Portable Power Station DIY Build -- My Portable Battery System

[Johnny Rebel]

Thanks! For my solar panel, since I likely won't be using it while driving, I'm envisioning sliding it underneath my roof rack's cross bars into some brackets I'll have to make. I want to be able to store them up there along with other stuff on top of the rack, while being able to easily slide them out when I get to camp.

I was watching an Everlanders video on YT a few months ago where he designed a slide-out solar panel array on his truck. I've wondered if something like that could be done on a Bronco. Can't wait to see what you come up with.

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[cr117]

Beautiful work and great design. Where did you tap ignition? I was looking for run indication for my charger, given auto-stop at traffic lights vs ignition.

I haven't gotten to the DC-DC charging setup yet, that'll be phase II. I wouldn't over-think it, the Bronco's system will know if the starter battery's voltage is too low for the auto-stop to engage. If you're pulling power to charge your second battery, it'll take that into consideration.

I was just about to reply and say the panels shouldn't be permanently setup on a roof rack. Although, while you're making brackets, you may want to consider both an adjustable-tilt easel-like stand for campground setup on the ground and a way to attach them to the rack after gear is off and you're parked. I'm sure you could incorporate both modes into one stand/brackets. Some campsites may have blocked sunlight and the Bronco will be your best bet as a surface.

That's a neat idea. I hadn't fully fleshed out the panel angling setup plan yet, was thinking I could just prop it up against something and that'd be fine. I like the mountable idea though.

 

[The Bronc]

BTW, @Tricky Mike, your compressor fits perfectly in the same case. I've been debating whether or not to modify a 2nd case I keep the compressor in to make it easier to plug in and connect hoses. The issue is I still have to open the lid to allow for air flow and cooling while in use, so there's not much benefit. We'll see if I get bored at some point in the future though, I might just come up with something for it.

What brand and model compressor is in the case?

 

[cynicalrider]

Awesome work! I have found those cases from HF are awesome for these types of projects. I made an electrical hub in the back of my Tacoma with the same case:

My wiring isn't anywhere near as clean as yours though ha.

 

[cr117]

What brand and model compressor is in the case?

It’s the Trickflate with a pressure sensor added.

 

[cr117]

Awesome work! I have found those cases from HF are awesome for these types of projects. I made an electrical hub in the back of my Tacoma with the same case:

My wiring isn't anywhere near as clean as yours though ha.

Nice! Looks like it gets the job done.

 

[Area51BS]

Figured there was enough interest from my post in the daily updates thread that I'd break this out to share more details about this project. Kind of long-winded, but I wanted to share my thought process and journey to maybe inspire others to do the same.

First, some background...

We got our Bronco specifically for the purpose of off roading and camping trips. In researching options for gear, and how it'll all fit in the Bronco, I decided it'd be more efficient to use a 12V fridge instead of cooler that constantly needed to be refilled with ice. To do that though, I wanted a power solution that was reliable and separate from the Bronco's electrical system to avoid draining the starter battery. So it was determined an auxiliary would be needed.

After more digging, I wasn't satisfied with any of the out of the box solutions out there. Most of them are too cube-shaped and they'd need to be packed in a specific orientation in order to plug things in while on the road. I was also concerned about the longevity of these units. If something breaks, I'd be at the mercy of the manufacturer's warranty to get it fixed/replaced. Additionally, whatever I bought today, I'd be stuck with. No opportunity for modifying or upgrading components as my needs change.

On to the integrated dual battery option. There are a couple of configurations out there that hide the battery & charger in the cargo area that I was really intrigued by. I liked the ability to quickly charge from the alternator while driving and we'd be able to design a system exactly to our needs. I was certain we'd go this route, but the one nagging concern I had was the portability aspect. It'd be awesome to be able to easily take the power source out of the vehicle to our tent or around camp and use it separate from the Bronco. Additionally, if we ever (heaven-forbid) replaced our Bronco with a new vehicle down the road, I'd have to start this whole dual battery install process over again. I wanted the customizability of the dual battery system as well as the portability of a solar generator unit.

My “Hybrid” Portable Dual Battery System Design

Drawing inspiration from various solutions out there, I settled on this hybrid approach to a dual battery system with a portable battery bank. This idea certainly isn't new, but I wanted to make sure I was designing something that fit my specific goals.

