This new PV current regulator is really a simpler version of the one I've had in service for the last 8 years or so. It's just a big linear series regulator. It's set up now for 0-5V current as control (through an opto-isolator) = 0-16 amps output (limited by the max output of the PV arrays). It uses seven 350V NPN Darlington power transistors (BU323) that are tough buggers designed for automotive ignition systems. It is a "low side" regulator, the PV negative is below the 0V of the 120V battery bank.

So it's really 3 different boards to do the charge regulation;

1. A Battery Regulator board; float, bulk and equalize, temp compensated 12V shunt regulator for each battery (10 total), with shunt current feedback. This lets me charge a large series string but baby each battery individually; that means adding only a gallon of water to the set of 10 every 2nd year. It's designed for AGMs, which I may use for my next battery set depending on prices at the time.

2. PV linear current regulator; just a linear series regulator for the 120V nominal array (120-220VDC). 0-5V in for 0-16 amps current. The previous design did fixed net charge selections of 0.5 amps (float), 2.5 amps (absorption), and max (PV limited to about 5.5 amps). The new BBC (see below) charges with a continuous adjustment of current as the batteries come up to full charge so will charge faster. Much faster with larger PV and AGM batteries; the cheap marine batteries I'm using now have moderate internal resistance and can't really absorb high charge currents as AGMs could.

3. Battery bank charge controller (BBC). This is a 3 year old newer all analog (op amps) design. that computes the real time minimum charge current to keep all the battery shunt regulators just barely regulating without exceeding the 3 amp shunt current limit and automatically transitions from bulk to absorption to float. It does this smoothly despite fast shifts in load or PV charge (sun). It also does the equalize timing.

Other projects in the works- updating my generator- DC charger to a fixed voltage (150VDC) 10 amp design that feeds into the PV regulator. The current design uses a homebuilt motorized variac and adjusts itself via PICaxe controller as the charge current tapers off. Charging is so infrequent that I may simplify this and ignore the minor loss of fuel efficiency of regulating via the PV charge regulator. I only charge about 2-3 hours per winter, total. With the new PV capacity that will lkely be zero.

Lastly, the newer (3 year old) analog battery bank controller board has room for expansion with an added embedded microcontroller. I may add that to continue to be able to use my remote terminals (LCD plus buttons) in the shop and house to monitor and control. I'd use this controller to for my low EMI inverter control and power management like pumping the well or pumping air when sun is available and demanded loads are low.

I'll take some pictures of the new boards on my bench tomorrow.