Auxiliary power setup (aka dual batteries)

I've seen lots of really good discussion on here about dual batteries, though they all seemed to center around putting both under the hood and relocating OEM equipment to do so. I figured I'd share my solution:



My Tundra is a recreational vehicle for my family. The goal here was simple: power a fridge and accessories all summer long while charging a lithium battery off both the alternator and solar.

I looked at a variety of solutions for charging. First consideration was using a Victron 12/12-18 charger and 75/15 MPPT solar controller. The issue with this was space; by themselves one of the chargers is compact, but both took up too much space. Additionally the Victron DC/DC chargers get hot and de-rate their output significantly (have one). That is where I kept coming back to the Redarc BCDC1225D. No other solution on the market offered a reliable, compact, all in one charger.

The Redarc is awesome. On a 2007 to 2021 Tundra you only need to connect it to the starting battery. Our trucks do not have a smart alternator, so the ignition trigger is not necessary. Turn the truck on and the Redarc senses the voltage increase and starts charging. Wiring the Redarc is extremely simple.

The Redarc unit is not without flaws. The solar input voltage is limited to 28v; going over that won't hurt it but it also shuts off charging. If you're running one panel it's fine but with two panels you need to wire them in parallel which increases amperage, but also requires a larger gauge connection.

I'm only running one 100w panel, which more than keeps up with the ARB fridge. With a 100w panel and full sunshine I've seen as much as 90 watts go into the battery. Right now, I just use a portable panel. Future plans include a bed rack to mount the solar and Starlink.

As far as wiring goes, I went with simple and modular. The panel has a common ground bar and a surface mount Blue Sea MRBF block behind it. The house circuits are ran through a separate Blue Sea ATC fuse block that is accessible from the front.

All connections to the power panel are made with color coded Anderson SB50s. By using different color SB50s for different connections, it's idiot proof. For example, you cannot connect a red SB50 to a gray SB50. The cables from the starting battery have a red SB50, the house battery as a gray SB50, and the solar uses a yellow SB50. The entire panel can be unplugged and removed from the truck by unbolting it from the bed rail system.

The 100ah LiTime battery is contained in a box that has it's own circuits for use as a portable battery. I need to redesign the box and likely go with a flush SB50 and a separate cable for plugging it into the panel, but for now it works good.

As far as the LiTime battery goes, it works. I have the Group 24 Bluetooth model that Will Prowse has commented favorably on. We'll see how long it lasts. There seems to be two categories of LFP batteries these days: insanely expensive (Battleborn) or generic Chinese.

I have about $800 into this and a few hours of labor. I could have easily gone with something like a Jackery, however it would not have charged as fast nor had the capacity of this system. I can also scale this up in the future if I decided I needed more battery capacity. For now, 100ah is enough to run my fridge for 3 days in triple digit temps without any charging. With solar, it's indefinite.

My next project will be come up with a better method of securing the compressor, battery, and water cans. What I have there works, but it's not terribly efficient.

 

Did a video overview of the system:



Also had the panel off the truck, so took a photo for anyone curious how this was wired up.


I went on another camping trip with this setup, and it continued to perform flawlessly. A 100w panel kept the battery topped off despite not having a full day of sunshine due to being in the woods. I ran my fridge and Starlink off of it the whole time.

For those considering a Starlink Mini for traveling; it's awesome. Being able to use it for work, WIFI calling, and WIFI texting is a game changer when you're out in the sticks. 50gb of data lasts a long time if you skip videos; the unlimited plan is not a bad deal either considering what you get. The biggest challenge is powering it. The Mini will run off 12v power, but you're either limited to a short cable or a large gauge wire to provide enough current to it. I have a 10ft 18 awg cable with a 12v plug on it and it works, but it's only 10ft.

I think I came up with a solution using a Victron Orion-TR 12/24-5a as a step up convertor and power supply. The Orion-TR 12/24 is a converter; it's not designed for battery charging or anything like that. It steps 12v up to 24v with a maximum of 5 amps. The output voltage is adjustable from 20v to 30v. The OEM Starlink 120vac pack puts out 60w (2a) 30vdc through the 15m DC cable. The Orion-TR should be able to provide sufficient voltage through the OEM cable to run the Mini. For now I'm just going to use a 5.5x2.1 female plug to test this theory out. More to come.

 

I wanted to add an inverter to my setup, taking care to ensure it's not too exposed to the elements in the bed of the truck. After some careful thought, I decided to go with a Milwaukee Packout XL Toolbox. The added bonus here is the heat from the inverter should help warm the battery in cold weather, and when it's hot I can simply pop the lid for ventilation. I decided against adding vents to the case to keep the case relatively sealed.

Still rocking the same Litime Group 24 smart battery. This battery has quite frankly impressed me as it's lived in my truck all winter with temps down to the low teens. The low temp cut charging cut off works great; below freezing the BMS will not allow the battery to charge. Litime states the BMS will not allow the battery to take a charge again until it's above 41f, however it seems somewhat inconsistent and seems to start charging above 37f. No issues to report from this. Temps have not been cold enough to trigger the low temp discharge function. I've ran it almost flat a couple times in cold temps running the Starlink. It seems to take the abuse just fine.

The inverter is a Samlex PST-600-12. The Samlex PST inverters are fantastic, not cheap but they will handle running at maximum output all day long. The PST-600 has no issues running a 750w 4 cup coffee maker. It even powered up a 1000w coffee maker, however it triggered the overload protection (which is good). Most of my loads on this will be less than 100w, but having the ability to pull over 600w when needed is nice. I scored this one off ebay for $150 shipped as it was an open box.

For power distribution, I went with the Blue Sea SafetyHub 150. This unit is not inexpensive, but it combines positive and negative bus bars, low current circuits, and high current circuits all in one unit simplifying wiring.

The wire runs were short. I consulted the Samlex manual and Blue Sea's wire chart and both showed 6 gauge was sufficient for this length so I went with it.

I had to do some thinking on how I was going to mount all this in the Packout:


After laying out the components, I built a chassis for the main hardware. The chassis was built out of scrap plywood I had laying around, so it's not pretty but it's also not visible.



The chassis has the BCDC-1225D, inverter, and 12v to 24v converter directly mounted to it. There are 2 fridge sockets, 2 cigarette plug sockets, and a USB socket on the front of the box. One side of the box will have a

$25 15A Weatherproof Outdoor Power Outlet by Journeyman-Pro 15 Amp 125 Volt NEMA 5-15R Receptacle Kit with Integrated 20" Inch Extension Cord + Waterproof Rubber Cover (GCR1-BLACK)

Journeyman Pro 15a socket and the Samlex inverter remote. The opposite side will have 4 Anderson SB50 connectors; 2 gray for outputs to the truck panel, 1 red for input from the truck battery, and 1 yellow for solar input.

The chassis has two skids on it that fit in the grooves in the bottom of the Packout. The skids prevent lateral movement. The base of the chassis fits snugly preventing fore and aft movement in the Packout. I used a Multitool to cut the divider tabs off the inside of the Packout. When this is ready to put together, I'll use heavy duty Velcro on the skids and the rear vertical on the chassis to secure it inside the Packout. This should retain everything, though worst case I'll add a couple tie down loops and a strap inside.

I have some more work to do on the Packout when the Samlex remote arrives. Once I have that installed, I'll have additional to share. The idea with this unit is I can now move it from vehicle to vehicle or use it as a standalone power pack.

My next project on the truck will be making a more compact house panel for the bed rails to provide DC power. Planning to mount a Packout plate to secure the box without needing straps (straps will be used merely as a backup). More to follow in the coming week when the remainder of my parts arrive.