Length of DC cables for charger to house bank.

I'm looking at upgrading my Freedom 20 inverter/charger to a Magnum 2812. The Freedom 20 is almost 15 years old.

The current and most convenient location of the current charger has about 17 feet of 2/0 AWG cable to the Blue Sea remote battery switch and another 7 feet to each of two battery boxes: one box with 4 T-105's and one box with 6 T-105's. That's almost 24 feet of cabling. That seems to me to be excessive. Thoughts?


Jim
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Yup! I'm looking at pages 16-17 of the manual and it looks like I need to get those wire runs shorter.

http://magnumenergy.com/wp-content/uploads/2012/08/64-0007-Rev-D-MS-Series_Web.pdf

Damn!


Jim
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Jim: We have an Outback similar sized inverter/charger. They also recommend #4/0 cable with a maximum 1 way run length of 5' between the battery bank and the inverter/charger.

First I am not sure why you have two house battery banks with a selector switch. But anyway:

assuming that the round trip (pos and neg) is 2 x (17+7) - 48 feet and that the maximum continuous current is 373 amps as given in Magnum's specs, then you will need at least 3/0 to safely carry the current and 4/0 to keep the voltage drop below 1 volt.

So you do not necessarily have to change your routing, just upgrade your cable size. Genuindealz.com is a good place to buy boat cable. They can also crimp on connectors for your custom measurements.

But also consider the maximum AC load that you are going to pull from the inverter. If the maximum is only 1,500 watts then put a 300 amp fuse to protect the existing 2/0 cable and the DC required to pull 1,500 watts AC is only about 200 amps which will keep the voltage drop down to about 0.7. You can actually pull about 2,000 watts and keep the DC voltage drop to about 1 volt, which was probably the criteria for your old Freedom 20.

To summarize, the solutions are: different routing, bigger cable or only use 2,000 watts and use your existing cable.

David

David. The two different boxes are wired as a single bank. We only use the "inverter" option occasionally. Even the microwave is not wired to operate on the inverter. We don't operate a TV right now. Nothing has been purchased yet, so yes there are options to explore. I have an email in to Magnum to see what they say.

Jim


Jim
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Have to ask where on a Krogen 42 have you put the inverter/charger that the distance is 17 feet? Suggest you move the charger to the engine room. Both of my inverter / chargers are directly above the battery bank.

The charger is affixed on a support on the aft end of the new fuel tanks. These are 9 feet long and you add another 8 feet of twists and turns. All of this work has been well done, but I am questioning the length of the cabling with the attendant voltage drops. All work has been done by the PO.

Jim


Jim
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