Blade engagement drains battery

P

pasbon

Forum Newbie
I have a 61" Scag Cheetah II with 38hp Kawasaki. I am having trouble with draining battery. With engine running at 1/2 throttle, output to battery is 13.5 volts. When I engage blades, I can get about 3.5 hours of mowing and machine goes into limp mode with battery light flashing and voltage low. I have changed battery due to load testing, and it showed bad. New battery does the same thing. If I shut off blades engine levels out, and after running with blades off, can turn them on again and will cut for a while then go into limp mode again with low battery flashing. The check engine light is not on but the dash lights for the pto, brakes, neutral, and seat usually stay lit. Any help will be appreciated. Thanks.
 
I hope you are not trying to mow at half throttle. Limiting rpm also will limit how much the charging system can produce.
 
Sounds like a partially shorted PTO clutch. Also it draws the same at half speed as it does at full speed but engine produces less voltage and current.

Check the current draw of the PTO or it resistance. In OHMs it be at least 1.7 ohms; preferable above 2.5 ohms.
 
No, I cut at full throttle, sitting still from idle to 1/2 throttle the voltage goes from 12 to 13.5. I have too much grass to cut at anything less than full throttle.
 
Is that voltage with blade engaged or not? Check it both ways. Check the resistance of the PTO clutch, as StarTech said.
 
Or clutch is drawing too much power. Comparing voltage between clutch engaged and not engaged would tell us something, as would the resistance of the clutch.
 
Douglas Lee said:
I'm thinking charging system not working!
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Charging system working. It just that PTO clutch is pulling more amps then charging system can provide so the battery is supplying the additional current thus draining the battery.

I have seen partially short to draw over 16 amps and still work; although, it is cooking the wiring. I even had one to just draw enough over current in 30 minutes that when the engine was shut down there wasn't enough battery capacity to even start the engine.
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Well thank you people for your help. At least I knew where to start looking. When I got under it and looked, the wiring harness was pulled so tight that it chafed one of the wires slightly and was causing a short. Fixed short and left a little more slack in wiring harness so it is not pulled tight against metal. Ohm'd out clutch while disconnected and it was 2.4 ohms. Now to go get 12 gallons of gas and start cutting again and try it out.
 
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