alternator question

[kiwiwonder]

Not sure where to post this. In this forum or the international one so I posted it in both.
I just got my alternator rebuilt. A 3b 12v alternator from an bj60 in an fj40 with a 3b motor. I was testing the voltage at the battery and at the terminal labled B on the alternator. (I assume where the alternator power goes out to the accessories and eventually the battery. is this correct?) In idle with no accessories going the volts at the battery were about 14.05V and at the b terminal on the alternator 14.2V. It is the same with rpm's higher. When the radio is on, fan on high, and the headlights on high, and the cruiser running higher rpm's (not sure how high as it has no rpm gage) the volts at the battery are 14.05V and at the b terminal on the alternator they are 15.55V. Is this normal. Why the .15v drop between the alternator b terminal and battery in idle and 1.5v drop when rpm's are high.

 

[Poser]

Do The Math!!!

 

[Poser]

P
I E


Anyone?!?!?!?!?!?!?

 

[toddslater]

I think what Poser is trying to say is...run it your fine.

 

[johnnyb_s]

You're still getting 14.05 at the battery in both scenerios, so it appears that the difference comes from the accessories you are running. In order to keep 14.05 at the battery and satisfy the demand of the accessories, the alternator has to put out more volts, which is what you were running at the higher rpms.

 

[kiwiwonder]

I figured that the alternator was putting out exra volts so the battery can get 14.05 volts and the accessories can still run. Is it bad for accessories to get 15.5volts. This did not quite make sence to me as through my logic which could be wrong why can't the alternator put out 14.05 volts at the amps needed to run the accessories and charge the battery. Do you get the voltage drop because of the voltage is running in and then out of each accessory and loses some voltage at each accessory. Does the power go from the alternator to all the accessories and then to the battery. Is this the way it should be or from the alternator to the battery and then from the battery to all the accessories. If it took the second rout alt to bat then bat to accessories then the alternator would always put out 14.05 or so volts but the last accessory in the line would get less than 14.05 volts. would this be bad.

 

[Pin_Head]

All of the accessories are in parallel with the battery, including the alternator.
The voltage drop at high load is due to the increased current output of the alternator and Ohm's law (V=IR). A 1.5 V drop seems a little high. Check the connections between the alternator and the battery, especially the fusible link and where the White wire attaches to the battery + post. !4 V is normal when the engine is running.