Ether,
Are you asking about the charging system in your car? Modern vehicles use an electronic form of battery charging. In older cars, they used stepped resistors to regulate charge current. The alternator output voltage is controlled to provide something higher than the terminal voltage on the battery. Typically some where between 14 and 15 volts. I read a paper a few years ago that stated the vehicle electrical system is one of the most harsh environments encountered in modern electronics. Power supplies vary from 7-8 volts to more than 18 volts and noise and various other transients even higher than that.
Cheap, line operated, automotive chargers simply rectify the output of a transformer and apply that to the battery. Some may have switched resistors to limit charge current. Smart chargers do a whole lot more.
Not exactly. You can get them quite cheap (if you look), and they can handle tremendous amperes of current. They also have large internal head sinks and large fans, meaning that the thermal capacity is even higher!
Power supplies like this are designed for bench use and for embedded controllers that use a standard or single board computer as part of the system. A plastic sign cutter I use has just such a high current computer supply. The 2D system uses stepper motors to drive the cutting head to mass produce things like the door signs you see at the doctor’s office.
I was referring to Doc Wu’s comment about battery chargers:
The DC regulation on many chargers is also poor. They are often puslating, unfiltered DC and could damage sensitive electronics.
And his cautionary warning not to use them on a battery which is installed:
Don’t ever attempt to charge a battery while it’s attached to the robot (or other device.)
… and wondering if that applies to an installed auto battery.
In other words, is the electrical system on most modern autos designed so that charging the battery (with an external smart charger, without disconnecting the battery) will not harm the car’s electrical system?
I’ve heard many opinions about this, but haven’t yet found anything authoritative.
In general there should be no problem. The cheap chargers while having an unfiltered output will be supplying this directly to the battery which will tend to flatten the output waveform to approximately the terminal voltage of the battery plus voltage dropped across the internal resistance and any resistance in the charger clamps. So while the unloaded voltage may exceed 20 volt peaks, the loaded voltage will be lower. The current will spike during charging but the current is going directly into the battery. Even fully charged, the excess current (once the charger voltage exceeds the charged voltage of the battery) is converted to heat in the battery. Remember that the output voltage of the charging system will change with engine RPM while the voltage regulator is trying to compensate while changing alternator field current.
I’m glad to hear that. I’ve been doing it successfully for years and always wondered if I was just cheating the hangman.
In older cars, they used stepped resistors to regulate charge current.
I vaguely remember adjusting the “voltage regulator” in my 68 Camaro in the dead of winter by bending something.
Those regulators required specific distances on the contacts of the relays in the regulator. The relay field coil(s) was part of the charging circuit.