MP4 48v 10ah setup fuse ideas

[Mgizen]

I looking for advice on fuse style and holder options. I'm running my motor at default setting so pull around 1300 watts. I was thinking a
40amp fuse protection would be ok but can't find an option. I have some ATO fuse style holders from automotive application but not
sure is holder is rated for voltage. If anyone has some input let me know.

[Bikemad]

The only problem I have experienced using automotive fuse holders with eBikes is the maximum current capability not the voltage. I have used these fuses on battery packs with nominal voltages of between 25.9V and 55.5V without any problem if the rated current is not greatly exceeded.

A 30A fuse should be suitable for a standard Magic Pie or Smart Pie and the 30A fuse holders should be fine. If you prefer to use a 40A fuse instead of a 30A fuse it should be fine, but I don't think it will be necessary.
I suggest you start with a 30A fuse, but carry a 40A spare fuse in case the 30A fuse ever blows.
If the 30A fuse does blow during normal use, then a 35A or 40A fuse will be required instead, but I don't think the 30A fuse is likely to blow under normal use with a standard Magic Pie or Smart Pie.

If there was an unexpected current overload (i.e. a short in the motor's battery supply wiring) the fuse should blow safely like mine did:



However, I did experience a problem while using a 40 Amp mini fuse to cope with the additional current being drawn by my modified (much higher current) controller as the fuse holder was only rated for 30 Amps.

After a few rides, I began to notice a drop in power under sustained heavy load and eventually discovered that the 45~50A maximum current was simply too much for the 30A rated fuse holder.
Although the intermittent bursts of high current were not enough to blow the 40A fuse, it did result in arcing between the fuse blades and the fuse holder contacts, which caused the loss of power and also generated enough heat to melt the plastic body of the fuse:



The 40A fuse shown on the left in the above picture was still working when I replaced it (along with the heat damaged fuse holder).



I replaced the above 30A fuse holder and 40A fuse with the homemade 80A fuse with soldered connections as shown here:



I realise that an 80A fuse is probably a bit over the top for my 50A max current draw, but I only had 40a fuses to hand at the time instead of 30A fuses. 

At least it will still blow and protect the wiring if there is a direct short.



Alan
 

[GM Canada]

I do know that some people have told me they use waterproof marine 30 amp DC circuit breakers instead of fuses. I have never used one so I don't want to recommend one in particular, but a quick google search does bring up marine suppliers that do carry these breakers.

http://bfy.tw/4Uf2

Gary

[Bikemad]

It's also worth mentioning that most of the marine circuit breakers are only rated for 12~24V operation so they might not be suitable for use with a 48V pack.

I have just had a quick look on eBay and found this 30A 50VDC circuit breaker available from China at a reasonable price, which might be more suitable for a 48V pack:



According to the following graph, it should also be able to supply 45 Amps for up to 11 second bursts or 60 Amps for 5 second bursts before it would actually trip:
 


This should be able to supply full current to a standard Magic Pie even under continuous high load conditions without tripping, but it should trip reasonably quickly if there was a direct short in the wiring (although I suspect that the battery's BMS may shut the power off first).

Alan
 

[Mgizen]

Thanks for the info both Gary and Alan. On the subject of BMS what happens when the BMS is over amped does it require you to cycle power switch or does it just momentarily cut shut down?

[Andrew]

Hi everyone, I use these for high amp application..... http://www.maplin.co.uk/p/water-resistant-maxi-fuse-holder-mx15r

They are a larger version of the fuse holder illustrated above by Bikemad, and they are very reasonable in price........ Even for you Alan.

Andrew 

[GM Canada]

Thanks for the info both Gary and Alan. On the subject of BMS what happens when the BMS is over amped does it require you to cycle power switch or does it just momentarily cut shut down?

Battery kicks out and you neeed to cycle the key to continue.

Gary

[Hastings]

Since I switched to Maxifuses and its more sturdy holder I have not melted any  connectors  they are just better at handling the current regardeless if you use 20-30 or 40 Amps fuses. Repeated heating leds to oxidation of standard automotive fuses and connectors so even if they work fine initially they will quit on you

[Mgizen]

Thanks Hastings I think I'll go with that option. Thanks for input.