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[jereboam]

Ho hum.  My old problem - battery drained itself since Saturday - locked out again.

Fortunately, I've now worked out how to get in - you have to turn the key AND lift the handle to get the boot open.  I fixed up a couple of 6 volt torch batteries which enable me to use the boot lamp to get enough power in to open the doors with the  remote.  And on Saturday, I went to Maplins and bought a jumpstarter thingy.  £25, reduced from £40.  It came more or less fully charged, and I left it on charge overnight, as the instructions suggested.  I really wasn't expecting to ohave to use it so soon .

I got the bonnet open this morning, connected my new yellow monster to it, and nothing whatsoever happened.  Checked the output voltage with both the inbuilt meter and my own meter - well over 12 volts. 

The yellow thing claims to have a "cranking power" of 400 amps.  Given that my car starts first time, every time (battery permitting, that is), I assumed that this would be sufficient.  It clearly isn't, so it's going back.

Anyone know how much "cranking power" is needed?  And how much would I have to pay to get a jumpstarter that delivers sufficient amps?

[Jimbob]

Ive had mixed results with those...

Got one from Aldi couple of years back...basically the same as you have the cheap ones are all made the same and then branded.

Worked once to start a car, despite monthly charges, never managed it again, even when left connected to the car for 1/2 hour before attempting a start.

Quite handy power on a campsite though, with fag lighters, compressor and torch, so not relagated it to the bin....just yet.


There are some good ones at around the £100 mark, but for most of us, they are not worth the investment imho.

[Kevin Wood]

Best way to start a car, if you have 15 minutes to spare and mains power, is to stick a charger on it IMHO.

I have the same Maplin pack and it's not man enough to start a car on its' own although it has got me out of trouble when the battery has been "almost but not quite" up to it.

Kevin

[Entwood]

I've had a Clarkes rather large one for several years .. never used it on my own car .. but have on several others on caravan rallies .. idiots who use the car battery to "top up" the 'van but don't even think they are flattening the car !!

Regardless of use it needs a 3 hour "top-up" charge every 3 months, and a lot of folks don't use them properly .....  the 0v (earth) should NOT be connected directly to the battery but to a good 0V point on the car, and once connected it should be left for about 5 minutes before cranking (10 is better but folks are impatient!). This puts very small amount into the "dead" battery, nowhere near enough to use, but plenty to reduce the internal resistance of the battery, so reducing the load on the booster when you actually start to crank

As in all things, you get what you pay for. This one was around £100 ... not cheap but far better than the £20 "yellow perils" I have seen some folks try to use ... Mine has started several large 4X4 diesels,  the yellow ones didn't even turn them over !!

[jereboam]

I've had a Clarkes rather large one for several years .. never used it on my own car .. but have on several others on caravan rallies .. idiots who use the car battery to "top up" the 'van but don't even think they are flattening the car !!

Regardless of use it needs a 3 hour "top-up" charge every 3 months, and a lot of folks don't use them properly .....  the 0v (earth) should NOT be connected directly to the battery but to a good 0V point on the car, and once connected it should be left for about 5 minutes before cranking (10 is better but folks are impatient!). This puts very small amount into the "dead" battery, nowhere near enough to use, but plenty to reduce the internal resistance of the battery, so reducing the load on the booster when you actually start to crank

As in all things, you get what you pay for. This one was around £100 ... not cheap but far better than the £20 "yellow perils" I have seen some folks try to use ... Mine has started several large 4X4 diesels,  the yellow ones didn't even turn them over !!

The instructions (I always read instructions) said leave it for a minute or two - I did.  And I connected it to a metallic bit of the engine - quite difficult to find, actually.  The battery's on the trickle charger now, and the yellow monster is plugged into the mains. 

I'm still considering taking it back, but I've noted your advice.  I may go and test it with the partially charged battery, but I mainly need the thing for the total battery failure situation, and if it won't cope with that, I don't really have much use for it, as I've resolved never to go camping again as long as I live, and I have no desire whatsoever to acquire a caravan.

And, I'm sure I've asked before, what is a good place to connect the negative side to? 

[Kevin Wood]

I'm still considering taking it back, but I've noted your advice.  I may go and test it with the partially charged battery, but I mainly need the thing for the total battery failure situation, and if it won't cope with that, I don't really have much use for it, as I've resolved never to go camping again as long as I live, and I have no desire whatsoever to acquire a caravan.

