Egis Mobile Electric XD Series: The Complete Guide to Their Battery Switches and VSRs

Marine Electrical Technology | In-Depth Review

If you've been shopping for marine battery management hardware in the last few years, you've probably encountered the name Egis Mobile Electric. Founded by a former Blue Sea Systems engineer, Egis has rapidly built a reputation for rethinking what marine battery switches, automatic charging relays (ACRs), and voltage sensing relays (VSRs) can be. Their flagship XD Series is the clearest expression of that philosophy — a modular, highly configurable family of relay-based products designed to replace the bulky, failure-prone legacy hardware that's been standard on boats for decades.

This guide covers the full XD Series battery switch and VSR lineup: what each product does, how the variants differ, and how to think about choosing the right configuration for your system.

The Problem with Traditional Marine Battery Management

Before diving into the products, it's worth understanding what Egis is solving. Traditional marine battery systems — whether a simple dual-bank setup on a center console or a multi-battery arrangement on a liveaboard — have typically relied on combinations of:

Mechanical rotary battery switches (the classic "1 / 2 / Both / Off" knob)
Individual standalone high-amp solenoids wired together with link cables
Separate ACR/VSR units that sense voltage and bridge banks during charging

The problems are well documented among anyone who's done serious marine electrical work. Link cables between relays vibrate loose. Individual solenoid units consume excessive parasitic current in standby. Multiple separate units consume far more mounting space than necessary. And traditional mechanical rotary switches require physical access to the battery compartment — which might be under a hatch, behind a bulkhead, or otherwise inconvenient.

Egis designed the XD Series to address all of these issues simultaneously.

XD Series Platform: What Every Product Shares

Before getting into specific models, it's worth understanding the shared DNA of the entire XD lineup.

Bi-Stable Solenoid Design: Unlike traditional solenoids that require continuous current to stay in the closed (on) position, XD relays use bi-stable solenoids that only draw current during switching events. In the open or closed state, the device holds its position without consuming power. Standby current is an extraordinary 1.2–1.3 mA — low enough that a Group 31 battery would take roughly nine years to discharge from the relay's quiescent draw alone. This is 70–95% less off-state current than comparable competitor products.

IP67/IP6K9K Sealing: Every XD product is sealed to IP67 and IP6K9K standards — fully waterproof and resistant to high-pressure water jets. A Gore-Tex vent regulates internal pressure to prevent moisture intrusion across seals, which is a failure mode that plagues cheaper relay products in marine environments.

Stainless Steel Hardware: Stainless steel cable lug studs with self-locking flanged nuts resist the corrosion and thread damage that chrome-plated copper studs develop in salt air environments.

Dip Switch Configuration: Rather than fixed-function hardware, XD products use dip switches hidden under a protective cover to configure relay behavior. Each position can be set as a remote relay/battery disconnect, a VSR/ACR, or (on capable models) a low voltage disconnect. A configuration guide is printed on the reverse of the dip switch cover.

35–75% Smaller Footprint: Compared to equivalent standalone relay setups, XD modules claim a 35–75% reduction in mounting space and product weight — a genuine advantage in tight engine compartments and helm panels.

Manual Override Knobs: Most XD products feature a bright yellow manual override knob per relay position. The knob provides three states: forced open (locked off), automatic/neutral, and forced closed (locked on). Critically, the knob design makes it visually unambiguous which state the override is in — something that traditional relay products get badly wrong.

Ignition Protection: All XD relays are ignition-protected, meaning they're safe for installation in gasoline-powered boats and other environments where combustible vapors may be present.

LED Status Indicators: Front-facing LEDs indicate relay state locally. Many models include a remote LED output wire, allowing you to replicate the status indicator at a helm panel or dashboard.

Legacy Compatibility: XD Series products with Deutsch DTM connectors are pin-for-pin compatible with Blue Sea Systems ML Series bi-stable relays, making drop-in replacement straightforward for boats already wired to that standard. Wire-for-wire compatibility with Blue Sea ML-solenoid and ML-remote battery switch products is also available on tinned-wire models.

