Originally Posted by
forumsKDC
Hello,
How does one keep a stable voltage to a Dry Cell while the vehicle Voltage Regulator/Charging system fluctuates between 12.8 and 14.8 volts?
One doesn't unless one is willing to spend hundreds of extra dollars for the extra electronics required to accomplish that particular task.
I have a PWM, when the voltage drops, the current drops.
14.8v is about 49 amps
12.8v is about 32 amps
When I start the engine, I get 14.8 volts. Over a period of time, it will fluctuate down to 12.8v. Once it gets down to that level, it stays there.
When you start the engine you pull a very heavy current to the starter, this slightly drains your battery. Your voltage regulator senses this loss of capacity and immediately begins to charge your battery back up at a high rate of charge (14.8v) as your battery gets nearer its proper voltage and state of charge, your voltage regulator tapers the charging voltage to follow the proper charging profile of a lead acid battery, having already completed the bulk charging portion of the task. It stays there at that level after the bulk charging is done to provide electricity for engine and vehicle systems, and to trickle charge your battery to keep it ready for the next time it is called upon to start your engine.
I kill the engine and then quickly start it back up. I get 14.8 volts with 49 amps. The time it takes to go from 14.8 to 12.8 varies. Sometimes 5 minutes, sometimes an hour, and all in between. Thought that head lights being on would the difference. It is vary random. Sometimes it will drop down to 13v, but will recover back up little or a lot. But once it hits 12.8, 12.9, it stays. I have never seen it drop fast.
12.8v - 12.9v indicates a fully charged battery and a healthy electrical system.
Your knowledge would greatly be appreciated.
You're welcome.
Have a Good Day!
