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Old 03-11-2011, 10:27 AM
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Uncle Ben Uncle Ben is offline
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On your setup a "smart" system is probably overkill. A simple single continuous duty relay linking both batteries together when the key is in the hot position is most likely all you need. "Smart" systems take it a step further and monitor the primary battery. They will do what the simple "dumb" relay will do and charge the second battery but they do it by voltage spike sensing. When there is a spike of 13.5+volts (engine running and charging) they will activate the relay. Where they shine is when you are over drawing and voltage drops below 11volts they will drop out, thus isolating the batteries so both are not discharged. "Smart" and "dumb" relay setups can both be set up to self jumpstart if the main (starting) battery is dead. The generic battery isolators that are basically a large finned aluminum heat sink and a healthy diode work fine for RV use also because of the long engine run times associated with RV's. They are not nearly as efficient as a relay set up because they generate massive heat. Heat takes energy to produce thus robbing energy from your charging system.

Originally Posted by Creap View Post

I own a conversion van and thinking a dual battery system may be nice. I think I understand what I need but wanted to clarify something.

I want to install a second battery that will power a inverter that will power a lcd tv, dvd player, charge a netbook or ipod, cell phone and such. The question I have is not really related to using the items when the van is off but when it is running.

Is there a issue to have these items running from the inverter connected to the 2nd battery as the van is driving down the highway. I am unclear on if there is a separation of where the power is coming from if the car is not turned off. And if that load will just get transferred to the alt and burn it up.
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