Fuse Size with FET - Please read if using an FET RR

[salty_monk]

This evening I have been fitting the FET RR to my Skunk. Once finished I fitted one of the new 30A fuses I picked up today (Haven't started the bike yet).

This reminded me that I didn't have a 30A for the 750 & went with the biggest in my stash which was a 20A. I thought this would be fine as the stock main fuses are only 15 or in the 750's case (I think) 20A.

I had a look at the 750's 20A fuse - blown! This bike has a redundant +ve in as much as I have routed the +ve from the RR to both the Loom +ve & also direct to the battery via the fuse. Seems like the fuse had blown & it was using the Loom +ve to continue to charge the battery (checked battery voltage & it is reading about 12.7v which is as good as I can expect on a bike I've not ridden for 2 weeks!)

I had read on various other forums that 20A would not do & that 25A was marginal, 30A required but as our main fuses are much smaller I assumed that it would be no big deal.... Lucky I had the redundant +ve or I probably would have been pushing already!!

I will report back when I ride it tomorrow with the 30A fuse fitted but I wanted to give everyone the heads up.

Dan

 

[posplayr]

This evening I have been fitting the FET RR to my Skunk. Once finished I fitted one of the new 30A fuses I picked up today (Haven't started the bike yet).

This reminded me that I didn't have a 30A for the 750 & went with the biggest in my stash which was a 20A. I thought this would be fine as the stock main fuses are only 15 or in the 750's case (I think) 20A.

I had a look at the 750's 20A fuse - blown! This bike has a redundant +ve in as much as I have routed the +ve from the RR to both the Loom +ve & also direct to the battery via the fuse. Seems like the fuse had blown & it was using the Loom +ve to continue to charge the battery (checked battery voltage & it is reading about 12.7v which is as good as I can expect on a bike I've not ridden for 2 weeks!)

I had read on various other forums that 20A would not do & that 25A was marginal, 30A required but as our main fuses are much smaller I assumed that it would be no big deal.... Lucky I had the redundant +ve or I probably would have been pushing already!!

I will report back when I ride it tomorrow with the 30A fuse fitted but I wanted to give everyone the heads up.

Dan

Dan ,
The only reason I can think you would need 30 amps is to feed a "short". Unless you have added a super deluxe set of headed gloves and muffler there should be no change from stock with a FET regulator. At best you might get an extra couple of extra amps.

Jim

 

[salty_monk]

Jim,

I agree. That bike does have heated grips but nothing else.

The fuse is only on the +ve wire direct from Regulator to the battery. There is definitely no short (if there was it would be in the loom so the main fuse would have blown as well!) I cannot see any reason for it to blow a 20A fuse (other than the information I have read which says that the initial loading on the fuse is somewhat higher so you need the 30A fuse to allow for that as a 20/25A will fatigue & blow over time).

This is the info on the TriumphRat site that has been linked to before that I have been reading...

My main point in posting was to prompt everyone else on here with this mod to go check their fuses... might save someone a long walk!!

Cheers,

Dan

 

[posplayr]

OK Dan,
I had not realized how people were wiring direct between R/R and Battery on the plus size.
Jim

 

[salty_monk]

Fired it up with the 30A & all good so far. No pop. No excess heat or smoke so I'm double sure it's not a short.

Please check your fuses. I know there are others out here running with smaller fuses.

Dan

 

[posplayr]

Fired it up with the 30A & all good so far. No pop. No excess heat or smoke so I'm double sure it's not a short.

Please check your fuses. I know there are others out here running with smaller fuses.

Dan

Dan can you run with a 20amp?

Is teh 30 in a holder between R/R and battery or in the fuse box?

 

[salty_monk]

I can run with a 20A but I suspect the same will happen as before over time.

The fuse is in an inline fuseholder (ATO Blade type) about 1.5" from the battery. From the other end of the fuse the wire goes to a point where it is joined (I never broke the large gauge wire direct to the battery, I just shaved insulation & spliced into it) by the original Loom RR +ve wire. From there it goes direct to the RR.

Ran about 60 miles with the FH010 on the Skunk & 30 Amp fuse today with no probs. I didn't splice the loom +ve into this one, just blanked it off so just one wire going direct from RR to battery.

Dan

 

[TheCafeKid]

So are you saying this happens over a period of time? Because I just installed a FET in my GS1100ES today wired the hot lead straight to the batt with an inline fuse just like you Dan. However, in my limited electrical knowledge I assumed that since the stock main fuse was only 15 amps, a 30 amp fuse would do nothing good if there were a short that the fuse should be protecting. Basicly saying, if you put a 30 amp fus in there expecting it to protect a system that at best puts out 15 amps or so, you're not protecting anything. So *I* installed a 20 amp (only because I didn't have another 15 amp handy) just so I could check everything was functioning properly and charging correctly. Happy to not that I'm charging at 13.25 at idle (about 13 flat with the brake light lit) and 14.25 at around 2K all the way to redline . But, as of yet, I've had no fuse blow. ???

 

[posplayr]

Because I just installed a FET in my GS1100ES today wired the hot lead straight to the batt with an inline fuse just like you Dan.

Josh,
Turns out there are different ways of doing this. As chance would have it , none of the common ways that are implement here would have ever occured to me .
Jim

 

[kinnet]

Jim- the way that Dan and I (tck) did this is the cleanest way as it eliminates all the connectors in the harness and reverts power directly from the regulator to the battery. By doing this you eliminate the chances of a bad connection in the harness creating heat. Any current overages that the bike doesn't consume go to charge the battery as in the stock configuration. It doesn't matter where the "T" is, it still works the same.

 

[salty_monk]

Josh - my 20A fuse lasted for a while... then it blew. Apparently from my research they can "fatigue" over time. I can put a 20A fuse in it now & it'll be ok for a while again.

The fuse can now get the "full belt" from the Stator/RR to the battery so I guess that's why you need the 30A.

I don't pretend to completely understand it but my research & practical experience has shown me that a 20A is not enough.

Dan