Dual battery systems; making sense of the options (2 Viewers)

[toadshade]

Very cool. I am building a battery tray now so I am looking forward to a week in the Red River Gorge in Kentucky. A stick shift is a nice insurance if my battery dies but it would be great if I could feel safe without having to park pointing downhill

 

[250below10]

Hi guys, really nice info rear.
So, I found a really good deal on a 12v fridge that I couldn’t pass on, but that made me revisit my electrical plans earlier than I have planned.
Right now my 80 has a group 24 wet cell from Napa that came with the truck when I bought it. Im planning for a nice and reliable dual battery system but Im also trying to keep cost down. I plan on using a Blue Sea ML-ACR to connect/isolate the batteries. My question is, could I run a dual battery system with my Napa battery as a starter battery and use an AGM 27F as a house battery (planning on hitting the OFF switch on the ACR every time the truck is no running) until I can save some more money to buy a second AGM 27F? Or should I just run a single battery system with the AGM battery until I can buy a second one?
Or should I just put this all on hold until I can afford to buy both AGMs at the same time?
TIA

 

[toadshade]

It’s a little complicated. Can you do both? Yes. But it will ultimately take a little more work. Two different battery types charge differently. You might be talking about a voltage regulator or dc/dc regulator. Look that up first and you will twist your mind with all the info on battery charging. The ACR will help but it could still result in a battery replacement sooner. Check out the KISS battery method too.

 

[bonestock]

It’s a little complicated. Can you do both? Yes. But it will ultimately take a little more work. Two different battery types charge differently. You might be talking about a voltage regulator or dc/dc regulator. Look that up first and you will twist your mind with all the info on battery charging. The ACR will help but it could still result in a battery replacement sooner. Check out the KISS battery method too.

My Redarc DCDC has been super reliable. I use a regular lead acid for my starting and an odyssey for my house battery. Put them to the test(ish) a couple weeks ago and I’ve never been happier. Install is stupid simple too.

 

[MCtree]

Hi All,
With this good information of the dual battery set-up options, I think I’m going with the redarc BCDC.
Is my understanding correct that, should I ever do something dumb like leave my headlights on overnight and kill my starter battery, I would need to have the Smart Start SBI 12V installed between the two batteries in order to jump the vehicle?

The BCDC itself doesn’t allow for the Aux battery to jump the starter? This seems like a deficiency.

Could I instead carry jumper cables and hook the Aux to the Starter?
Or would a deep cycle battery not be sufficient to jump the starter battery via jumper cables?

 

[bonestock]

I just carry jumper cables in case I need to self-jump. There's a guy on here that has one for sale. For Sale - Tucson - Redarc BCDC1225 - https://forum.ih8mud.com/threads/tucson-redarc-bcdc1225.1239522/

As info, I had everything needed to upgrade to the Sequoia Alternator. I just liked the idea of hooking a Redarc BCDC up and letting it figure out the rest.

 

[Shoredreamer]

If your need for the second battery is only to be backup/self jump start, I would suggest keeping it simple and carry jumper cables. You could dodge the unnecessary SBI relay and have a little slicker “jumper cable” setup by grounding your second battery to the passenger side engine block when doing your battery install. Then run a 2awg positive cable from each battery with a high amp manual switch between the two. You would be able to join the batteries in parallel with that switch if you ever needed. You would also want to run an inline breaker on the BCDC input cable from the start battery to the BCDC though and break that circuit if you choose to switch to parallel. This is useful for self jump, doubling capacity for winching or high amp short loads, or if you reverse charge solar via Redarc and would like to charge both batteries in parallel via solar charge.

 

[MCtree]

If your need for the second battery is only to be backup/self jump start, I would suggest keeping it simple and carry jumper cables. You could dodge the unnecessary SBI relay and have a little slicker “jumper cable” setup by grounding your second battery to the passenger side engine block when doing your battery install. Then run a 2awg positive cable from each battery with a high amp manual switch between the two. You would be able to join the batteries in parallel with that switch if you ever needed. You would also want to run an inline breaker on the BCDC input cable from the start battery to the BCDC though and break that circuit if you choose to switch to parallel. This is useful for self jump, doubling capacity for winching or high amp short loads, or if you reverse charge solar via Redarc and would like to charge both batteries in parallel via solar charge.

Shoredreamer,
I think I like where you are going with this, but I don’t really understand it. Could you elaborate? (Jumping a land cruiser via a second battery for dummies)

Also, does it change anything if I am not getting the second battery only for back-up starts/self jumps? I mean, this is the primary reason, but as long as I’m getting it, I might as well get it set up for a fridge should I ever want one.

