It all depends if the cars designed to charge at that rate , then the ecu will be matched to the voltage .
You can obtain lamps in several voltages for cars , however anything outside the normal 12/14 volt ones are usally only available from dealers
Ill try and find the article later on today refereing to the vehicles with higher charge or variable charge rates
I'm sure they vary but some use the full 12 volts to fire the injectors etc. The regulated volts are kept for the logic side.
I'd expect all car electronics to be protected up to about 40 volts or so
- the rubbish you get on the supply lines is often this high.
Throw the bloody thing in the bin. Any type of test instrument that gives false readings is worse than not having it at all.
Most ECUs will flag a fault once the voltage goes too high, and most will shut down if it goes above a set limit (about 18V IIRC), in an attempt to protect itself.
Sensors generally run of a regulated 5V source from the ECU, with solenoids running of battery volatge and the ECU switching the earth. Petrol injectors can vary from 5V to ignition voltage, with common rail diesel injectors running at 70V+ generated by the ECU (common rail diesels fail to run with a battery voltage below about 10.5V, as the voltage multpilier circuit won't generate enough voltage below that).
Certainly with a semi decent battery fitted, even with a car alternator that's jammed on full output (they'll only hit about 18volts with a battery still connected), the electronics should be able to withstand it for a short period of time.
We maintain vehicles at work that have a battery management system installed that overrides the alternator regulator to provide a higher charging rate, and they can fail in such away the alternator remains on permanent full output. We've never had any cook any electronics yet, as the batteries or alternator fail first.
Yes. The trip computer on my car did that when the regulator went intermittent causing the alternator to be turned hard on - I'd guess to protect the LED display in the main as these ain't tolerant of overvoltage
- or rather too much current.
ZF autos do much the same - they go into limp home mode if the volts to them are low for any reason. I'd not considered they might use a voltage multiplier - but they well might for the solenoids, etc.
Yes - I saw just over 17 volts. Of course if the battery had high impedance for any reason - failed cell etc - it could go much higher.
My old Rover SD1 has an early EFI system - as well as other electronics. One day while out it wouldn't turn over - seemed to be a failed or sticky starter motor solenoid as the battery was fine. I called out the RAC and was horrified to see him start the car by connecting his slave battery in series with mine - so 24 volts. And nothing got damaged. I'd guess he'd used this trick before. And the car - and my heart survived. ;-)
The works MKII Escort rally cars had this built in!
If they spun on a stage and stalled, they wouldn't crank over enough to restart. If you bumped them, the cam belt jumped a tooth or three.
Ford came up with a solution that had two batteries mounted where the rear seats were, and a system of heavy duty relays to connect the batteries in series when cranking.
Originally, the second battery was not charged, and at every other service they were swapped over. Later, they charged the second battery with a caravan type split-charge unit.
I looked after the electrics on a car run by a national level competitor, and duplicated the system for him.
Chris
I always 24 volted the 12v starters when stock car racing, I never had a starter fail in several years of racing.
With a smell of rotting eggs! Once sniffed never forgotten.
The tolerance on lamp voltage is suprisingly high. Sometimes as much as 25%
With what effect on life?
Chris
Suprisingly little. The main problem with filaments occur when they get too hot they are more liable to shock damage. You can take them up to
18V or more without damage if they are kept still in a jig.
That's not what the manufacturers say!
It's generally accepted that reducing the voltage to a lamp by 5% of nominal will more than double its life.
Although a filament may survive significant over voltage for brief periods, one operated in that way permanently will soon fail.
Chris
Even expensive calibrated Flukes have this problem. Some DVMs tell you the battery is low, and it shouldn't be ignored.
No DVM is going to be 100% accurate. But pretty well all give their tolerance in the handbook. It will vary according to the range.
An easy simple rough check is to buy a new pack of AA *carbon/zinc* cells from the likes of Tesco and check that open circuit on the 2 volt range. It should read 1.6 volts. Alkaline batteries won't be the same and aren't so good for this.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required