Egis Mobile Electric XD Flex L Lithium Battery ACR & Switch

The Egis Mobile Electric XD Flex L is a combined battery management unit built for boats running lithium house banks. It pairs a 500 amp rotary disconnect switch with an automatic charging relay in one compact housing, so you get manual battery isolation and hands-off charge management from a single unit. Rated for 8 to 36 volt DC systems, it drops into 12 volt and 24 volt setups without any fuss.

Here's what the relay side does. When a charging source brings the voltage up, whether that's the alternator, a shore charger, or solar, it ties your banks together so everything tops off. When charging stops, it isolates the banks again so your start battery stays protected and ready. You turn the key, the engine cranks. That's the whole job of an automatic charging relay, and Egis built this one to hold 500 amps continuous with a 1500 amp max cranking rating, so it won't flinch on a hard start.

The Flex L is the lithium-focused version of the XD line. If you've moved your house bank over to LiFePO4, you already know charge handling and isolation matter more than they did with old flooded batteries. This unit manages the handoff between a lithium house bank and a conventional start battery, keeping both charged when power's coming in and cleanly separated when it isn't. Lithium banks can accept a lot of current fast, so having the switch and relay rated to match keeps the whole path honest.

The rotary switch up front gives you a real mechanical disconnect. Twist the knob and the circuit is open, which is exactly what you want when you're working on wiring, leaving the boat for a while, or chasing a problem at the panel. Egis uses stainless steel self-locking hardware on the terminals, and the whole unit is rated from -40 to 221 degrees Fahrenheit. So it takes a hot engine room or a freezing winter layup in stride.

At 3.15 inches long, 2.59 wide, and 1.96 tall, it tucks into tight spaces. Owners running 22 to 26 foot center consoles have had good luck fitting it under the console, though on bigger boats with heavy cable runs you'll want to plan the space around your lugs. And size that cable to the load. For anything pushing toward the 500 amp rating, run heavy gauge cable and proper fusing so your lugs don't overheat. The 6P ATM/DTM connector handles the control-side wiring.

One thing worth knowing up front. This unit has a 1.3 amp off-state current draw, so if you leave the boat on a mooring for weeks at a time, that draw adds up. Plenty of owners wire in a separate main cutoff for long-term storage, or just count on shore power or solar to keep the bank topped. It's not a flaw. It's how an active unit like this works, and it's easy to plan around.

For an install that lasts, hit the terminals with dielectric grease to keep corrosion out, especially if the unit lives anywhere near the bilge. A little anti-seize on the stainless threads doesn't hurt either, since salt air is hard on hardware. Do that, torque your lugs properly, and this becomes a set-it-and-forget-it part of your electrical system. That kind of attention pays off a few seasons down the line, when the boat next to yours has green crust on every terminal and yours still looks clean.

So who's this for? Anglers and cruisers running a lithium house bank who want automatic charging plus a solid manual disconnect without bolting up two separate devices. If you're still on a single flooded battery, it's more switch than you need. But if you've built out a real house bank, the XD Flex L earns its spot on the bulkhead.