I need to jump start my car; the shop nearby sells jump leads in 120AMP and 400AMP - which should I buy?

Question

Both cars (i.e. the one with the dead and the one with the live battery) are Renault Clios.
Thank you!

Also I know I need to run the car for half an hour or so once it is up and running again; do I need to do this while driving out and about or can I just put my foot on the accelerator while in neutral for 30 minutes to recharge it?

Answer 1

bigger is always better
what ever cables you buy follow these directions
first hook them up with both cars off
now start car with good battery let idle 5 minuets Thain turn off
car now try to start car with dead battery if it starts let idle 2 minuets before removing cables now let car run at least 30 minuets idling is OK driving is better you don't need to sit there pushing the gas
if it didn't start repeat until it does the extra amps you draw from the alternator while trying to start the dead battery car may burn out a alternator
these instructions are so you don't burn out the alternator in the car your jumping with

Answer 2

The 120a would probably be OK but the 400a would be what I would get because they are made from heavier gauge wire and the clamps are a better grade. Also when you jump the car off the battery will recharge either way unless there is a dead cell in the battery or something is wrong with the alternator. Also just because you take the battery to a auto parts store to test and they say the battery is good it may not be the case. I learned the hard way.

Answer 3

For something with a battery as small as this, 120amp jumpers will be more than sufficient. As far as charging, I would drive the vehicle around for a bit, reason is while the engine is running at a higher rmp driving, its going to be turning the alternator at a higher rmp as well giving you a higher steady charge rate versus minimal output while idling. Also after your vehicle has ran for a bit and has a good enough charge to re-start, Check the voltage at the battery, then check it again the next day to see if your cells are holding a charge, if not then the battery might need to be replaced or your alternator might be bad.

Answer 4

The 400 amp are much better at transferring power and I would recommend keeping the cars jumped together for 20 minutes at fast idle...around 1200 rpm..to spread the charging load over two alternators...charging a dead or severely discharged battery with your own alternator can put a severe strain on it and burn it out. Best to buy a portable charger of around 75-100 amp capacity and charge the battery for a few hours.

Answer 5

Personally, I'd buy the 400 AMP ones as you may require them for "jumping" something larger sometime. However, There are batterypacks/ booster packs available that are a combination of a small but powerful battery and a short set of cables attached. See your auto parts dealer. But why not just buy a replacement battery for the dead one?
As for recharging the dead one over 30 minutes, if you're going to use the gas anyway, why not see a little countryside while you do.

Answer 6

If you can afford it get the higher rated leads - 400A.

When the car is started, you dont need to rev the engine to charge the battery, letting it idle will do the trick (the idea of reving the engine comes from when cars had generators and not alternators, the output from the alternator will be the current requirement of the car regardless of the engines speed).

You could do other jobs on the car while you are waiting, perhaps it needs a wash?

Answer 7

120 amp just be enough, on jump leads. You can put a brick on the accelerator for a period of time, such a waste of fuel, much better to do around 30 miles to top up the battery. It would be cheaper in the long run to just buy a new batteries for the cars.

Answer 8

No car battery will deliver 400 amps so 120 would be OK. What is the price difference?
You could buy a battery charger for £15.00 at Argos and do the job properly so long as the batteries are not u/s
RoyS

Answer 9

Go for the heavier one, it'll pass more current without overheating (and be useful in future if you have something with a heavier battery.)

Once it's started just take it for a run to recharge, try and avoid using heavy current users like heated rear window to give the alternator a chance. It should, in fact, charge on tickover, but that's a waste of precious petrol, giving it a run uses the higher revs to help it along. You have checked the water/acid levels in the dead 'un, haven't you?

Answer 10

THE LARGER ONES WOULD BE BETTER BUT RUNNING THE VEHICLE FOR 30 MINUTES OR 30 DAYS WILL NOT COMPLETELY RECHARGE THE BATTERY.

YOU WILL NEED TO PUT THE BATTERY ON A SLOW CHARGER AND THIS WILL TAKE BETWEEN 24 TO 72 HOURS FOR THE BATTERY TO REACH A TOTAL RECHARGE.

IF YOU DO NOT DO THIS YOU WILL LEAVE THE BATTERY UNDERCHARGED AND CAUSE THE ALTERNATOR TO BURN UP.