I recently picked up one of the Sterling Pro Reg D alternator regulators and will eventually give it a try. Sterling products are, and have been, available in Europe for a number of years. Despite a quirky and somewhat controversial company owner they seem to build some unique products that have a decent rep in Europe.
Sterling Power Products USA
I have long been on a quest for the "ultimate" regulator but have yet to find it. I like the MC-612/614 Balmar's but it's a little quirkier in programing than I would like.
I don't think this Pro Reg D is the "ultimate" either but it has some decent features and benefits at a very fair price. I won't be able to give a full review for a while unless I install it on another boat other than mine, which I may.
Currently I am in the midst of a long term test of my own with a bank of Wal*Mart batteries and a dumb regulated alternator so I want to continue on my path to year five, next year. I will probably monkey around with this unit and then eventually install it on my boat after I am done my little experiment.
Sterling's US distributor is in Elliot, ME and can ship anywhere. Mark, the US distributor, came from Professional Mariner which is now the makers of the ProSport line of battery chargers. The Pro Reg D that I bought runs $181.00...
For those wanting or needing external regulation due to AGM's or Gels, or you just have to have it for your wet cells, due to a low volt output internal regulator such as 13.6 - 13.8V, I think this reg makes a good low cost option to the more expensive Ample Power and Balmar regulators. It comes standard with both alternator and battery temperature sensing something which is an extra option on Balmar & Ample.
Things I like:
Alt & Battery Temp Sensing Standard
Can Be Installed In Engine Spaces (Has Built In Cooling Fan)
Works On 12 & 24V Systems
Works on Positive & Negative Field Alternators
Smart Software & Processor Means Charge Time Parameter is Set Each Time
Has An Optional Remote Control Panel (though it is pricey)
2 Year Warranty = Double Balmar
Simple Dip Switches To Choose Battery Type
Things I don't Like:
Marketing claims are flat out MISLEADING
No Small Engine Mode
No Current Limiting/Amp Manager/Belt Manger (IMPORTANT FEATURE)
8 Screws To Remove Cover = PITA In A Tight Space
Wiring Harness Is Soldered TO PC Board and Not Replaceable
Wet Cell Target Voltage is 14.8 Which Will Use A Lot of Water (you could use other settings)
Can it REALLY be installed in engine spaces?
Manual is HORRIBLE
I don't like the idea of relying on a small computer type fan, in the marine environment, to keep my regulator cool.
If that fan fails, then what?
This is NOT a review of actual performance just an overview of what I see as good and bad about the product without having yet used it. Many people do not yet know these are available in the US so I thought I would let the cat out of the bag so to say..
I have installed a couple of these and then gone straight back to Balmar. The Balmar regs are head and shoulders above these but are also more expensive. While the price is attractive the execution is, IMHO, cobbled and without Amp Manager/Belt Manager it is a deal breaker for many installations that send the alt right into temp limiting thus resulting in very poor performance.. Sterling does make some excellent products I just don't find this one to be it when compared with offerings from other manufacturers.