Need some help designing my dual battery setup

Sunpilot

Observer
First, I'll give you some background. I have a 4th gen V8 4Runner. It has a standard 130a alternator. I'm making an overland rig out of it. I already have cables installed through the firewall to a rear distribution box and switches for aux. lights, ham radio, fridge, etc. The next part of my project entails adding a second battery (house battery). Actually, since my main battery is getting a bit old, I intend on replacing it when I install the house battery. I'll be going with agm batteries for both main and house. Not sure on brand yet (still researching). I will probably add solar power at a later date. I don't see me staying in one place for more than a day or two, so the vehicle will be getting charge from alternator every other day or so. Here are my questions:

I want to avoid current draining diode designed battery idolators, so I will be looking at a few VSRs/ACRs. I see many sellers, mostly on Amazon, offer VSRs (dual sensing) in the 120 amp continuous duty range that can support higher current draw for short periods. Would these be sufficient for my use, or will I need to use a higher amp unit? I see Cole Hersee offers a smart VSR that has 200a continuous rating but it is not dual sensing and might not be as flexible as the dual sensing units. BlueSea also offers dual sensing ACR but mostly in the 120a range. (they list a minuscule standby drain in the miliamp range though.. I assume it is because the unit has an led light to indicate ACR state). BlueSea also has a beefier unit at over double the price (rated at 500amp continuous). Will the 120 amp VSRs/ACRs be sufficient or should I go with the Cole Hersee or more pricey Bluesea heavy duty option?

Is there any other setup that would take care of my charging needs and provide possible solar control if I add solar later? I'm trying to do this job without killing my bank account.

Any thoughts on battery brands are welcome also. I've heard some negative opinions on Optima, but have never used them. Odyssey sounds very reliable as do Northstar, and X2

I've been reading many hundred posts here and elsewhere. Everyone has their own thoughts and there are many opinions out there. Given my requirements, what are your opinions? I really appreciate any thoughts you may offer.
 

snare

Adventurer
I suggest getting a dual voltage sensing ACR and just running the solar through a separate solar controller to the auxiliary battery .

Another option for a dual sensing ACR is the Samlex 160. It is fully potted and waterproof, and it has the ability to run a manual override switch ( self jump and force separate the batteries) and an indicator LED.
 

Rando

Explorer
The Bluesea SI-ACR should work just fine for what you want to do, and is good value at ~$85. It is dual sensing, which is a key if your are planning on adding solar, and you can add a remote status light and disconnect over ride if you want. There is really no need for the higher capacity relay in your situation.
 

Sunpilot

Observer
The Bluesea SI-ACR should work just fine for what you want to do, and is good value at ~$85. It is dual sensing, which is a key if your are planning on adding solar, and you can add a remote status light and disconnect over ride if you want. There is really no need for the higher capacity relay in your situation.

Would I be able to combine both batteries for emergency starting should the main be too weak to start the vehicle? Perhaps with a manual switch?
 

Rando

Explorer
No, there is no manual override to combine on the SI-ACR. In 10 years of having a dual battery system I have never needed that capability, and if I did I would just use my jumper cables. The whole point of a dual battery system is to avoid having a flat starter battery.
 

DaveInDenver

Middle Income Semi-Redneck
No, there is no manual override to combine on the SI-ACR. In 10 years of having a dual battery system I have never needed that capability, and if I did I would just use my jumper cables. The whole point of a dual battery system is to avoid having a flat starter battery.
Precisely. I have a ML-ACR and while in theory being able to parallel them for winching and jumping is there I've never needed it. If I could go back and not spend the money I'd get something sized appropriately to my alternator (I've also never hooked up the remote switch, so auto-only mode with perhaps a local manual is more than sufficient) and use the remaining money for beer. It's not like I'm going to leave the jumper cables behind even with this capability, so this is an unnecessary feature IMO.
 

v_man

Explorer
I may be confused here with all the acronyms flying around, but in my dual setup I went with a simple solenoid controlled by me with an in cab switch. It's completely manual, both batteries can be linked at any time, regardless of their respective voltages, or wether an 'intelligent' solenoid deems it appropriate.

The two situations I thought it would be useful to have a manual solenoid would be:

1) Starting battery has somehow been drained, maybe child/wife leaves a light on or something charging overnight, who knows. Link batteries and start your car.

2) I need the extra aH capacity when winching with the vehicle off, or unable to start. Long shot scenario but who knows...

Also a simple solenoid with a manual switch is cheap. And FWIW my second battery is a deep cycle Optima and I've had positive experiences with other Optimas as well...Dual install is in my build thread.
 

Sunpilot

Observer
I thought about a simple solenoid but I'm afraid I may forget to switch it properly and leave myself stranded. Smart relays avoid this. I was really concerned that the Bluesea 7610 and 7611 might not be enough, since they are rated at 120 amps continuous, and even their own website cautions that the unit should be rated for at least the alternator output, which in my case is 130 amps. The website does say that it will withstand 210 amps for 5 minutes though. That's a long time in my opinion. Maybe the 7610 is the way to go. I do have one more question that I am not clear on. If I was using the 7610, let's say, and I wanted to charge just one or the other battery alone, like with a battery charger at home, would I need to disconnect the link between the batteries? I'm thinking the 7610 would just combine them. Am I correct? If that is the case, I could use a manual disconnect on the house battery while the charger was on.
 

dwh

Tail-End Charlie
Dumb ignition-controlled solenoid is automatic - turn the key off and it disconnects the batteries. Forgetting is not an issue.

So charging the batteries independently is easy - just leave the key off.

Dual sensing relays are handy if you have alternative charging, such as solar or a shore-power charger - AND - you want to charge both batteries at once. But you could just use single sensing and do the same thing - just hook the solar or shore charger to the engine battery.

Dual sensing relays are not good for independent battery charging unless they have some sort of manual override ability.


Edit: But if the batteries are roughly the same, might as well charge both when the shore charger is plugged in anyway.
 

martnH

Member
Your alternator maybe rated at 130A, It will never produce that much current outside of its testing lab.
As an alternator heats up, (either from loading it, or simply alongside your hot motor) its output drops off.
I dont envision scenario where that might be useful. On the odd chance you really needed to isolate a battery, That could be as easy as unscrewing a connector, or opening an OCPD.
I installed a amps meter. It's actually a multimeter by blue sea

It sometimes reads 150amps on bulking charging and if you use the winch, the winch will draw from both batteries (because the car is running the relay will connect them both), and the current can be up to 400 amps

Sent from my LG-H870DS using Tapatalk
 

Stephan07

New member
I'm in the very early stages of planning a dual battery system like yours, wired to the back of my 2017 4Runner. I plan on using a dc-dc charger at the battery box that has mppt port for solar as well. I have a question about wire size and fuses. I was planning on running 4guage wire with a 100amp fuse in the cable leading to the bed. When I look at some of the kits on line, such as the Luna kit and the wire kit from Australian Direct, looks like AD is using 8
guage and a 50amp fuse. national Luna uses a 16mm which is 6guage, but it comes with a 100amp fuse and 50amp anderson connector.

I would imagine its safe to use 6 or 8 guage as long as I fuse it correctly. I was surprised to only see a 50amp fuse from australian direct.

Thanks!!
 
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