When a battery is really DEAD

[packardv8]

I've been cutting with riding mowers for more than fifty years. A battery usually lasts two years, seldom more than three. I keep it on a trickle charger, but sometimes, toward the end of its dying season, like now, it gets weak enough to require a jump start. Today, on the Timecutter SS4235, after a jump start, I began mowing. Halfway through the first round, it began to sputter and die. Disengaging the PTO switch the engine would run fine. I checked the wiring, just to be sure, but the workaround was to put the jump start battery and cables between my legs and power the electrics that way.

First time in all the years, the mower charging system didn't have enough output and/or the battery was so dead, it couldn't handle the amp draw from the PTO with the engine at full throttle.

jack vines

 

[Rivets]

Sounds like your charging system is not working. With engine running, at full speed, and no blade engagement, measure voltage across the battery terminals. It should read more than 13 VDC. Less than that I suspect bad voltage regulator or stator.

 

[StarTech]

Also can be a partially shorted PTO clutch. They can as much as 15+ amps and still work. This can overtax the charging system.

 

[packardv8]

NO!! I'd much rather it was just a dead battery.

Actually, thanks for the suggestions. Got to fix what's wrong, even though it cost more.

jack vines

 

[Mark H_NO]

Also can be a partially shorted PTO clutch. They can as much as 15+ amps and still work. This can overtax the charging system.

What should the resistance of the clutch be, or is it specific to engine type?

 

[ILENGINE]

What should the resistance of the clutch be, or is it specific to engine type?

Most are in the range of 2.3-3.3 ohms.

 

[Mark H_NO]

Thanks Ilengine.

So Packard, measure the resistance of the clutch. At 1 ohm, it'll draw over 12 amps, 2 ohms 6 amps, roughly. It depends on the voltage with engine running.

 

[ILENGINE]

Thanks Ilengine.

So Packard, measure the resistance of the clutch. At 1 ohm, it'll draw over 12 amps, 2 ohms 6 amps, roughly. It depends on the voltage with engine running.

2.5-5 amp is roughly the norm.

 

[StarTech]

Why do you think some OEMs actually fuse the PTO circuit with a 7.5 amp fuse on lawnmowers? When the PTO clutch is first turned on there is an inrush of current that settles down to normal. I have dealt with wiring harnesses melted down because there was no fuse which is why I install a fuse during PTO clutch replacements. I rather replace fuses than repair a damage harness. It isn't because I don't have the splices, wire terminals, terminal housings, wire, heat shrink, and of course fuses. But I hate doing that when it was not necessary if a fuse was used. And I have the Pac Conn III fuse holders and terminals so it is easy to add a fuse in a few minutes.

And as mention make sure the battery is charging at a normal rate. Somewhere around 13.8 - 14.5 VDC. Just note that just after starting it take time to reach this level. Even at startup it should above 12 VDC and climbing. Voltage regulators do fail.