12 volt transfer switch

[Arbee]

I'm sure that many of you are familiar with RV 120VAC transfer switches that, for example, will allow an RVs 120 VAC appliances to be run from a shore power hookup over, say, an inverter connected to a house battery in the absence of such shore power availability.

Ok, sorry for the stupid question but is there something like this transfer switch only for strictly 12V DC appliances?

Imagine a bunch of 12V DC appliances in a vehcile that get charged off of a house battery, itself connected to solar. When the vehicle's engine cranks maybe I want those appliance's power to come from the alternator, or maybe, when the vehicle is parked I want those appliance's power to come from a 120VAC to 12V DC power supply I have hooked up.

...or maybe I'm just approaching this problem all wrong....

TIA

 

[Q-Dog]

Most RVs have a converter that charges the house battery and/or powers the DC loads when plugged into 120v power. You can also have a DC to DC charger to charge the house battery from the engine battery when the alternator is running.

 

[time2roll]

When 12v appliances are connected to the battery... the battery is only depleted if there are no other sources keeping the battery charged. If the solar or alternator are providing sufficient power these sources will power the load and the battery will not be depleted. If the solar encounters shade it will be up to the alternator to supply all power. Likewise if the vehicle shuts off to get fuel or something the solar would provide the power. And then it follows that if both stop providing power, the battery will begin supplying the power. As the power sources are restored they will again power the load and begin recharging the battery.

Is there an automated switch to control all this? No not really. Could add manual switches but that may cause more issues than it resolves.

 

[Larry-Cleveland]

Whatever you have on (light, fan) and hooked to a battery will run from the battery's power. The battery can be charged for your alternator or solar. From shore power, you can just plug in a battery charger.

I will be doing the same thing with this device.

DC to DC charger

 

[Arbee]

I think I sought something like this: https://www.amazon.com/Automatic-Tr...0&psc=1&mcid=8e7c4554f16a358fa2d370cdf4050176

..something that might be able to take over in lieu of cranking the engine on a cloudy day in which solar's contribution is less that stellar, should shore power be available.

Feel free to critique this product or my approach; just be kind: I'm a newbie who'se ignorant, not stupid.

 

[time2roll]

Are you looking for an isolator? Many vehicles have a relay that only provides power from the chassis system to the house system while the engine is running and powered by the alternator. This prevents depleting the chassis start battery.

Or looking for a combiner that will provide power from the house to the chassis system when charging voltage is available such as from solar or a utility powered charger? This will prevent the chassis start battery from getting depleted when stored for an extended period.

 

[Arbee]

Are you looking for an isolator? Many vehicles have a relay that only provides power from the chassis system to the house system while the engine is running and powered by the alternator. This prevents depleting the chassis start battery.

Or looking for a combiner that will provide power from the house to the chassis system when charging voltage is available such as from solar or a utility powered charger? This will prevent the chassis start battery from getting depleted when stored for an extended period.

Thank you for giving terminology to my problem set. From your description it is an isolater I seek.

 

[time2roll]

..something that might be able to take over in lieu of cranking the engine on a cloudy day in which solar's contribution is less that stellar, should shore power be available.

If utility power is available the on board charging system will power all the loads direct and keep the battery charged. No switch needed.

 

[time2roll]

Thank you for giving terminology to my problem set. From your description it is an isolater I seek.

So the house battery is currently connected direct to the chassis battery? Best to break this connection with an isolator so that power only flows to the house system when the engine is running.

Maybe something like this: https://www.amazon.com/Dual-Battery-Isolator-Waterproof-Compatible/dp/B0CCRQXQNM

This item is designed for lead-acid voltages. May need something different if batteries are lithium.

 

[mikefitz]

When the vehicle's engine cranks maybe I want those appliance's power to come from the alternator, or maybe, when the vehicle is parked I want those appliance's power to come from a 120VAC to 12V DC power supply I have hooked up.

All the 12v appliances run of the 12v house battery.
A DC to DC charger connected between starter battery and house battery will provide part one of your requirements.
When parked up the AC to 12v charger will charge the house battery and power loads.
Both chargers can be permanent connected to the house battery, no need for switches.
The selection of DC to DC charger current output will depend on the rated output of your alternator , 30% is a safe limit.

 

[Scycle]

I'm wondering if anyone has experience with Power Max transfer switches? I know they're based in Florida, but not sure it's US made. I want to use one in my system but since the generator is priority, I would wire shore power to GEN connections and my inverter to the shore power connections. This way if the inverter is on and I plug in to shore power it will have priority. I would also wire my charger to the GEN connections along with the shore power. The Go Power in my diagram is wired this way and I don't have a problem with them, but cost twice as much and not sure they are us made either.