Expandability via Busbars: Optional 8790 and 8791 link bars allow multiple XD modules to be joined side-by-side, sharing power connections and enabling configurations that support three, four, or more battery banks without running extensive additional cabling.

The XD Series Product Families

Egis organizes the XD lineup around three dimensions:

Circuit count — Single, Dual, or Triple relay positions in one housing
Flex variant — Which firmware/voltage profile each relay position is pre-configured for (though all can be reconfigured via dip switches)
Wiring interface — Tinned control wires, or Deutsch DT/DTM connectors

Here's how the family breaks down.

Remote Battery Switches (87 Series)

The simplest XD product is the Remote Battery Switch — a high-amp relay that operates as a remotely controllable on/off disconnect. Think of it as the electronic replacement for the mechanical rotary battery switch: instead of a large physical knob mounted at the batteries, you get a compact solenoid that can be operated from a small switch at the helm, keyswitch, or any remote control input.

Key part numbers:

8710-1500 — Single XD Remote Battery Switch with Knob, Tinned Wires
8720-1390 — Dual XD Flex 2 ACR/Mechanical Switch with Knobs, Tinned Wires
8730-series — Triple XD Remote Battery Switch configurations

Rated at 500A continuous, XD remote battery switches are capable of handling any practical marine load. Remote ON/OFF/Auto control inputs allow forced-open, forced-closed, or automatic-operation modes. These are the right choice when you want to eliminate a physical battery switch at the battery location and replace it with a small dash-mounted toggle.

Flex 2 — VSR/Relay (Standard AGM/Lead-Acid)

The Flex 2 designation indicates factory default voltage settings optimized for lead-acid and AGM battery chemistries. This is the most common variant and covers the majority of existing marine installations.

Each relay position is pre-configured via dip switches but can be reconfigured to operate as:

A simple remote relay / battery disconnect
A Voltage Sensing Relay (VSR) / Automatic Charging Relay (ACR)

Default VSR trigger points are 13.1V on (120-second average) and 12.7V off for 12V systems — values chosen to share charge current from an alternator while protecting the start battery from deep cycle loads.

Single Flex 2 (8810/8510 Series)

The entry point into the Flex family. One relay position in a compact housing with forward-facing power studs. Common configurations:

8810-1300 / 8510-series — Single Flex 2 ACR-Relay with Knob, Tinned Wires: Factory-set as an ACR. Used in simple dual-bank setups to automatically share alternator charge between a house bank and start battery.
Single Flex 2 Relay-ACR with DTM Connector: Same functionality, Deutsch DTM control connector for sealed plug-and-play wiring.

The Single is the building block of the XD system. For a single-engine boat with two batteries requiring load isolation and a charging relay, you might use two Single XD units: one set as a battery disconnect relay per bank, and one set as an ACR. But for that exact scenario, the Dual and Triple configurations offer a better solution.

Dual Flex 2 (8820/8720 Series)

Two relay positions in a single housing. The most common use case is a dual-battery system: one relay for Battery 1 load switching, one relay for Battery 2 load switching, with the VSR function providing automatic charge sharing when the engine is running.

8820-1390 — Dual XD Flex 2 Relay-ACR with Knobs, Tinned Wires
8720-1390 — Dual XD Flex 2 ACR/Mechanical Switch with Knobs, Tinned Wires

The Dual occupies roughly the space of one traditional solenoid while providing two independent switched relay positions.

Triple Flex 2 (8830/8730 Series — including the 8830-2535)

Three relay positions in one housing. This is where the XD platform's space savings become most dramatic. The 8830-2535 that started this discussion is a Triple Flex 2 product: two outer relay positions for bank switching, and a center VSR/ACR position for automatic charge sharing.

8830-2535 — Triple Flex 2 Relay/VSR/Relay with Knobs, 12P DT Connector: The flagship triple, pre-configured as Relay | VSR | Relay, suitable for 3-battery systems or dual-battery systems requiring two independent relay disconnects flanking a central ACR.
8730-series — Triple XD with tinned wires variants

For 3–4 battery systems that previously required two or three separate ACR units, a single Triple Flex 2 provides all the ACR functionality in one housing with dramatically reduced quiescent current draw and wiring complexity.

