12v blade fuses at 36v and they worked to my satisfaction.
If u want to experiment try 2 low voltage fuses in series. Find out if the arc can jump across 2 fuses. I think NOT, but i could be wrong.

[Tench]

I have some of these, more than I need in fact, It is a fuse/trip that is also a switch so you can use it to isolate your pack, good upto 80v dc, trips at 50a so should be ok for continuous currents up to 40a.

They are rated at 65v and 40a, 80v and 50a is maximum capacity. So should be good for any DC voltage below that running under 50a.

Higher DC voltages are more difficult to interrupt due to the arc so you should not use DC breakers that are not rated high enough for your purpose, they could trip and continue to arc then melt etc!

[alsmith]

Can you post a link where you get these? I can use them for my ride.

For yours can't you just put one per 24v worth of cells? Like if you have a 36v pack put one between the 24v series link then another at the end (which would be 12v), or one in the closest middle series link and one at the end.

There are many suppliers on both ebay and aliexpress (little price difference), an most large electrical suppliers should stock them.

It's not particularly straightforward splitting cells out of a pack with a bms to try and use 2 fuses, far easier to derate.

[alsmith]

I have some of these, more than I need in fact, It is a fuse/trip that is also a switch so you can use it to isolate your pack, good upto 80v dc, trips at 50a so should be ok for continuous currents up to 40a.

They are rated at 65v and 40a, 80v and 50a is maximum capacity. So should be good for any DC voltage below that running under 50a.

Higher DC voltages are more difficult to interrupt due to the arc so you should not use DC breakers that are not rated high enough for your purpose, they could trip and continue to arc then melt etc!

I'm looking for higher continuous and trip ratings than that. I'll hunt out that style to see if I can find higher ratings.

[wesnewell]

With DC voltage it's all about the gap. The higher the voltage the wider the gap needs to be regardless of the amperage. I wouldn't go over 48V on a device rated for 24V. Well I would and did, but I know that if there's problem my atc blade fuse will just burn up the whole thing and that's oj with me since the holder only cost $1.28 and I've got plenty of 40A fuses. Probably should have just soldered the fuse in line so it would break away easily if it blew. Anyway if you want a proper fuse for over 48V, then look at ANL or ANN fuses. They are rated for up to 80VDC.
http://www.ebay.com/sch/i.html?_trksid= ... w=anl+fuse
If you want a higher rating than that, you should find it here.
http://www.ebay.com/sch/i.html?_trksid= ... 00vdc+fuse

[Tench]

Some of the higher voltage DC breakers use a magnet to repel the arc making its path longer to make it extinguish or a gate moves into its path to cool and extinguish it. A lower rated one that appears to be constructed the same as a similar higher voltage one may have quite different internals.
When I was looking for one suitable for 72v and 40a I couldn't find anything in the uk except ones approved for boats which are very expensive.

[alsmith]

Some of the higher voltage DC breakers use a magnet to repel the arc making its path longer to make it extinguish or a gate moves into its path to cool and extinguish it. A lower rated one that appears to be constructed the same as a similar higher voltage one may have quite different internals.
When I was looking for one suitable for 72v and 40a I couldn't find anything in the uk except ones approved for boats which are very expensive.

I came across the same problem. I started re-looking because I'll be changing my rack/battery layout soon. It'd be nice if I could design in the little niceties from the off.

[parabellum]

Fuse is actually used not to avoid damage but to minimize it. If your fuse blows, then you are "far" over designed system capability. Options are:
1) There is a fault mode. (look for appropriate fuse, no compromise) (perhaps, reverse polarity may be only exception, if you have few packs then you will be able to pull the not melted connectors apart) 2 fuses in series will probably not help because only one will burn first raising resistance, lowering current and saving next fuse, but current still flows.

2) The fuse is underrated. (It just trips when overheated and arc distinguish it self in some point, remember, we are pulse feeding the motor, so there is almost 0 in some point, at least when your throttle is low)

[TMaster]

I have been using a 32V - 60A Maxi blade type fuse for the last 4 years and have not blown or burnt it up yet. I push peaks of 110A through it and some constants of 30-50 amps @ 65V-76V I actually have 4mm bullet connectors soldered right to the blades, because the normal fuse holder is freaking huge and wouldn't fit for my setup. Long story short according to the blow delay curve in the link provided below it would take about 20 seconds at 110A to blow the 60A fuse. Since I peak at 110A and its only for 1 or 2 seconds it has never happened. I would also have to pull 60A or more for over 1 minute to blow the fuse. This doesn't make me feel too good if a problem came about. The only thing that I feel good about is that the size or mass of the fuse break is smaller than any connection or connector on my wiring harness. I may try a 50 amp fuse and see what happens, It would probably work for a while I'm guessing. I do carry a spare 80A fuse with my bike just incase I would blow the 60 and not be stranded. http://www.bluesea.com/products/5141/MAXI_Fuse_-_60_Amp

[alsmith]

I've got large sized blade fuses and holders from the last time I'd asked - it seemed the best option. But I'd bet the spare fuse would be missing if it blew, where I haven't heard of a reset button getting lost......

