Charging car battery by leaving running idle

gilbert_and_sullivan

No good for this time but grab one of the smart chargers that Lidl or Aldi sell every now and again, usually £13/14.

Don't need to disconnect battery, and can be left on permanently if required, used periodically to fully charge and condtion your battery will ensure a longer battery life, those who run old cars for summer pleasure use them a lot.

pvt

How old is the battery? If it more than 5 years old and you've allowed it to go flat and stay flat for any length of time then it'll be cream crackered anyway, as forgotmyname has already suggested.

Strider590

Nodding_Donkey wrote: »

Get a solar powered trickle charge.

Starter motor draws around 250Amps surge and around 150Amps thereafter until the car starts.

The 4W (about the best at the moment) solar chargers, charge at a rate of 0.3Amps IF they're in good direct sunlight and completely facing the sun.

The performance of those devices does not match up to their hype...........

If you want to use solar to keep a car battery topped up, you need a panel as big as your parcel shelf and a solar charge controller.

Which is probably going to set you back £50 + time to build it and set it up.

Iceweasel

I would take all the guess work away by buying a small cheapo digital volt-meter for around £5.00

If the battery voltage has gone below 10.5v then the battery is into 'deep discharge' and the changes of it ever recovering are pretty slim.

Running the engine will not do much good and as said earlier bump starting is not a good idea with modern cars with loads of electrickery.

If it has a chance of being OK - perhaps only been flat for a short time then get yourself a charger and do the thing properly.

I no longer disconnect batteries to charge them as you can land up will all sorts of things needing to be re-coded and giving all sorts of silly readings on guages etc.

If you do decide to disconnect it make sure you have any radio security code that may be needed.

Good luck.

Strider590

Iceweasel wrote: »

I would take all the guess work away by buying a small cheapo digital volt-meter for around £5.00

If the battery voltage has gone below 10.5v then the battery is into 'deep discharge' and the changes of it ever recovering are pretty slim.

Running the engine will not do much good and as said earlier bump starting is not a good idea with modern cars with loads of electrickery.

If it has a chance of being OK - perhaps only been flat for a short time then get yourself a charger and do the thing properly.

I no longer disconnect batteries to charge them as you can land up will all sorts of things needing to be re-coded and giving all sorts of silly readings on guages etc.

If you do decide to disconnect it make sure you have any radio security code that may be needed.

Good luck.

I get around that with a small 12 SLA battery connected in parallel with the main battery, clip its +/- to the positive terminal and the engine block respectively, disconnect the main battery and you don't need to worry about losing anything as long as you don't try to run any electrics whilst the main battery is off the of car

As a side bonus, because my car stupidly flashes the main beams when you reconnect the battery (causing massive sparks to come off the terminal in your hands), having the small 12v battery connected will stop this happening...... Everyone's a winner!

Good idea to use a small value current limiting resistor though (2ohms will do), just to stop the small battery rapidly discharging into the main.

arcon5

The battery has generally been run down moving car from drive to garage and visa versa. I also turned the headlights on to light up my car when doing work to it on the drive one dull evening. It finally run out last night when it was switched to position 2 so I could read the fault codes on it.

Anyway, bearing in mind the comments made here, i've today bought a charger from Wilkinsons, called "12v 4A(RMS) Battery Charger"... on charge now - in fact has been on charge for over 2 hours now!!

How long you think this should take?

arcon5

I've taken the charger off the battery and my voltmeter is showing 12.8. Still is pretty much what you'd expect a battery to be right? The charger itself still shows as charging - but it can't be far from charged now, right?

arcon5

Thanks everyone, just put the battery back in the car and it starts exactly as it should

Iceweasel

Good - I like a happy ending. :j

I think that several folks, me included, were concerned that the battery had perhaps gone flat through sitting idle for several weeks or months and would possibly have reached a stage where no comeback was possible.

If you check the voltage with the engine running and find that it's around 14.2volts then I would think that all will be well.

However - a couple of hours may well have been enough to get the car started, but it's far from fully charged - I would give it a further 3 or 4 hours on charge or you may have difficulties tomorrow.

pvt

Strider590 wrote: »

The 4W (about the best at the moment) solar chargers, charge at a rate of 0.3Amps IF they're in good direct sunlight and completely facing the sun.

The performance of those devices does not match up to their hype...........

A solar charger is not intended as a device to charge a flat battery. It is a device that will keep a charged battery from self-discharging, and is ideal for a car that might be left idle for a long time.


Keeping a lead acid battery fully charged will prolong its life very considerably - and one of these cheap solar chargers might well pay for itself by extending a battery's life by a few years.