high charging voltage??

[Crazy8 55]

I have a C-121 with K301 Kohler engine. I noticed that I am reading just over 17 volts at the battery shortly after starting the engine and running at 3/4 throttle. The battery is nearly brand new and was just fully trickle charged before installing it. Is 17 volts excessively high? I didn't wait and watch it for very long to see if it tapered off any.

 

Thanks

[WHX?? 50,792]

Way too high. You'll trash the battery. Replace the voltage regulator.

[squonk 42,614]

Test it with a multimeter first. Factory gauges are not the most accurate things on the planet.

[Crazy8 55]

Yes I was using my Klein digital multimeter. What should I expect to see at the battery? 14 volts or so? This tractor has the 3 terminal rectifier in it.

[Crazy8 55]

The service manual calls for 13.5 volts charging voltage at the battery.

[kpinnc 13,834]

Let me add this: 16 or so volts is not too high after something like a longer cranking session, but it should dribble back down to 13 or so within a few minutes. Your rectifier should respond to the load placed on it, and the overall condition of the charging circuit will definitely affect it. Even a brand new battery can have high resistance or a bad cell. Of course if it does I would return it. 

 

 

[oldlineman 1,495]

Make sure your rectifier is grounded very well.

[953 nut 58,081]

             If there is high resistance between the regulator/rectifier body and the battery "-" terminal it will try to overcome it by producing a higher voltage.

 

Here is an explanation of the problems that can be caused by corrosion on electrical connections that was provided by @Save Old Iron

 

The  connectors used in this tractor series are in a harsh, corrosive environment caused by vapors from the battery being charged over a few decades.. Vibration causes the connections to loosen - corrosion starts within the metal terminals and a voltage drop develops across the corrosion.

If you have a 10 amp current flowing across a 1 ohm resistance (contact corrosion) the electrical formula to calculate power is current squared times resistance

so 10 amps x 10amps x 1 ohm resistance = 100 watts !!

100 watts of connector heating is the same as laying a 100 watt soldering iron on the connector

[oldlineman 1,495]

Very good Richard, I thought those diagrams looked like Save Old Irons, he was a very knowledgeable member such as you and many others.  Thank you all for sharing your great and variable knowledge, has helped me many times. Bob 

[pacer 3,176]

13 hours ago, kpinnc said:

16 or so volts is not too high after something like a longer cranking session, but it should dribble back down to 13 or so within a few minutes. Your rectifier should respond to the load placed on it, and the overall condition of the charging circuit will definitely affect it. Even a brand new battery can have high resistance or a bad cell. Of course if it does I would return it.

 

I've had a few tractors do this -- on start up show 15-16-17 volts and as I run it, will slowly taper off to the more common 13-14 volts.