Car battery

[mm0fmf]

The battery charging isn't that complicated TBH not like the advanced cowpiss injection system (AdBlue diesel exhaust NOx reduction). It's mainly software monitoring stuff that is already been measured anyway. You pay to write the software, you pay to test it, you pay to fix bugs. But once written and suitably bug free enough to release on paying customers you only need to recover the development costs and it's then free to fit.

The AdBlue system has lots and expensive components in it. It's why you pay (through the nose) for the extended warranty. The AdBlue fluid is not expensive as mine did 20500 miles before it told me I could start topping up the tank.

[John Walliker]

"When you lift off and the car either coasts (the auto box can drop in neutral) or just is on overrun and / or you brake, then battery charging starts again the energy needed comes from the motion of the car." Something that I am trying to understand from your description is how the battery gets charged from the motion of the car when the auto gearbox is in neutral?

John

[Andy Burns]

On mine (classed as a mild hybrid) the starter motor doubles as the alternator, and runs from the main belt, the dash display only shows the recuperative charging when you're braking or slowing but it hasn't decided to drop into neutral.

[Tim+]

More likely the other way around I would have thought, alternator doubling as a starter (when the engine is warm). I suspect there is still a high torque gear driven starter motor for cold starts.

Tim

[SteveW]

I don't know which cars use them, but some years ago, the combined starter/alternator consisted of coils, electronics and a toothed ring surrounding the toothed flywheel. There were no gears or belts needed at all for starting or charging. This was supposed to be the way that stop-start systems were going, due to the lack of wear on starting frequently.

[Fredxx]

It's to eke out the last vestiges of economy, while still making the car drivable.

If you can shovel power into the battery while slowing down, it's free energy. If the battery is measured as being more than 80% capacity, some systems won't charge on idle.

Alternators running at maximum capacity are notoriously inefficient, so running at lower output, for longer is better, once you've got the battery up to 80%.

[Tim+]

Citroen dynalto? Built into the flywheel IRRC. Seemed like a good idea but seems to have vanished. Not sure it was ever put into production.

Tim

[John Walliker]

All the above comments sound very reasonable, but they don't explain how the battery gets charged "from the motion of the car" when it is in neutral. Unless the "motion" was meant to include angular momentum in the engine and flywheel as distinct from forward motion of the whole vehicle.

John

[Rod Speed]

Bullshit. Its easy to boil off the water in the electrolyte.

More bullshit with an old battery that is near the end of its life. .

That's not what he said.

[Fredxx]

"from the motion" of car does assume you're in gear and above idle. Sorry if that wasn't obvious.

[Fredxx]

No current charging system will apply enough volts, unless in a fault condition, to cause any gassing.

If you boil the electrolyte, something has already gone drastically wrong.

A battery that is no longer capable of starting an engine can still have a modest capacity left.

I'm sure the Pope said something different too.

[chop]

Fark. good reason to avoid frog cars.

[John J]

A small dynamo driven by contact with a tyre? It worked for bicycle lights before hub dynamos took over.

[Rod Speed]

Bullshit.

Bullshit.

But %age charge is not dictated by voltage and time.

You are pathetic.

[The Natural Philosopher]

I get 285bhp out of a 3000 cc diesel.

So no, its nothing special

[Andy Burns]

There was a recall on my combined alternator, apparently some sort of fire risk. Then a tensioner on the belt failed so that was replaced under warranty, immediately after that work the belt started squealing so was replaced too ... ok now fingers crossed.

[Tim Lamb]

Perhaps. Rather a lot more than Ford get out of a similar age Fiesta with the same basic engine (88bhp) though.

>

[John Walliker]

I agree. That is why I was challenging the following assertion:

My interpretation of the quoted text is that energy can be extracted from the motion of the car when the auto box is in neutral. Perhaps that is not what the writer intended to convey?

[Animal]

this is one of the upsides of a firewall in a vehicle. Without one you can suddenly discover when driving happily along that you can no longer breathe.

[Fredxx]

I can't imagine many happily driving along with a raging fire under their battery. I would expect the odd flash from passing traffic?