The general idea is the portable power station will be charged by the vehicle while driving, which can also power a fridge or charge other devices. When camping, I can leave the power supply connected to the Bronco to continue to use it as the power source for everything. Alternatively, I could remove the power station and bring it into our tent for the night, but still have the ability to utilize the starter battery for small loads, like exterior & interior lighting.

Here's a simplified diagram of my initial concept:

View attachment 633166

Planning & Design

Phase I of this whole project would be to build the portable power station. It'd be something I could use immediately, before the rest of the DC-DC charging and integrated components were installed in the Bronco.

I started with the battery and case. I was targeting a 100Ah battery so I'd be good for a couple of days without a recharge. Based on manufacturers' dimensions I found a battery/case combo that I new would work. From there, I added other components that I could see myself using. I may have gone slightly overboard with trying to cram so much into a tight space, but I kept finding ways to mount/orient things within the defined area that made things more efficient. I wasn't originally even going to have a solar controller built in, but it fit and I decided it'd be convenient to have already integrated. One less thing to worry about packing. I included 2 50A Anderson plugs so I could potentially have a high-wattage charging input at the same time as outputting power to an inverter, or even a secondary battery bank.

All design work was done in SketchUp so I could visualize how all the parts would come together and insure there wouldn't be any interferences. I also wanted to design a robust frame to ensure the battery or any of the components wouldn't bounce around inside the case. There's a provision for running wires from one side of the box to the other via a channel underneath the battery, down the center. The battery is centered in the frame for even weight distribution and so I can have ports on opposite sides. I wanted to be able to have the case lay flat or stand on it's bottom edge, have things packed on either side, and still be able to access all the plugs.

I also sketched out a wiring diagram of just the portable power station so I knew going in what needed to be connected to what.

Here's the final parts list for the build. This doesn't include miscellaneous materials like the boards, wires, terminals, etc. that I had already laying around my garage.

Component​	Price​	Quantity​	Total​
Apache 3800 carrying case	$ 40.00​	1​	$ 40.00
100ah 12V LiFePO4 Battery	$ 250.00​	1​	$ 250.00
Circuit breaker	$ 43.00	1​	$ 43.00
Power cutoff relay	$ 12.00	1​	$ 12.00
Power switch	$ 9.00	1​	$ 9.00
Terminal stud bus bar pair	$ 11.00	2​	$ 22.00
4 circuit fuse block	$ 20.00	1​	$ 20.00
50A fuse w/ holder (2 pack)	$ 13.00	1​	$ 13.00
50A Anderson plug (2 pack)	$ 12.00	1​	$ 12.00
Dual Anderson power pole connector mount	$ 27.00	1​	$ 27.00
Single Anderson power pole connector mount	$ 27.00	1​	$ 27.00
Dual 12v outlet panel	$ 17.00	1​	$ 17.00
Battery monitor shunt w/ display	$ 50.00	1​	$ 50.00
Temperature controller relay switch	$ 12.00	1​	$ 12.00
Blower fan	$ 9.00	1​	$ 9.00
Victron MPPT 75/15	$ 68.00	1​	$ 68.00

Grand total for everything above comes out to $631.

The Build

Here are several photos of the progress of the build from start to finish. I started with assembling the frame out of HDPE boards I had leftover from another project. This stuff is awesome. It's got a lot of the same properties as wood, but the density is more consistent, making tapped & screwed connections much more secure. Plus, they come in black, so I don't have to do any sort of painting to make it all look nice.

Fits like a glove!

Cutting holes in the case and mounting all the components...

I designed the frame to be completely removable so I could easily connect all the wiring and service components down the road if needed without having to take everything apart. A strap was installed to secure the battery to the platform. It wasn't moving around before adding the strap, but I found that with the battery's weight, it was nearly impossible to lift the whole assembly out of the case without something easy to grab onto.

Wire thickness was probably a bit overkill for this setup, but it's better to be safe than sorry. Everything connected to the battery on its own circuit is appropriately fused to prevent it all from melting down.

Final assembly was a bit of a pain, just because I didn't leave much room for my fat fingers to connect all the plugs. After some minor adjustments, everything fit nicely together. The left side of the power station will be used for charging devices (phones, laptops, flashlight batteries, etc.) as well as running a fridge or camp lights. The battery monitor display is also on this side for easy access.

