Fine if you want to always charge the battery at a certain voltage. But a decent charger will charge at 14.4V then drop to 13.8V float. This requires it to know the battery charging current.
I remember old batteries that would die if you ran them totally flat twice. Nowadays that's more like 50 times.
I guess it depends on the physical position of the main components. In every car I've had (about 10 of various makes), the alternator, starter, and main fusebox are nowhere near each other, so there would be no point in using the same cable for more than one of them. The best idea is to have the shortest run from the battery to each of them, that way you lose less voltage.
I'm quite sure the designer of the car knows what wire was used.
Or a known resistance already in the circuit, like the feed wire.
How much did it cost? Now think of that price being added to a car. And bear in mind it has to be able to report the readings to the ECU.
My Toyota has the *equivalent*.
No wonder companies like Dacia are making cars at half the price, without all that stuff you don't really need. And if they were allowed to not bother with all that safety s*it like airbags, they'd cost even less.
If it's set to 13.8, it won't get above it no matter what battery I connect.
Wrong yet again. I've changed the battery twice. It's consuming power overnight - presumably the alarm - I've actually measured up to 4 amps (randomly, sometimes it consumes nothing) coming off the battery with a meter when all the fuses are pulled. The alarm (to stop theives) cannot be disabled with a fuse. To remove the alarm or replace it involves dismantling pretty much the entire front of the car.
After several false alarms at 3am, I took mine to the dealer and had them disable it. Might have been an hour labor charge.
Probably could have disconnected the battery and pulled the fuses and traced it out with a signal injector but that thought didn't really appeal to me so I threw some money at it.
It might depend on the car, but I was told (either for this one or the Golf I had two cars ago with the same problem) that an entire dashboard dismantling would be needed, a whole day's work for a garage. Although when I had a Ford Mondeo 17 years ago, the AA disabled the alarm (which was preventing me using the car and disturbing the neighbours) by simply cutting (believe it or not) the red wire (!) under the steering wheel.
Sounds more like a wiring fault. An alarm shouldn’t ever take anything like that when its not sounding.
Bet you’d find the fault still there with the alarm disconnected.
Can be a real bugger to find if it’s a pinched wire somewhere if it isnt obvious where a wire can be pinched like at one of the doors etc.
The ADVANTAGE of an alternator is it CAN produce full output at low RPM. (compared to a DC generator)
What an 80 amp alternator has trouble with in many cases is producing that power at low speeds without melting down (due to reduced cooling air flow at low speeds)
But if it's broken....
Surely a physical short like that would just burn out eventually.
When a car is sat stationary, the cooling fan will be on for the engine. This will most likely also cool the alternator. Mine is for example only a foot away from the fan.
There is no fault in an alarm that would produce a result like that.
Nope, 4A isnt enough to do that.
I don't know enough about alarms to disagree, but couldn't it be sounding the alarm without noise as something is broken? It's never tried to prevent me starting the engine though.
I can't see a loose wire doing that. At some point it will either burn itself or a fuse. It's been doing it for 3 years. 4A at 12V is 48 watts, a lot of power. Think how hot a 48W bulb gets.
Nope. It’s the sound that takes the current. It if isnt sounding, there isnt the current.
Yeah, it wont be an alarm fault.
Its not a loose wire, it’s a wire jammed between two pieces of metal with an edge cutting thru the insulation.
Not with 4A it wont.
It cant be a fused line given that you still get the battery flattened with no fuses installed.
That’s with the entire 48W being dissipated in the very small filament. With a pinched wire, that’s mostly going thru the metal of the car body.
How long does the 4A last for ?
If you can somehow rig up something that allows you to see or hear the current draw, or have someone else watch the meter, you may be able to see if it’s a door by doing that and operating the doors.
I've only ever seen it by leaving a multimeter connected with a maximum function running. Car sat perfectly still, it just does it sometimes overnight.
A speaker with a short? If you played your stereo into a shorted speaker, it would consume a fair bit of power.
I would have thought a wire severed as you stated would use more than 4A. Either that or part of it would become hot enough to stop being there and shorting.
Which means it has to be quite a heavy guage wire, so a low amperage seems odd.
Surely most heat would be where the resistance is highest, at the pinch.
It can flatten the (new 50Ah) battery overnight.
Yeah, you really need a proper data logger. Not expensive.
And that would allow you to see which door is the problem too if it is one of the doors pinching a cable as its closed.
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