Author Topic: Fuse value  (Read 132 times)

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Offline MilitaryRon

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Fuse value
« on: January 06, 2019, 06:43:25 pm »
What is considered to be the normal value amps for an in line fuse on the live battery lead of a 6V bike please.  Ron

Online Owen

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Re: Fuse value
« Reply #1 on: January 06, 2019, 06:45:07 pm »
I use a 15A fuse on mine
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline MilitaryRon

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Re: Fuse value
« Reply #2 on: January 06, 2019, 07:48:26 pm »
Ah that's good. 15Amp is what I just put in a newly fitted fuse holder.  Ta Ron

Online Owen

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Re: Fuse value
« Reply #3 on: January 06, 2019, 08:04:51 pm »
If you add it up
Horn 4A
Headlight (non LED) 6A (30W)
Speedometer light  (non LED) 0.1A
rear light  (non LED) 1A
Brake light (non LED)  3.5A (21w)
Ignition 4A
18.6A Total estimated.
But the chances of that happening all at once is very small
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Online hampshirebiker

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Re: Fuse value
« Reply #4 on: January 06, 2019, 08:11:18 pm »
Add 6w to the headlamp.
Postal - Liphook Hants - But just into West Sussex.

Online Owen

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Re: Fuse value
« Reply #5 on: January 06, 2019, 08:14:03 pm »
The side light usually turns off when headlight is on.
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Online hampshirebiker

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Re: Fuse value
« Reply #6 on: January 06, 2019, 08:44:32 pm »
I was referring to the arithmetic. 6 x 6 = 36. (V x A = W). I'm not trying to be picky, but I think a 15a is too tight. The principal function of a main fuse is to protect the wiring. A 25 or 30a fuse would not be too high and would prevent the possibility of nuisance blowing.
Postal - Liphook Hants - But just into West Sussex.

Offline Vreagh

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Re: Fuse value
« Reply #7 on: January 06, 2019, 10:23:55 pm »
The problem with a high amperage fuse is two fold. Unless a quick blow type fuse is fitted (not easy to obtain suitable for auto use) the fuse will take some seconds to blow at the rated amps. Also, can the average 6v battery supply sufficient current to blow a 30 amp fuse before a lower current rated cable has melted ?  I've had no problems with a 15amp fuse even on night trips of 300 miles with 6v dynamo.

Online hampshirebiker

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Re: Fuse value
« Reply #8 on: January 06, 2019, 10:55:19 pm »
If a 15a fuse works OK then fine, but even several seconds to blow the higher rated fuse will not be long enough to melt correctly sized cables. As I said it's the cables you're trying to protect with the main fuse. However the amp capacity claimed for their cables by some of the principal suppliers is hard to believe. Use 1 or 1,5 mm cable and a fuse up to 30a will be fine.
Postal - Liphook Hants - But just into West Sussex.

Offline timsdad

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Re: Fuse value
« Reply #9 on: January 07, 2019, 08:49:01 am »
I usually put a 15 amp jobbie in all mine that have just a single fuse but, if I can't find one in my muddled boxes, then I'll just bung a bigger one in. Anything is better than nothing.

There are several different types in my range of Brit and furren bikes of various ages but I suppose I'll now have to sort my fuses out and replace all the missing ones.


Ray
Just a motorcyclist.

Online Tman

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Re: Fuse value
« Reply #10 on: January 07, 2019, 11:09:51 am »
The best way would be to separately fuse the horn circuit (originally the horn was straight off the battery on many bikes) and derate the main (so-called battery) fuse to 10-15A.
That way the fuse will blow long before the wiring starts even getting warm, which, given the mighty output of the  C range dynamo/alt and the power consumption of the various components, will only ever happen with some form of short circuit.