Charging system problem, I think!

[hoghead]

Ok all you mechanics ,or want to be mechanics...I have a woods 3 cyl. diesel mower that I have had to replace the battery in for each of the 2 yrs I've owned it..At idle the battery voltage is about 13.5 volts.at full throttle the voltage is about 14.5 volts.This indicates to me that the altenator is working , but my question is whether the voltage reg, is shutting off the charging cycle when fully charged. Clamp on amp guage on the battery cable reads 3.5 amps all the time. batteries have been dry on both end cells when I checked them.Could it be that the charging system does not quit , and overcharges the battery causing it to boil dry?By the way, this application is a woods 6215 , with a 3cyl. kubota motor. motor model is722e.Maybe kubmech or some other one could give a diagnosis on this problem

 

[skent]

14.5 sounds OK for a 12 volt battery. Check voltage after you are done using tractor (like after an hour or two). As long as it's under 14.75 it should be OK.

 

[Bird]

Hoghead, I'm not familiar with that machine, but it does sound to me like you've figured out the problem; overcharging them. Sounds like you need a regulator to cut back when the battery is fully charged.

 

[jinman]

Hoghead, I agree with you and Bird that the charging system is not regulating the voltage down and you are constantly trying to charge the battery. 3.5 amps is high in my estimation. If you have a clamp-on ammeter, check your car/truck after it has run for awhile and see what kind of current you draw there just for comparison. The fact that you keep boiling cells dry is also a clue. Do you know whether the regulator is internal to the alternator or external? Many times alternator shops or autoparts shops can check alternators and regulators; however, the charging system might not be Kubota. Good luck.

 

[kubmech]

Just a couple of thoughts, most regulators read battery state of charge and respond accordingly. The lower the battery state of charge the more current (amp) output to bring it back up. If the regulator is sensing the battery needs to be "pumped up" then it's going to to do it. Up to a point that the charging system is designed to "shut-off". After you initially start the machine (if you had an amp gauge installed) you would see a pretty solid amount of amperage going to the battery to bring it back up, then gradually taper off to whatever the electrical system requires to keep things running. If your showing a constant 3-3.5 amp draw while it's running I'll take a geuss and say your engine has the fuel solenoid that continuously holds the fuel shut-off in the open position (another clue would be it's a mower and that works better with the operator present saftey system) Another draw to the sytem possibly in your machine would be the electric pto clutch. That's worth about 5 amps (keep in mind if it's drawing more than 5 amps that could be another source of the problem the charging system is working overtime to keep up) An electric pto drawing more than 5 amps is usually do to the windings getting overheated and shorting. Some of the other things I've seen cause this problem are; Battery too small for the system, it may start the machine just fine, but may also overcharge. Another problem I've seen is putting grease, anti-sieze or other similiar product on the terminals then putting the cables on. Now I don't mean just coating the outside when the cables are installed, that's not a problem. I mean coating the posts then installing the cables. I'll look at some specs for you tommorow if I get a chance.

 

[jinman]

Kubmech, your raise some very valid points. All those "accessory" drains would pull current from the alternator, but if the physical connection is not on the battery terminal (like most of our cars/trucks are) reading with a current probe right at the battery should only show charging amps. For example, if the accessories are powered from a connection at the starter solenoid, you could read current at the alternator and current at the battery and the difference would be the accessory drain. At least, I think that's how it works. It's very hard to say without seeing the circuit and your experience may indicate that I may be missing something.

 

[kubmech]

No Jim you're not missing anything, I missed the part in his original post about where he was checking current./w3tcompact/icons/blush.gif Then off I go on a tangent as if he had an amp gauge in the system. Kind of got off track a little. Alot of the older mowers had them in the dash, made troubleshooting a little easier (that is if the darn amp gauge was'nt broke). As far as how it's wired. More than likely the "main power" lead is hooked where the POS battery cable bolts to the starter.
Looked up some specs today, now this does'nt necessarily mean that's what Woods is using, but I bet it's close. I'm counting on the fact that this engine most likely has a "dynamo". That's the little alternator with two ac leads coming out of it (same color). Which requires a seperate voltage regulator (most likely buried so deep under the dash you can't see it, much less get at the wires with a meter). To test the Dynamo, set your meter for ac volts. Disconnect the two leads from the harness and hook both leads up to the wires. Start the engine and run it at full throtle. You should see 20 acv minimum output, most likely it'll
read about 36-45 acv. I doubt you'll find a problem there. Those little dynamos rarely fail. But part of troubleshooting is finding what is'nt the problem, and that's an easy enough check.
Now, normal output from the regulator is 14-15 amps/14-15 volts @ full throttle.
Battery specs for this system are: 45 amp/hour x 6 = 270 cold cranking amps.
So give the battery a good charge, with a battery charger. Start the machine and let it run about 10 minutes at full throttle. Check intitial current output, then compare initial with
what it's putting out after running 10 minutes and see if there is a difference. If it's the same it's a good bet the regulator is at fault.

