Jump start bike with car?

[hongman]

Well, MOT day tomorrow, only just remembered :rolleyes:

Last time I tried to start the bike it took a worryingly long time to come to life after all that time sitting in the cold. That was a over a month ago, I havent dared start it since.

I had planned on getting a charger before the MOT but it seems I had my dates mixed up...

So, worse comes to worse, if she doesnt fire tomorrow, is it safe to jump it off the car? Google tells me I can but there are a few mumurs of damage possible due to the car battery pushing more amps or something.

Rather trust the org to tell me - safe enough to do?

[TSM]

yes fine, just dont start the car engine as the car generates too much power to charge the bike battery, starting the bike has little effect on the car battery overall

[Sid Squid]

just dont start the car engine as the car generates too much power to charge the bike battery
Care to explain why? As long as it's a 12V system you can do what you like, of course the car's battery won't even notice the bike is there so there's not even any need to have it running.

There is no such thing as 'generates too much power' in this circumstance.

[sunshine]

i agree with tsm mostly
depending on your car you could still have the engine running like my Suzuki Alto, the battery is same amps and amp/hrs only bigger in actual size.

[Sid Squid]

Battery capacity is irrelevant, a 12V system is a 12V system.

[hongman]

Battery capacity is irrelevant, a 12V system is a 12V system.

That's what I was hoping, but had to check!

I cant visualise my battery terminals...will I have space to get jump leads down there (the ones I have are quite chunky car ones) or will I have to manipulate the battery?

[TSM]

Care to explain why? As long as it's a 12V system you can do what you like, of course the car's battery won't even notice the bike is there so there's not even any need to have it running.

There is no such thing as 'generates too much power' in this circumstance.

too much current then, you should not charge a bike battery with high current or it can damage the battery, prolly a long time thing rather than a one min dont know

[TSM]

That's what I was hoping, but had to check!

I cant visualise my battery terminals...will I have space to get jump leads down there (the ones I have are quite chunky car ones) or will I have to manipulate the battery?

i just clamp negative to bike frame and then leaves me only to deal with positive terminal while handling the battery for positive connectio

[beabert]

I with sid squid on this one, you wont need to start it, but it will charge if the car was on.

[TSM]

I with sid squid on this one, you wont need to start it, but it will charge if the car was on.
it will charge regardless anyway even with the car off as it will draw current from the car battery till its either full or balanced between
SidSquid will prolly write somthing far better to understand than me

[hongman]

i just clamp negative to bike frame and then leaves me only to deal with positive terminal while handling the battery for positive connectio

Thanks for that tip, didnt know I could do that.

I with sid squid on this one, you wont need to start it, but it will charge if the car was on.

It will? Handy to know :)

Hopefully it wont come to this, but sods law and all that.

[Sid Squid]

you should not charge a bike battery with high current or it can damage the battery,
For the duration of a jump start it won't make any difference.

[_Stretchie_]

I've started the Thundercat loads of times from my 1.5 Civic and with the Civic running but not being revved.

But I was told to clamp the negative on the receiving (flat) vehicle to an earth point and not to the battery as it can upset engine management systems if present, and the Haynes book of lies backs that up, so that's what I do.

[benji106]

Dont try and start a bike while its connected to a battery charger though or you will blow a fuse in the battery charger. Or so i have been told... :thumright:

[TSM]

Dont try and start a bike while its connected to a battery charger though or you will blow a fuse in the battery charger. Or so i have been told... :thumright:
never happened to me

[hongman]

Dont try and start a bike while its connected to a battery charger though or you will blow a fuse in the battery charger. Or so i have been told... :thumright:

Lol. Unlucky ;)

I'm nervous about my mot. Dunno why. I'm missing that rear numberplate reflector thing but hopefully he'll letme off.

[Sid Squid]

The 'not connecting the neg lead to the battery' is a hangover from the days of unsealed batteries, there could be some flammable gas from the battery and if there were a spark on connecting the second lead - you do connect the leads in the right order, don't you? ;)

Even if it were not for that, connecting the neg lead directly to, preferably, the engine ensures the least resistance in the jump circuit.

If connecting the neg jump lead to the battery made the electronics suffer so would connecting the lead to the frame/engine - the engine, battery, frame are directly connected together already, the engine and frame by being big metal things bolted together, and the battery has a fat lead that goes from the neg terminal to a bolt on the engine.

[yorkie_chris]

Care to explain why?

Explanation I heard that if your olde schoole shunt reg-rec was 'set' at say 13.8V and the car alternator regulated to put out 14.5V it could result in the reg-rec attempting to dump more excess energy than it was designed to and overheat it.

Bad luck, probably nothing bad happens in most cases, but plausible.

[Sid Squid]

Honestly, I've tested this, and that was some years ago when such things were significantly less robust than they are now. We tried every combination of electronic and electro-mechanical device that could be found and could not make a unit fail using jump leads correctly from another vehicle.
Also I have never encountered a plausible story of failure in such circumstances, there are stories, but all that I have been faced with are accounted for with a very technical explanation: put the leads on the right way round. I will see if I can find the article into which all this testing went.
We even used two 12V batteries to apply 24V and couldn't make a regulator or electronic ignition unit fail. I really woudn't recommend that even though I know of someone on here who successfully jumped his SV from a tractor with a 24V system.

[beabert]

it will charge regardless anyway even with the car off as it will draw current from the car battery till its either full or balanced between
SidSquid will prolly write somthing far better to understand than me

I know that, but it was in reponse to your post saying it wouldn't lol.

