So I built my dual battery setup just about 1.5 years ago. Which consists of two AGM batteries connected via a National Luna Intelligent solenoid. It has been working really well with close to 60 days of camping under its belt. Details on the build are here: Dual Battery Setup (5th Gen Toyota 4runner) - Google Docs
I've recently noticed that my secondary battery hasn't been holding a charge sitting at around 12.2 volts after charging from the alternator for three hours. My battery isolator also will disconnect the batteries when the engine is running if I turn on all my off-road lights at the same time at night while traversing trails. I think some of this may be related to battery degradation especially since our alternator's charging voltage isnt ideal for AGM.
I dont have the ability to charge both batteries via shore power unfortunately. So I'm trying to find a solution. It would seem that ripping out the current solenoid system for an intelligent DC-DC charger would make the most sense but one of my requirements is the ability to link the batteries to winch or jump start the vehicle. With a DC-DC charger this would not be possible.
I know there are other folks here who have similar setups. What have you been doing? Augmenting with solar? Moving back to lead acid?
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'12 Silver 4Runner SR5: 14+ facelift, CBI front, CBI Rear, Warn EVO 10-S, ARB Snorkel, Baja Designs 30" S8, Squadron Sports, S2 Rack Lights, King 2.5 Suspension, OME 899, 33" Cooper ST Maxx, Full CBI Skids, Metaltech Sliders, GFC Tent, ARB Awning
A DC-DC is the best because it can optimize the charging profile, you could always just carry jump leads to jump from your second battery (or carry a jump pack)
Solar is good to keep things topped off, but it's still going to struggle if you dont fix the charging
(Also, get a voltage booster to keep the starting battery in good condition)
Have you looked at your power needs vs battery size?
Here’s a state of charge charge for generic 12v AGM.
As you can see using 50% of the capacity will cut the battery life in half vs using 35% of the charge, using to much of its capacity between charges is damaging.
DC/DC is the way to go, make sure to get a diode to bump the alternator outage for AGM applications as well.
In my dual battery setup I only have 1 AGM battery. I have added the diode module to kick-up the alternator voltage some. I have a shore power ctek charger to use periodically to charge the AGM with its programmed profile to hopefully recondition as needed.
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Michael
2021 Pro Lunar Rock: RCI tranny/transfer case/tank skids, Victory roof rack
2014 LE Nautical Blue: 285/70R17 Falken A/T3W, FX Pro wheels, Fox TRD Pro suspension with Wescott lift, Dobinson UCA's, Metal Tech sliders
I have set up a system for my girls 5th gen that addresses all of these things. First, the charging of the secondary battery is done via roof mounted solar through an MPPT charge controller. It is never connected to the engine, but runs a dometic fridge infinitely unless the engine is started, then the solar charger tops off the battery while driving and runs the accessories off of the engine, thereby reducing the wear on the secondary battery while still charging the main battery. Next, the secondary battery is this:
Which is the probably best battery option you can get. Its lighter and more powerful than any other battery type, is fireproof, lasts 20 years and made in the US. Also, it accepts 20A continuous charge and is fully charged by Solar at 9am every morning even while running a fridge the entire night. The starting battery never gets discharged and the aux battery remains fully charged at all times either by the sun or if there is a problem by the alternator using a completely separate circuit that cannot drain the main battery.
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2005 Blue SR5 v8
3" suspension lift, 1" body lift, 315's, rear Elocker, on-board air system, slider air tanks, full skid plates, front Demello bumper, rear HMF plate/tube bumper, rear 9000lb hidden winch, front 10000lb winch, dual electric fans (in cab adjustable temp), rock lights, 25W LED projector lights.
I had the same issues with my NL system when I had my Land Cruiser, Tacoma and FJ. Paul May at Equipt was very helpful but nothing seemed to work. If I decide to put dual battery setups in my T4Rs I’m going with Redarc.
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2015 Nautical Blue Trail Premium 4WD w/KDSS
2016 Magnetic Gray Limited 4WD
2000 Land Cruiser
So I built my dual battery setup just about 1.5 years ago. Which consists of two AGM batteries connected via a National Luna Intelligent solenoid. It has been working really well with close to 60 days of camping under its belt. Details on the build are here: Dual Battery Setup (5th Gen Toyota 4runner) - Google Docs
I've recently noticed that my secondary battery hasn't been holding a charge sitting at around 12.2 volts after charging from the alternator for three hours. My battery isolator also will disconnect the batteries when the engine is running if I turn on all my off-road lights at the same time at night while traversing trails. I think some of this may be related to battery degradation especially since our alternator's charging voltage isnt ideal for AGM.
I dont have the ability to charge both batteries via shore power unfortunately. So I'm trying to find a solution. It would seem that ripping out the current solenoid system for an intelligent DC-DC charger would make the most sense but one of my requirements is the ability to link the batteries to winch or jump start the vehicle. With a DC-DC charger this would not be possible.
I know there are other folks here who have similar setups. What have you been doing? Augmenting with solar? Moving back to lead acid?
