How do I use my auto jump starter?

GAZ237

red_eye wrote: »

wow, have a look at the fuse on the lighter socket is it 15amp? so that's cable that is about 2-3mm thick a typical starter motor draws 250amps though a 10mm thick cable

Better have 999 on speed dial

You connect it to the car battery to start the car, you plank.

You charge it through the cigarette lighter socket.

alastairq

We've got one in the village..it's in a yellow box outside the pub......

keith1950

These are pretty much next to useless unless the car battery is only slightly discharged.

Something like this , although dearer , will start most cars even when fully discharged.

http://www.machinemart.co.uk/shop/product/details/jump-start-900

Joe_Horner

GAZ237 wrote: »

You connect it to the car battery to start the car, you plank.

You charge it through the cigarette lighter socket.

Depends what type it is. If it's this one (or similar):

http://www.easylifegroup.com/power-jump-5550

then it's not technically a jump pack, but a battery powered fast charger.

You charge it by plugging into the cigarette lighter socket then, if you have a flat battery, it shoves its stored energy back through the socket at a higher voltage (they seem to claim 30 volts on this one) over about 15 minutes - it's basically like connecting your battery to a fast charger for 1/4 hour or so.

How advisable it is to connect 30v to modern car systems is questionable, but most should be protected against over-voltage to at least that that as long as you don't try to actually start the car with it connected!

keith1950

With 30 volts of power, you'll have your petrol or diesel car started in a jiffy, about 10 to 15 minutes

The whole advert seems to be hype, as if they are trying impress the customer with facts.

Their quote above says ' 30 volts of power '........power is measured in watts not volts.

It's all about the amount of current needed to crank an engine so for a given battery pack size, by increasing the voltage from the usual 12-14 volts to 30 volts you are reducing the available current by 50%.

Also unless this pack has some kind of invertor in it , how can you charge it's pack to 30 volts from the cars 12-14 volts battery ?

colino

That smacks of the old desperate trick of hooking up two batteries in series to get an old trade-in started. Even with built in protection that all cars have nowadays, wouldn't even consider frying the multiple ecus in todays cars by attempting to fire it up with, "30 volts of power". If this is the one you've bought, get a refund and throw it away.

geek84

Good Morning folks

Many thanks for your replies.

The jump starter that Joe Horner mentions is slightly similar to the one I got - however mine is a rectangluar shape, rather than a box shape.

However, I still need some advice from you kind folks out there in terms of -

I haven't got much of an idea of how to use it, how long to use it for, how to check if the car battery is fully/partly charged, and if the auto charger would need charging itself !

I would be most grateful if someone could give some advice?

Thanks in advance

anotherbaldrick

alastairq wrote: »

We've got one in the village..it's in a yellow box outside the pub......

That's a jump starter for You, not the car

keith1950

As others have already said you should return it and get a refund, it's a waste of money.....honestly, I have encountered these occasionally and they're s***.

Joe_Horner

keith1950 wrote: »

It's all about the amount of current needed to crank an engine so for a given battery pack size, by increasing the voltage from the usual 12-14 volts to 30 volts you are reducing the available current by 50%.

Also unless this pack has some kind of invertor in it , how can you charge it's pack to 30 volts from the cars 12-14 volts battery ?

They're not designed to provide starting current like a "traditional" jump pack. Inside there will be a set of rechargeable batteries (probably Li-ion) like in a laptop battery*.

The pack will be made up of individual 3.6v cells, probably 8 of them, with a capacity of around 1000mAh each. So the whole pack, when charged, will have a capacity of about 8Ah.

When you're charging the pack from the car, it will internally connect those cells in 2 parallel banks of 4 cells to give a charging voltage of 14.4v - near enough to be charged by most cars.

When you need to use it, the 2 banks will switch (either automatically or manually) to 8 cells in series. That gives a total voltage of 28.8v which is then connected, through the cigarette lighter socket, to the car battery. Because the voltage of the pack is (considerably) higher than the voltage of the battery the stored energy from the pack will flow into the car battery, charging it.

If it "charges" with 100% efficiency, and transfers all its charge, at the full 15 amps allowed by most sockets then it would dump its full 8Ah of charge into the car battery in about half an hour. In practice there's no such thing as full efficiency, and it won't be able to push all its charge across anyway. But it will still put maybe 2 or 3 Ah of charge into the car over the 15 minutes they suggest.

If the starter draws 100 amps, that (say) 2 Ah that's now in the car battery will be enough to run the starter for about a minute, which will hopefully get you moving.

Note that the figures above are only very wide approximations seeing as I don't have one of these things in front of me to actually measure.

The idea's actually quite sound - it's much the same as giving a quick half hour on a normal home charger just to get going again - but it's only really of use when you've left lights on, the car's been standing a little too long, or something like that and it's still cranking but too sluggish to start.

If the battery's completely flat it's unlikely to provide enough to do anything useful. Also, if you've hammered the battery flat trying to start it then the chance of the minute or so it'll give you being enough to get going is slim!



* In fact, I've jury-rigged the cells from a laptop battery to do just this in the past when I had a flat battery on a campsite in the middle of no-where