OT Car batteries going flat.

[NY]

Ah, right. I'd always assumed that if you let the car idle, it would take a

*lot* longer to charge the battery than if the car was being driven and the engine was averaging a higher speed.

For a typical car, how long must the engine (and therefore the alternator) be run to put back the charge taken by the starter motor. That's assuming that the engine starts first time and that the oil isn't so cold that it's significantly more viscous than usual.

Is there a table of battery terminal voltage versus proportion of charge in the battery, so someone can determine whether they need to top up the battery without actually trying (and maybe failing) to start the engine?

What is the current (scuse the totally unintentional pun) advice on using a second car to jump start a car with a dead battery? I know that the main rule is to make the last contact as the negative lead to a part of the car some distance from the battery, and not onto the battery's negative pole, so that the spark doesn't ignite any hydrogen that is given off from the dead battery. But is it advised nowadays than the "donor" car should have its engine running or that it should be turned off? I tend to have my engine running at a normal driving speed (1500-2000 rpm) when I'm giving someone a jump start, but I never know whether that's the right thing to do.

The last time I had to jump start a vehicle was when we were moving house. The removal van (a Luton-sized van) had been left with its hazard lights on all the time the guys were loading up, because it was parked half on the kerb and was a hazard to oncoming traffic. And after a few hours of this, the battery would not start the van. Even with my engine running fast, I heard the revs drop and saw my courtesy light dim when the van tried to start, so my alternator was obviously having to work hard, even with the reserve of charge in my battery. I prefer not to remember that day, because it was the house removal from hell - never use one of these online AnyVan companies; always use a local company who can come beforehand to size up the job. And make sure they are competent to load and unload the furniture without damaging it. And make sure if there *is* any damage, that you make a claim immediately - we both had flu immediately after and by the time I was well enough to make a claim, it was too late. I had thought that filling in the delivery note with a statement "damage has occurred to several bookcases, but it will take time to assess and photograph *all* the instances of it" on the driver's form was enough as a "foot in the door".

[bert]

In article [e-mail]>, Marland [e-mail]> writes

Section 6 Para 2 (a). essential upkeep, maintenance and functioning of the household. (Reasons for leaving where you live)

[bert]

In article [e-mail]>, "Dave Plowman (News)" [e-mail]> writes

Just scan mine onto computer in a folder called Receipts :-)

[T i m]

<snip>

Yes, but it can vary quite a bit with temperature and the actual battery capacity etc.

From

I think the issue there is that you are trying to start the car from your cars alternator, not your or the batteries or you simply charging their battery. I would hook the two together, run the charging vehicle for a while (5 mins, seems like a lifetime when you are doing it), then switch off mine and try to start theirs.

Cheers, T i m

[tabbypurr]

No. Why are you fond of asking dumb questions?

Nonsense. Look at the Meanwell MTTF, it's not low end consumer junk.

NT

[tabbypurr]

Filament lamps change efficacy & thus output a lot with even small voltage changes. LEDs are generally regulated, meaning near zero change in light output.

NT

[tabbypurr]

Look up voltage versus charge tables for lead acid batteries

right action but wrong reason. H2 is only produced during overcharging, and dissipates fast. You're not going to get it off a dead car battery IRL.

if not running it won't charge the dead battery. Starting via the jump lead resistance generally doesn't work.

something else was wrong then. It should have run those all day.

NT

[Brian Gaff (Sofa 2)]

Does anyone know why we use the term going flat? It confuses people who are learning English. After all its not like its a pumped up device, the physical size does not change.

Brian

[harry]

Well it ticks so I suppose its mechanical.

[harry]

You can get some idea of the charge of a lead acid battery by putting a heavy load on it and measuring the voltage. But the open circuit voltage gives no clue.

[ARW]

That's what I sometimes do.

But no need for the extra revs IMHO.

[Harry Bloomfield, Esq.]

harry was thinking very hard :

Probably similar to the analogue clock in my car - a quartz oscillator, output to a divider, dividing down to one pulse output every 5 seconds, which then powers a tiny solenoid to move the hands.

Monitoring the battery discharge, I can see the 5 second impulse of an extra couple of milliamps. I can also see what I imagine must be the security system, drawing a brief pulse of 10mA of current every 15 or so seconds.

[Harry Bloomfield, Esq.]

on 04/04/2020, Brian Gaff (Sofa 2) supposed :

The charge, voltage disappears, goes down / flat. The pressure in a tyre is lost, so the tyre goes flat.

[Harry Bloomfield, Esq.]

It happens that Harry Bloomfield, Esq. formulated :

Someone who dies, 'flat lines'.

[Robin]

It's Shakespeare, innit? From Cymbeline:

"be it but to fortify her judgment, which else an easy battery might lay flat"

[Dave Plowman (News)]

HID even better. Running on high voltage, the battery volts make no difference at all - until too low to provide enough current.

[Dave Plowman (News)]

Many modern alternators will charge the battery at maximum even at idle. If you have other things on like lights, heater defroster etc. that will divert some of the available output away from battery charging at low revs. Most alternators have plenty reserve capacity at normal revs these days no matter the load, though. Unlike once.

[Dave Plowman (News)]

Have Lidl etc accepted this?

I just stuff the ones I want to keep into a paper folder. Despite having loads of Lidl power tools etc, never needed to claim down the line.

Did buy a graphics tablet ages ago which was useless and just got my money back.

[Dave Plowman (News)]

And that is a similar battery charger?

[Dave Plowman (News)]

Think it is a Kienzle. Plenty other makers used them too, before the days of quartz units. Very decent timepiece, but the winding fault not unknown, even when it seems to function OK. But your battery draining could be lots of other reasons.