For some insane reason, our Airstream came from the factory with a single-stage charger. When connected to shore power (or a generator), the converter provides both 12V DC power to the Airstream, and also charges the house batteries. As a single-stage converter, it has only one mode: charge.

This single charge mode is neither fast nor smart. It takes a few days to charge the house batteries fully, and then will continue applying the charge, causing the flooded cells to boil and the electrolyte liquid to evaporate.

A bit over a year ago, I had replaced our two Group 24 flooded batteries, and in the following year, our lovely single-stage converter had boiled enough liquid out of the batteries to cause a significant decrease in capacity. I set out to resolve the issue, first with a new set of batteries, and then a converter upgrade.

Our Airstream came with a Parallax 7355 power center. The unit has both a converter in the lower section, and AC and DC distribution panels in the upper section. I found a new converter designed to be a drop-in upgrade to the converter portion of the power center. The Progressive Dynamics 55 amp (PD4655V) unit was the right drop in replacement. I found it first over at bestconverter.com, but I couldn’t get them on the phone to ask about shipping time. I ended up ordering the unit from Amazon (Prime Shipable!) and had it shipped to Heather and Jeff (AudreyAirstream) who lived nearby. (Thanks again!)

Installation

I didn’t install the unit till we were in Death Valley, where I pulled out my tools to do the drop in replacement. In hindsight, this was a bad plan. If anything went pear-shaped, the nearest hardware store was quite a drive. Nothing bad happened during the install, and it worked fine.

The back side of the power panel, with screws to loosen to allow slack in the wires.

I used only a screwdriver (with a few assorted tips) and a pair of pliers for the install. The instructions included with the new converter were pretty clear. I removed the old converter, and then moved all the wires from the old DC distribution board to the new DC distribution board. This was the most difficult part, because the old board had the connections on the bottom of the front panel, and the new board had the connections on the top of the distribution panel. Wrangling the huge-gauge wire was a little hard, but manageable.

The only thing I did different from the instructions was pull out the whole power center unit (only a couple of screws) so that I could loosen the clamp around the wires to the battery. With loose wires, I could manipulate them into their new routing path around the top of the board. Getting the new distribution board screwed back into place took some finagling, as I needed to get the wires positioned just right, and the large-gauge wire was difficult to bend.

Done

After finishing the wire connections, I reconnected the battery and started up the generator. It worked! The new converter board has a LED light on it which indicates it’s status. Constant means bulk charging mode, fast blink means trickle charge (last 90%), and a slow blink means float mode.

It is worth noting that the LED is on all the time, even if no AC is connected and no charging is occurring. For the past few weeks, the light has operated as my poor-man’s battery monitor, at least in the higher stages of charging.

So that’s all there is to it! For only $200ish, I have can reduce my generator time and avoid cooking my batteries.