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I'm not sure if my battery is getting to many volts while running full throttle


whitey_86's Avatar
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Join Date: Jun 2014
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ME

06-05-14, 02:29 PM   #1  
I'm not sure if my tractor battery is getting to many volts at full throttle

I have a craftsman tractor model 917256571 with a briggs engine model number 42A707-1624-01. Initially I was having a problem with the battery not starting the tractor, but I could jump start it with my truck, and the tractor not starting after the engine got hot. The battery that was in it didn't have enough cca according the the manual so I bought one that is 300 cca. I had read that the valve clearance could also effect starting so I checked them and they are within the range listed on briggs website. Since I had the engine apart I replaced the valve cover, head, and crankcase gaskets since I bought the tractor 2nd hand and didn't know the last time they had been done. I also replaced my ignition coil and my ignition switch(since I broke it). After all of this the issues I was having seem to be resolved.
Now to my current problem? I put a question mark as I do not know much about the electrical system so I'm not sure if I have a problem but I feel like there is one. When I put a meter on the battery terminals with the tractor off I am reading 12.75 dc volts. When I turn the tractor on and go full throttle the volts slowly go up. I mowed for about 15 mins and took a reading, it was 15.80 dc volts, I mowed for another 10 mins or so and took a reading and it seemed to top out at 16.15/16.14 back and forth, I kept the meter on the battery for a few mins to make sure that it didn't climb any higher. When I idled down the throttle the volts started to slowly drop and now that its been sitting off for a while it is down to 12.93.
All of that to ask this, I feel like this is to much voltage for the battery, is this the case and if so what can I do to get it running at a safe level?

 
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cheese's Avatar
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06-05-14, 10:46 PM   #2  
It should be fine. Most times the engine is under a load and I suspect the voltage will run closer to 15 volts. I wouldn't worry about it, sounds like the charging system is in good shape.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
whitey_86's Avatar
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ME

06-06-14, 10:22 AM   #3  
My wife actually found this thread and posted for me, so I have a few more questions. First off I just wanted to say previous info you have posted has been very helpful, the work I have done to this tractor has been bittersweet for sure! I have read that I should be getting from the DC (diode) wire off the stator 3 amps, 18-30 Vdc and maybe 5 Vac at full throttle. I am ACTUALY getting like 9 amps, 14 Vdc and over 18 Vac! Yet at the battery (with the Neg. wire unhooked, putting multimeter connected to neg. wire and pos. terminal) I am getting 12.5 amps at full throttle and 31 or so Vdc. BUT with neg. wire hooked up and putting meter on two terminals of the battery I get 4.5 amps and a slow climb up to 16.1 Vdc. I did check Ohms @ the diode (like you suggested to another person) and that checked out. I have been told that I should not see more then 13-14.5 Vdc at the battery, and I am just scared I might end up destroying a nice (expensive) new battery! One last thing, my tractor does not have a voltage regulator, like others I have seen, how does this system achieve that function? Thanks again for your help!

 
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06-06-14, 05:22 PM   #4  
It doesn't regulate. It produces what it produces and that's it. 16 volts is okay. The amperage it puts out depends on how dead your battery is. It is capable of producing 9 amps or 15 amps, depending on which stator yours came with. The battery won't take more than it needs unless you have enough amperage to force it (40 amps could cook it, but it would take a long time for 9 amps to do any harm, especially at 15 or 16 volts). It's like blowing up a tire. The flatter it is, the faster it will take air. The more it fills up, the slower it takes it until it matches the pressure from your pump, or you stop filling it. You can possibly see up to around 30 volts from the A/C side of the charging system, but that side only runs the headlights and has nothing to do with charging. If you have 16 volts from the D/C leg and the diode checks out to be fine, it should be fine. Are you having some kind of battery issue that is making you concerned with this? Check your battery vents after moving for a while. If it is cooking the battery, you will have some wetness coming from the vents.

Glad you have found some helpful info here, and welcome to the forum!


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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