If you bought it specifically to start a car, I would be inclined to take it back. You followed the instructions and it didn't work. IME, they aren't really man enough, and I'd be surprised if you could get the promised 400 amps out of one.

I bought it for camping, and it excels at that, but I think there are better solutions for getting your car started, especially if you can get a mains charger to it.

Kevin

[PhilRich]

I've had a Clarkes rather large one for several years .. never used it on my own car .. but have on several others on caravan rallies .. idiots who use the car battery to "top up" the 'van but don't even think they are flattening the car !!

Regardless of use it needs a 3 hour "top-up" charge every 3 months, and a lot of folks don't use them properly .....  the 0v (earth) should NOT be connected directly to the battery but to a good 0V point on the car, and once connected it should be left for about 5 minutes before cranking (10 is better but folks are impatient!). This puts very small amount into the "dead" battery, nowhere near enough to use, but plenty to reduce the internal resistance of the battery, so reducing the load on the booster when you actually start to crank

As in all things, you get what you pay for. This one was around £100 ... not cheap but far better than the £20 "yellow perils" I have seen some folks try to use ... Mine has started several large 4X4 diesels,  the yellow ones didn't even turn them over !!

The instructions (I always read instructions) said leave it for a minute or two - I did.  And I connected it to a metallic bit of the engine - quite difficult to find, actually.  The battery's on the trickle charger now, and the yellow monster is plugged into the mains. 

I'm still considering taking it back, but I've noted your advice.  I may go and test it with the partially charged battery, but I mainly need the thing for the total battery failure situation, and if it won't cope with that, I don't really have much use for it, as I've resolved never to go camping again as long as I live, and I have no desire whatsoever to acquire a caravan.

And, I'm sure I've asked before, what is a good place to connect the negative side to? 

I use the engine lifting bracket on my 2.2 as it's just opposite the battery and so very handy? I'm afraid i'm not sure about the V6 lump as i've never seen one in the flesh so to speak :-/

[TheBoy]

Best way to start a car, if you have 15 minutes to spare and mains power, is to stick a charger on it IMHO.

I have the same Maplin pack and it's not man enough to start a car on its' own although it has got me out of trouble when the battery has been "almost but not quite" up to it.

Kevin

I have a Maplins one - quite old now (had it in Aylesbury, so at least 10yrs old).

It used to do the job of sorting a flat battery fine, but got really abused during the Tractor Engine Swap saga, and is only now used as a high current 12v supply now (as my bench PSU is only good for 2A - not enough to power up a CID).

[tigers_gonads]

i got the halfrauds one 

built in 300 wat inverter
pump for my tyres and airbed
12 volt output to plug in the fag lighter ( beware, its fused .......... don't try and stat the car on it  )
mini strip light and jump leads to start the motor 

had it about 4 years old now and still going strong but abit pricey though
about 80 quid but if you can get hold of a halfrauds trade card, 50 quid ish 

its saved my ars* a few times and starts my v6 from nearly flat without a problem 
but beware, you must have atleast 3 volt in the battery to trigger the in built relay so the jump leads work 

[jereboam]

Best way to start a car, if you have 15 minutes to spare and mains power, is to stick a charger on it IMHO.

I have the same Maplin pack and it's not man enough to start a car on its' own although it has got me out of trouble when the battery has been "almost but not quite" up to it.

Kevin

I've been thinking about this, and I'm confused.  How come it takes 16 hours or whatever to fully charge the battery, but you can get enough juice in to start the car in 15 minutes (or half an hour, which the quickest I've ever tried)?

How many amps does a trickle charger deliver?

[Varche]

I have been thinking of getting one of the yellow perils.

About every two years (summer after using air con a lot) my battery packs up. A neighbour has a yellow peril and it does the trick - no fuss.

[KW]

The yellow thing claims to have a "cranking power" of 400 amps.  Given that my car starts first time, every time (battery permitting, that is), I assumed that this would be sufficient.  It clearly isn't, so it's going back.

Our neighbour bought one of those maplin efforts and it couldn't even start his 1.8 Mondy (which didn't surprise me when I read the specs on it).
As a further test, I connected it to the old lady's 750/4 (Honda), killed the ignition circuit so it couldn't start and went through a standard procedure that most would do when the vehicle doesn't start first time (try 10 secs, let it rest for 10 secs, try again, etc).
The booster was on it's back within 30 seconds, which is quite disappointing considering the bikes own battery will take that sort of abuse for a good 2 minutes.

