Hi,
I recently performed this on my 92 Previa and thought it would be a helpful write up.
Part one: How to Bypass Alternator with a Switch
Part two: Add a Solar Array for Trickle Charging
The first part of this project was to replace the existing starting battery with a deep cycle battery. I decided to go ahead with this project now because my starting battery was dying anyways, and because of that, it is a fairly cheap mod. Some people use 2 batteries though. I will try one for now, due to my short commutes and other tricks up my sleeve.
The next step is to turn the alternator on and off.
Listen up, this is very important! You can not simply disconnect the alternator from the battery. The alternator will continue to output power and will blow up.
“Automotive alternators require a voltage regulator which operates by modulating the small
field current in order to produce a constant voltage at the battery terminals.” – Wikipedia
So, by disrupting the
Field Circuit, we stop power output even thought the alternator is still spinning. And, because the field in no longer complete, there is no resistance that the alternator has to over come via the engine.
I confirmed that I had the correct wire (B/O) by running the van and checking the voltage at the battery. It was only 12.5 , so I knew the alternator was not producing and charge. Had it been charging the multimeter would have read ~14.5 volts. The engine ran smoother also.
Next, I installed:
- ran the wire for the dash switch
- spliced into the field circuit wire and connected it to the relay
This finishes the alternator control circuit. I can keep tabs on the battery with a volt meter. I also posted an image of a relay diagram that I found.
I will post the solar installation when the parts come.
I hope this helps some one.
