Egis Mobile XD Flex 2 Single VSR Battery Switch with Knob

Egis Mobile has been building marine and fleet electrical gear for over 25 years, and the XD Flex 2 Single is a good example of what that experience buys you. It's a single-relay battery management switch that handles the two jobs every dual-battery boat needs done. It keeps your start battery isolated so you always have a crank, and it combines your banks for charging when there's power to share. All in a housing that measures just 3.15 by 2.59 by 1.96 inches.

The heart of it is the VSR setting, short for voltage sensitive relay. Here's how that works. When your engine's charging system brings the battery voltage up past the combine threshold, the relay closes and both banks charge together off the alternator. When you shut down and the voltage drops, it opens back up and separates the banks. So your house loads can't ever pull your start battery flat. You don't touch a thing. It reads the voltage and decides. That's the whole point of an automatic charging relay, and it's the setup we recommend for most boaters running a start bank and a house bank.

But you're not locked into automatic. The rotary knob up top gives you manual control right at the switch. Turn it and you can force the banks together for an emergency parallel start, or lock everything off when the boat's on the hard. The XD Flex 2 is programmable too, so the combine and disconnect behavior can be tuned to how your boat actually charges. Set it once and forget it.

On the numbers, this is a serious relay. 500 amps continuous carry, and 1500 amps of max cranking current for those brief high-draw moments when the starter spins. That's enough to handle the diesels on most cruising boats and a lot of larger outboards. The 8 to 36 volt DC range means it drops into a 12-volt or a 24-volt system without a second thought. And the operating range runs from minus 40 all the way to 105 degrees Celsius, so it'll take a cold northern winter or a hot engine room and keep working.

We see these go into everything from center consoles with a start and a house battery to sailboats that need the house bank charged off the engine but the start battery protected. If you've ever come back to a boat with a dead starter because the stereo and the fridge drained everything overnight, this is the part that prevents that from happening again.

Installation is straightforward for anyone comfortable with battery cabling. The main terminals take your battery lugs, and the smaller tinned control wires run to your sense points and ground. A tip from the field: run the VSR sense leads straight to the battery posts rather than picking up voltage somewhere down a long cable run. That keeps the relay reading true battery voltage and combining at the right moment. The mounting hardware is stainless steel with a self-locking design, which is exactly what you want in a damp bilge. Hit the threads with a little anti-seize on install and they'll come apart clean years later.

One thing we'll be straight about. This relay has a 1.3 amp off-state current draw, which is worth planning around. If the boat sits for weeks at a time without a charger on it, that draw adds up and can pull a bank down. The simple fix is a manual battery disconnect on the house side for long-term storage, or just keep a maintainer plugged in. On a boat that gets used regularly or lives on shore power, it's a non-issue.

Between the automatic VSR protection, the manual override knob, and the heavy current ratings, the XD Flex 2 Single covers the whole job on a two-battery boat. The compact footprint tucks under floorboards and into tight battery boxes where a bigger switch won't go. It's the kind of part you install once and stop thinking about, which is the best thing you can say about any piece of electrical gear.