 

[Keoke]

Hoghead, an amp gauge at the battery would read current going to battery NOT current coming out of alternator. Current coming out of alternator goes first to your loads and what is left, if any, goes to battery to replace starter draw. If your amp meter is correct you are taking care of your loads and pumping 3.5 amps to battery. Word of caution, inductive amp meters are far from accurate. Better to put a series meter in the circuit for accurate measurement. If amps going to battery is to high (3.5 amps constant) put a coil of 14 gauge wire on the DC output lead in series from alt or external rectifier/regulator to lower amps to battery. Make sure coil is downstream from load take off point. You don't want resistance between loads and alt. A couple of amps constant should be enough here. Vary the length (turns) of the coil to get the amps to battery you want. This may be a cheaper way to get the current going to battery under control.
The Europeans and Japanese call alternators dynamo's, the AC can be internal or external rectified to DC. Most small dynamo's use external rectifiers.

george, keoke

 

[hoghead]

"I'll take a geuss and say your engine has the fuel solenoid that continuously holds the fuel shut-off in the open position" !!!
Yes kubmech it does but i didn't think that would draw that much! and yes it does have an external voltage reg and beilieve it or not ,I can get a meter to the output wire on it.That is were I tested voltage at.Voltage at full throttle=14.5volts..Voltage at idle =13.5 volts..I guess i am going to have to put am ammeter "in line"right at the voltage reg output.
I did charge the battery before i did all the tests, and I did check the voltage at the regulator output, and the voltage never drops at the regulator output wire.My friend has the same mower and has the same problem.Dealer says he has not had any other like this but would call Woods to inquire.I would just go ahead and swap the reg, but it is like Kubmech says, diagnosing is what really make a mechanic..My dad was a mechanic for 40 years before his passing and he always taught me not to be a "parts changer" but rather to diagnose the problem.. I owe all the knowlege of mechanics to him because he always made me figure out the problem, before he would come and help!!

 

[hoghead]

and also the pto clutch is disengaged when I was running tests so the only draw should have been the fuel solenoid..No lights or other appliances were on and since this motor does not require voltage for ignition, that should be all that is drawing juice!

 

[Keoke]

Hoghead, it looks like both you and your neighbor are cooking your batteries through overcharging. You probably got a solid state voltage regulator, which means it is non-adjustable. You are down to two choice's. One, go to a larger pulley on alternator, this is not good for loads at idle. Also, this may or may not be practiable due all kinds of reasons. The easy way out is to limit alt current flow to battery but not to elec loads. Do this by inserting resistance downstream from where loads take off the alt to bat current line so that only the current continuing on to the battery goes through this added on resistor. Use a long piece of 14 gauge wire to get the current down from your 3.5a to a more sensible value. Then coil and tape the long wire. Or you can buy a heavy duty reostat (40 watts or better) and vary the current flow down to what you want. A old car heater blower motor switch may work here and would give you a number of different charge rate choices.
If you are using an inductive amp meter (lays on the wire type) to get the 3.5a reading it is probably reading to low.
Try putting in series a 0/10 amp digital meter at the battery terminals to get a true reading of what that alt is pumping into your battery. There is a good chance it my be higher then you think. Most trickle charges run from 1 to 3 amps but even that low amount may boil a small battery dry given enough time.

 

[EdKing]

If you don't have access to a good ammeter, you can put a 0.1 ohm 50 watt resistor in series with the battery terminal, then measure the voltage across the resistor. You should read 100 milivolts per amp of current. This is much more accurate than a clamp on ammeter, especialy at low voltages.

Hope this helps,

Ed King

 

[kubmech]

Hoghead, judging from where you are taking your readings you would be measuring "system current", I have'nt had a need to measure what the solenoid draws but I would'nt be suprised if it pulls 3.5 amps. By the way, initial engagement of that solenoid is pulled during starter engagement (that's why it has 3 wires, in case you were wondering). It needs the extra amperage tapped off of the starter to initially engage.
Now you say "charge" never drops off. Try taking the reading directly off of the battery. Without looking at your wiring diagram, I'm going to say that the lead that comes off of the starter main power lead goes to the ignition switch (B terminal) when the key is switched to the run position battery power runs to the fuel solenoid, (but does not engage the solenoid, hold power only) completes the circuit from the DC output lead from the regulator back to the battery through the ignition switch. Completes the circuit for your lights, up to the light switch (if applicable) and makes power available for the starter solenoid, glow plugs and PTO clutch. Probably gets your hour meter turning as well. (which would be a very minor load, most likely miliamps). So anyway that is how the out put from the regulator (in the case of the Dynamo, rectifier/regulator) gets back to the battery as well as the other components in the system. Now that we've been talking about this a bit, I remember the Bobcat Jaguars with a Mitsubishi deisel had a ballast resistor installed. Now I wonder if Woods left this component out of the system. What do you think George? Have a ballast resistor between the starter lead and the B post of the ignition switch, could solve the problem? That would allow the regulator to take care of the system loads due to path of least resistence and any "overflow" would push past the resistor to get to the battery.

