I don't know if this will be used on an Arduino project but it's an electronics question.
Is there an easy way to limit amperage to a circuit?
I have an OLD car and the amp gauge is rated to 35 amps. I want to add a bigger alternator that can output 105 amps.
If the car battery goes dead and the car is jump started, the alternator will kick out more than 35 amps.
The way the car is wired, every ounce of juice goes through that amp gauge. Any amp past 35 could release magic smoke from the gauge.
If I split the return from the alternator, it won't blow the gauge but then the gauge barely reads the current.
So, What I'd like to do is limit the maximum amount of juice that can get to the gauge without sacrificing the benefit of the extra output of the alternator.
An amperage limiter that would shunt excess amperage over 30ish amps?
I don't think you have all your facts correct and I don't think you have a need to limit the current in any way. The fact is when you start any car there are hundreds of amps flowing from the battery to the starter motor for a brief period, so I don't think your amp gauge is reading starting motor current, but rather just the alternator output current once the motor is running at normal RPMs at idle or higher.
The fact that you have a new alternator that has a higher output current capacity then the original alternator, does not mean that anything in the car will automatically start drawing more current, load resistance determines actual current that flow not the capacity of the voltage source, the alternator when the motor is running, or the battery when the motor is not running.
The charging regulator should control the current, if its working. Its job is to
protect the battery from overcharging and that will prevent overcurrent.
A working regulator means the battery voltage rises to 13.8V on normal running,
which is the safe upper limit for lead-acid battery. (Any higher and bulbs will start
to burnout). In itself that should limit current to the battery
Do you have a wiring diagram for the vehicle? Or specs of the regulator - probably
good to try and check out its function.
Almost certainly the ammeter does not have 35A going "through" it but is measuring the voltage across a very low resistance shunt. Now, if you are installing something in your car that is going to require 70A of additional current beyond the current alternator's 35A capability, you could possibly start a fire if some conductor designed to carry only 35A suddenly has to carry 105A. In addition, the shunt your ammeter uses to convert voltage to amps could overheat, just like a fuse. The best way is to replace the shunt by one designed for higher amperage.
I assure you all that I have my facts correct. The amp meter gauge will fry if not protected from a 105 amp alternator trying to charge a dead battery.
It's an old car and not the best wiring engineering.. The gauge is protected while cranking the starter with an ignition disconnect.
The current from the alternator goes directly through the gauge and then to the fuse box. Without the gauge the car has no power.
Bittsen:
I assure you all that I have my facts correct. The amp meter gauge will fry if not protected from a 105 amp alternator trying to charge a dead battery.
It's an old car and not the best wiring engineering.. The gauge is protected while cranking the starter with an ignition disconnect.
The current from the alternator goes directly through the gauge and then to the fuse box. Without the gauge the car has no power.
I will see about posting a wiring diagram later.
Well a dead battery can't start the engine so the alternator will never put out any current. Charge the battery with a battery charger and then you can start the car and it won't try to draw 130 amps from the alternator because the battery is no longer a dead battery.
Perchance you missed the part about it being an OLD car. Funny things happen with OLD cars. Sometimes they won't want to start and you have to run the battery pretty low while troubleshooting at the bottom of a mountain. Yes, that happened.
In OLD cars, jumper cables are like spare tires. You don't want to pull out of your driveway without them.