The snow is melting and I'm beginning to formulate plans for getting our cargo van converted for our 2 week trek to Maine in October. I'm installing a 110 ah 12v battery as the auxiliary battery under the van and later on I may hook up another in parallel if I need the additional reserves. Just plan on running some led lights and a 50 quart ARB fridge. I'll be hooking it up to shorepower as well as letting the alternator charge them when the vehicle is running. I understand I need an isolater switch between auxiliary batteries and the cranking battery . When charging auxiliary batteries with shorepower would I isolate the cranking battery? Would I somehow damage it if I did not? I plan to run the shorepower wiring through the rear bumper. I know some people on the forum have done this so any link appreciated. Lastly, any recommendations for AC/DC transfer switches appreciated.
Hooking up auxilliary batteries
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Our system is pretty much as you describe. We use a Surepower isolator. My understanding, though, is that adding another battery "later" is a no-no. Batteries in parallel are supposed to be equal in all ways possible, including age and use history. We didn't know that, and are now trapped with our one battery. So if you contemplate that you might want two, do it now.
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While it's certainly true that it's best to have identical batteries (age, manufacture, capacity, etc) when connecting them in parallel, life is not always simple and if you need/want another battery I wouldn't hesitate to add one, particularly within a year or so. Personally, I've done it with never a problem even several years apart.
Ms,
I got my 100ah AGM last August, and I'm just about ready to get a second one. One works well for just about everything, but the microwave doesn't like it, so I think another 100ah AGM will do it. No solar for me either. Parked under a carport most of the time, it wouldn't make much voltage!
Not too concerned about being less than a year apart in age. Some trips coming up on April, so...
After months of deciding, I just ordered an Engel! Based on your recommendation, (and not being able to find a lot of bad press anywhere) I decided on the MR40. It's the plastic covered version of your 45. I'm really looking forward to getting it and figuring out the best place to put it. It's also a chest ref/freezer, so I like the way you set your up in a cabinet. I may do a similar install, with a cover that hinges up to get access.
Thanks, your thoughts and remarks on the Engel were helpful!
Ed
I got my 100ah AGM last August, and I'm just about ready to get a second one. One works well for just about everything, but the microwave doesn't like it, so I think another 100ah AGM will do it. No solar for me either. Parked under a carport most of the time, it wouldn't make much voltage!
Not too concerned about being less than a year apart in age. Some trips coming up on April, so...
After months of deciding, I just ordered an Engel! Based on your recommendation, (and not being able to find a lot of bad press anywhere) I decided on the MR40. It's the plastic covered version of your 45. I'm really looking forward to getting it and figuring out the best place to put it. It's also a chest ref/freezer, so I like the way you set your up in a cabinet. I may do a similar install, with a cover that hinges up to get access.
Thanks, your thoughts and remarks on the Engel were helpful!
Ed
Just get ready for people to not believe how good it is. 
The Trimetric monitor is verifying my original estimates: Set at 37°, it runs up to about 10% of the time when the outside temps are 70°+ (about 2 minutes 2-3 times/hour). Last summer at 90°+, it was cycling 3/hour. When running, it uses up to 2.5 amps and sometimes less than an amp as the literature says. I don't know what determines how much it uses in a cycle--I thought it might be temperature setting, but it isn't, nor is it outside temperature. Parked the van 5 days ago. Cold nights, warm days. Down 20AH including some lights and charging.
The Trimetric monitor is verifying my original estimates: Set at 37°, it runs up to about 10% of the time when the outside temps are 70°+ (about 2 minutes 2-3 times/hour). Last summer at 90°+, it was cycling 3/hour. When running, it uses up to 2.5 amps and sometimes less than an amp as the literature says. I don't know what determines how much it uses in a cycle--I thought it might be temperature setting, but it isn't, nor is it outside temperature. Parked the van 5 days ago. Cold nights, warm days. Down 20AH including some lights and charging.
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I have the MR040 and I have it right behind the drivers seat. Works out great- I can grab a cold drink while driving. It's exactly as wide as the seat so it doesn't block the isle. It doesn't take up much floor space because of how it fits "under" the seat back. Before my aux battery was hooked up I had let it run for up to 3 days without issue.
Re: the thread topic- I put a yellow top under the drivers seat like slamit did with a battery doctor isolator. Couldn't be happier. I had enough room left over under the seat to fit a small sine wave inverter.
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