measuring voltage

[Farm130]

Where is the best place to measure the voltage being generated by the genny as it charges the battery while the tractor is running? I have I 130 with a VR.

 

[Bob]

Well, what's REALLY important is the voltage AT THE BATTERY. You want to keep it fully-charged, and not overcharge it, so voltage at the battery has to be held within a pretty close range.

That's why many newer systems with alternators often have a "voltage sense" lead that runs back to the (+) battery cable, to provide "feedback" to the regulator as to the actual voltage at the battery.

On a system with wire of adequate size, and CLEAN, BRIGHT, and TIGHT connections, the voltage measured at the output of the generator or alternator will be only a small fraction of a Volt higher than the voltage measured across the battery terminals.

So, if you meaure at both places, and see a LARGE voltage drop, it's time to clean up and repair the charging circuit.

 

[Hugh MacKay]

Farm130: I always check voltage at the battery, however I don't think it matters where you attach the volt meter. It's more a case of engine running or not running. When the engine is stopped, you know you have battery voltage, and with engine running if that voltage is not 1-2 volts higher you very likely have charging problems. If the engine running voltage is lower than non running you know you've got charging problems.

 

[Farm130]

Bob - How do I measure the voltage at the generator?

 

[John T]

Farm, Any open unloaded output voltage reading taken direct from a genny dont really tell you all that much which is why I agree 100% with Bob n Hugh below. Its the voltage the genny can supply when coupled up to a load that counts. If a charging system is working properly, battery voltage should rise from 6.3 to 6.5 to around 7 on a 6 volt battery and twice that on a 12 volt. Once the gennys output voltage rises higher then the batterys, the cutout relay should close in whch case (notwithstandign voltage drops) the battery voltage n the gennys would be near the same.

John T

 

[Bob]

From the "A" terminal on the generator to chassis ground.