A CCA of 400 is fine for a matchbox car (although as Kevin said, I don't for one minute believe the cheap ones hit 400 CCA), but certainly nowhere near man enough for anything bigger. You need to start looking at one rated at 600 CCA minimum, and avoid the cheap chinese poor ones that the likes of maplin sell (look around the £100 mark for a booster that actually works).

[Kevin Wood]

I've been thinking about this, and I'm confused.  How come it takes 16 hours or whatever to fully charge the battery, but you can get enough juice in to start the car in 15 minutes (or half an hour, which the quickest I've ever tried)?

How many amps does a trickle charger deliver?

Well, a trickle charger will often be an amp or less, so won't start a car very quickly. I was thinking about your standard mains powered battery charger. About 5-10 amps output on average.

Battery is typically 70 or 80 amp-hours capacity so a 5 amp battery charger will take at least 16 hours to fully charge a flat one (probably double that, as the current will tail off as the battery gets full).

However, if the battery is otherwise in good nick, it doesn't have to be fully charged to start a car.

To start a car you will probably need to deliver a very high initial peak of about 500 amps to get it cranking followed by perhaps 150-200 amps for a couple of seconds before it fires.

So. let's say 500 amps for a second plus 200 amps for 2 seconds. That's 900 amp-seconds. 3600 seconds in an hour so that's 900/3600 = 0.25 amp hours. A 5 amp charger will supply that in a few minutes.

Now, there will be huge inefficiencies in the battery that I haven't taken into account but you can see that it doesn't need a lot of charge to start a car. Just a lot of current for a short period of time.

You need to start looking at one rated at 600 CCA minimum, and avoid the cheap chinese crap ones that the likes of maplin sell (look around the £100 mark for a booster that actually works).

Agreed. I got caught with a flat battery in the Kit Car last year. There was a Honda dealership round the corner just shutting up shop, so I asked if they could help. They gave me a (physically) very small booster pack and said they had no idea when it was last charged but it was the best they could do.

Not expecting a lot I connected it up and it fired up straight away.

The difference was that this was a professional quality pack.

Kevin

[TheBoy]

Look at what car dealers use

Would appear I've been really lucky with my old one, but its now knackered.


Hmmm, decisions, decisions

[jereboam]

I've been thinking about this, and I'm confused.  How come it takes 16 hours or whatever to fully charge the battery, but you can get enough juice in to start the car in 15 minutes (or half an hour, which the quickest I've ever tried)?

How many amps does a trickle charger deliver?

Well, a trickle charger will often be an amp or less, so won't start a car very quickly. I was thinking about your standard mains powered battery charger. About 5-10 amps output on average.

Battery is typically 70 or 80 amp-hours capacity so a 5 amp battery charger will take at least 16 hours to fully charge a flat one (probably double that, as the current will tail off as the battery gets full).

However, if the battery is otherwise in good nick, it doesn't have to be fully charged to start a car.

To start a car you will probably need to deliver a very high initial peak of about 500 amps to get it cranking followed by perhaps 150-200 amps for a couple of seconds before it fires.

So. let's say 500 amps for a second plus 200 amps for 2 seconds. That's 900 amp-seconds. 3600 seconds in an hour so that's 900/3600 = 0.25 amp hours. A 5 amp charger will supply that in a few minutes.

Now, there will be huge inefficiencies in the battery that I haven't taken into account but you can see that it doesn't need a lot of charge to start a car. Just a lot of current for a short period of time.

You need to start looking at one rated at 600 CCA minimum, and avoid the cheap chinese crap ones that the likes of maplin sell (look around the £100 mark for a booster that actually works).

Agreed. I got caught with a flat battery in the Kit Car last year. There was a Honda dealership round the corner just shutting up shop, so I asked if they could help. They gave me a (physically) very small booster pack and said they had no idea when it was last charged but it was the best they could do.

Not expecting a lot I connected it up and it fired up straight away.

The difference was that this was a professional quality pack.

Kevin

All is explained!  I've got what you describe as a standard mains battery charger.  I always thought that it was a trickle charger, supplying 0.25A or thereabouts.  If, as you point out, it's actually delivering >5A, the sums make sense, and I can see why I can start the car after only 15 minutes.