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Old 29-08-2014, 07:15   #1
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Battery Charging via Inverter from 12V Outlet

Good morning!

I am hoping for your advice and guidance on the topic of charging a 12V battery from a 12V outlet via an inverter while anchored.

I have a trolling motor on our boat, which is powered by a Group 24 battery. As we don't have a generator and built-in inverters, I would like to charge said battery using a Minn Kota MK-105P portable charger, which has an output of 5 amps.

The idea is to plug an inverter into a 12V outlet in my electrical panel at the nav station and then plug the charger into that.

If memory serves, 5 amps x 12 volts = 60 watt draw. So a regular old 300W inverter I purchased eons ago for the car should work, right?

I'm thinking I could even run the boat's engine to keep the two house batteries topped off. (Wouldn't want the house batteries to drain just to fill up the dinghy battery.)

Anyway, am I being a complete nimrod or is this doable?

Thanks again in advance!

Nico
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Old 29-08-2014, 07:39   #2
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Re: Battery Charging via Inverter from 12V Outlet

NPower Power Cable with Clips - 12 Volt, 18 Ga. x 36 in. L by NPower http://www.amazon.com/dp/B00BJ2B7V4/..._.iiaub0QCNQVA


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Old 29-08-2014, 07:52   #3
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Re: Battery Charging via Inverter from 12V Outlet

You'll just flatten your house bank. Use a solar charger or portable generator.
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Old 29-08-2014, 08:10   #4
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Re: Battery Charging via Inverter from 12V Outlet

Sure it's doable, but it's not very efficient. Many folks (including me) do this all the time when we plug in our laptop chargers into a small inverter and plug that into a cig socket. You're going from DC-AC back to DC... just because the plugs all fit and the voltages and charge rates get controlled. And in the process lose a shitload of efficiency.

Since you're going from one 12vdc battery to another 12vdc battery, then just use a set of clips like the poster above suggested, or (like I've done - i also have a trolling motor) wire in a permanent, fused 12 V power line with connectors that you can plug in to your dinghy battery when needed, but will stay coiled up under cockpit seat or locket lid when not needed. No conversion issues or losses.

Note that you will still be draining house batts, but if you're running the main engine to charge then you should be fine (assuming the alternator is up to the task of adding another battery and you aren't coking up your engine by running under too light a load for too long.. yada yada).

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Old 29-08-2014, 08:18   #5
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Re: Battery Charging via Inverter from 12V Outlet

Agreed,

And in your house bank is hooked to a nice solar panel all the better.


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Old 29-08-2014, 08:34   #6
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Re: Battery Charging via Inverter from 12V Outlet

Maybe you want to go with something like this.

Amazon.com: CTEK Multi US 3300 12-Volt Smart Battery Charger: Automotive
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Old 29-08-2014, 11:18   #7
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Re: Battery Charging via Inverter from 12V Outlet

get a 12v to 12v charger. something like this (first one that came up in google, no idea on brand / qual) probably others out there.

connecting leads from house bank to battery isn't going to do anything unless the house bank is charging also (engine running)

12V input lead acid battery charger for 12V batteries; taper-style DC Input 12V Battery Chargers useful for charging electric golf trolley in cars from PowerStream
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Old 29-08-2014, 11:34   #8
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Re: Battery Charging via Inverter from 12V Outlet

Thank you all for your input on this - I really appreciate it.

Overall, it sounds like a more permanent solution in the form of a solar panel would work, and I will look into that.

In the short term, I think I'll hook the dinghy battery up to one of the house batteries (- to - and + to +) while underway, so at least it will get charged via the alternator while in transit. That should tide us over for this weekend.

Thanks again all!

Nico
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