The right side is for connecting utilities, like my AC charger, the DC-DC charger (once that gets installed in the Bronco), or outputting to a small inverter run things on AC. There's also the solar input for charging the battery on its own. The hole cutout serves as the intake for air to get pulled in across the length of the case by the exhaust fan on the other side. The fan is controlled by the programmable temperature relay switch with the thermometer mounted next to the solar charger (because that is likely to get the hottest during operation).

The single power button on the front acts as the cutoff switch for the entire battery via the large relay. With the power off, all internal circuits are disabled and no electricity will be able to run in or out of the box. This will be useful to easily power it all down when not in use.

All buttoned up and ready to go!

Here are the high-level specs at a glance:

• 12V 100Ah LiFePO4 battery
• 15A solar MPPT charger
• Battery monitor with color LCD screen
• Temperature-controlled cooling fan
• Single power button battery disconnect
• 2x 20W USB-C ports
• 1x 18W USB-A port
• 1x 300W 12V cigarette lighter port
• 2x 30A Anderson Powerpole ports (input/output)
• 2x 50A Anderson plug ports (input/output)
• 1x 30A Anderson Powerpole solar input

Next steps are to do some calibrating with the battery monitor to ensure I'm getting accurate readings and estimations for energy input/output and then it's on to field testing. I'll be sure to keep this thread updated if I discover anything new along the way.

Very cool

 

[Kun zhao]

that's a very interesting idea. do you charge the battery through on-board generator?

 

[cr117]

that's a very interesting idea. do you charge the battery through on-board generator?

Right now I’ve just been just using my AC battery charger at home. The plan is to add a DC-DC charger to the Bronco which I’d be able to plug into this box and charge while I’m driving. Once at camp, I can continue to charge the battery with solar panels.

 

[cr117]

Testing out the new Victron pure sine wave inverter I picked up to power the handful of device chargers that have to run on AC. This thing is awesome, its zero-load power requirement is less than 1 Watt. I crimped on a 50A Anderson plug so I could easily connect it only when I need it. It’s so efficient, I may end up mounting it inside the bronco and leave it on whenever the power station is plugged in and turned on.

 

[cr117]

Updating the wiring diagram concept in my original post. This version includes the solar panel(s) and the optional inverter.

 

[Ocnorb]

Very cool, nice design work. Is the DC-DC setup so that you can basically get max amps for charging possible? It would otherwise seem overcomplicated and overkill to me to be worth it. Then again, my power station is tiny in comparison, so I could see this being useful!

 

[cr117]

Very cool, nice design work. Is the DC-DC setup so that you can basically get max amps for charging possible? It would otherwise seem overcomplicated and overkill to me to be worth it. Then again, my power station is tiny in comparison, so I could see this being useful!

The DC-DC charger will charge the battery at a much higher rate (up to 50A) than what I'd be able to get out of one of the 12V sockets (10A). With my 100Ah battery, I'd be able to full recharge it in as little as 2 hours of driving time. If aux battery is smaller, you probably wouldn't see as much of an advantage. It also monitors the voltage on the connected lithium battery and can adjust the charging profile to maximize the battery's capacity and longevity.

 

[Shrek27]

The DC-DC charger will charge the battery at a much higher rate (up to 50A) than what I'd be able to get out of one of the 12V sockets (10A). With my 100Ah battery, I'd be able to full recharge it in as little as 2 hours of driving time. If aux battery is smaller, you probably wouldn't see as much of an advantage. It also monitors the voltage on the connected lithium battery and can adjust the charging profile to maximize the battery's capacity and longevity.

When does the alternator become a limiting factor with this setup?

 

[cr117]

When does the alternator become a limiting factor with this setup?

Good rule of thumb is to size the DC-DC charger at 25% of your alternator's max rating. At 50A, that's well below the 25% threshold of the 250A alternator that came with the Bronco.

The nice thing about the DC-DC charger I'm planning on using (this one) is I'd be able to control the charging amperage going to my aux battery. I'll probably usually set it at 30A to keep the load on the alternator low while still being able to completely recharge my battery from 0-100% in around 3.5 hours of driving time.

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