John Deere X540 Overcharging Battery??

[Venturabass]

Hi all, I have a 2009 John Deere X540 that I picked up used earlier this year. The machine is in great shape, I'm the second owner, and it only has 250 hours, and I love it.

I've slowly been performing all my maintenance on the tractor and one of the last things I did was check the battery voltage with the tractor running and off just for kicks, and what I found was rather surprising, now I don't know what to think.

I don't know the age of the battery, but I can say it's not the original. With the tractor off and after sitting for 1 week, the battery reads 12.53V. When I start the tractor the battery reads 15.31V. This seemed a little high to me. The other interesting thing is that the voltage stays perfectly constant at 15.31V whether I run the tractor at idle, full speed, and even after running it for 15 minutes at full speed. I checked with 2 different voltage meters with fresh batteries too.

This machine has the Kawasaki FD731V 26hp v-twin liquid cooled motor. I was able to find the service manual on the Kawasaki website. When I went to the section on the voltage regulator it told me the regulator will regulate the voltage between battery voltage (machine off) up to 15V, and that the voltage will increase with engine speed. If not it stated there could be a problem with the regulator.

The manual also showed the procedure for checking whether the regulator was good or not by resistance the voltage off the 6 pins in the harness. Each pin set should be within a certain ohm range, which was anywhere from 1,000ohms to 36,000ohms depending on the pin set. I measured all of them, again with 2 different meters, and the results showed resistance on the order of 1,000,000 ohms???

I'm really confused here, and am worried I have a problem with the regulator. I spoke to my local dealer and they thought the regulator was on its way out, but didn't have a way to test it off the machine? That's weird, as the manual described a simple procedure.

I don't know enough about these types of charging systems, but I'm hoping someone can help guide me on what to do next. Has anyone experienced this? Would someone mind taking a few measurements with their machine off, idle, full throttle? By the way, the battery is a sealed unit and looks like it has vents on the ends, but I don't see any type of fluid leaking from it.

Lastly, without taking voltage measurements, I have no other perceived issues that would cause alert other than that when I engage the mower deck it can nearly stall the tractor. My workaround for that is choking it ever so slightly which greatly improves this, a recommendation from a flow chart John Deere has published on the web. I can't see how an overvoltage issue would have caused this other than as a secondary affect if my PTO clutch has been running hot for quite some time.

Thanks,
Dave

 

[beenthere]

Sounds like something not quite right.
If it were me, and I was at all worried about it, I'd just put on a new regulator. But from what you describe, am thinking I wouldn't do a thing.

The choke-a-bit to help the engine out when engaging the PTO is common, but usually not necessary if the engine is warmed up a bit and usually won't kill the engine if not choked.
I do that on my 425 mostly out of habit.. short burst of extra gas when engaging PTO and cold engine.

 

[Kish318420]

I would also check to see if that model has a battery discharge sensor that is causing the VR to overcharge the battery. Overcharging can boil or cook a battery over time. How long is the unknown.

So ...

1.) check for battery discharge sensor (operational or bad)
2.) pull battery and take and get it checked out - fluid levels, acid %, full test including load testing. If bad replace
3.) recheck VR output

 

[jenkinsph]

I would clean the terminals on the battery first. Make sure the replacement battery is a 500 amp battery that is a match for the original battery specifications.

Check the voltage with the electric pto clutch engaged and engine running. Be careful doing this.

Last, all my Fluke test equipment reads to four digits as you are describing. A simple vom meter would be reading 15 volts not 15.33 would you still be concerned?

 

[Venturabass]

So I went through the machine this weekend. Cleaned the battery terminals, grounds, checked for voltage drops and even added an extra ground cable from the VR directly back to the battery ground location. No change. I also brought the battery into be load tested. The spec is 450 CCA but the battery measured at 572 CCA and the guy said he has never seen that before.

Also got my service manual in the mail and to my suprise JD lists resistance ratings across the VR terminals in the million ohm range while Kawasaki lists only in the 1k-10k ohm range??? Called a couple dealers and they told me theyve never had luck diagnosing a VR in this fashion.

