Renogy MPPT dual dc-dc charger question

[DugStar]

I'm thinking about doing a DC change over kit on my Norcold rv refrigerator to allow better and consistent temperatures. This helps with less energy consumed as well as maintaining good low temp while driving long distances. This would require me to install a Renogy dual MPPT dc-dc charger from my truck to my lithium battery bank in my fifth wheel rv. My rv has a 640 watt solar panel array, 60 amp mppt charge controller, two 100 ah renogy smart lithium batteries, and a 2000 watt inverter. I built this system to fast without doing proper research first. My stupid beginner question is do i still need my charge controller along with the dc-dc charger? Thanks for any feedback

 

[Tomthumb62]

Just buy a decent DC DC charger. The MPPT in the renogy combo kit is useless compared to what you already have. MPPT max voltage input is like 25v.

 

[DugStar]

Just buy a decent DC DC charger. The MPPT in the renogy combo kit is useless compared to what you already have. MPPT max voltage input is like 25v.

Thanks. Do i still need a charge controller?

 

[Tomthumb62]

My rv has a 640 watt solar panel array, 60 amp mppt charge controller,

Thanks. Do i still need a charge controller?

You already have one. Just leave it there and add the DC DC charger.

 

[mikefitz]

The DC to DC charger, sometimes referred to as a 'battery to battery charger, connects between the starter battery and house battery. This will require suitable cable, fuse at each battery.
It's probable the existing 12v circuits to the RV from the vehicle will not carry the 30 to 60 amps of charging current. Perhaps make up a suitable cable and connector.

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[mikefitz]

This would require me to install a Renogy dual MPPT dc-dc charger from my truck to my lithium battery bank in my fifth wheel rv.

See,

 

[DugStar]

You already have one. Just leave it there and add the DC DC charger.

Thanks Tom and Mike, much appreciated