Perfect cruising day: light wind, waves, and current on our stern. We arrived in Kilmarnock VA, took on fuel and ice at Chesapeake Boat Basin. Nice to see them selling diesel for under $5 / gallon. We got fuel here for $3.999999 last spring! Well under the norm both then and now. It’s all self serve here. They have completed construction of their transient docks and transient shower house and laundry. Very nice.

Well, they also have a decent Ships Store that had a few key items that I needed to finish our solar project. They even had AWG 2/0 cable and crimp ends, ANL fuse block and fuses, and other ancillary electrical stuff I needed to finish up this project right! I was very excited.

This final step was to add a DC-DC Charger to keep the main bank charged up when at anchor. The main bank is a traditional flooded lead acid bank of Interstate batteries. The new Victronenergy.com charger didn’t have a “preset” menu option for charging lead acid batteries?!?! Odd! “Consult your battery manufacturer,” is what the manual said to do. So I called and left a voice mail to Interstate seeking that information.

I got a call back from “Jeff” in Engineering at Interstate Batteries. He directed me to use 14.4 VDC for both Bulk and Absorption stages of the charge cycle, with a 6 hour maximum time limit. He further instructed me to use no more than 13.3 VDC for the Float stage. This is very helpful information indeed… which I could not find anywhere online. Thanks Jeff!

This DC-DC Charger is the only connection between the new solar system and the rest of the boat’s electrical system. Two different chemistry battery banks require this type of interconnection (if any) as the optimal charging profile is different enough between the two. Charging and using two different types of batteries will do damage to one bank or both over time.

The reason for us selectively interconnecting the two is because our (lead acid) main bank on the starboard side still has some house loads on it (e.g. anchor light, cabin lights, etc.) These drain the starting battery bank when at anchor. Changing that would require a wholesale rewiring effort to move those loads off the main bank to the LiFePO4 bank on the port side.

So, now we can use this DC-DC charger; the solar system can charge both banks as want… whenever needed.