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Re: DIY dc generators discussion !

PostPosted: Tue Mar 21, 2017 12:36 pm
by jaahn
Hi :)
Some more notes on using alternators for charging, that I forgot.
The alternator must be running in the correct direction so the cooling fan works correctly. That is usually clockwise looking at the pulley. This is important as it is running full output if relying on it self controlling the current, and it is important to run it at up around 6000 RPM as that is recommended as a good speed for full output. :idea:

The old Bosch alternators had a reverse direction fan available if you really want one. I have the part number filed somewhere. Putting the alternator beside the motor is a more compact layout ! :o

I guess the reason for making your own charger is really that you hope not to have to use it much ! I would spend any excess money on panels first. Just the occasional use during the rainy bits for the genny, so it seems a waste to spend much hard earned money on something you will keep in the shed. I intend to make another one for that purpose soon. For my 24V battery bank and I have a 12V 120A Bosch alternator put aside and a 5HP Honda also. This time I will use a different excitation I think which will give better control. A PWM DC motor speed control unit. :geek:
Cheers Jaahn

Re: DIY dc generators discussion !

PostPosted: Sat Apr 08, 2017 2:54 pm
by jaahn
Hi, :)
Here is the biggest and best generator. After using the 24V 50A alternator for some time as the main charging system, with only a few solar panels to help, it was decided to do something better, quieter and MORE AMPS to speed up charging. The 2500AHr LA battery bank was from a mine transport vehicle. This is an abreviated summary of the job to give you ideas.

An old early Toyota diesel ute was procured, twin cab with a canopy over the tub, 2.2L 4 cyl diesel in fair condition (been resting for a while :-)). No worries, a clean up, service, oil and filters changed and a good cheap unit. Then an EMF 275Amp DC belt driven welder that had been liberated from a scrap dealer previously and repaired a bit. The 'plan', as it evolved was to put the welder in the back under the canopy, driven by the tailshaft, which was relocated up through a slot cut in the floor etc as necessary. The welder belt pulley was machined and drilled to suit the rear uni joint flange, the tray floor reinforced by some thick ply and holes drilled to get the tailshaft length correct. Being a two piece shaft the center bearing was moved up above the floor inside and bolted in. Mechanicals done !! worked well ! Key start too. Drive method reversible too(30 min) so the vehicle could be driven around the property ?

The cab had a small tacho and hand throttle as standard. I fitted a voltmeter and current meter with a hand made shunt on the output, so the 'driver' could setup the engine revs from the front seat. The welder already had its own controls for the excitation with some big resistors and a rehostat so that was easy enough to get right. These old welders were set up for 32V DC operation also, so were almost made for the job ! That unit would jog along very quiet at 2-2500 revs, full muffler system and an extra muffler, the bonnet up for cooling and all electrics under cover at the rear. Bonus was the use of a good powerful welder as required !!. Great welders these old units !

This setup worked so well using biodiesel the owner decided to fit a 240V AC generator alongside the welder in the back. So a suitable belt pulley size was selected to run that at 1500 RPM with multi B section pulley driven from the welders coupling/pulley. Worked OK and the biodiesel plant could be run + any other stuff, on 240AC while the battery bank charged. I had recommended reduced amps as a continuous rating but my 'mate' did like to run it at max output most of the time ? . So it did that OK for quite some time until accidently running out of fuel while charging and was stalled unattended for "some time", resulting in the welder 'cooking' the armature. :cry: I was astonished !!

So another old welder was found, Lincoln 250A DC tractor pac style. This was fitted in the back with a bit of shuffling and the output fitted with a very large diode(SKN 240/02) rated at 240A, on a big heat sink. Not sure where I sourced those from (still got one). As far as I know that rig is still operational, now used mostly for welding or 240V AC as there have been a lot of solar panels fitted since then.
Cheers Jaahn, :lol:
good luck with your tinkering