using an alternator as input source for solar charge controller

[Dr_Zogg]

howdey all,

i have a 140A ford alternator that i have setup with external rectifiers and a home built regulator that has set the output at 60v. (the rotor is driven by a 12v source from the drive engine so that it isn't burt out) . what i am hoping to do is use this as an input into a cheap 60a so called mppt charge controller that i have to use for backup charging on my 48v battery bank. do you guys think this will work, or should you not use this type of dc source as an input?


Cheers,
           Zogg

[oztules]

If I had a alternator set for 60v.... I'd hook it straight to the battery bank... without  question.
I am about to do the same thing very soon.

Better still bring a pot out from the regulator so you can control the voltage auto/manually as well... best of all worlds then.

MPPT is useless in this scenario, and a silicon fix is already in.... in the form of field control via your regulator set up.

my thought anyway.


.............oztules

[Pete]

Hi Dr Zogg, I go along with Oztules on this one, I have a 12 volt system and use an 80 amp alternator with a 5 hp petrol engine as my charger. I bought a 50 ohm 50 watt wirewound potentiometer and use that to control the field current. I don't bother with a regulator, I just turn the amps to around 50 ( which the alternator doesn't even get hot at) and leave it. I check every now and then on the battery charge state.
Seems a waste to me to run an engine with a regulator, once the alternator regulates the engine is just running wasting fuel. Unless of course you used the regulator to switch a relay that turns the motor off when the batteries are charged.

[Dr_Zogg]

the main reason for running the controller is that my batteries are 2 banks of 250ah agm's and i didn't want to risk over charging them. i thought it might be a safer route?


Cheers,
            Zogg

[rossw]

Worth doing, worth over-doing!

How about sensing the charge current and controlling the throttle/governor to use only just as much fuel as required for the power you're delivering? Use the engine itself as the "regulator"

The controls for that could include voltage and timing functions, to taper off the charge and shutdown the engine when done, plus the usual supervisory stuff - oil, temperature etc. And an engine-hours meter to remind you when to change oil. And autostart to make the system as autonomous as possible. And a web interface so you can check it from the comfort of your lounge....

[oztules]

Hmmm....mmmmm.....
My thoughts on this are;
1. I like fla as you can flog them .
2. for agm, I would like to see a smaller alternator ...50 amps

Now you mention the agm's I need to be a lot more careful.
First, I believe that you only use the genny to get to 80% charge, or your wasting energy. The last 20% is not easy to push into the bank fast, so practically, 80-85%  is as far as you might usefully go.... solar for the rest of it, or if you have free fuel.
This stops the over charging anyway.

The alternator by it's design is current regulated.. ie it cant over current in most cases, as the back MMF beats the rotor mmf, and it stabilizes at it's peak.
If you think about this, this is why your car doesn't stall or shred belts when your battery is flat, and the alternator could ... under high rpm on flat battery have massive current... but it does not... the regulator is not the reason, it only see's volts... so it has to be something else, and that something is that the field in the rotor can't get anymore flux into the stator, because the back MMF flux is cancelling most of it out.... ie the stator exhibits equal and opposite field against the rotor flux... that why it is harder for the engine to turn it under high current. When back MMF  stops any more MMF from the rotor getting into the stator, we are in peak current mode, and the alt does not burn out as a rule... only if cooling is blocked etc.

In the case of the 140a unit, it could be that you restrict the rotor voltage to a lower amount to try to keep current down to safer level for agm's... ie this limits the rotor flux that the regulator can drive into the rotor.

Just my thoughts on it.... use a pot to regulate the regulator, as your start up currents for the first few minutes may be very high indeed.

I suspect Ross would actually do what he says too

I am going to use a $180 6.5HP electric start motor, a 50 amp alternator, and my normal regulator circuit with 13v limit on the drive transistor, and a pot for start conditions that are too stiff for the motor...
 I talk about it here: http://www.anotherpower.com/board/index.php/topic,492.0.html
and here: http://www.anotherpower.com/board/index.php/topic,500.0.html


...........oztules

[Dr_Zogg]

i would absolutely love to go with what you say ross but unfortunately i am smart enough to understand how it would work but i lack the intellect to implement it haha 
I was kind of hoping that by hooking it up to the charge controller it would take care of the charging regime and just use the alternator as a current source?

Cheers,
            Zogg

[Dr_Zogg]

oh and regarding having the agm's i was going to go fla but these came up at a price i couldn't refuse. hard to pass up a bargain haha.

Cheers,
           Zogg

[Pete]

Hi Dr Zogg, many years ago a clever friend of mine made his own governor for a car engine that he used as a generator motor.
What he did was use a car fan motor as a tacho generator and then used another fan motor hooked to the throttle of the engine. He used a transistor to turn the throttle motor on and off. What happened was as the tacho generator output rose it turned the transistor off more so the throttle motor had less voltage and therefore less power and vice versa when the motor slowed down. The throttle motor was not turning just working an arm against a spring. It worked great.
You could use your regulator to drive a solenoid or similar throttle motor so that as the batteries charged the motor driving your alternator slowed down. That may be an easier solution.

[Dr_Zogg]

thanks for that Pete it is definitely food for thought especially for another project i have coming up. i want to run a generator head off of a car motor i have so any ideas for a simple governor setup would be appreciated.

Cheers,
            Zogg

[solarnewbee]

Dr_Zogg,

Or you could try this pictured below unless you just want to experiment. It runs on gasoline or LPG. this one is 24v and monitors the battery bank and charges appropriately and auto-starts and stops. $699 plus I got 15% off for ordering from www.12voltgridtiepowerinverters.com just pay all up front and email them (find in your paypal transaction) about the discount and they are forthecoming.



Regards,

SN

[Dr_Zogg]

i have seen those and they look great. but i am trying to kill a few birds with one stone haha. i am wanting to run the alternator, backup generator and 3 phase generator all from the one car engine (only using one generator at a time.) do you guys think the charge controller will accept the alternator input or am i likely to let the smoke out ?

also are there any other ideas out there for rpm control? (keeping in mind that I am coding impaired lol)

Cheers,
           Zogg

[rossw]

i am wanting to run the alternator, backup generator and 3 phase generator all from the one car engine (only using one generator at a time.) do you guys think the charge controller will accept the alternator input or am i likely to let the smoke out ?

I'm not sure it's worth running 3 devices - the overheads of each, and additional run-time, wear on bearings etc, might just outweigh the savings... one properly matched device and rectifiers/converters/whatever might be better in the overall scheme of things.

also are there any other ideas out there for rpm control? (keeping in mind that I am coding impaired lol)

Woodward make some nice electronic governors APECS-4000 being one example; and they drive various linear actuators directly. Here's a couple of pics of part of my car-engine-come-genset





Or a whole bunch more pics here: http://house.albury.net/generator.htm

[Dr_Zogg]

i have seen your setup and it is awesome. do you want to build me one of your controllers 

Cheers,
           Zogg

[rossw]

i have seen your setup and it is awesome. do you want to build me one of your controllers 

12 years on, I certainly wouldn't do it quite the same again now... but there are also plenty of surprisingly inexpensive genset controllers that seem to do much or most of what mine do.

I'd be happy enough to build you one if you really want it though...