[embee]

Connecting one flat 12V battery to a moderately charged one won't usually charge it very much (it will a little), a lead acid battery needs more volts to charge than one can usually produce (say >13.5V to charge well, a good battery will only be around 12.7V or so).

The usual advice when jumping one car from another is to connect the jump leads, then start and run the donor for 5mins or so to give the recipient battery a bit of a kick (it'll warm it up a bit if nothing else), then stop the donor and try a start. If you try starting the recipient with the donor running you more or less short circuit the alternator output into the starter motor (can take a few hundred amps on a decent sized engine) which can do it a nasty if you're unlucky. You'll probably get away with it but it can be a bit expensive if it does fry.

[beabert]

The 'not connecting the neg lead to the battery' is a hangover from the days of unsealed batteries, there could be some flammable gas from the battery and if there were a spark on connecting the second lead - you do connect the leads in the right order, don't you? ;)

Even if it were not for that, connecting the neg lead directly to, preferably, the engine ensures the least resistance in the jump circuit.

If connecting the neg jump lead to the battery made the electronics suffer so would connecting the lead to the frame/engine - the engine, battery, frame are directly connected together already, the engine and frame by being big metal things bolted together, and the battery has a fat lead that goes from the neg terminal to a bolt on the engine.

Im glad you brought this up.

The other month, I was trying to figure out why everyone was saying connect - to frame not terminal for reason other than ignition of gases risk.
I read every where that there was risk of damaging electronics? but i could not see how its all connected to each other, i then searched online and couldn't find any explanation either, just rumours.

[Harry_Mc]

dont think id want to be connecting a jump lead to the frame... it'll scratch it... car jump leads wont be easy to connect to a bike battery as they are huge

[tigersaw]

you do connect the leads in the right order, don't you? ;)



I was taught,
Connect the positive lead first, ground lead second.
Remove ground lead first, positive lead second.

Reason being that if you connect the ground first, then when you have the positive jump lead in your hand and catch it on any bit of metal.. crackle .. doesn't happen the other round.
Of course if you remember +ve earth cars it doesnt apply. They were always tricky to fit a radio as I recall.

[beabert]

yep, i caught the spanner on the bodywork before lol soon learnt.

[Stuuk1]

Before recently replacing my battery I was always jumping off a running car, no probs.

[Stig]

I tend to connect the negative lead directly to the main earth point on the bike. But then if it's a faired bike, that point is likely to be hidden and inaccessable.

[_Stretchie_]

I then searched online and couldn't find any explanation either, just rumours.

In the front of Haynes manuals. I'm sure, It's just I was told this, and then when I got my first Haynes it also said that.

Interesting reading though..... This thread, not the Haynes
;)

[hongman]

Well, had a fright this morning.

Key in, lights on, thumb starter, nothing. Zilch.

Check kill switch, check N light/side stand, all ok.

Hmm.

Turned out that with the new adjustable levers, I have to have it at max setting to hit the clutch switch...took me a few mins to figure that one out!

I thought it might be useful as a theft deterrant until I realised that would hardly stop a determined thief. Once on my way I readjusted down to minimal setting and it rides fine.

So I'll probably bypass it at some point.

Passed MOT, no issues! :D

Taxed on the way back, rode it to work....ahhh, the adrenaline and sense of freedom returns :D

[keith_d]

The usual advice when jumping one car from another is to connect the jump leads, then start and run the donor for 5mins or so to give the recipient battery a bit of a kick (it'll warm it up a bit if nothing else), then stop the donor and try a start. If you try starting the recipient with the donor running you more or less short circuit the alternator output into the starter motor (can take a few hundred amps on a decent sized engine) which can do it a nasty if you're unlucky. You'll probably get away with it but it can be a bit expensive if it does fry.

Most jump leads aren't able to carry the full starter current for a car, even my old 10mm leads were only rated for 100A for short periods. By charging the battery for 10 minutes we can get a large part of the starter current from the recipient's battery.

I wouldn't worry about shorting the alternator to ground. A fully charged car battery can deliver a huge current (over 100A) with very modest voltage drops because of the low cell resistance. So the voltage at the donor end of the jump leads shouldn't drop far enough to damage the alternator.

Keith.

[Geodude]

Glad it passed with no issues, was that without the number plate reflector? my mot place said no reflector no mot doh!

[thefallenangel]

mine said £2 for the reflector and had already written out the pass cert.

[hongman]

Nope, didnt mention the reflector at all.

I asked him if I could watch (politely of ocurse, I know it bugs some people). He said no probs and was actually quite chatty as he is a friend's friend's friend etc. Maybe he forgot coz we were chatting :D

I had a single advisory for the aftermarket exhaust, that was it. It just said "Aftermarket Exhaust fitted". lol.

He even sorted me out a couple bolts for my exhaust hanger, as they were mismatching ones I had lying around.

I bought a can of lube from him as well, even though I dont need any yet, just as a kind gesture for being so nice.

[Geodude]

Ahh ok nice one hongman, so for my next mot im taking a packet of hobnobs for the mot bloke along with some decent banter hehe ;)

[hongman]

:D

[-Ralph-]

If you are having difficulty getting jump leads onto your battery terminals, clip a pair of mole grips the positive terminal and the jump lead onto that. As said there's lots of places you can put the negative.

[yorkie_chris]

You don't need to put it on battery, or even clip it anywhere, just touch positive to the contact on starter motor to crank engine

[hongman]

That would involve removing fairing tho, I'd be too lazy for that!