Flex 1 — VSR/Relay/LVD/TDR

The Flex 1 adds two capabilities not present in Flex 2: Low Voltage Disconnect (LVD) and Time Delay Relay (TDR) functionality. This makes it better suited for systems where battery protection under load is a priority — for example, protecting lithium auxiliary banks from over-discharge, or managing loads that should time-out automatically.

Key features beyond Flex 2:

LVD: Automatically opens the relay when battery voltage drops below a configurable threshold, protecting batteries from damaging deep discharge
TDR: Closes or opens the relay after a programmable time delay

The Flex 1 is particularly useful in applications like refrigeration control, bilge pump monitoring, and any load where a time-based or voltage-based cutoff is needed without a separate control module.

Flex 3 — BEP Control Scheme Compatible

Flex 3 maintains the same core relay/VSR functionality as Flex 2, but with control input wiring and logic configured to be compatible with BEP Marine control schemes and interfaces. This is a drop-in replacement option for boats originally wired with BEP battery management components, allowing XD hardware to slot in without rewiring the existing control harness.

Flex L — Lithium Battery Systems

The Flex L designation indicates voltage settings and logic optimized for lithium (LiFePO4) battery systems. Lithium batteries operate at different resting and charge voltages than lead-acid chemistries — typically higher — and require different VSR trigger points to function correctly.

Flex L products ship with factory dip switch settings tuned for lithium charge/discharge voltage profiles. They support the higher on-trigger voltages that lithium systems require to correctly detect a charging condition, and the lower off-trigger voltages compatible with lithium's flatter discharge curve.

Single Flex L:

8610-6300 — Single XD Flex Lithium ACR with Knobs, Deutsch Connector
8510-1300 — Single Flex L Programmable VSR/Relay with Knob, Tinned Wires

Triple Flex L:

8630-2535 — Triple XD Flex Lithium Relay/ACR/LVD with Knob, Tinned Wires
8530-1535 — Triple XD Flex Lithium Relay/ACR/Relay with Knobs, Tinned Wires

The Triple Flex L with LVD is particularly well-suited to lithium house bank installations where both automatic charge management and low-voltage protection are required — a common combination in liveaboard and off-grid marine applications.

Ground Control Relay (77 Series)

A specialized variant: the Ground Control Relay switches the negative/ground side of the circuit rather than the positive. This approach is useful in specific OEM and commercial applications where positive-side switching is impractical or where the control scheme requires ground-side interruption.

7710-1600 — Single XD Ground Control Relay/VSR, No Knob, Tinned Wires (Bulk Pack)

Ground control switching is less common in recreational marine installations but frequently appears in RV, commercial vehicle, and certain industrial marine applications.

Low Voltage Disconnect Series (LVD)

Egis offers dedicated Low Voltage Disconnect configurations as standalone products within the XD lineup — separate from the Flex 1 multi-mode units. These are pre-configured specifically for load shedding when battery voltage drops to critical levels, with no VSR or ACR functionality enabled.

Key specification: 500A continuous capability per relay position. The LVD series is appropriate for protecting large loads (inverters, windlasses, bow thrusters) from battery damage during extended use without a charge source.

NMEA 2000 / J1939 Digital Switching (98 Series)

The newest and arguably most significant addition to the XD lineup, introduced at IBEX 2024. The NMEA 2000 series integrates directly with vessel networks, allowing battery switch control and monitoring via any NMEA 2000 compatible multifunction display.

9811-4500 — Single XD NMEA 2000 Relay with Knobs, 4-Position DT Connector
9821-8550 — Dual XD NMEA 2000 Relay/Relay with Knobs, 8P DT Connector

These represent an industry first: the CAN-bus controlled XD switches are the first battery switches to natively integrate NMEA 2000 without requiring an intermediate gateway device. Prior to the XD NMEA 2000 series, the only way to achieve this was through workarounds like a Maretron DCR100 controlling a Blue Sea RBS.

