OT Car batteries going flat.

[Jimk]

Once you've opened the bonnet, closed the bonnet & repeated when you want to hook it up again.... So minutes, not seconds....

[Marland]

Had to happen, heard for the first time in years the unmistakable sound of an engine turning ever slower as the owner optimistically made attempts to start their car. Old couple who have stayed at home for about 3 weeks now , they still don?t intend to go out but decided to start the car only to find the battery had deteriorated further than they allowed for. No problem for them as they have a charger and the car is off road and they can start it anytime without straying off their property though the battery is probably US now. There must be some people who live in flats or cannot get their car parked on street outside where they live who would find connecting a charger difficult . I wonder how the old bill would react if they pulled over someone who was taking their car for a quick run to top the battery up , would they accept that it was an essential thing to do or get heavy handed and issue a fine. It won?t happen to me as our cars are also kept on our property and the missus is still working at a care home so the cars are used but theoretically if it did I think I would ignore the fine amd wait to get into court and argue that a quick 15 min drive would see barring the slim chance of an accident no contact with other people compared with having to get one of the rescue organisations, a garage or a neighbour with jump leads to start the car and then possibly attending somewhere else for a new battery.

GH

[Chris Hogg]

Do you actually have to drive anywhere? Can't you just start it and let it tick over, possibly with you sitting in the driving seat reading a book, listening to a CD, whatever, with your foot lightly pressed on the accelerator to keep the engine revs up slightly? Or perhaps just a brick on the accelerator?

[Brian Gaff (Sofa 2)]

Lets face it you could need to walk to the shops and get run over by somebody on the way. Brian

[harry]

The cure is simple. Isolate the battery when you park up at your home. This what I do & never have a problem. I have replaced the earth strap bolt with a "wing bolt", takes seconds to remove,

[tabbypurr]

You may find the legal system could not care less. You might go out to the car intending to get food, and defeated walk back with the battery so you can go out tomorrow.

NT

[polygonum_on_google]

For us, our nearest supermarket is so close that we probably do not recover the battery juice used starting the car.

Awareness is the answer for many, like us, we just make sure our shopping takes a somewhat circuitous route. Easy enough for many. But if you have not thought about it, then it could be a problem.

I anticipate a large number of replacement batteries will be required over the next few months.

[NY]

The charging current and therefore the rate at which the battery was recharged depends on the alternator speed. At idling speed (eg 900 rpm) it would take a lot longer to recharge the battery than at normal driving speed (eg 2000 rpm) - those are engine rather than alternator speeds. But, yes, a brick on the accelerator would achieve the same result!

[NY]

Plus the time to remember how to reset the radio's security code and to re-add all the stations to the memory...

[charles]

Last week, my car having not been moved for 10 days, I found the battery down to 60%, so I put it on charge. Time, for another go, I suspect. How long before all the oil dries up? Should I run the engine to keep all the lubrication going?

[The Natural Philosopher]

Actually whilst this was true of the old mechanical voltage regulators and dynamos - who remembers the dull flickering if the 'charge warning light' at tickover - once solid state rectifiers and field current limiters were available, the move to far higher output (and brushless) alternators rendered the charge current fairly independent of RPM. Couple that with solid state injection and an engine that would no longer stall at tickover because the alternator was drawing a brake horsepower or three, and a modern car will ram in nearly full charge current at any engine speed.

[The Natural Philosopher]

Perhaps

How

About ten years

Every other year, perhaps

More likely problems are rusting brake disks, seized calipers and a clutch rusted to the flywheel

[Harry Bloomfield, Esq.]

NY explained on 03/04/2020 :

Modern alternators are not quite that bad - at tick over, providing all other loads are turned off such as lights, heater fan etc., a modern alternator will output full voltage at no more than a tick over. Point is, that a car engine will need to run for around 20 minutes, just to replace the discharge from the battery from starting up the engine.

[charles]

Does this apply to a modern engine with an ecu? Whats happens with a radio that's security coded?

[charles]

i won't have the latter - it's an automatic. ;-)

[NY]

When we go on a cruise from Southampton, the car is parked for a week or a fortnight at a hotel near "the sea air" (OK, what sea air there is several miles up Southampton Water!). The first few times I found that the hand brake had started to stick to the disc, and there would be a drumming sound when I applied the footbrake after that. Since then, I've tended to leave the car in gear with the handbrake off.

If a car is left for several/many weeks, it's probably a good idea to start it and run it occasionally, moving it slightly so the brake pads don't adhere and the pressure is on a different part of the tyres, and so make sure the clutch doesn't stick. On the other hand, that will use a little bit of the charge in the battery.

[T i m]

<snip>

<snip>

I think, if you on the public highway (and you might as if on your own property you could probably use a battery charger) then I think you are obliged to be able to control the vehicle.

"Rule 123, Highway Code

The Driver and the Environment. You MUST NOT leave a parked vehicle unattended with the engine running."

You might also get done for idling. ;-)

I have successfully used a solar panel, laid on the dashboard and connected to the battery to keep a car battery topped up. It only needs to offset any parasitic currents applied by alarms and central locking etc, you don't really need to 'charge' anything (although you will be to cover the load at night etc).

As has been mentioned elsewhere, having a means of disconnecting the battery [1] can go a long way to elevating that problem but you would have to have your radio codes and I'm not sure that all modern cars would 'like it' (holding certain dynamic engine management parameters etc).

Cheers, T i m

[1] I have one of those red plastic key type isolators on the kitcar and it will generally restart ok after being left for a good few months.

[T i m]

<snip>

That will generally clean themselves in the first few miles of use.

They shouldn't, if they weren't defective in the first place.

That one I get on the kitcar. Staring it with my foot on the clutch and it in 1st gear normally releases it. [1]

Cheers, T i m

[1] Given it's a cable clutch I had considered leaving the clutch partially operated (a bit of wood between the pedal and seat frame)?

[tabbypurr]

many years

no

NT

[tabbypurr]

the latter I'm sure.

except idle, where it gives less v out resulting in slower recharge. Don't take my word, try the lights against a wall at night, then you'll know what yours is like.