Dual battery question: Mixing battery types & sizes

[TsherryUSA]

Hi All, with all the downtime at home I'm finally getting around to building out the back of my 99 Explorer with drawers and a sleeping platform for camping.

Background:
I'd like to run some lights and other accessories off of a second battery. Most of the info on dual batteries I can find is for adding a second full size battery to run MEGAWINCH7000. I'm not doing that. Just LED lights, phone charging, bike computer charging, camera battery charging, etc. I know I would probably be fine just running off my 750 CCA starter battery, but I like the piece of mind of having the accessory battery for trips where I'm parked a few days in a row.

I've read through much of Expedition Portal's famous cheap dual battery setup: https://expeditionportal.com/forum/threads/how-to-make-a-cheap-isolated-dual-battery-setup-for-50.77503/

As for location, I am thinking of locating it in the back of the vehicle, either on the left or right side. I'm undecided as of now, if anyone has suggestions, I'm all ears.

Question: Is it safe to set up a small sealed lead acid battery like: https://www.amazon.com/dp/B00K8V2VD0/ as a dual battery with a solenoid as suggested in the Expedition Portal thread? I am worried about overcharging a small battery.
Would I be better off getting one of those "smart battery isolators" https://www.amazon.com/dp/B00WTAFR5W?
With the smart style isolator, do I still have to run a wire between negative terminals on both batteries?

Thanks for reading.
-Tim

 

[BKennedy]

You might be better off getting a small solar panel to keep your single battery charged while charging those small items. I don't know what the charge requirements are for those smaller batteries. You would need to find out from the manufacture of data sheets of the individual battery's. Or maybe get a separate charging station type battery like this Suaoki S270 Portable Charging Station 150Wh Solar Generator Camping Emergency 689997460693 | eBay (This is just an example I found with a quick eBay search, I have no information about its quality). I have two of the same Optima red tops in my Explorer, but I have had one red and one yellow, and one red and one blue before the current setup. Its currently like that due to the very high cost of the yellow and blue tops that don't seem to last. I have mine wired about the same as that expeditionportal diagram, but am using 200 amp manual reset breakers instead of fuses, along with a 450 amp mega fuse at the secondary battery for good measure. My secondary battery is in the space where the spare used to reside. I think you can put them side by side in the engine compartment of a 2nd Gen Explorer.

Quick search of the forum shows dozens of threads on this topic, but none relating specifically to your wish to use non automotive batteries. However, I did find a thread about dual batteries located within the engine compartment of a 2nd gen

Dual Battery Setup - Dual Optimas

Here are some pictures of the dual battery setup I have. The mount is a small tray that required moving the ABS pump back and cutting into the body a bit. I still have not added anothing to keep the batteries down, but they are in very tight...

www.explorerforum.com

Search results for query: dual battery

www.explorerforum.com

 

[TsherryUSA]

You might be better off getting a small solar panel to keep your single battery charged while charging those small items. I don't know what the charge requirements are for those smaller batteries. You would need to find out from the manufacture of data sheets of the individual battery's. Or maybe get a separate charging station type battery like this Suaoki S270 Portable Charging Station 150Wh Solar Generator Camping Emergency 689997460693 | eBay (This is just an example I found with a quick eBay search, I have no information about its quality). I have two of the same Optima red tops in my Explorer, but I have had one red and one yellow, and one red and one blue before the current setup. Its currently like that due to the very high cost of the yellow and blue tops that don't seem to last. I have mine wired about the same as that expeditionportal diagram, but am using 200 amp manual reset breakers instead of fuses, along with a 450 amp mega fuse at the secondary battery for good measure. My secondary battery is in the space where the spare used to reside. I think you can put them side by side in the engine compartment of a 2nd Gen Explorer.

Quick search of the forum shows dozens of threads on this topic, but none relating specifically to your wish to use non automotive batteries. However, I did find a thread about dual batteries located within the engine compartment of a 2nd gen

Dual Battery Setup - Dual Optimas

Here are some pictures of the dual battery setup I have. The mount is a small tray that required moving the ABS pump back and cutting into the body a bit. I still have not added anothing to keep the batteries down, but they are in very tight...

www.explorerforum.com

Search results for query: dual battery

www.explorerforum.com

Thanks for the ideas, BKennedy.

Ah, I thought I had read through all the dual battery threads. Missed those photos of the double optimas. Looks like those optima dims might be a bit more compact and thus can squeeze two side by side, rotated 90 deg relative to the stock battery orientation. I'll take another look at dropping something like that in at that location .

Per your charging station recommendation. A friend actually made the same rec, but for this unit: https://www.amazon.com/dp/B07FYJVFNK. His pitch was that it would be useful to have in the earthquake / emergency kit if the power is out in the house. Definitely something to consider especially since it is the "EASY BUTTON" option.

I have a spreadsheet going tracking costs. It may end up being cheaper to just get that portable unit plus a portable jump battery for emergencies.