Charging system problem, I think!

[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?