cheap & dirty way to charge a 12v car battery? charger gone awol....

[Jim K]

is there a method of charging a 12v car battery without using a charger?

(jump leads won't reach, charger gone awol)

Cheers

Jim K

[Tim+]

Move the batteries closer together (removing one from a vehicle if necessary). ;-)

Tim

[Dave Liquorice]

Jump leads implies that there is another car battery just out of reach.

Any sort of reasonable connection between the two batteries will do to charge. Got a suitable length of 2.5 T&E kicking about, make that two lengths and parallel up all the conductors in each and you'll have

6.5mm^2. I'd say that is probably more than the CSA in a set of lightweight jump leads...

Making sound connections to the batteries might be the hard bit if you want to try starting the vehicle with the flat battery rather than just charge it's battery from the other one (will need the donor engine running).

Or take the battery out and move it to within jump lead distance but that means codes and possibly and engine management reset for the donor car unless you have a small 12v SLA to keep the donor car alive via the ciggy socket. You might need to put the ignition switch into the "accessory" position to connect the ciggy socket to the cars 12 V rail.

Personally with the driving powder snow and wind chill between -15 and

-20 C we have faffing about providing a backup and removing batteries is not on. Preparing suitable lenghts of T&E indoors is much better proposition. B-)

[Bob Minchin]

It does rather depend on what you have to hand. A bench power supply set to 14 volts would be my first choice, otherwise why not buy a cheapo charger or a longer set of jump leads.

[ARW]

Something about putting the words "CSA" and "lightweight jump" in the same sentence just does not seem right:-)

[Jim K]

its to start the tractor loader to dig me out so (amongst other things) I can get to the shops to buy a charger without shagging the car too... ;>) feckin snow.

borrowed a (distant) neighbours charger but thanks for the helpful replies

Cheers Jim K

[Jules Richardson]

I've never heard of that before. Which is to say that it's not the case* on anything that I've ever owned, and now that you've mentioned it I'll make sure that it isn't on anything that I may own in the future. That kind of shonky "design" I can do without! :-)

• although if the van's battery goes flat, it has a habit of "rebooting" with the dashboard display in Spanish.

cheers

Jules

[Owain]

In the days of DC mains, you could just use a lightbulb as a dropper.

Owain

[Bill Wright]

You can't really charge a battery from another battery. It works for a while but the recipient battery ends up still pretty well flat. The voltage of the good battery will not overcome the surface charge that builds up on the recipient battery and the current flow ceases. Also, when the voltage difference between a battery being charged and the charging source is almost zero, as in this case, the resistance of the connecting leads becomes very significant. You need around 15V to charge a car battery at a reasonable rate. 11 or 12V will do nothing.

Bill

[polygonum]

You could try tucking the lance under your arm and simply running. But, obviously, a horse is the right way of doing it.

[Dave Liquorice]

Selective quoting. Read the end of the next para:

"Making sound connections to the batteries might be the hard bit if you want to try starting the vehicle with the flat battery rather than just charge it's battery from the other one (will need the donor engine running)."

[Dave Liquorice]

Which bit? The code (for the radio), engine management reset (goes to default settings, needs a 100 miles or so to "relearn" the engine) or using a 12 V SLA via the ciggy socket to keep the car alive.

This side of the pond anything fairly recent (10 years or more...) will suffer the radio code problem and probably the engine management reset. How much you notice the former is variable. I can tell on mine, it feels sluggish (well more so than normal...) you have press the "go" pedal a bit further and even then it doesn't respond as well.

[The Natural Philosopher]

best trick is to pull battery that works out of summat and jump from that. If its fully charged that will get the car started.

can be a pain if it e.g. resets your car computer tho.

I haver a leisure battery in the camper I use for this sort of work..

[meow2222]

any source of current limited 14v would do. They're not fussy, as long as you dont dirty charge frequently

NT

[harry]

Use the telephone line. Used to work in days gone by. Not sure about these days!

[Jethro_uk]

Is that suggesting swapping batteries while the engines running ?

Isn't that a bad idea ?

[The Natural Philosopher]

Yes. It would be, but it was not suggested.

[Jim K]

so buying a charger:-

screwfux have a 4A at £20 & a 6A at £30.

the 4A one is "not recommended for batteries over 50Ah" ?

(my borrowed charger has a "2A trickle charge" setting....)

So is that just marketing bullshit to induce me to buy the more expensive charger? or is there a basis?

Jim K