12 volt power (using optimiser lead)

For my forthcoming 1st camping trip (I'm sure I mentioned it) I have bought a 12 volt pump for my airbed. A friend suggested instead of messing about fitting a cigarette lighter adapter I buy a compatable connection for the optimiser already installed.

On doing this and connecting it the inline fuse blew immediately. Not saved the messing about after all!!

I checked and assume that because the optimiser is a trickle charger delivering a maximum of 6 volts charge the inline fuse was only a small amp one though it doesn't actually say so on the fuse.

Do you think I would be safe to put a beefier fuse in for the purpose of running the pump or should I find an alternative way of powering it??

Thanks as always

I've got a cigarette socket and just wired it straight to the battery without a fuse. It's probably centre positive but might be worth checking online or with a voltmeter.

Never had any problems.....yet.

The fuse blew when you turned the pump on, or just connecting the adapter?

Your Optimiser ought to be delivering 12V, usual charge of 0.6 Amp. It is quite possible the in-line fuse has a low rating. I think they are colour coded to denote the current rating.

Pumps can draw a large current especially on start up, if I was in doubt about this I quickly found out when connecting a cig lighter adapter with a compressor plugged in. The connection cable heated up, melted the plastic and burnt my hand.

Check what Amp or wattage is required by the pump (hopefully it should tell you), then see if you can get the rating for the Optimate adapter.
Maybe the adapter wiring is quite thin, in which case you don't want to have a molten mess like I had.

If the pump gives you the requirements in watts, work out the Amperage (Watts/Volts) e.g. 60w would be 5 Amps (60/12).
The sparkies and electrical buffs could argue the simplicity of the calculation, but it been good enough for me.

Rosco wrote:Never had any problems.....yet.

That the same one I managed to melt?

My memory is crap. Was this when my back tyre wouldn't inflate after last year's big mac?

I seem to remember something melting but can't remember what exactly.

Sure it was Wee Mac I, after lunch in Inverurie, bike next to mine had a partially deflated tyre. I think there is a pic somewhere of me attaching the wires to the battery and DBD all set to give me a fright but I spoilt the fun when the burn happened and I jumped back. I got my own back by saying the most likely cause was because I was running a 24 volt system on my bike

Sorry for trashing your thread Steve

Not a spark myself either, the fuse is a clear on with silver ends and I can't see a rating on it as far as I can tell. It says 7L 250V on it which tells ME nothing!!

The point about the wiring is interesting though, the optimiser wire is quite thin looking but then again nothing thinner than the wiring from the pump. Incidentally the pump is 12V, 24watt. I think it may be worthwhile trying a heftier fuse in it and giving it a thorough check in service to make sure nothing is getting too hot unless anyone has any other suggestions.

Appreciate the replies as always chaps

SteveCat wrote:Sorry for trashing your thread Steve

No harm done lol

That a glass fuse? The first number should be the current rating, could it possibly be 1L (1 Amp)? not sure what the L means, stand corrected but you get quick, normal and slow blow fuses.

Your pump runs at 2 Amp, but would imagine it might be double that at least on start-up. I'm sure you'll be fine with a 5Amp or 7.5A fuse.

The problem I had was the pump was turned on when I was connecting to the battery. If the wires were on properly and was then switched on I doubt I'd have had the burn, but worth keeping an eye out the first time the pump fires up.

SteveCat wrote:The fuse blew when you turned the pump on, or just connecting the adapter?

Your Optimiser ought to be delivering 12V, usual charge of 0.6 Amp. It is quite possible the in-line fuse has a low rating. I think they are colour coded to denote the current rating.

Pumps can draw a large current especially on start up, if I was in doubt about this I quickly found out when connecting a cig lighter adapter with a compressor plugged in. The connection cable heated up, melted the plastic and burnt my hand.

Check what Amp or wattage is required by the pump (hopefully it should tell you), then see if you can get the rating for the Optimate adapter.
Maybe the adapter wiring is quite thin, in which case you don't want to have a molten mess like I had.

If the pump gives you the requirements in watts, work out the Amperage (Watts/Volts) e.g. 60w would be 5 Amps (60/12).
The sparkies and electrical buffs could argue the simplicity of the calculation, but it been good enough for me.

Steve you calculations are correct
P=V x I

Indeed 'Ivy Watts was a powerful girl'

That's how I was taught to remember it!
Either that or you've just triggered a suppressed memory

I found an online user manual for the Optimate 4 which states the fuse is 7.5A (I think the lead with the fuse is the same as for the Optimate 3).

That's a pretty hefty fuse, which ought to put up with most 12v accessories.

SteveCat wrote:Sure it was Wee Mac I, after lunch in Inverurie, bike next to mine had a partially deflated tyre. I think there is a pic somewhere of me attaching the wires to the battery and DBD all set to give me a fright but I spoilt the fun when the burn happened and I jumped back. I got my own back by saying the most likely cause was because I was running a 24 volt system on my bike

Sorry for trashing your thread Steve

Might as well keep trashing then.

I do remember that - think it was Rob's R1.
What wires melted though? Was it your extension or was it from my compressor or ... ? I was probably taking a picture!
I guess the wires were probably too thin and just heated up instead. Some bright spark (probably DBD) will be along shortly to stick his three finger rule up at me)


Cheers
Ross