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A Flat Battery Can Strand You..... What Would You Do ?


Justin Smith
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Has anyone got any advice as to what to do to get the car started if you get an absolutely flat battery ?

My 2006 Focus had a totally flat battery, I think the lights had been left on, but I couldn`t seem to bump start it. The road wasn`t that long but I`m sure every other car I`ve had would have bump started there. I was wondering if all the electronic crap they put on it stops the alternator providing enough current to run the ignition circuit when there`s no charge in the battery ?

Next some kind lady offered to give me a jump start, but when I went round to the boot to get the jump leads out I couldn`t open it ! I couldn`t open the back doors either come to that ! !There`s no separate key switch for either of them and so with no charge in the battery I couldn`t get to the jump leads to get a jump start ! How ridiculous is that..... If it hadn`t been for the fact my shop was just round the corner and I had another set of jump leads there I`d have had to call out the bleedin` AA !

CRAZY

What would you have done ?

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get into the boot by dropping the back seats? lower the drivers/passenger seat low enough to get into the back or squeeze through if you aint a big fella.

get your battery checked out just in case it is faulty.

come to think of it, last time i looked i couldnt access the earth cable due to how the battery is situated so jump starting could have been a big no no. looks like keeping a spare battery is the only way to go!

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Put the seats down and get in boot.

That`d have been "interesting", bearing in mind I couldn`t open the back doors !

The problem is that the jump leads are stored on top of the spare wheel, i.e. under the rear load compartment. Can you get the cover open (i.e. the floor up) with the rear door shut ? I didn`t think I`d be able to hence walking round to my shop to get the spare jump leads

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Buy a booster pack.

I have one and it saved me 3 times in one week until I could get a new battery.

You don't need to connect to the earth strap from the battery, any earthed metal part in the engine bay will suffice.

there is an earth point next to the battery for this situation as you cant see the battery negative post.

you can now get lithium battery packs specifically for this situation that you can keep in the glove box, . just a bit bigger than a large mobile phone, google them , and youtube to see them in action

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Those little lithium batteries will not start a car with a flat battery, they are just about able to boost a fairly full battery. They are about 5 Amp hour max, your battery is 70-80

Don't waste your money on them

If you buy a booster pack. buy the biggest capacity you can afford. I have a Heavy Duty 22 Amp Hour one and it can only just start the wifes 950cc engine that has a 40 Amp hour battery if the battery is totally gone, even that would struggle to start a very flat Focus and if the battery was so dead the doors wont open then there is no way anything short of a huge commercial boost charger or another battery attached to a running engine will work

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Got to admit the lithium one I tried was apparently quite expensive, just checked, it was good though, started dead flat transit no problem, that one not for keeping in the glove box just in case.

So I take that back about buying a cheap one for your car , probably wont work

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What amp hour was it? Lithiums can generate quite a current for a very short time if you short them, not good for a long life though. generally those packs are really just RC race car motor packs wired for 12v rather than 7.2v

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This is the one I have-

http://www.halfords.com/motoring-travel/tools-diy/jump-leads/phaze-4-in-1-jump-starter

Only 17ahc but has saved me time waiting for recovery or begging for a jump start (not good to jump from modern cars anyway).

I have used mine on my car 3 times and also two guys at work and still not needed to recharge it since the initial 24 hour charge I gave it on purchase.

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What amp hour was it? Lithiums can generate quite a current for a very short time if you short them, not good for a long life though. generally those packs are really just RC race car motor packs wired for 12v rather than 7.2v

The ones that can catch fire if you're not too particular how you treat them???

Really don't know if bump starting would ever work on a modern car, recall many moons back that once voltage dropped below a certain level the ECU won't want to play because the operation/behaviour of injectors is related to the voltage supplied. If this gets too low the injection system just says no, don't think the bump starting would get voltage back up enough in such a short time.

Is it also likely that in cases where the battery is totally dead, when you connect up for a jump start the duff battery itself sucks up some of the available current provided from the other car so you're not always guaranteed to get running?

That's assuming you've not kept the jump leads in the boot like 99% of drivers probably do, myself included :rolleyes:

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Yes, if the battery is totally dead you can push/drag the car as much as you like and its not going to do anything. if there is enough charge to unlock the door and power up the dash then it may start, but on a button press start like mine. I suspect you have to press the starter with clutch down to put it in engine run mode.doubt if a single press with clutch up actually puts it in run mode. Of course that will try and run the starter motor which will kill the battery even more

I did flatten mine once by leaving my HUD connected and it didn't power down, didn't even try to start here, just but the battery charger on her and left her overnight to fully charge and run a de-sulphate cycle to try and reverse any damage done

Running a starting lead acid to below about 40% will definitely damage it and at minimum loose some capacity, even deep cycle batteries suffer when under 10%

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I like the battery booster stoney has linked to there.

Im thinking of buying on of these for the car to keep in boot so whats the best sort of spec to look out for in terms of amp/hr ect?

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Tbh, the one I have is a practical size without being too heavy to lug around in the car.

For a high ahc kit in fairness you're looking at the trolley type packs that garages use.

Not particularly practical to have one of those permanently stuck in the boot.

It's a balance of practicality and price over capacity.

Mine is rated as starting cars up to 2.0 but it has been reported to jump bigger blocks without problems.

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ive never felt the need to have a battery pack in the car in 35yrs of driving, probably only ever had flat battery 3-4times in those years and jump leads normally suffice,

just have a decent car battery to start with , and dont be a !Removed! and leave your lights etc on.lol#

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I suspect that a battery booster would be particularly useful if driving in more remote areas, like the Australian outback lol.

On this tiny (overcrowded) island, help is always available a few feet away. :)

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This is the one I have-

http://www.halfords.com/motoring-travel/tools-diy/jump-leads/phaze-4-in-1-jump-starter

Only 17ahc but has saved me time waiting for recovery or begging for a jump start (not good to jump from modern cars anyway).

I have used mine on my car 3 times and also two guys at work and still not needed to recharge it since the initial 24 hour charge I gave it on purchase.

Lead acid batteries should be given a top up charge every 1-2 months even when not used. Also recommended they are charged filly after each use. Otherwise you will significantly reduce it's life span. Doing well to have started 5 cars without it dying though.

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Lead acid batteries should be given a top up charge every 1-2 months even when not used. Also recommended they are charged filly after each use. Otherwise you will significantly reduce it's life span. Doing well to have started 5 cars without it dying though.

I think so too.

To be fair the batteries weren't fully dead but were too weak to spin the starters over.

Instructions do advise recharging after every use but I'm lazy :d.

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I`ve checked and a fairly (heavy duty) jump lead will fit in each of the side compartments in the loading bay. If I put one in each that`s a pair stored where I could hopefully get at them via the back seat.......

Does anyone actually know if you can get the spare wheel cover (= the boot floor) open from the inside with the rear door shut ?

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