[wesnewell]

The fuse serves only one purpose as far as I'm concerned, and that's to keep from shorting the battery for so long it burns up the power wiring insulation and causes the batteries to ignite in flames. It's not there to protect the controller or motor. That's where the problem that blows the fuse will happen.

[drsolly]

I've got large sized blade fuses and holders from the last time I'd asked - it seemed the best option. But I'd bet the spare fuse would be missing if it blew, where I haven't heard of a reset button getting lost......

I carry a couple of spare fuses in my puncture repair kit.

[alsmith]

I've got large sized blade fuses and holders from the last time I'd asked - it seemed the best option. But I'd bet the spare fuse would be missing if it blew, where I haven't heard of a reset button getting lost......

I carry a couple of spare fuses in my puncture repair kit.

That's handy to know, but I'm 300 miles away

[drsolly]

I've got large sized blade fuses and holders from the last time I'd asked - it seemed the best option. But I'd bet the spare fuse would be missing if it blew, where I haven't heard of a reset button getting lost......

I carry a couple of spare fuses in my puncture repair kit.

That's handy to know, but I'm 300 miles away

Not always. Sometimes I go north of Watford.

[alsmith]

Not always. Sometimes I go north of Watford.

I've been to Watford a few times- can't remember a thing about the place though. Don't forget to carry a compass to get back south, and a flat cap to fit in when you hit the North.

[Emoto]

alsmith here is a common house ac breaker [ 240v/100amp ] i like how its a resettable fuse and switch all in one im hoping to use on 72v setup, any reason you wouldnt use one.

[drsolly]

Not always. Sometimes I go north of Watford.

I've been to Watford a few times- can't remember a thing about the place though. Don't forget to carry a compass to get back south, and a flat cap to fit in when you hit the North.

Do I wear the flat cap over or under my bike helmet?

[drsolly]

alsmith here is a common house ac breaker [ 240v/100amp ] i like how its a resettable fuse and switch all in one im hoping to use on 72v setup, any reason you wouldnt use one.

I use one of those, it's a 65 amp one.

I have a 220 ohm resistor across the switch, so that as soon as I plug the driver harness (which incorporates this) into the battery and controller, it starts to charge up the controller capacitor, so by the time I switch it on, there's not going to be any arcing. I also have a blade fuse in series with this, because I want the fuse to blow at 40 amps; then the 65 amp circuit breaker is just another extra safety. I'm not actually convinced that it will break the circuit when there's 65 amps going through it, because it's designed for AC, not DC. But the 40 amp fuse will definitely blow. And it's astonishingly cheap, so I think I get the best of both worlds.

I've also incorporated the shunt for the handlebar ammeter into the package (a few inches of 10AWG), and also the watt-hour/amps/volt meter that you get off Ebay for £9, so when I change the battery, I know how many AH the previous battery gave me.
.

[parabellum]

alsmith here is a common house ac breaker [ 240v/100amp ] i like how its a resettable fuse and switch all in one im hoping to use on 72v setup, any reason you wouldnt use one.

Yes, they are cool, you hear loud click when the breaker switches off, but current stops flowing only after you twist down the throttle . At 24s LiPo at least.

P.S. Those C marked ones are very slow as well, you can see high short current spikes and in will take 100A for minutes if I remember well. You should take A or B or lower amp.

[alsmith]

When I looked for specific advice about ratings I couldn't find anything- it was all too vague. Like if you use 36V DC and want the fuse to blow at 60 Amps which 220V AC rating should you use? Which 110V AC rating should you use? The same rating for 110V as for 220V, or some set ratio difference?
What is the effect of using 72V DC instead of 36V- do you use the same AC rating or derate further, and by how much?

It seems to be a case of stick one in and if t doesn't blow then it's ok. BUT how much protection is it giving, is it giving protection that is actually of real practical value? It seems almost accepted that if it isn't blowing then the rating is ok- but that may just protect from a dead short. Or is that all they are being used for (in which case why not just use 100A, or 200A)?

