I am using the second battery for my cabover camper. I am wiring in an isolator, which are rated depending on the size of your alternator. In my case it was a 120amp. I am also putting an inline breaker. SurePower has been making isolators for years. The circuit breaker is made by Stinger and is rated at 80amps. I will take pictures of the whole setup once I am done. Total cost on the project including new #6 gauge wire and the used battery tray was about $150. The main reason I didn't want to rewire and/or cut hoses on the emission stuff was this way, I can take all my extra battery stuff out and everything else goes right back together the way it was supposed to. Not sure how long I'll keep this truck.

 

lol

 

I think this is what I am going to use
http://www.powerstream.com/battery-isolator.htm
I also just got 50ft of 1/0 awg welding cable given to me!!!! I just need to find the time to get it all in. I am going to use the aux battery for back up starting and for all my added accessory's including my on-board air system.

 

I don't like those diode isolators since even the Schottkey ones like in the link have a fairly large voltage drop. I much prefer the relay isolators even though they have a shorter life span. Or there is always solid state $$$$. With the diode drop and IR drop in the long cable from battery to camper alot of 12VDC electronics aren't going to be happy. Also if there are coach batteries they would never get all the way charged off the alternator due to all the V drop with diodes in there.

 

^^We had so many different 12v charging systems on the boats it was just nuts, but we never had any problems with the 12v equipment at all, that’s from gps to marine vhf radios and all the lighting on the boats. They only really use these on the small boats 18' x 45' usally two 6v in series, all the batts are within 6' of the motor in the well, and one 12v start batt, all off a 160 amp alt, these boats did not have any 120v in them. In the big boats it’s up to 10 6v batts in series to make 12v then hooked in parallel to the next set of series 6v batts and so on but that’s not even close to what we are talking here. There are so many thoughts on doing this right and what equipment to use it can go on for ever. I would like to see some more info on the other isolators so I can learn and compare to what I know, do you have any links? Yes charge time for dead cabin batts was about 6-8hr at 1500+ rpm, less if they were smart and shut stuff off.
Batt maintenance was a must every day.

 

I'm surprised to hear you say it. I'd expect analog gear like the radios to be the touchiest. Maybe marine electronics is designed to be extra robust against voltage fluctuations. It seems like alot of automotive equipment just ungracefully craps out.

Here is an SSR but there are other companies. It's just an example.

http://hellroaring.com/bic75300.php

When I say relay I'm just talking about the contactor solenids I'd be surprised if you arent't already familiar with. for example:

http://www.amazon.com/PAC-PAC200-Bat.../dp/B000CEBXRS

I'm not sure why either type ^^ circuit couldn't be adapted for maritime duty but perhaps the solenoid idea would be frowned on due to the fairly limited life span of switching contacter type gear. Maybe that stuff is just too unreliable for sea fairing vehicles. I don't see any reason why a SSR wouldn't be a great option other than cost though. Spec'd properly they are rugged as anything. Upsides are they have extremely low on resistance, about as good as a relay contact, which is ideal for charging system builders seeking maximum efficiency and minimum charge times. The beauty is they dn't go dead all the tinme like a relay assuming they are prperly rated for the job. The downside is SSR's do have a very tiny leakage current when off unlike a relay but any diode solution would have small reverse bias leakage currents anyways. Oh yeah did I mention? proper SSR's are $$$$$ but oh so sweet for a charging system.

 

Thanks for the links very much appreciated. I have been down the Battery Isolator,Relay thing years back but it did not just work well at that time for the boats. Have you used this product over time? Hellroaring Technologies, inc, I would like to yap more about this with you but really not dodge related.

 

I've never used them for this application. I've seen them used in other apps with decades of reliability and counting. I have never bought anything frrom Hellroaring and have no idea about quality etc. It was just an example that popped up in a search. I believe there are several companies making potential candidates for your app though, but I've not researched it enough to say.

For my camper the relay reliability is no big issue and since the relays still rule for lowest voltage drop that's what's in my truck to isolate the camper batteries. One of these days I'd like to add another underhood battery tray and a deep cycle battery isolated from starter battery in parallel with camper power wiring that would serve as more amp hours for the camper. We enjoy an energy hog rating and could always use more house batteries. Maybe even add a small inverteer to the cab for some AC in there. Who knows?