In a previous 4Runner I had, I was using two AGMs (a group 31 and a group 34) tied together with a Blue Sea ML-ACR. That setup ran for many trouble free years with a fridge on 24/7/365 and a variety of lights, radios etc. all being fed from that system. The ML-ACR has a manual activation mode that can be triggered either with an in-cab switch or manually using a knob on the relay box itself.
I just got into a new 2020 4Runner and I'll likely be using the same ACR for the charging system as I get the build together. I'm not likely to use a group 31 again though as the weight is extreme with a second battery as backup. Probably a pair of Group 27 AGMs.
__________________ '20 Army Green 4Runner TRD PRO '16 Quicksand Tundra TRD PRO Gone '08 Salsa Red Pearl 4x4Runner SE V6: Gone
You probably nuked (sulfation) it by just letting the stock alternator charge it for the entirety of it's life. AGM's want to charge between 14.1-14.9v and your stock alternator isn't going to give you that kind of output.
I run a voltage booster + solar + charge at home very occasionally and haven't had any problems.
Noticed the same after about a year with my National Luna.
I have the factory Panasonic? battery and an Optima Yellowtop and was noticing I just couldn't get enough charge into the Optima.
Recently replaced and rewired for a Redarc 25. I noticed an immediate difference. I don't have all the fancy voltage monitors but I could tell my ARB 63 which is always on was running all week with no change to drive times/alt charging times.
I still use 'shore power' if ARB is on and I'm not using 4runner for a few days. I've an on-board NOCO for that.
Meandering point is...after a year or so with the National Luna, I recently swapped for Redarc 25 and I noticed a significant enough improvement to (for me) warrant the cost and effort of the swap.
I have set up a system for my girls 5th gen that addresses all of these things. First, the charging of the secondary battery is done via roof mounted solar through an MPPT charge controller. It is never connected to the engine, but runs a dometic fridge infinitely unless the engine is started, then the solar charger tops off the battery while driving and runs the accessories off of the engine, thereby reducing the wear on the secondary battery while still charging the main battery. Next, the secondary battery is this:
Which is the probably best battery option you can get. Its lighter and more powerful than any other battery type, is fireproof, lasts 20 years and made in the US. Also, it accepts 20A continuous charge and is fully charged by Solar at 9am every morning even while running a fridge the entire night. The starting battery never gets discharged and the aux battery remains fully charged at all times either by the sun or if there is a problem by the alternator using a completely separate circuit that cannot drain the main battery.
Do you have more details on this setup? How much total do you have invested?
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2015 Trail Premium Super White
2018 TRD PRO Super White
I'm not a fan of the NL system. I've ran into all these issues in the past... charging, maintenance, and battery degradation is one thing, but even with a healthy system and a very high load, it can cause the second battery to disconnect with the engine running due to the voltage drop.
For those who don't go the direction of a DC-DC, and use a charge relay, I really think the Blue Sea #7611 is an excellent option if you don't want to spend money on the larger ML series.
During high load, if the system voltage drops under 12.75 it can cause the ACR to go open, which only compounds the problem.
The 7611 has an option to drop (via switch or ignition control) the low open voltage to 12.25 volts. This is primarily done to increase capacity as it allows the starter to participate in feeding the load, but also helps combat against high load open conditions.
I use this ACR a lot in my builds, but these days am building a lot more custom lithium systems using a DC-DC as the advantages are huge.
I have set up a system for my girls 5th gen that addresses all of these things. First, the charging of the secondary battery is done via roof mounted solar through an MPPT charge controller. It is never connected to the engine, but runs a dometic fridge infinitely unless the engine is started, then the solar charger tops off the battery while driving and runs the accessories off of the engine, thereby reducing the wear on the secondary battery while still charging the main battery. Next, the secondary battery is this:
Which is the probably best battery option you can get. Its lighter and more powerful than any other battery type, is fireproof, lasts 20 years and made in the US. Also, it accepts 20A continuous charge and is fully charged by Solar at 9am every morning even while running a fridge the entire night. The starting battery never gets discharged and the aux battery remains fully charged at all times either by the sun or if there is a problem by the alternator using a completely separate circuit that cannot drain the main battery.
Can you self jump, i.e. connect the two batteries together if needed? Other than using jumper cables.
__________________
Michael
2021 Pro Lunar Rock: RCI tranny/transfer case/tank skids, Victory roof rack
2014 LE Nautical Blue: 285/70R17 Falken A/T3W, FX Pro wheels, Fox TRD Pro suspension with Wescott lift, Dobinson UCA's, Metal Tech sliders
Do you have more details on this setup? How much total do you have invested?
Sure, what details are you interested in? Her truck was in the Rebelle rally this year, heres a pic of it with the roof rack and integrated solar panel. We made the rack and battery holder ourselves since nothing exists that we wanted.
Full disclosure: She is sponsored by Bioenno, so of course we used their battery.
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2005 Blue SR5 v8
3" suspension lift, 1" body lift, 315's, rear Elocker, on-board air system, slider air tanks, full skid plates, front Demello bumper, rear HMF plate/tube bumper, rear 9000lb hidden winch, front 10000lb winch, dual electric fans (in cab adjustable temp), rock lights, 25W LED projector lights.