Wanting to install a dc to dc charger for new lithium battery - Fiberglass RV
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Old 06-17-2021, 10:12 AM   #1
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Name: Steven
Trailer: 2005 Fleetwood Allegiance
CA
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Wanting to install a dc to dc charger for new lithium battery

I would like to install a renogy dc to dc charger with mppt. However, the electrical routes in my trailer are making this difficult. I have a wf-8725 that takes the power from my 7way and distributes in to the dc system and to my house battery. If my understanding is correct, the dc to dc charger will only allow current in one direction. If I put it between the wf-8725 and the house battery, would it isolate the battery from the trailer? If so, where should I put the dc to dc charger in my system. I only have one lead on my new lithium battery.

Side note, I really like my renogy 100ah lithium battery.
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Old 06-17-2021, 02:29 PM   #2
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Name: Pat
Trailer: Scamp
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I'd like to hear more on this topic too. And there are other 12 VDC to 12 VDC chargers on the market. I have a new to me Scamp 19 that I am considering upgrading to lithium.
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Old 06-17-2021, 03:29 PM   #3
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Steven,
A good way to get much higher amperage and avoid other issues is to install an Anderson plug at the rear of your tow vehicle. Then have an Anderson plug on a separate pigtail on the trailer, that you plug in when you connect the seven pin. On the trailer side, the wires go directly to the battery, or to a DC-DC charger, that then charges the battery. With that, your entire system, as it is now, is left alone. You can also plug in a suitcase solar into the trailer Anderson plug to charge the trailer batteries.

The power wire in the seven pin bundle is very low amps, but the Anderson can provide 50 amps or more, depending on what size wire you use and the breaker you install.
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Old 06-17-2021, 04:28 PM   #4
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I like Raspy's solution.

As a regular at Princess Auto, I purchased these on sale. I got the 3 wire, #8 connectors just because they use the same plastic as the 2 wire ones, and they were on sale for the same price. They shold be good for 40A, or more. I also like that the plug is female, so no accidental shorts:
https://www.princessauto.com/en/3-pi...t/PA0008556318
https://www.princessauto.com/en/3-pi...t/PA0008556631
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Old 06-19-2021, 09:47 AM   #5
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Name: Pat
Trailer: Scamp
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Quote:
Originally Posted by Raspy View Post
Steven,
A good way to get much higher amperage and avoid other issues is to install an Anderson plug at the rear of your tow vehicle. Then have an Anderson plug on a separate pigtail on the trailer, that you plug in when you connect the seven pin. On the trailer side, the wires go directly to the battery, or to a DC-DC charger, that then charges the battery. With that, your entire system, as it is now, is left alone. You can also plug in a suitcase solar into the trailer Anderson plug to charge the trailer batteries.

The power wire in the seven pin bundle is very low amps, but the Anderson can provide 50 amps or more, depending on what size wire you use and the breaker you install.
Like!!! - have the same connectors on my John Deere garden tractor for charging. They are excellent! And any good independent auto parts shop should have them.
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Old 06-19-2021, 10:02 AM   #6
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Name: John
Trailer: 1979 Boler 1700
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Quote:
Originally Posted by Bigpapa559 View Post
I would like to install a renogy dc to dc charger with mppt. However, the electrical routes in my trailer are making this difficult. I have a wf-8725 that takes the power from my 7way and distributes in to the dc system and to my house battery. If my understanding is correct, the dc to dc charger will only allow current in one direction. If I put it between the wf-8725 and the house battery, would it isolate the battery from the trailer? If so, where should I put the dc to dc charger in my system. I only have one lead on my new lithium battery.

Side note, I really like my renogy 100ah lithium battery.
REPLY:

All DC loads in the trailer normally are powered from the wf-8725 fuse panel. Yes, putting the Renogy DC-DC/MPPT device BETWEEN the wf-8725 and the battery would isolate the battery, so don't do that. You could connect the Renogy DC-DC/MPPT device to the battery while leaving the wf-8725 to battery connection alone.
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