I've been running RedArc solenoids for over 10 years they are bullet proof never had an issue, and I spend a fair bit time out in remote locations and deserts. So to keep these expensive batteries conditioned I've installed;

- a 20Amp MPPT solar PV regulator/charger (with good quality electronics around $30-$40) - along with 120W solar panel (integrated into the roof racks) - Digital power meter (wired inline with the solar panel to get PV current and battery voltage readings).

This will auto trickle charge both batteries 365 days of the year and these bad boys will last 10 years along with the reliability of a RedArc isolator.

Hi will...with what you describe You will end up with a voltage drop in the rear and your second battery will not get a full charge...with a dc to dc charger in the rear as well as the battery...problem solved..as the dc to dc charger senses the type of battery and gives it the appropriate 3stage charge up to 20amps and 14.5 volts..supplied from your alt up front ..you won't get that from your alternator without a dc to dc and with a under the bonnet battery you will have to run big cable to deliver the same voltage as under the bonnet to the rear ...much larger and cumbersome than 6mm2.I have a ctec duel...dc to dc charger in the rear with 6mm2 cable run from the under the bonnet supplying the correct voltage and amps to my large battery in the tub...and the ctec has an inbuilt solar charger...a set and forget 2nd battery management system...trust me I'm a boatbuulder and I've tryed everything...all other systems are just old tech nothing but a dc to dc charger will charge your battery as well...I recommend a AGM battery(safe in your rear cabin space)...my system has a 165ah AGM and a secondary ctec unit called a smart pass that can handle 80amps and a low voltage cut out.used in conjunction with my ctek duel.post script to get that charge rate you have to run25mm2 cable..to the tub.

https://youtu.be/tVQGfFIMYFoWatch this guys videos he explains the new tech really well and his gear is of high quality...He has many videos on his web page explaining 12v electrics abate with his brand..

I've described it's function above...it handles up to 80amps for large battery's and has a dedicated low voltage cut out..when combined with a ctek duel..with the usual features of solar charging and when the storage battery is charged the staring battery will be charged via solar or a 240v charger...the later connected to the storage battery..

ok so how are you getting the 80amps from the altinator to the smart pass in your canopy ? would have to be one very thick cable, the smart pass doesn't produce 80 amps, however it's capable of distributing it 4mmsq cable does not carry 80 amps

Whoops snakesoup !!! I'm quoting from the instruction book now..lol...ok my mistake I'm going to correct my posts... I should have checked my cable is 6mm2 40amp cable...from when I had the duel only..that's the recommended cable for a 5 mtr run ..for the duel ...the smart pass is a recent addition..for the smart pass it recommends 25mm2 for the same distance......stupid me I read and interpreted that the smart pass produced 80 amps...( it only handles it) ...so ...if I increase the size of my cable will it make a difference in the charge rate..so far I have only observed 20amps charge on my amp meter ..(I gather that the ctek senses a safe current to draw?)with a ml alternator..will I Get a higher charge rate from it...?pondering new cable now..

wasn't trying to rain on ya parade either mate it was just an observation, I really like what you have done and love the big ass battery, beef up that cable run and you should be good to go and thumping the current into that battery..

Thanks !...No not a problem mate ...thanks for pointing out my mistake ...on thinking about it the smart pass does turn on then off and switch over to the duel ...thinking that's because of the small cable run $120 should get me some 25mm2 Tinned marine cable..more pics in my build thread...

In all for a simple system without separate components and without running cable everywhere ..just two boxes in the tub and two cable runs...I like its simplicity and it does everything...If you get the pair of units it comes in a 4x4 pack with amp an and volt guage.....even a bluetooth app for your phone..(separately)

Hi Tomola,Just seen your dual battery install - looks good. It’s a similar setup to what I am trying to achieve although my aux battery is under the tray.I am running a projecta battery isolator but am finding that my aux battery is going flat after 3 days or running the waeco.I am wanting to install a 20amp MPPT dual solar controller http://s.aliexpress.com/ramuQv6j

My question is, can I leave the battery isolator in place so the battery still charges whilst driving at night, then the solar should charge the aux battery and trickle charge the main during the day.Just not sure if it would be ok to have the aux being charged by the alternator and solar at the same time?