Adding inline fuse to volt display

[awol]

I don't know much about electronics and my wiring isn't the best but I am adding one of these volt displays to my handlebars
http://www.ebay.co.uk/itm/261242417255?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT
Because the wires are exposed at the back I want to make it a bit safer by adding a small inline fuse between it and the battery wire.
I have found these holders
http://www.ebay.co.uk/itm/10-AGC-5-x-20mm-5x20-Fuse-Holder-Case-In-Line-Screw-with-22AWG-Wire-Cable-DT-/171503279529?pt=LH_DefaultDomain_3&hash=item27ee645da9
The volt display spec says 20ma, will one of these 100ma fuses be ok or am I wasting my time?
http://www.ebay.co.uk/itm/10-PCS-5-X-20MM-FAST-ACTING-QUICK-BLOW-GLASS-TUBE-FUSES-100MA-TO-20-AMP-/181021643228?pt=LH_DefaultDomain_3&var=480200850857&hash=item2a25bb11dc
or is there a better solution available.

 

[Deleted member 4366]

I wouldn't bother. The only thing you're protecting against is the wires catching fire if they short together, which is not very likely as long as you route them carefully.

 

[shemozzle999]

If you are going to fuse the circuit it has to be placed at the source of the supply i.e. the controller.

I fuse all my controllers internally with these type:

http://uk.rs-online.com/web/c/fuses-sockets-circuit-breakers/fuses-pcb/non-resettable-wire-ended-fuses/

It protects the cable harness and display units should something go amiss, if you don't, then you rely on the main battery fuse to blow by which time the damage will be done.

It really should be a standard fitment on all controllers as the cost is insignificant.

To do it you remove the supply wire from the controller circuit board and then fit one end of the fuse into the newly acquired hole and solder it, trim the other end and solder the supply wire onto it and heatshrink sleeve it, reassemble, then forget about it knowing that you are protected.

 

[awol]

Ah, I have it really wrong about electrics then as I thought the fuse was to be at the battery, so I knocked this up the other day.
Will this not protect from fire and should I not bother with another I was going to make?
any chance shemozzle999 could help me choose one of those wire-end fuses as I've no idea which one on the list is suitable, it's just those lipo batteries look a bit scary if something was to short somewhere.

 

[Deleted member 4366]

That will be sufficient.

 

[shemozzle999]

Most commercial battery packs have internal fuses that connect to the controller but the feed to the auxiliary devices i.e. the LCD or LED display with the on/off button or throttles with battery level displays require a lower rating than that. I have used a 250mA one in my controllers which is sufficient to drive the LEDs or LCD handlebar display plus enough current for the return feed back to the controller to drive its control circuitry.

If I was to use your voltage display I would modify the controller first and then run a short spur cable from the handlebar display picking up on the return live supply and earth (0 volts) rather than run a new cable from the battery.

 

[awol]

To do it you remove the supply wire from the controller circuit board and then fit one end of the fuse into the newly acquired hole and solder it, trim the other end and solder the supply wire onto it and heatshrink sleeve it, reassemble, then forget about it knowing that you are protected.

I am now happy my wire is protecting from serious short (fire) and now fancy having a go at that LCD to controller fuse (for the challenge) on a spare controller first.
To confirm I am putting this fuse between the thin red wire between the LCD and the circuit board.
http://uk.rs-online.com/web/p/non-resettable-wire-ended-fuses/5413243/

then open up LCD and solder onto the red&black wire for my volt display.

 

[Deleted member 4366]

You're making it too complicated and increasing the risk of something going wrong. I've never heard of a LCD shorting out and setting the bike on fire, so what advantage are you hoping to gain?

 

[awol]

"You're making it too complicated" That's me all the time, following a lot of your tips is helping me with that !
My initial concern was the exposed connections on the back of that volt meter, one come very loose so I was concerned about one coming off and shorting out and also with soon switching to lipo's was bothered about fire risk but as you said above that if I am careful with the initial wiring I should avoid any chance of a short and now my battery fuse will blow before the batteries.
I will put a dollop of silicon on the exposed terminals which is far simpler.

 

[Deleted member 4366]

For every difficult problem, there's always a simple solution!
Corollary: Every simple task becomes difficult.

 

[Croxden]

The bane of my working life was folk wanting high tech solutions to low tech problems.

 

[shemozzle999]

I am now happy my wire is protecting from serious short (fire) and now fancy having a go at that LCD to controller fuse (for the challenge) on a spare controller first.
To confirm I am putting this fuse between the thin red wire between the LCD and the circuit board.
http://uk.rs-online.com/web/p/non-resettable-wire-ended-fuses/5413243/

then open up LCD and solder onto the red&black wire for my volt display.

You need to identify the wire carrying the working battery voltage with a voltmeter then trace it to both the controller and the display to be able to carry out the modifications as described earlier.

By selecting this wire your volt meter will be powered up when you turn on the battery with the key switch and before switching on the motor with the LCD display, a useful reminder to turn off the battery at the end of a ride.