3 stage battery charger question

[jcizek]

Hi Folks,
I'm brand new to this forum, but after a couple hours searching for this, didn't find anything matching so decided to post for some input.

I am trying to design/build a 3 stage PIC controlled wet lead/acid battery charger that charges the correct way.  Stage one is wide open, as much voltage and current as the charger can give (typically about 14.5 to 15 volts and am designing for 10 amps) until the battery terminal voltage reaches 14.4 volts. At that point, it switches to "absorption charge" mode where the charger ouput is clamped at 14.4v and current is monitored until it falls below an amp. Then stage 3 fires up and is a voltage and current limited output, with 13.4 volts and no more than an amp of current.

My question is what is the best way to implement stages 2 and 3... 2 is probably easy with a simple voltage regulator capable of handling all the current... but my 2 ideas for stage 3 are either a voltage regulator feeding a buck converter, or maybe an LM317 in voltage regulation configuration feeding another LM317 in current limiting configuration.  Any input for me on wheather either of these ideas are worthy or if there is a better one?  Many thanks ahead of time! -James

 

[indulis]

Go to http://www.ti.com/ and look up UC3906, application notes U-131 & U-104.

 

[jcizek]

Wouldn't ya know it... a single chip that does all...  I had looked at the microhip PTx00 series and the Maxim offerings but neither really fit the bill.  Looks like this ti is the ticket.  Thanks very much for the lead on this!  -James

 

[Kevin Weddle]

Voltage regulators are available for all voltage and current requirements. A typical high power battery charger might have a microcontroller and a voltage regulator. Efficiency is the main concern with high power battery chargers.