Lawn mower generator with 12 volt battery and inverter

What to do with an extra lawn mower? Make a generator of course!

I've owned the donor lawn mower since new, and the engine is in excellent shape. I bought a new GM 94 amp alternator, a 2500w continuous /5000w peak inverter which turned out to be a bit oversized for this application, a pulley and a new deep cycle battery.

Since putting it together in 2006, I've used it several times and it works great. I get about an hour of run time per tank with a moderate load, and when it gets too late I can shut the engine off and get about another hour of run time from the battery.

The switch on the left is a N.O. momentary contact switch, the alternator doesn't start making power until you energize the field, that's what this switch does. The switch on the right is the on/off switch for the engine. While the engine is warming up, the speed will hunt around a little, but levels out when warmed up. The governer was set to an engine speed of 3750rpm, which gave the alternator a speed of 3375rpm, I didn't want to set the lawn mower engine speed too high and shorten its life span. Looking at an RPM/output chart for this alternator showed this rpm gave me approximately a 75amp output, which is about 1100 watts at 14.7 volts. That is why the inverter is oversized. I did try running a larger diameter pulley on the lawn mower to spin the alternator faster, but a large enough load would stall the engine.

The alternator brackets are made from an old bed frame, the main deck is two pieces of 3/4" plywood laminated together and coated with deck stain. Overall it was a fun project that has actually been useful!

Category:

Science & Technology

Tags:

• lawnmower
• lawn
• mower
• generator
• generater
• inverter
• 12v
• 12
• volt
• invertor
• alternater
• alternator
• gm
• brigs
• briggs
• stratton
• deep
• cycle
• battery
• engine
• b&s
• tecumseh
• horizontal
• vertical
• shaft
• pulley

[EvendimataE]

is that better than regular generators..or just puting old stuff into good use?

[wegfam]

@EvendimataE

Mostly just putting old stuff to good use and tinkering around for fun.

[mle2763]

HOW MUCH GAS DO THAT USE

[wegfam]

@mle2763 A tank of gas lasts about an hour with a moderate load, but remember lawn mower gas tanks are *much* smaller than the gas tanks on a generator you would buy.

[STARFIRESOLAR]

Why didn't you put a load on it, saw a board or run a TV or something? Just asking....

[wegfam]

@STARFIRESOLAR Just didn't think to do that I guess, that would have been a good idea.

[ne8r]

You say you have a 94 amp alternator and it is probably running around 13.8+ volts, you should be able to draw about 1,300 watts from the alternator - higher from the inverter if you start drawing from the battery. Keep in mind that an automotive alternator will not survive very long at 100% duty cycle. Very nice set up. On my setup I added an orange "trailer type" marker light next to the "alternator" switch to alert me that the alternator is on so I don't run down the battery.

[youroldbuddy1]

That's some sweet shit right there

[empirical008]

I would suggest a larger drive pulley on the mower....equates to more rpm into the alternator, and then higher voltage....I've got a 4"ID drive on my rc lawnmower and I get excellent voltage & wattage...check out my lawnmower videos...

[Townsonbck]

I'm thinking of going with a pma. do you know weather it would give me more power at a low rpm? I know just to create a magnetic field with the alt robs about 40% of the power. I run a coffee maker witch is 900 watts and a toster oven at my camp. Not at the same time but the alt will get hot! At times it even has a funny smell to it! (I know, not good.) Other than that the thing works great! used it many times now!