 

[FrazzledHunter]

If your need for the second battery is only to be backup/self jump start, I would suggest keeping it simple and carry jumper cables. You could dodge the unnecessary SBI relay and have a little slicker “jumper cable” setup by grounding your second battery to the passenger side engine block when doing your battery install. Then run a 2awg positive cable from each battery with a high amp manual switch between the two. You would be able to join the batteries in parallel with that switch if you ever needed. You would also want to run an inline breaker on the BCDC input cable from the start battery to the BCDC though and break that circuit if you choose to switch to parallel. This is useful for self jump, doubling capacity for winching or high amp short loads, or if you reverse charge solar via Redarc and would like to charge both batteries in parallel via solar charge.

THIS. I could have done literally anything but I chose to handle the scenario with jumper cable. I'll spend the $ it would have cost me for a SBI relay etc... on beer.

 

[MCtree]

THIS. I could have done literally anything but I chose to handle the scenario with jumper cable. I'll spend the $ it would have cost me for a SBI relay etc... on beer.

I’m torn.
I completely agree with the KiSS concept. The fewer things that can break the better.
On the other hand, I am also a minimalist and if I don’t have to carry jumpers, that is a plus in the other column. I like the neatness and elegance of having it pre-wired.

 

[FrazzledHunter]

I’m torn.
I completely agree with the KiSS concept. The fewer things that can break the better.
On the other hand, I am also a minimalist and if I don’t have to carry jumpers, that is a plus in the other column. I like the neatness and elegance of having it pre-wired.

Well OK - but I'm a preparedness nut. You might need/want to carry jumpers anyway if, however unlikely, you run both batteries down or you wish to be a good Samaritan and be prepared to help out someone else.

 

[toadshade]

Everyone has their own version of KISS. In my mind I believe that means electronic, (that being digital) switching. Instead of jumper cables, I have a marine switch and single ought cable. I don’t believe that is breaking the KISS rules personally. It is nice and neat and very easy. But I still carry jumpers to be a nice guy. And you never know when you are going to be in the middle of nowhere and you forgot you left your inverter on

 

[BillyGoatMTB]

Morning Mud

I decided to try something new different and went RedArc, put a short video together showing the install.

I'm happy with it and the use of space.

 

[ntsqd]

On my last project vehicle I ran a BEP Marine battery combiner switch that allows me to start off of either or both batteries. In parallel with that is a Blue Sea Systems Automatic Charge Relay. I'd have preferred to use a BEP Marine Voltage Sensing Relay, but I could not find any in inventory at the time. If they're placed near each other then that makes the wiring and cabling simple and short. Note that this is a 'dumb' alternator vehicle, no need for a DC-DC converter or anything that sophisticated. A photo from during working out how to route all of the various wires and cables:

The next project vehicle will use LiFePO or something like that chemistry for it's 'house' battery.

 

[jatree]

Getting ready to replace a 5-year old battery. I sometimes carry a lithium battery jump pack but am trying to figure out a longer term plan for my 80 series. I'll never have a fridge or be off grid for weeks at a time. At most, I'll want to add a winch, maybe a compressor or accessory area to plug a speaker or something in while camping. So a secondary battery for accessories and self-jump seems like a potentially good idea. But does it make sense to do with my current battery (no issues with it) or would that have to be 2x new ones?

I'm also learning about portable power stations but similar to the jump pack, don't like the idea of just leaving that in the truck all the time.

 

[spressomon]

Consistently getting 10-years+ out of my Odyssey AGM batteries. Keep them on a good quality charger/maintainer when you're not driving the rig and you're golden.

Yeah, they cost more...but you get more . If you don't have a fridge/freezer then keep it simple with a Group 31 if you can fit it in. Carry a lithium jump pack for back-up and you're set.

 

[ntsqd]

Given the stated use, I tend to agree. Put a quality battery in the starting position and keep the jump-pack charged. Most of those can be used for other things besides a self jump-start.

I've been looking at timer relays to drive the charging of a couple items that stay in one truck in particular. One that I've found will run for a programmed duration with every key-on, and then turn off so that I'm not always charging those tools.

 

[jatree]

Appreciate the thoughts...timer relay sounds interesting for your use case.

 

[LandLocked93]

What the actual balls is going on here?!
Loads of what-if's and if-so's.

There is a direct way to store and use current (several actually) at will.
PM for discussion if all the previous does not suffice.