Instead of voltage boosters why not a smart isolator for yoiur dual battery setup?
Battery Doctor Isolator | 100 Amp Battery Isolator
http://www.batterymart.com/p-acc-200...-isolator.html

150 amp version is the one I use. No problems and I use a 24f and 31 agm batteries.

ordered the hkb one for now. put in a 31AGM battery, and dont think its charging properly

How does that solve the problem of the voltage not being high enough to charge the battery? That just looks like an iolator, it serves a completely separate purpose

it gets the voltage into spec for the battery

I am worried about it not being enough though, i haven't seen mine ever charge at 14V so I would need more of a boost

Yeah that's what I'm worried about also, sweet spot for AGM is 14.4v -14.6v and I'm only seeing 14.2v at my 2nd battery.

I'm already using one, National Luna Smart dual battery system. It does not help th voltage situation.

Sub'd interested to hear the results of the Fuse and other ideas.

It is an isolator. I forgot to point out ( my bad) that I have zero gauge for both batteries and 30a fuses along the battery run to protect everything. I am also using Northstar AGM batteries as well. My setup was professionally installed and I was told I did not need a higher output alternator. I also had the vehicle grounds more robust which helps out as well.

I hope this clarifies if I made a wrong conclusion.

Higher output alternator and voltage booster are not the same thing, one is amps (and maybe also volts) and the other is volts. You probably don't need more amps unless you've added a lot, but if you have a marine or deep cycle battery you probably need more volts. You'll need to check the stats for your Northstar battery but I bet it wants about 14.4V; the stock charging system as is provides less than 14V. The problem with not having hig uhh enough voltage is that your battery won't be full6 charged which means you will get salfation which will prematurely kill your battery

Sent from my SM-G930V using Tapatalk

Perhaps I'm missing something here, but shouldn't a dual battery setup, equalize it's voltage automatically. With two batteries installed, it's like having one large battery provided they are not isolated. I would think the batteries would simply equalize after time. A normal battery will charge up with anything greater than 12.6 volts right, and the voltage is how you control the rate of charge. If you have a dead battery and jump and start, you will have a high voltage like 15-18 volts charging up the battery, that voltage will slowly creep down back to 13 something over time.

As far as amps, I don't think that has anything to do with it, deep cycle batteries should not be charged at greater than 10amps anyhow, so any alternator will output that and almost all of the time, your alternator isn't putting out hardly anything, until you turn on your headlights which take more than everything else combined. Looking into dual battery setups and deep cycles, I was more concerned with charging the battery too fast, compared to not charging it at all. Perhaps the AGM deep cycles can be charged at a faster rate, but normally deep cycle fast charge is a no no. A normal car battery will charge up in less than an hour usually, they are built to charge up extremely quickly, but should never go below 50-75% charge or damage will start.

What your referring to is a battery bank, I'm running two batteries that are connected via a intelligent solenoid that separates the batteries when at rest. Tractors, boats, and heavy equipment typically have battery banks because of the energy needed to start large engines.

AGMs need much higher than 10v to even maintain charge under load, from my research a typical AGM will not charge under 13.6v. You are correct old school lead acid deep-cycle plate batteries should be charged long and low.

Don't they make some kind of DC to DC charger that would simply charge your secondary battery from the provided voltage and regulate(boost) the voltage as needed for the AGM, so input voltage could even be the static 12.6 and still charge up?

Really you just need something to boost and regulate the voltage, however I don't like the idea of altering the systems current running voltage system, seems like it would be better to boost the voltage from the supplied voltage by using a DC-DC charger.

They do, but DC-DC converts Amps into Volts and from what i have read, from those across the pacific, is that the DC-DC chargers are fire hazards and do more damage... not to say putting a resistor in my fuse box is not a fire hazard but i couldn't find any documented issues with the fuse solution.

Update: it appears like the fuse allows for just enough amps to charge my AGM battery.

Sunday morning my AGM battery showed 11.6v this morning it shows 12.2v. Yesterday I drove approximately 2hrs of mostly highway, parked and let my fridge run all night. Prior to installing the fuse my AGM battery would be critical unless I plugged into shore power. Initially this fuse appears to charge the AMG at a rate to overcome overnight discharge.

One thing to note, my primary (oem) battery typically shows higher volts than what it is showing this morning. It will be interesting to see if this trend continues.


I will keep updating this thread


Sent from my iPhone using Tapatalk

why is your fridge drawing down your starting battery, i thought you had it isolated?