Thinking of Replacing Battery Isolation Solenoid with Renogy DC/DC Charger

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John Hilley

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I have to replace the Battery Isolation Solenoid. I'm thinking of adding a Renogy 20 amp DC to DC Charger.

https://www.renogy.com/renogy-12v-dc-to-dc-on-board-battery-charger/

I am thinking of keeping the Battery Isolation Solenoid and moving the ignition coil lead to the DC/DC Charger and leaving the Dash Boost Switch on the Battery Isolation Solenoid.

Configured this way, the alternator would charge the House Batteries via the Renogy DC to DC Charger and the Boost Switch would Boost by connecting batteries together. The Battery Isolation Solenoid would rarely be used instead of all the time the engine is running
 

Lou Schneider

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The only way this would be useful is for charging trailer batteries from the towing vehicle's alternator.  Here the gauge and the length of the charging wire between the vehicle engine and the trailer batteries limits the charging amperage to relatively low values, around 5-10 amps.

Since the Renogy provides full output with as low as 8 volts input, it could be used at the trailer batteries to boost the voltage coming out of the charging wire.

I don't see any advantage to using it in a motorhome, though.  Here the house batteries are only a short distance away so there isn't enough wire loss to worry about.
 

John Hilley

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It eliminates the need for a solenoid whose coil is activated whenever the engine is running. It provides a solid state 3 stage charge and Battery Isolation, Over-voltage safety, Overheat protection, and Reverse polarity protection.
 

Gary RV_Wizard

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Solenoids designed for this purpose are a latching (continuous duty) type, meaning no current is required to keep it closed.  Example: the Intelletec Big Boy 120 relay.
 

John Canfield

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Interesting idea John. Like Gary and Lou I'm not sure this would be an ideal application for the device. Have you thought about one of the Blue Sea products to replace the Trombetta solenoid? They are intelligent unlike the Trombetta (and last longer than two years  ;D unlike the Trombetta.)
 

John Hilley

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I was leaning toward a Blue Sea Automatic Battery Link. The Renogy provides 3 stage charging to the auxillary battery, I have never liked directly connecting the two battery banks with alternator. The Renogy provides a modicum of protection to the alternator as well.
 

John Canfield

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John Hilley said:
...I have never liked directly connecting the two battery banks with alternator. ...
And that's a valid concern that I've thought of over the years after I switched to AGM house batteries. Different battery chemistries have different charge and float requirements.
 
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