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Jeffrey Wildrick avatar image
Jeffrey Wildrick asked

Choosing and installing DC/DC Charger for motorhome

I am upgrading from lead acid to two lithium house batteries and need help choosing the right DC/DC charger and confirming if my install plan is correct. This will be in a 2004 37foot Fleetwood Southwind. The house batteries are connected to a battery control center with an “Automatic Charging and Aux Start Relay" between the chassis battery and the house batteries. This stops the house batteries from charging until the chassis battery is full.

I'm not sure of the gauge of the battery cable. The diameter is about 12mm including the insulation. Will this be a problem for using a Victron DC/DC charger?

My plan is to install a DC/DC charger in a compartment next to the house batteries (they are under the steps), but I need some advice. What model DC/DC charger (or converter?) is the best choice? Do I need to install a fuse somewhere in the system, and if so, where? Will I need any special tools?

Thanks!

dc-dc charger
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kevgermany avatar image kevgermany ♦♦ commented ·
Need more info

What voltage and current is the alternator? Guessing it's not 'smart'.

How large will the lithium bank be and what voltage?

Any other charging used?

Guessing that the relay you mention simply puts the house batteries across the alternator, implying common voltage between house and chassis. If so, it means some wiring changes and can probably be replaced by the automatic switching in the Orions.



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Jeffrey Wildrick avatar image Jeffrey Wildrick kevgermany ♦♦ commented ·

Thanks for the questions. I'm attaching a schematic of the battery controller. It looks to me as though the alternator connects to the chassis battery, which when fully charged connects to the house batteries. The entire system is 12 volts. The alternator is 145 amps and it's not a smart alternator. screenshot-2023-12-29-at-90153am.pngI am replacing 12v 100 ah lead acid with two 12v 100 ah lithium ion batteries. The house batteries also charge through a 120ac/12dc converter when the rig is plugged into 120v shore power, and I realize that I'll need to replace that with a lithium capable converter.

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outdoorshedman avatar image
outdoorshedman answered ·

You will need a fuse near the chassis battery for the lead to the orion. And a fuse for the lead from the orion to household batteries

I chose to stay under 0.2 c to go easy on the batteries and the alternator.

I went with the 12-12/30 victron , advises a 60 amp fuse for this charger.

Keep in mind you can not reduce the amps with an orion in Victronconnect.

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