Capabilities include:

Control relay open/close state from any NMEA 2000 compatible MFD or controller
Monitor relay status and battery voltage via NMEA 2000 network PGNs
J1939 compatibility for commercial marine and OEM applications
Flexible control: operates via NMEA 2000 network commands or discrete analog inputs for redundancy

A note on availability: As of the IBEX 2024 announcement, the NMEA 2000 XD variants were not yet fully listed on Egis' website. Verify current availability with distributors before specifying these for a project.

Wiring Interface Options: Tinned Wires vs. Deutsch DTM Connectors

Most XD products are available in two wiring configurations:

Tinned Wires (87/88 Series prefix endings in -00 or wire variants): Flying leads with tinned ends, terminated in your enclosure using ring terminals or connection blocks. Familiar to any marine electrician and compatible with standard practice.

Deutsch DTM Connectors: Sealed plug-and-play connectors using industry-standard Deutsch DTM hardware. The DTM series provides superior resistance to vibration-induced connection failure and moisture ingress. For new builds or professional installs, the DTM variant is the better long-term choice. Pin-for-pin compatible with Blue Sea ML Series connectors.

Circuit Count: Single, Dual, or Triple?

The right circuit count depends on your system architecture:

Single makes sense when you're replacing one legacy solenoid or ACR, or when you need the XD's improved performance in a simple two-battery system and already have other relay hardware in place.

Dual covers the most common recreational marine scenario: a two-battery system (house and start) where you want independent positive-side switching for each bank and automatic charge sharing via the VSR position.

Triple handles anything from a three-battery system with independent bank switching to a dual-battery setup requiring an additional ACR or low-voltage disconnect. It also replaces multi-ACR setups for 3–4 battery systems in a single housing.

Compatibility and Replacement Guide

One of Egis' deliberate design decisions is backward compatibility with the two dominant legacy systems:

Legacy System	Compatible XD Option
Blue Sea ML-Solenoid	XD Remote Battery Switch, wire-for-wire
Blue Sea ML-RBS	XD Remote Battery Switch with knob
Blue Sea ML Bi-Stable Relay	XD Flex with DTM connector (pin compatible)
BEP Marine control schemes	Flex 3 variant

This makes the XD series a practical upgrade path rather than a full rewire for many existing installations.

Who Each Product Is For

Product	Best Fit
Single Flex 2 ACR/Relay	Simple 2-battery systems; adding ACR to existing relay setup
Dual Flex 2 Relay/ACR	Most common 2-battery installs; single engine boats
Triple Flex 2 (8830-2535)	2-4 battery systems; replacing multiple ACRs; space-constrained installs
Flex L (Single/Triple)	Lithium battery systems requiring correct charge voltage profiles
Flex 1 LVD/TDR	Systems requiring automatic load shedding or time-delayed switching
Flex 3	BEP Marine control harness compatibility
Ground Control (77 Series)	OEM/commercial applications using ground-side switching
NMEA 2000 (98 Series)	Integrated digital switching via MFD/NMEA 2000 network
Remote Battery Switch (87 Series)	Replacing mechanical rotary switches with remote-operated disconnect

Final Thoughts

The Egis XD Series represents the most thoughtfully engineered approach to marine battery management hardware currently available. The combination of bi-stable solenoid technology, aggressive space reduction, dip-switch configurability, legacy system compatibility, and genuine environmental sealing addresses every practical objection to the legacy relay systems that have frustrated marine electricians for decades.

For new builds, the Triple Flex 2 or Triple Flex L handles the vast majority of multi-battery architectures in a single compact module. For boats being rewired or upgraded, the XD series drops in where Blue Sea and BEP hardware previously lived, with meaningful improvements in reliability, standby current draw, and operational clarity.

The NMEA 2000 integration, now available in single and dual configurations, points toward where marine electrical is heading — fully networked, monitor-able from the helm, and controllable from the same MFD screen that handles your charts and engine data. It's an architecture that makes sense, and Egis appears to be the first manufacturer to execute it natively at the relay level.

Egis Mobile Electric XD Series products are available through authorized marine distributors including Fisheries Supply, West Marine, Defender Marine, and specialty chandleries. Contact Egis directly at sales@egismobile.com for OEM pricing and custom product configurations including specific voltage settings, time delays, and dip switch pre-sets.

EGIS Battery Switches / VSR