Battery Isolators

[K2e2vin]

i was searching for info on "split charging"(what the brits call it im guessing since ive only seen that term on uk sites) aka battery isolation. well i was trying to debate between a diode type and a relay type and came across this page: http://www.antares.co.uk/split_charging.htm

at the end, if you dont want to read it, it talks about a hybrid type switch but is vague about the design. it says its pretty much a relay type isolator but uses a differet trigger:

The switch only operates when the alternator/charger can supply the loads without drawing on the primary battery.

any ideas on how to make a standard relay isolator work like that?

 

[cheese9988]

They sell alot of isolators at rv places or marine stores, where people need multiple batteries, check them out.

 

[hcivic.com]

they cost like 20 bucks or so

 

[K2e2vin]

yes i know but what they sell at the rv stores but how would i go about rigging it the "hybrid" method? the diode types are simple enough but heat up and cause voltage drops, while the relay type may open the circuit while you're cranking the car.

 

[cycloneb18c3]

ive got one on my F250. its got 3 hookups on it, one for the alternator excitor wire, and 2 positive hookups, one for each battery. the grounds just get grounded to the chassis. I think mine is diode, and I havent had any problems with it.
and mine was about 100 bucks....
edit:
I have this one:
http://www.westmarine.com/webapp/wcs/store...=544&storeNum=9