Charging two batteries

[crzr]

Hi,
I am getting ready to wire the aux battery in my slide-in camper to the truck charging system for charging when on the go. Plan on using a continuous duty solenoid to protect the primary battery, which is standard automotive issue. The aux battery is deep cycle. Recently I heard that batteries of different types should not share the same charging system as this will keep one of them from getting fully charged. Should I scrap my plan?
thanks!

 

[Just Lou]

No need to scrap your plan.  This is exactly how most motorhomes accomplish their battery charging needs. 

 

[John From Detroit]

And nearly every trailer out there too.. Though there are SLIGHT differences, .. There is a lot of wire between the front end of your tow vehicle and the trailer battery, Wire = voltage loss, thus the trailer battery is protected should it need a bit less voltage and if it needs more all it means it it won't reach full charge (Since the vehicle system is set for maintenance free starting battery.

It will work, and it will work very well.  It is the industry standard.  NOTE: many people THINK they have deep cycle when what they have is "Marine/Deep cycle" this is a starting battery for all purposes and intents.

 

[Mopar1973Man]

I would skip on the solenoid idea and switch to a isolator. Little more expense but no moving part and totally automatic and no trigger leads.
Diode Isolator

 

[Just Lou]

A diode isolator is certainly feasible, but not as versatile if you want to also effect charging of the truck battery from the camper converter or implement a simple emergency/aux start function.  In addition, the diode based isolators generally cause a small voltage drop in the charge path.

Ideally, a BIRD function solenoid would be my choice.