battery chargers

[tanick]

How long to battery chargers take to charge?? Mine was flat this afternoon when I went to move it out of the garage. I pushed it out while I tidied up then put it on charge and 2 hrs later it started and I drove it back into the garage. Its still on charge - should I turn it off before I go to bed or are modern chargers able to sort themselves out?

[pmjt]

How long to battery chargers take to charge?? Mine was flat this afternoon when I went to move it out of the garage. I pushed it out while I tidied up then put it on charge and 2 hrs later it started and I drove it back into the garage. Its still on charge - should I turn it off before I go to bed or are modern chargers able to sort themselves out?

It depends on the type of charger and the type and condition of the battery

If it's a maintenance type, open the cell water filler caps and just leave it on overnight - if it was flat this should bring it back PROVIDED the electrolyte is just above the elements. If it's too low there's a risk of boiling the battery.

Personally, I always whip the battery out of the car and charge it in a well ventilated space for safety - leaving a sealed battery on charge too long can be dangerous.

P

[hot66]

do you have a local friendly garage? If you do take the car round to them & they will have a fancy battery tester that can tell if the battery is shagged or not.

My batteries went flat earlier in the year, but when I tested them with the battery tested it showed both had come to the end of their life and would never hold a decent charge.

2 new Bosch Silvers and all is now well

[Cortina]

Some sums will give you an idea of max time to recharge.
What AH (Amp Hours) of battery is fitted ? Typically could be a figure of maybe 70. What current is charger pulling - starts high , maybe 5 amps if battery low .. assume average of 3.5 for above example. Divide your AH by current , and you have fig in hours to fully charge from flat. In this case 20 hrs..
Low current is kinder on batteries (3 amps not 10 say) , and current pulled will drop off with time ... closer to full charge , the lower the current - this gives idea of how things are progressing.

[tanick]

Thanks all, I should have been a bot more specific really. Batteries (Bosch silver of course) were new last year and the I flattened the battery by trying to start the car when the king HT lead was knackered. I didn't charge it properly after that so its been a bit touch and go since then. Anyway, I left it all night and the charger was showing is as 80% charged. Got me around all day so no problem. I just wondered really if it was OK to leave on all night.