DIY Portable Power Station w/ MPPT

[BarracudaBob]

Very nice build. Has the fan been working out alright with keeping the MPPT cool enough? I’m about to put together a portable power station for the same use and will probably copy your build. Any changes you make if you could do it again? Thanks

I have the inverters mounted horizontally. I am thinking of moving them vertically. My concern was heating the battery cabinet but it became more of an issue of pushing it against the wall and the air flow was affected. The picture it is sitting almost in the middle of the room. The EG4 3K are great units but still trying to wrap my head around fans blowing heat down against the convection air flow. I mounted Anderson connectors on the back to plug in other batteries. That has worked out well. Like most of my projects I keep upgrading them and trying to make them better.

 

[meetyg]

Very nice build! Nice and compact.

Just a note on that relay you are using: Did you verify that is rated for continuous use?
I have played around with these automotive type relays and most of them are meant for intermittent use, not continuous. If you use them continuously, they tend to heat up alot and fail prematurely.

Double check the heat from the relay after about 20 minutes of use. If it's hot to the touch, I wouldn't use it.
They also take alot of power just to hold the coil. A better option would be a Tyco contactor with optimiser. You can but them for fairly cheap on Batteryhookup.com or on Aliexpress (just make sure they include the optimiser). These are beasts meant for continuous use and take only a small amount of power after initial contact of the coil. No excessive heat either.

 

[DatacomGuy]

Great build! Have given me some ideas.

 

[Oggie]

I know there's a lot of these builds like this out there, but I'm surprised at how well this turned out. It was a good excuse to try working with new materials, tools, and components.

Primary goal for this was to build something compact that I could take with me camping so I'd have power to run a fridge, camp lights, and charge devices. During the planning stage, I started spiraling into the idea of adding solar charging capability and stumbled upon this forum.

My design considerations include:

• Rigid frame to secure battery and all components that could easily be removed if something needed servicing
• The ability to store the box flat or horizontally, while still allowing access to all the ports and air flow for the cooling system
• Single power button to cut off everything connected to the battery
• Expansion ports to connect other devices (inverter) or for charging (AC charger or DC-DC charger)
• Programmable temperature-controlled fan to pull air through the box only when needed
• Keeping everything as tidy as possible

With space being a premium, I needed to be strategic about where all the major components would go and also account for the wiring between them. I used sketchup to find the best placement of things and to optimize the support frame.

View attachment 213098 View attachment 213099

I also sketched out a wiring diagram of everything so I knew going in what needed to be connected to what.

View attachment 213100

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.

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

As mentioned earlier, I wanted to design 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. Since the frame was custom fit to the box and braced in all directions, it's not actually secured to the case itself. 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 (hopefully).

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 an AC charger, a DC-DC charger, 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. I placed it there to protect it from getting accidentally pushed when moving it around or packing it in next to other things. 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.

Believe it or not, it all fits in there with the lid closed.

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

 

[Oggie]

I'm currently making a unit based on your impressive design. Thanks for all the details. Are there any changes you would make if you were to build another one?
And what gauge wire did you use for the battery connections? I am guessing 6 gauge.

 

[satoshisean]

Hi, this is great! I'm new here and joined specifically because I wanted ideas for a similar build. Can you tell me why you use a relay to shut the power to everything off instead of just a switch?

 

[BarracudaBob]

I have the inverters mounted horizontally. I am thinking of moving them vertically. My concern was heating the battery cabinet but it became more of an issue of pushing it against the wall and the air flow was affected. The picture it is sitting almost in the middle of the room. The EG4 3K are great units but still trying to wrap my head around fans blowing heat down against the convection air flow. I mounted Anderson connectors on the back to plug in other batteries. That has worked out well. Like most of my projects I keep upgrading them and trying to make them better.

Update to this Post. Horizontally was much quieter and zero heat issues. Made the wires shorter for my custom build.