Anyway, it seems clear the battery is being overcharged. The service manual recommends to replace the VR as the next step. I ordered one up so hopefully that fixes the issue.

 

[Zebrafive]

Just curious if your battery was original? Was it marked as John Deere? Did it have a JD P/N? Original will have different P/N than the JD replacement P/N. Original will also NOT have a spot to "peel" out month and year. Somewhere there should be a date code too, such as G9, which = July 2009.

 

[Richard001]

Anyway, it seems clear the battery is being overcharged. The service manual recommends to replace the VR as the next step. I ordered one up so hopefully that fixes the issue.

I disagree. Your battery is not being overcharged. First of all, it it was being over charged, it would be spitting out fluid from the vents. Second, I think your battery is either low on water or just about ready to give up the ghost.

Here is what your battery voltage should be when fully charged:
A fully charged cell at 80 degrees F would show a specific gravity of 1.265. If all six cells are fully charged, an accurate digital voltmeter reading of battery voltage would show 12.68 volts.


You stated that your measured voltage was: the battery reads 12.53V

Your battery voltage is somewhat less than what it should be. The alternator is trying to charge up a battery the is not getting up to full charge, so thus the higher than expected voltage from the regulator.

You might try measuring the charge current. If you have a meter that will go up to about 10amps or more, give it a try.

I don't think you have a problem.

Richard

 

[Venturabass]

The battery in the tractor is not the original, it is a Napa Autoparts battery. I saw the mo/yr peel outs, but they're not peeled out for some reason.

It's a sealed battery so I can't check the specific gravity unfortunately. I just ordered the service manual, I want to say 100% charge voltage was spec'd at 12.56V? Regardless, don't know if I trust that since its not an OEM battery, and it also wasn't 80F out that's for sure.

I can't comment on what state of overcharge the battery should start spewing acid. I don't know. But I feel pretty confident if the charging voltage is over spec, and the load test was 572 CCA vs. 450 CCA, then there's something not right here. VR comes in the mail Saturday, I'll report back!

 

[Venturabass]

I finally solved the overcharging problem. Manual in hand, I went through every system. It wasn't the voltage regulator that I replaced, stator was fine, all ground and continuity in all wires. Then I realized I overlooked something in the manual. The X520 and X540 have a 6 wire voltage regulator, while the X500 and X534 only had a 3 wire. One of the extra wires on my X540 is actually a voltage sensing line to provide battery voltage feedback back to the regulator so it can adjust output voltage accordingly. So when measuring 15.33V at the battery, I was getting 14.48V at the sensing line going back to the the VR.

Following the wiring diagram, power from the battery is sent through connectors, fuse block, and key switch. When the key is on, it sends switched power to the interlock module under the dash, where all the safety switch signal inputs enter. If the key is on, and either the seat switch or brake switch are closed, then the module sends secondary switched power to the fuel solenoid to open. A spliced line off this circuit is then sent to the voltage regulator as the sensing line. I traced the voltage drop back to the voltage leaving the interlock module, so there is about 0.8-0.9 voltage drop between power in and out from the interlock module.

This got me thinking why I couldn't just run a line from the battery directly to the voltage regulator sensing line. I did some more searching on the forums however, and discovered the old John Deere 332, 322, 430, etc had a similar issue where they had a sensing wire from the battery that went through several switches, and with enough voltage drop it tricked the voltage regulator to overcharge the system. John Deere actually put out a service bulletin DTAC #M5927 I believe, where their solution was to wire a simple relay to send switched battery voltage back to the VR through the sensing wire only when the key is switched on. The JD relay kit is $40, but I just bought my own for $10 at the parts store. I wired it up and voila, I now get 14.50V at the battery with the engine running! So basically the VR was overcharging the battery because it was being tripped into thinking the battery was at a lower voltage due to the voltage drop through the sensing line.

The manual says the regulated stator voltage specs are 14.2-14.7VDC, so I'm right in that band now.

Hopefully others may find this post useful.

 

[jenkinsph]

Good follow up.:thumbsup: Learn something everyday here.