This Dual battery controller is working Great! (EBI Pro from Intervolt)

[007]

http://www.intervolt.com/products/electronic-battery-isolator/ebi-series.aspx

You can adjust the combine and isolate voltages to whatever you want, and it has an illuminated switch that displays when you are "combined". It also alerts for things such as under/over voltage, shorts etc.

The switch also acts as a manual battery combiner.

The MOSFETT style isolater also allows you to charge both batteries off one shore charger or your solar.

It cost about $230.00 u.s. and shipped pretty fast from Australia.

I like it because of the versatility, if I want to run on both batteries I can, If I want to Isolate my starter battery, I can. If I want my charger to combine at a certain voltage it will.

 

[DiploStrat]

Looks very nice, but can only handle 100A continuously. Lot of vehicles have much larger alternators. I do like the variable combine/isolate voltages and timings. That is nice.

This model handles 150A: http://www.intervolt.com/products/voltage-sensing-relays/psr-series.aspx

 

[dwh]

This model handles 150A: http://www.intervolt.com/products/voltage-sensing-relays/psr-series.aspx

That second model can also be had in either 12v or 24v versions, whereas the first one is 12v only.


I also see another unit that looks like it could be handy in the right situation; a 24v -> 12v converter that is an adjustable (12.0v - 14.0v) regulated power supply, that can also be put into battery charger mode and do a 2-stage (14.4v bulk, 13.6v float) charge. Available in either 25a or 35a versions:

http://www.intervolt.com/products/voltage-converters/svc-maxi-series-gen-ii.aspx


And a similar fully isolated unit in 12v -> 12v but only 10a or 20a size, and 24v -> 24v in 10a or 20a size:

http://www.intervolt.com/products/power-conditioners/spci-maxi-series.aspx


Interesting options for certain situations.

 

[007]

Looks very nice, but can only handle 100A continuously. Lot of vehicles have much larger alternators. I do like the variable combine/isolate voltages and timings. That is nice.

This model handles 150A: http://www.intervolt.com/products/voltage-sensing-relays/psr-series.aspx

That is a very good point, and certainly a concern of mine as I have a 130amp alternator. When I inquired about the rating they said the EBI Pro's published rating of 100amps is for 140f degree temps. If you drop the temp to 104F the rating is 150amps (the one you linked is 150amps at 104F).

I was still concerned because I know my under hood temps can get high and that is were my isolator is, but they said the rating is VERY conservative and by the time the heat sinks into the isolator to lower the rating, my alternator has long stopped putting out its peak amperage even if the Batteries have not been recharged. If it ever did exceed the rating of the Isolator, it would just shut off and reset, which mine has never done, fingers crossed!

I also called Odyssey to see what my battery demands for Amperage are and they said it can take very high amps if forced (500), but the alternator will not actually read a huge draw from the battery, so what goes into the battery (and through the isolator) is going to be much less.

So this raises the question, what kind of amperage actually goes into recharging an aux. battery? Obviously this would depend on alternator output and the gauge wire going to your battery and the battery size/type, and its S.O.C.

I'm very curious to see actual readings or info on this matter.

 

[DiploStrat]

So this raises the question, what kind of amperage actually goes into recharging an aux. battery? Obviously this would depend on alternator output and the gauge wire going to your battery and the battery size/type, and its S.O.C.

I'm very curious to see actual readings or info on this matter.

I have a 600Ah AGM battery bank and 2x125A alternators. (Stock 2013 Chevrolet Duramax option.) I routinely see charge rates of between 150 and 200A. BUT, there is always a "but."

-- Only if the batteries are more than 200Ah down and, even with an electric cooktop, that doesn't happen much. Will have to wait for warmer weather to fully assess the impact of running the air conditioner.

-- When it does happen, it only happens for about an hour or so. Why? Because as has been noted, once lead acid batteries reach the 80% charge zone, their ability to take a charge drops.

I use a Blue Sea relay rated at 200A continuous. Doing it again, I would go with the Blue Sea Automatic Charge Relay rated at 500A. https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

I suspect that the Intervolt product would probably be fine with a 130A alternator, but why pay much more for an imported product? I went to great lengths to set up a system with a high voltage cutout, only to discover that it wasn't required and that I actually had to cobble up a force close option because I actually need charging voltages of up to 15.5v when the temperature is below freezing.