DIY 12V DC 70A Petrol Generator

petrol/gas powered car alternator max output of 70Amps.The purpose of this device is to charge or supply additional 12V DC to a battery bank.As when there is a heavy load ,or when there is insufficient current being supplied by solar panels or wind turbine.Or when you want to keep your batteries fully charged during the day and let them discharge at night with no generator noise.

Category:

Howto & Style

Tags:

• 12V
• DC
• generator
• alternator

[ohyrag]

A car alternator is not very efficient as it needs to excite the field, if you get a permanent magnet alternator it saves having to generate power for the field. I am building a similar setup using a Fisher Paykel washing machine motor. You can find the same type of motor in direct drive LG washers also. I also intend to use a regulator to control the engine throttle with a soleniod so as the batteries reach charge the engine will slow down.

[videokfm]

@ohyrag thanks for your info.I will start looking out for a washer motor like that.

[jib1000]

They sell gas generators at the hardware store already guy...

[videokfm]

@jib1000

Here where I live I have only ever seen AC generators not DC generators.

[jib1000]

@videokfm They don't have batteries where you live? Transformers?

[videokfm]

@jib1000 I said that generators here are  AC.I need to charge deep cycle batteries directly off the generator thus it must be DC.Most people just use an AC gen,then power a battery charger to charge the deep cycle battery bank,but this way has too many losses.My next project will most probably have a brushless permanent magnet alternator." They don't have batteries where you live? Transformers?"??

[gooseknack]

Good idea, more efficient than an ac generator and battery charger. Alternator speed versus power output is an interesting one, and I've seen these work quite efficiently with only a 4 inch pulley on the motor and the standard pulley on the alternator. Most alternators are capable of producing close to max amps at between 2500 and 3500 rpm(depends on the car). the trade off with the bigger pulley is lower engine revs, quieter running and less fuel usage, but lower amps.

[gooseknack]

@ohyrag actually, a car alternator is fine for this application, as the staionary motor has enough speed to run an alternator(usually 2 to 3000 rpm at the alternator is fine), it's only the initial start up that's the problem, as you mentioned, it needs to exite the field, once that happens and the alternators turning, it keeps itself going. A pm alternator would be advantages, they can generate a high output at much lower rpm's, not to mention, they need no power to start generating!

[gooseknack]

@jib1000 sometimes a store bought generator just isn't any good for some applications. Believe me, when your living off solar power a generator like this is invaluable, as, if it's setup correctly, is able to rapidly charge a 12 volt battery bank due to the high amp output of the alternator(an hour or 2 rather than a whole day of running). Off the shelf battery chargers and 120/240 volt generators with 12 volt output don't even compare to an alternators amp output!!

[MrMicraphone]

@videokfm LOL they do sell converters .. ; )

[chiefkyle1]

@videokfm Efficiency - Only lazy people think "Just buy an Ac one, use an inefficient inverter, connected to an inefficient battery charger, to charge your batteries." This would be why we waste so much, lazy people.

Great video - great point about why you built this.

[stdavross666]

Hey mate nice video. I have a suggestion to modify your setup with a simple to program micro controller such as a PICAXE etc that would take engine RPM OR throttle position and alternator load as an input to operate a small servo that could automatically adjust engine RPM to the load? Hi from Perth Western Australia. OK back to the beers.