[parabellum]

When I looked for specific advice about ratings I couldn't find anything- it was all too vague. Like if you use 36V DC and want the fuse to blow at 60 Amps which 220V AC rating should you use? Which 110V AC rating should you use? The same rating for 110V as for 220V, or some set ratio difference?
What is the effect of using 72V DC instead of 36V- do you use the same AC rating or derate further, and by how much?

It seems to be a case of stick one in and if t doesn't blow then it's ok. BUT how much protection is it giving, is it giving protection that is actually of real practical value? It seems almost accepted that if it isn't blowing then the rating is ok- but that may just protect from a dead short. Or is that all they are being used for (in which case why not just use 100A, or 200A)?

Those fuses have 2 triggers.

1st is bi metal and it only cares about heating (Voltage has nothing to do with it, hypothetically it acts equal on 5VDC and 220VAC). Just on the rated current, it takes minutes to trigger and if it is substantially higher then seconds. Bi metal triggers are very slow and lame, blow fuse is much quicker.

2nd is magnetic trigger or instantaneous triggerand those B,C etc. ratings. I have the impression they act equal on AC and DC spikes.

International Standard--- IEC 60898-1 and European Standard EN 60898-1 define the rated current In of a circuit breaker for low voltage distribution applications as the maximum current that the breaker is designed to carry continuously (at an ambient air temperature of 30 °C). The commonly-available preferred values for the rated current are 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A, 80 A, 100 A,[5] and 125 A (Renard series, slightly modified to include current limit of British BS 1363 sockets). The circuit breaker is labeled with the rated current in amperes, but without the unit symbol "A". Instead, the ampere figure is preceded by a letter "B", "C" or "D", which indicates the instantaneous tripping current — that is, the minimum value of current that causes the circuit breaker to trip without intentional time delay (i.e., in less than 100 ms), expressed in terms of In:

Type Instantaneous tripping current
B above 3 In up to and including 5 In
C above 5 In up to and including 10 In
D above 10 In up to and including 20 In
K above 8 In up to and including 12 In
For the protection of loads that cause frequent short duration (approximately 400 ms to 2 s) current peaks in normal operation.

Z above 2 In up to and including 3 In for periods in the order of tens of seconds.
For the protection of loads such as semiconductor devices or measuring circuits using current transformers.

http://en.wikipedia.org/wiki/Circuit_br ... terruption
Anyway, DC has no 0V cross point and arc extinguishing must be done by reaching certain gap distance between contacts for certain V, in AC the distance must be sufficient to not allow a jump over, which is harder to make starting from 0A. To know how many V can be interrupted by specific breaker, you need to know the air gap distance on open state (I suppose it varies by maker, they only have to provide required minimum gap or greater). I think, digging in to specs sheets is way to determine VDC capabilities. 220V breakers have wider gap requirement.

[alsmith]

Thanks, that gives some comfort knowing what to expect from those breakers.

[Emoto]

When I looked for specific advice about ratings I couldn't find anything- it was all too vague. Like if you use 36V DC and want the fuse to blow at 60 Amps which 220V AC rating should you use? Which 110V AC rating should you use? The same rating for 110V as for 220V, or some set ratio difference?
What is the effect of using 72V DC instead of 36V- do you use the same AC rating or derate further, and by how much?

It seems to be a case of stick one in and if t doesn't blow then it's ok. BUT how much protection is it giving, is it giving protection that is actually of real practical value? It seems almost accepted that if it isn't blowing then the rating is ok- but that may just protect from a dead short. Or is that all they are being used for (in which case why not just use 100A, or 200A)?

Yeah i agree especially on the ac breakers.

alsmith here is a common house ac breaker [ 240v/100amp ] i like how its a resettable fuse and switch all in one im hoping to use on 72v setup, any reason you wouldnt use one.

Yes, they are cool, you hear loud click when the breaker switches off, but current stops flowing only after you twist down the throttle . At 24s LiPo at least.

P.S. Those C marked ones are very slow as well, you can see high short current spikes and in will take 100A for minutes if I remember well. You should take A or B or lower amp.

parabellum thanks man, as you say ill have to grab a lower amperage breaker of course depending on the class b/c/d ect ill try for something around 60/70.

What voltage are you using and what amp / rating b/c/d or? plus any other information/advice you can give would be great.

I heard that on some of these breakers after they have been triggered/triped for the first time the contact is not the same as new because of the arcing, then pos higher resistance
But i still think these breakers are a good idea as a main switch that just happen to have a fuse.