Charging a car battery

[Bill Wright]

No. Two days at most. You never get 75Ah out of a 75Ah battery.

Bill

[Bill Wright]

Why not start it once a week, give it a good revving then let it tick over for ten minutes? That will stir the battery electrolyte a bit and also keep the engine happy. Move it backwards and forwards a bit so the clutch and brakes don't rust up.

If your only concern is the battery you could follow my method, which is to have the charger powered from a circuit that is only on occasionally. In my case it's the power to an outbuilding, which might be on for half an hour a week.

Bill

[Chris Green]

Which doesn't actually need any power, flash memory retains its contents with no power. Older radios used to use powered memory to retain things but I'm not sure that modern ones do.

[tabbypurr]

Older ones didn't have memories, they had valves. And at least some proudly declared 'transistor' on the front regardless.

NT

[Harry Bloomfield]

F submitted this idea :

If the charger is a modern controlled charger, no problem - just connect and charge despite the warnings. I would not leave it permanently on charge, even though the charger instructions might suggest you can do this. Initially bring it to a fully charged condition, maybe 24 hours, then every month or so repeat. That assumes that your car has no major sources of discharge/faults - It should discharge at less than 50mA-ish, depending on the model and its age.

[Harry Bloomfield]

Huge explained :

At that level of discharge, I would suggest the vehicle has a fault - something is not properly going into sleep mode and the reason needs to be investigated.

[Harry Bloomfield]

charles explained on 08/02/2018 :

Wrong - only the memories and clock are maintained with power off, a matter of uA or a mA or so. My own car which is packed with maintained electronics, satnav, TV and radio plus an alarm system, only draws 20ma when in sleep mode after 1 minute.

[Harry Bloomfield]

on 08/02/2018, Johnny B Good supposed :

You are spot on with that. I have several such batteries and having wrecked a few in the past, by using 13.8v 'maintenance' chargers, my regime now is one of bringing them up to a full charge once every 1 or

2 months. The diodes trick will only work, where the charger will charge irrespective of seeing a voltage across its output.

[Harry Bloomfield]

Dave Plowman (News) laid this down on his screen :

Even an old fashioned transformer, rectifier - raw DC of stated 4amp output is more than capable of wrecking a perfectly good battery, if left on charge. I know, I have done it.

[Harry Bloomfield]

on 08/02/2018, Dave Plowman (News) supposed :

Modern ones, draw micro-amps. All of that wakes up when a signal is received, otherwise asleep for the most part.

[F]

Thanks, all!

I'll clamp the leads on with the battery still connected and put the charger on a timer to top it up for 30 minutes a day.

Sounds like a plan?

As for the rusting brakes issue, it's in the garage, I've left the handbrake off, and I've put a brick behind the rear wheel to stop it moving and jamming the garage door.

The clutch might need to gather a little rust as I expect my soon-to-be-replaced knee won't like exercising the clutch pedal for some times.

[Huge]

Some of them do. Not all.

[Huge]

and ~£70.

My £6 one works just as well.

[Huge]

It's what I used to do before I bought a proper trickle charger.

[dennis]

75ahr at what rate? Low rate discharge usually gets far more energy out of the battery than the 20hr rate and a hell of a lot more than cold starting a diesel engine.

[T i m]

I'd say, if you can't get a timer to turn it on once a week (what car can't be left a week with no issues)?

If you had a DMM I'd just monitor it the first time and watch the voltage (and / or current) to see if both 'flatten out'. If they do then your on time was sufficient.

Good idea.

My kitcar clutch is currently seized on and my std release process is to first start it and get the engine warm then once warm, stop the engine, put it in first and start it again and with the clutch fully depressed then 'kangaroo' it on the throttle ... that usually does it. (If I can't get it to release with the handbrake on and in first, just using the starter motor).

Given it's a cable clutch I was wondering if it should be left with some pressure on the clutch pedal, maybe just enough to get the clutch to separate from the flywheel and pressure plate 'slightly'?

Cheers, T i m

[bert]

But they will still flatten the battery.

[bert]

They're not older, they're ancient:)

[charles]

my Citroen C5 used to warn that the battery was getting low and certain functions would be switched off,

[Archibald Tarquin Blenkinsopp]

Spoken by someone no doubt that thinks a vibrator was something that came from Anne Summers :-)

[Not the best thing for long wave incidentally]

AB