Category Archives: Magnum MS2012

Magnum® MS2012™ Inverter/Charger

In October, 2008, we selected and fit-up a Magnum® MS2012™ Pure Sine Wave inverter/charger for use aboard Sanctuary.  The unit is a combination 2KW inverter and a 12V, 100A battery charger.  We use the inverter to power 120VAC appliances: TV, satellite receiver/DVR, computer, network router, infrared wi-fi cameras, computer and cell phone battery chargers, space lighting, microwave oven, coffee maker, crock pot, electric heating pad, etc.  The charger maintains our combination house/start battery bank.  On those occasions when we lose shore power, the MS2012™ changes mode from “pass-thru” shore power to “invert” mode fast enough that the TV, DVR, Satellite Receiver and other on-board electronics are generally not interrupted.

Magnum® emphasizes that the inverter/charger should be physically located as close to its associated battery bank as possible.   This is to minimize the cable losses in the high current DC cables that connect the inverter/charger to its battery bank.  This circuit carries very high current when charging batteries and when drawing large inverter loads.   REMEMBER WHEN SIZING THESE 12V POWER CABLES, IT IS THE COMBINED TOTAL LENGTH OF BOTH THE B+ SUPPLY CABLE AND THE NEGATIVE RETURN CABLE THAT ESTABLISH THE AMPACITY RATING OF THESE CONDUCTORS, NOT THE STRAIGHT LINE DISTANCE ALONE. The magnum® installation manuals do a very good job of explaining that, and I strongly recommend (for fire safety) that you follow those installation instructions to the letter!

The MS-series Magnum® inverter/chargers can be mounted in any position.  Aboard Sanctuary, in order to minimize cable lengths, our unit is mounted “upside down” on the overhead in our engine room, near, but not over, the battery bank.

There is sometimes concern for temperatures when locating the inverter/charger unit in a boat’s engine room.   Our inverter/charger unit is located in the air stream of combustion air entering the engine room space.  The owner’s manual “specifications”  page for all of the MS-series units lists their “operating temperature” at -20°C to +60°C (-4°F to +140°F).  The engine room aboard Sanctuary stabilizes between 110°F – 115°F in the summertime, which is well within the MS-series “operating temperature” specs.  Furthermore, we rarely run our genset while underway, so the spec that applies to us is the “non-operating temperature” spec of -40°C to +70°C (-40°F to +158°F).  Finally, even on those rare occasions when we do run our genset while under way, we still charge the boat’s batteries via the engine alternator, not via the inverter/charger.  Our engine room does get warmer for a while after we shut down at the end of the day, when the cooling effect of draw-in combustion air stops.  But at that point, there is also very little load on the inverter, and no charger demand (since the batteries are fully charged by the engine alternator after the day’s run), so the MS series inverter/charger device is not stressed for cooling at it’s specified operating temperatures.

Our MS2012™ is fit with an ME-RC™ Remote Control, which is mounted on the boat’s utility wall with all other boat electrical operations switchgear.  Our Magnum® ME-BMK™ Battery Monitor module is mounted at the inverter/charger unit.  The battery monitor module automatically calculates Peukert’s Factor and Charge Efficiency Factor (CEF) in real time.  The MS-series™ units have several “equalize charge” programs for a variety of lead acid battery technologies.  MS-Series™ units can be “piggy backed.”  Magnum® is an American company, and has a superior reputation for post-sales service and support.  The unit complies with ABYC® A-31 and E-11 Standards.

The inverters of the Magnum® MS-Series™ are intended to be integrated into a boat’s onboard electrical system.  This is also typical of other manufacturer’s inverter and inverter/charger units.  The Magnum® User Manual installation instructions are very good for the unit itself.  There are, however, associated changes that must be made in the OEM host AC electrical system that are not within the scope of the unit’s install instructions.  These associated AC system modifications must be within the knowledge and skill level of the unit installer.

With the addition of an inverter/charger, AC power can be present even when shore power is not.  Whenever working on the AC system of a boat with an inverter/charger, disconnect and remove the shore power cords from the pedestal and disconnect the DC power source from the inverter/charger.

DIY installation project plan:

Install Mangum Inverter/Charger

Locate/prepare installation space

Physically mount inverter/charger unit, Remote Control Unit

Remove existing BlueSea Systems ACR

Prepare existing DC Buss wiring for changes

Reconfigure AC Load Center; split/re-wire AC hot buss

Reconfigure AC Load Center; divide/isolate AC neutral buss

Reconfigure AC Load Center; reconfigure neutral for panel power “on”  indicator lights for circuits powered by the inverter

Fabricate/install #10 AWG AC line-in and load-out wiring

Update AC Circuit Breaker to 30A for Charger supply

Fabricate/install 2-0 AWG battery interconnect cables

Reconfigure Alternator attachment to house battery bank

Reconfigure existing Pro Mariner battery charger

Reconfigure Xantrex Battery Monitor (if installed)

Fabricate/connect 2-0 AWG DC fuse/supply to inverter/charger

Re-program Xantrex Link-20 battery monitor for larger capacity battery bank (if installed)

Program Magnum Remote Control

Update AC and DC boat electrical drawings

Update vessel ops procedures, circuit breaker descriptions, etc

On the assumption the inverter/charger will only power a subset of the AC circuits aboard a boat, which is our case, the AC “hot” buss of the boat’s AC Load Center must be split into two parts.  One part will continue to feed the original non-inverted shore power loads and the other part will feed the loads to be powered via the inverter.  The AC neutral buss must also be split into two parts, so that the neutrals of circuits powered only by shore power are separate and isolated from the neutrals of circuits powered by the inverter/charger.

I found that reconfiguring the neutrals was the most tedious and time consuming part of our installation.  Aboard Sanctuary, the OEM neutrals all ran to a single buss bar.  The circuits that we do not power with the inverter include the refrigerator/freezer (runs on DC), the genset battery charger, the hot water heater and the MS-2012™ inverter/charger, itself.  The neutrals from those circuits must be separated from the neutrals of the utility outlets and lighting circuits aboard.  Fortunately, most of our neutral conductors run in one of two wire retaining ducts.  I was able to isolate the neutrals that had to be reconfigured by first turning all AC loads “off,” and then sequentially powering individual circuits “on” and “off,” one-at-a-time, while clamping the neutral conductor(s) with a clamp-on AC ammeter.

IMPORTANT: as part of isolating the neutral buss, it is also necessary to modify the neutral connections on the main power panel for branch circuit breaker “power on” indicator lights.  In the OEM configuration, all of the panel’s power “on” indicator lights are connected to the panel manufacturer’s OEM shore power common neutral.  The indicator lights for circuits powered by the inverter must be reconfigured to instead be connected to the new inverter neutral buss.  If not reconfigured, these small lights will provide a leakage (fault) path that cross-connects to the shore power neutral.  Symptoms will vary from installation to installation.  This item is very easy to overlook.

In the DC system, preparation and fitting up the crimps on the DC battery cables is the most technical DC task of the project. The Magnum® User Manual instructions for both the AC and DC wiring is clear and complete, and has been further improved since I installed our unit.  With basic electrical skills and the ability to read safety notices and follow directions, DIY installation of the inverter/charger is a project of moderate-to-high complexity.

Including the AC and DC cabling, Class “T” fuse and fuse holder, DC disconnect switch, remote control and battery monitor accessories, the cost for our installation was about $2K.  It was purchased from a local Annapolis business at the Annapolis Boat Show.  I installed the unit myself, so there is no labor component in that cost figure.