Briggs charging at 16.9 volts

[ripcord]

The battery in my rider has been getting weak and it's due for a change. I charged the battery in it so it would start today so I could use it to pull my garden trailer around the place. Just for grins, I pull my volt meter on it while it was running as I already had it out. I was surprised to see that it was putting out 16.9V at full speed. This was with a tired but fully charged battery. I'm surprised this battery has lasted 5 years if it's been running this way all the time.

Thoughts? Is this common or normal for these? I don't think I've ever tested the voltage on a Briggs before.

 

[andyd]

The battery in my rider has been getting weak and it's due for a change. I charged the battery in it so it would start today so I could use it to pull my garden trailer around the place. Just for grins, I pull my volt meter on it while it was running as I already had it out. I was surprised to see that it was putting out 16.9V at full speed. This was with a tired but fully charged battery. I'm surprised this battery has lasted 5 years if it's been running this way all the time.

Thoughts? Is this common or normal for these? I don't think I've ever tested the voltage on a Briggs before.

 

[Gyro Gearloose]

Check your engine model number to see if it has voltage regulator. Some do. My lawnmower charges at 13-13.5 V depending on engine speed but mine doesn't have a regulator that I can find, just a diode.

 

[ripcord]

Thanks Gyro. I've been reading up on these and just went out to look at the machine. It has a diode on the wire from the stator so it must be the unregulated type of system. The fact that I had just charged the battery is probably why the voltage was so high.

 

[mk378]

The unregulated system is prone to overcharge especially if your use cycle is to start once and mow for a long time. The battery doesn't power anything but the starter-- the headlights run directly on AC from another coil under the flywheel. For better battery life you may want to disconnect the charging system and just charge the battery from the grid after using.

 

[ripcord]

Would it be possible or useful to install a regulator after the diode?

https://www.amazon.com/YEAPHI-794360-Voltage-Regulator-28M700-28Q700/dp/B0B5TSKC8Z

 

[eljefino]

Any other signs of overcharging, like boiling water off the battery?

I wonder if the very weakness of the battery is allowing the dirty power from the charging circuit to show as higher than normal.

Aren't these just pulses when the flywheel passes by/ through the magneto? Maybe your digital voltmeter sees the peaks of the pulses.

I'd try a new battery, briefly. Put an analog voltmeter on it when running.

 

[ripcord]

I checked the cells, all have enough electrolyte and I've never watered this battery, so no obvious signs of over charging. I guess the charging depends on the batteries internal resistance for regulation, like you implied. I have seen old dirt bikes blow the headlight when the battery is disconnected or bad, so I think you're probably right, eljefino. I was reading up on it some more and the stator produces AC current at between 28 and 32 volts and this is 'converted' into DC power with a diode on the charge wire which blocks half of the wave form.

I'll test it again when I've put a new battery in it.

 

[Gyro Gearloose]

No idea if the amazon part would work but it looks to be cheap enough to try. I would put a low amperage fuse on the input wire when testing to keep the magic smoke from escaping out of something expensive if the idea doesn't work.

 

[supton]

I agree, I wonder if the meter is picking up voltage peaks. Still, it’s troubling. The regulator sounds interesting, not sure what it could hurt to try. That or just disconnect the charging bit and keep the battery topped off.

I could see dirt bikes blowing bulbs sans battery, the battery itself can charge quickly, absorbing current peaks, effectively limiting max voltage. Removing it allows that high voltage to exist, which can kill bulbs. In cars it’s a bad idea to remove the battery from a running car, same issue, the system is designed to have this reservoir as part of the control loop. We do a “load dump test” to simulate this issue, and the testing is at 100V for some period of time (our devices are rated for like 24V max!).