 

[Keoke]

Kubmech, you make some very good points. The current path you mentioned seems logical. I did not realize that this unit had that large an alternator. As you know every voltage regulator has a "sensor" tap or wire take goes directly to the battery to sense battery strength voltage. If this sensor wire to regulator has resistance between it and the battery then the VR will see a lower battery voltage then what really is the true battery voltage. The VR then thinks the battery is weak and sends a higher field current an thus a higher charge rate comes from alt to a battery that does not really need it. We are talking of only tenths of a volt here. Given the battery overcharge we are getting this may bare looking into. Also, resistance in the VR base ground will cause this problem as well. EG: if the VR base has .3v instead of 0v and the alt voltage is 14.3 then the VR unit sees 14.0v as the battery voltage charges higher then it should. Alum VR base to steel grounds are a real pain here. If circuit does not already have one, a 14 gauge wire from alt case to VR case is a good idea if you want the VR unit to see true alt voltage. This is especially true if the VR unit is mounted to the chassis instead of the engine block.
On the ballast resistor between the B+ post and the bat term on ignition sw. Yes, this would cut down current from alt to battery, the down side to that, however, is when engine is off all current coming from battery to sw will endure a voltage drop across the resistor. Once engine starts this wont be a problem. Also, the pull in windings on the starter and fuel solenoids may come short here. If you don't want this voltage drop with engine off a high watt diode in parallel with resistor should take care of the problem. Diode must be forward bias from Bat to ign sw. This will force alt to bat current through resistor (limiting) but bat to sw current will only have a small volatage drop across the diode. The RV people make a good diode for this.
This thing is getting more complicated by the minute.
Bottom line, if the system was desinged correctly and every thing in the system is doing what it is SUPPOSED to do it ought to work as you bought it. However, like you say, these limited production units using components from different manufactures some time don't come together just right. If this is the case, then somone has to tweak it a bit to make it right.

 

[kubmech]

George, if woods is using a kubota regulator the VR case ground should be on it, but that's a good place to check. If it does'nt have one, install one and use shake proof washers to get a good connection. As far as the voltage drop through the resistor to the switch I wonder if it would be significant enough to matter. The fuel sol. pull lead mounts to the motor side of the starter and is not in the "B" circuit so that would'nt be a factor. The starter solenoid only needs 9 volts minimum to actuate so that may not be a factor (even if it was, a small relay hooked in from the B+ cable to the solenoid would take care of that, being that the voltage from the ignition switch could even be lower. But then the diode would do a good job too, and probably cheaper than the relay. But the relay also tackles another problem with machines that have numerous saftey start switches, that starter solenoid power runs through before reaching the sol from the key switch, and over time build up resistence and eventually cause a voltage drop below 9 volts. Rather than replace all the switches the relay takes care of the problem.

<font color=blue>It's fun to tweak</font color=blue>

 

[Keoke]

Kubmech, I hear you on the multiple safety switches wired in series causing big time voltage drops to the starter solenoid. I agree a relay is the way to go here. Chy makes a super relay (OEM Chy starter relay, 60/90's models).
This relay switches low (safety sw provides armature winding gnd) as wired on Chy vehicles. However, it can be wired hi as well and is made to carry 60 amps. It is cheap and easy to get at any auto parts house. Average battery voltage on most starter circuits while cranking is about 10.2 volts. So you can see where it wont take much of a voltage drop to arrive at the starter solenoid with less then 9 volts.
On the overcharging problem. I forgot to mention that hooking the VR sensor wire directly to the alternators dc output terminal, instead of the battery will cause it to read the higher upstream voltage seen there. This would trick the VR into thinking battery is stronger then it actually is. Accordingly, this will lower the charging current amount to battery. With luck, this may be enough to take care of the overcharge condition he seems to be having.

 

[kubmech]

Well George that might be worth a try, however without knowing what regulator he's using, it may be tough to find the lead. Remember were not dealing with a typical alternator here. The Dynamo has two AC leads coming out and hook up to the regulator (and that's all) the regulator then does the rectifiing to DC (most likely a bridge rectifier or possibly a zener diode). So may sense battery state of charge internally, we don't want to let the smoke out of anything here. If the Woods electrical system was designed, say, mostly for an air-cooled gas engine with stator outputs much less than what the dynamo is producing, and they slapped the deisel in and wired it the same, this could be the root of the problem.

Anyway, Hoghead are you still with us? any ideas make any sense to you so far?