Is it safe to use a jump starter on all cars ? | Technical matters | Back Room Forum

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Sun 22 Oct 2017 15:33

Is it safe to use a jump starter on all cars ? - Lrac

I have recently been thinking about buying a battery jump starter. I do not want one with an internal battery.

Whilst I will probably never need to use it on my own cars I do not doubt the opportunity to use it on colleagues cars will arise. I do not expect any of my colleagues would carry their cars hand books with them and I would have reservations about jump starting say for example a year old Toyota Land Cruiser in which case we are probably back to square one and waiting for the breakdown services.

Whats the general concensus? Anyone know if there are current cars that you definately should not jump start this way? I would give any hybrid a miss. I wouldn't buy a pack with a battery.

Years ago on this site I read that as the earths deteriated with age, Passat dash circuits used to fry themselfs if anyone tried to use a jump starter.

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Sun 22 Oct 2017 15:49

Is it safe to use a jump starter on all cars ? - gordonbennet

What jump starter comes without an internal battery?, it must be me being thick but that doesn't compute.

I have a jump pack (said Clarke) though carry jump leads in my car and anyone who wants a jump start off my Landcruiser does so at their own risk, a friend fried the digi dash on his Laguna 1 jump starting someone, circa £600 when the car was current, no pun.

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Sun 22 Oct 2017 15:56

Is it safe to use a jump starter on all cars ? - RobJP

Lots of cars these days you don't connect to the battery, rather a 'post' in the engine bay, if needing to jump-start.

Get it wrong and you fry all the electrics.

Which could cost thousands to fix. And the person is going to be looking for 'someone' to put the blame on for, and guess who is going to be in the firing line ...

I'd not jump-start any car apart from one of my own.

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Sun 22 Oct 2017 17:47

Is it safe to use a jump starter on all cars ? - hardway

As most people don't know how to "jump" a vehicle and I'm guessing you don't either all your doing is opening yourself up for the blame.

But if you insist and want to avoid voltage spike that can fry electrics remember this.

JUMP PACK RED CLIP TO DEAD CAR BATTERY POS+

JUMP PACK BLACK LEAD CLAMP ONTO CLEAN ENGINE OR GEARBOX METAL.

NOT AND I REPEAT NOT ONTO THE BATTERY NEGATIVE TERMINAL.

And I know I shouting I hope it registers.

And if you want the simple reason why it's DC battery's the power that actually does anything comes out of the negative terminal into the chassis/engine not out of the pos+.

DC current is electrons which are negative charged,

I repeat electricity comes out of the negative battery terminal.

There are a few other reason for this procedure but this covers the most important aspects.

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Sun 22 Oct 2017 18:47

Is it safe to use a jump starter on all cars ? - Lrac

Are you saying you have 100% confidence in your claim that your procedure is safe for any car ?

Why do you assume I am not familiar with your procedure? or conventional flow? It is because I also have a knowlege of the pit falls that I ask this question.

The starter packs without a battery take a "hit" from the dead battery to charge a capacitor. They can also be given a charge from an external means

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Sun 22 Oct 2017 17:49

Is it safe to use a jump starter on all cars ? - madf

Jump starting a petrol hybrid is a no go area.

Personally, modern car electronics are very complex and some makers so bad at electronics and some owners so dim, I would not offer to help anyone with a post 2000 car.

Period..

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Sun 22 Oct 2017 18:54

Is it safe to use a jump starter on all cars ? - Lrac

I think you have hit the nail on the head. I agree with you 100%. I may still chuck a starter in the boot as I know there is no problem with my cars but you are correct its not worth the hassle / grief of trying to help when the consequences could be so dire.

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Sun 22 Oct 2017 18:55

Is it safe to use a jump starter on all cars ? - Lrac

Would still like to hear about any well known issues

Edited by Lrac on 22/10/2017 at 18:58

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Sun 22 Oct 2017 20:03

Is it safe to use a jump starter on all cars ? - Manatee

E&OE, I am not a real electrician. Do your own research.

The stuff about charge on electrons and direction of flow is I believe irrelevant. If it was a +ve earth car, you would connect the -ve terminal first and the negative to the chassis.

The reasons for doing this are, to the best of my knowledge:

- that a discharged battery can gas off and if making the second connection creates a spark it is better a distance from the discharged battery

- that if the negative/earth side was connected first, any accidental contact of the +ve jumper cable with the chassis would short the jump source.

- the return path to the jump source is said to be shorter/lower resistance from the chassis ground than from the negative terminal and the dead battery earth cable - I can't think this is very material, but I have seen it cited as a reason.

It's mainly the safety aspect - avoiding the slim possibility of fire or explosion, and the accidental shorting of the donor battery.

Regarding voltage spikes, they can arise when the dead car is connected to a second car with the engine running, or to a mains powered booster pack which I have seen 17-18V on (this on a decades-old garage one owned by a friend - he uses it on old classic cars). So don't use mains boosters, and don't run the engine on a donor car. A 12V nominal battery powered jumper pack is much safer and I have used one on (my) modern cars without damage. I have also used a second car battery that I keep charged up, and some jump leads, without problems.

Your risk of course.

Edited by Manatee on 22/10/2017 at 20:05

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Thu 26 Oct 2017 09:15

Is it safe to use a jump starter on all cars ? - edlithgow

Would still like to hear about any well known issues

Dunno if its a well known issue, but its one I've been aware of recently. My battery is overdue for replacement and I've had to jump start off the previous one (kept on a smart charger) a few times recently.

Once or twice, after a minute or fews run time, turning off, and disconnecting, there hasn't been enough juice in the car battery to re-start, so I've had to disconnect the jump lead with the engine running.

I think this is bad practice because the moribund car battery may not be capable of absorbing any damaging spikes. I seem to have got away with it on my old car, which only has electronics in the alternator, but on something newer it might be more destructive, and its something an impatient owner might be likely to do.

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Thu 26 Oct 2017 09:42

Is it safe to use a jump starter on all cars ? - gordonbennet

Years ago in car storage compounds we found that after a jump start car and leaving it to tickover to put a bit of charge in the battery you could leave it ticking over all day and it wouldn't put an ounce of charge in, presumably little to no drain no reason to charge, most noticeable on Fords.

You had to give it something to work on, hence once started put the sidelights or heater fan on to give the system something to work at, in practice at most compounds they standardized on leaving the hazard lights on, this way if the car was due to be moved again, ie loaded onto a transporter the driver would be pre warned the vehicle was likely to be a non starter at destination so should be able to put it somewhere on the transporter suitable for jump or bump start, a non starter on the over the cab peak deck is not exactly handy, and if it was only being moved in the compound then someone would notice especially when it got dark and not leaving it ticking over for hours/days.

The other thing to be careful of jump starting any car is to make sure the driver's door is open or the keys in your hand before you connect the jump leads/pack, many cars (again Fords are in the frame for this) will lock the doors instantly and if the keys are in the ignition, well you know the rest.

Edited by gordonbennet on 26/10/2017 at 09:58

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