Lawn tractor battery doesn't charge

I have a six-year-old John Deere 145 lawn tractor. The battery seemed to not be holding a charge, so I bought a new battery. This one has the same problem - it holds a charge if I put it on my battery charger, but the battery drains as I drive it.

Appreciate any help.

 

Do you have a voltmeter and have you checked the voltage with the engine running?

 

No, I don't have a voltmeter. Would this be a good one to buy: Shop Amprobe VPC-10 Voltage and Continuity tester at Lowes.com

 

I'm not sure about that one, but it helps if you have a digital read out for the voltage. A lot of them will also check resistance.


They aren't too expensive and come in handy for household, automotive, and lawn/garden stuff.

This is one at Harbor Freight. It's not a high dollar job, but does all the stuff a DIY'er needs. I like it since it does the voltage readings below one volt. That's handy for checking reference voltage on ECU controlled automotive.

http://www.harborfreight.com/media/c...mage_21044.jpg

This one is about $14.00 or you can go into the fifty dollar range for the better ones. Those are more durable for frequent users, but have about the same functions.

 

I think I'd pass on that one a lowes as well. It's very limited as to what it can do. You want an autoranging digital multimeter if you plan on having one you can use without having to learn a lot of things and read easily/

 

Thanks. We have a Harbor Freight here in town, so I'll pick up one of these this week. What do I do then?

 

Check DC voltage at the battery with the engine at full throttle and report it here.

 

OK, I tested the voltage before I mowed today, and it was 12 both with the engine running and without. I mowed for an hour or more, and then when I turned it off it wouldn't start, acting as though the battery were dead. I checked the voltage and it was 12. I put the charger on it, and it started fine after 10 minutes or so.

 

Did it start fine with the charger actually connected while you tried to start it ?

 

The charger was still connected to the battery when I started it.

 

If it only shows 12 with the engine running full throttle, it is not charging. Look on the side of the engine for a red and black wire coming from under the flywheel near the starter. The red one should have a lump in it under a black piece of insulation. Unplug these wires and check the voltage on the red one on the engine side with the engine running full throttle. This is the wire coming from the alternator and it should show 14+ volts.

 

If the battery is always 12 volts then it sounds like it's not connected to machine. Possible bad connection between battery post and clamp. Corrosion ? That's why it started with battery charger. Check voltage at battery clamps and then on battery posts directly. When you put a load on I'll bet the battery voltage stays high and the voltage on the clamps goes down.

 

The tractor has been sitting out in my barn for 24 hours. The voltage is 12 going post to post, and also going from a wiring harness which the 5-inch positive battery cable connects to to the bolt on the chassis which the 18-inch negative battery cable connects to. All of this is without the engine running.

 

Really sounds like a bad charging system, either in a rectifier or alternator, or circuit. You can check a couple of other things, though. Charge the battery, let it sit overnight, then hook it up and see if it starts.

Then after the battery is charged fully, hook up the positive cable only and check for continuity between the negative post and the frame with the negative cable disconnected. If you get a continuity reading, that will tell you if you have some kind of parasite drain on the battery when it's shut off.

I think the point you'll wind up at, though, is the charging system isn't doing its job.

 

Appreciate the help. I won't have a chance to check it out until the weekend. I'll give it a shot then.

 

Well, the tractor sat in the barn through 8 weeks of winter without me touching it, but we had a warm day today. There were 12 volts from pole to pole on the battery, and plenty of charge in to crank and crank until it started.