Meet the Mastervolt Charge Mate Pro 40 (Model 83304002) — an intelligent dual-battery charging coupler designed for boats and other multi-battery setups. It smartly charges two banks (starter and service) with priority to the main battery, while isolating banks during discharge to protect the electrical system.
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Output current: 40 A to the secondary battery (maximum)
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Battery outlets: 2
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Input voltage range: 9–32 V
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Parallel configuration: Yes
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Battery voltage automatic detection: 12/24 V detection
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Remote switch functions: On, Off, Auto, Start Assist
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Bypass / emergency start: Optional switch provides emergency start functionality
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Monitoring: LED status / warnings
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Protection: IP65
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Switch on voltage: 13.5 V (12 V) / 27 V (24 V)
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Switch on delay: 5 seconds
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Switch off voltage: 12.75 V (12 V) / 25.5 V (24 V)
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Switch off delay: 2.5 seconds
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Relay: Electronically controlled MOSFETs with low voltage drop (max 0.2 V)
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Connection options: 3 x fast-on connectors (switch, ground, status); compatible with an optional ON-OFF-ON remote switch and LED indicator
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Temperature range: -40°C to 60°C
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Dimensions: 6.2" H x 5.5" W x 3.1" D
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Weight: 1.9 lb
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Battery types: All types (Lithium Ion protection via multi-purpose contact)
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Power consumption: < 1 mA when the switch is open (12/24 V DC)
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Construction: Marine-grade with corrosion-resistant casing and aluminum heat sinks
By distributing charging current intelligently and keeping banks isolated during discharge, the Charge Mate Pro 40 reduces the risk of a flat starter battery and ensures both banks are charged when connected to compatible chargers or alternators. It automatically prioritizes the main battery during charging, supports all battery types (with Lithium Ion protection via a multi-purpose contact), and offers an optional bypass switch for emergency starts. LED monitoring provides quick status checks, and the rugged IP65 enclosure along with marine-grade hardware delivers reliable performance in demanding conditions.
| Monitoring |
LED (warnings and status indication) |
| Output current |
limited to 40 A |
| Number of battery outlets |
2 |
| Input voltage range |
9-32 V |
| Parallel configuration |
yes |
| Battery voltage |
automatic 12/24 V detection |
| Remote switch functions |
on, off, auto, start assist |
| Dimensions, hxwxd |
6.2 x 5.5 x 3.1 inch |
| Weight |
1.9 lb |
| Technical specifications |
| Connection possibilities |
3 x fast-on connectors (switch, ground and status) switch: for an optional single pole ON-OFF-ON switch for remote operation status: for an optional LED indicator |
| Power consumption |
switch open: < 1 mA at 12/24 V DC |
| Battery types |
all types (Lithium Ion protection via Multi purpose contact, product code 77030500) |
| Switch on voltage |
13.5 V (12 V) / 27 V (24 V) |
| Switch on delay |
5 sec |
| Switch off voltage |
12.75 V (12 V) / 25.5 V (24 V) |
| Switch off delay |
2.5 sec |
| Relay |
electronically (mosfets with low voltage drop of max 0.2 V) |
| Temperature range (ambient temp.) |
-40 °C to 60 |
| Protection degree |
IP65 |
