The methods used in alternators such as the automotive type, was originally this method, using a simple electromechanical regulator that just switched the field to either the supply when below the 14.5 and to common or chassis ground when above the 14.5.I want to build a regulator for my little portable generator. (battery, small engine, alternator) In looking on the internet it looks like they just turn the field on below 14.6 volts and off above 14.6. Is it really that simple?
I used a single power FET for the 240v 200amp Gen, the field was around 20amps.I'm thinking of using FETs because the field current is high (250 amp alternator) so I tried to slow them down a bit,
The peak (worst case) charge current in automotive charging is limited by lots of factors; wiring resistance, alternator winding resistance, magnetic saturation, bettery internal resistance etc etc. Generally they all add up to quite a significant impedance that limits the worst case current.Thanks guys.
The big question I am asking myself is the bang bang (full on / full off) ok? I'm thinking to much probably. The real question is lets say I turn it on because the battery voltage is 12 volts. The alternator will dump full current into the battery. Is that ok? ...
Sorry RB, I must disagree. Automotive electrical has been my life and I rebuilt alternators, starters and generators for a living for quite some time. When a battery is in a low state of charge, the alternator will do everything in it's power do recharge the battery straight away and there is no measurable impedance that will stop it. I have had 105 amp alternators charging at 100 amps on startup with nothing on in the vehicle but the engine. The problem was the battery and it is one of the most misdiagnosed problems in auto electrics. Alternators fail, they get replaced and the battery remains only to take out a new alternator. Of course the alternator must have been bad coming off the shelf, right? Wrong. Anyways, wiring resistance in DC wiring on vehicles is minimum if the circuit is clean. We allow up to 0.3VDC drop from alternator to battery. Hope this clears things up a bit.The peak (worst case) charge current in automotive charging is limited by lots of factors; wiring resistance, alternator winding resistance, magnetic saturation, bettery internal resistance etc etc. Generally they all add up to quite a significant impedance that limits the worst case current.
I'm agreeing with you. A 35A alternator will put approx 35A into a battery worst case. If your 105A alternator was putting 300A into the battery that would be a different matter.Sorry RB, I must disagree. Automotive electrical has been my life and I rebuilt alternators, starters and generators for a living for quite some time. When a battery is in a low state of charge, the alternator will do everything in it's power do recharge the battery straight away and there is no measurable impedance that will stop it. I have had 105 amp alternators charging at 100 amps on startup with nothing on in the vehicle but the engine. The problem was the battery and it is one of the most misdiagnosed problems in auto electrics. Alternators fail, they get replaced and the battery remains only to take out a new alternator. Of course the alternator must have been bad coming off the shelf, right? Wrong. Anyways, wiring resistance in DC wiring on vehicles is minimum if the circuit is clean. We allow up to 0.3VDC drop from alternator to battery. Hope this clears things up a bit.
Sorry RB, I must have misread your post. All goodI'm agreeing with you. A 35A alternator will put approx 35A into a battery worst case. If your 105A alternator was putting 300A into the battery that would be a different matter.
by Jake Hertz
by Duane Benson
by Jake Hertz