Creating a DIY Powerwall: A Pragmatic Alternative to Tesla's Product

As an individual who relies on solar energy to power their garage, it is essential to have a reliable and efficient method for storing excess energy. The original capacity of lead acid batteries used in my garage has decreased noticeably over time, prompting me to search for more modern alternatives. After researching various options, I discovered the Tesla Powerwall, a container filled with batteries, an inverter to supply mains voltage, and a cooling system. However, I was deterred by the high cost ($7600) and unnecessary features that did not align with my specific needs.

To create a more affordable and functional DIY Powerwall, I decided to take matters into my own hands. The three main ingredients for this project are batteries, a decent BMS (Battery Management System) to protect them from mishandling, and a suitable enclosure. My first step was to calculate the capacity of my original lead acid battery, which was around 1.2kWh. I then determined that I would need approximately 134 Samsung INR 18650-25R batteries, each with a capacity of around 10Ah. This calculation would provide me with an equivalent capacity of 1200Ah, more than sufficient for my needs.

To achieve this capacity, I needed to design and build the enclosure for the battery pack. I chose a slightly oversized electrical cabinet made from tough steel sheet, which not only provided the necessary structural support but also met various safety standards. After measuring the dimensions of the battery pack, I drilled big holes in the bottom lid of the cabinet to mount a cable feedthrough and secured it through plastic anchors and big screws.

The next step was to connect the battery pack to a BMS board. The BMS board provided me with the necessary features, including temperature measurements, analog and digital inputs, partly outputs, logging of battery activities, and even temperature sensors. I added a fuse to the plus terminal and another terminal connector to the minus terminal, which I then soldered to the B+ and B- solder pad on the battery pack through thick 12AWG wire. Next, I removed all the wires from the BMS balance connector except for the top five, which I either soldered to the terminals or locked in place with screws according to a specific scheme.

After securing the BMS in place and tidying up the wiring, the hardware of the battery pack was largely complete. To connect the included USB UART converter to the BMS and a computer, I started using the Battery Insider software. This allowed me to define all the max and minimum voltage, current, and temperature values, as well as whether I wanted to use the dual port or single port mode.

The dual port means that my charger and load circuit are not the same, thus requiring separate inputs for each. Since I am using an MPPT charge controller, which offers a load output on its own, I needed the single port mode. This meant connecting the charge controller to the B+ and C- solder pad. To finish the software part of this project, I set the voltage and current values according to the LiFePO4 profile that my MPPT charge controller came with.

With the battery pack ready for installation inside the housing, I measured its dimensions and chose a slightly oversized cabinet to ensure it would fit comfortably. After drilling big holes in the bottom lid of the cabinet, I secured it through plastic anchors and big screws to mount a cable feedthrough. Next, I prepared two conduit pipes which through the help of pipe clamps I then secured to the wall.

To complete my DIY Powerwall project, I guided thick wire into the electrical cabinet, placed the battery pack inside it, and hooked up the B+ and C- pads up to the wire which I then connected to the charge controller. This completed my unique take on the DIY Powerwall project, allowing me to enjoy efficient energy storage while minimizing costs.

While my solution is a tiny bit more expensive in comparison to Tesla's product when considering kWh per €, I can easily modify it by adding more batteries to not only increase capacity but also change voltage up to 51.2V. With this feature in mind, I hope you enjoyed watching my DIY Powerwall project and look forward to your feedback through liking, sharing, subscribing, and hitting the notification bell. Stay creative, and I will see you next time.

WEBVTTKind: captionsLanguage: enAs you might know the electrical energy inmy garage is created by solar energy whichon the other hand is getting stored in a bigand heavy lead acid battery.Only problem is that the original capacityof this battery decreased noticeable over time.That is why I have been searching for moremodern alternatives to this energy storage problem.And what I found was the Tesla Powerwall,which is basically a container filled up with batteries,an inverter to supply mains voltageand a cooling system.But honestly speaking, I don’t need theinverter, nor a capacity of 13.5kWh and Iespecially do not want to pay $7600 for it.So in this video I will be showing you howI created my more or less crude but stillfunctional DIY Powerwall.Let’s get started!This video is sponsored by JLCPCB, whose officeswere visited by more than 100 customers inthe past year.And you can meet them as well at the MakerFaire in Rome this year, where they will begiving out gifts.The three main ingredients for a DIY Powerwallare of course the batteries which will formthe battery pack, a decent BMS to protectthem from all kinds of mishandling and ofcourse a suitable enclosure.So, let’s start off with the battery pack.According to Wikipedia, the Tesla Powerwallconsists of Lithium Ion cells.Out of such batteries I already created severalbattery packs in the past, so this shouldbe an easy job, right?Well, to do this I firstly calculated thecapacity of my original lead acid batterywhich was around 1.2kWh.For the battery cell itself I went with theSamsung INR 18650-25R whose capacity shouldbe around 9Wh.That means I would need around 134 off thosecells which would set me back around 448€.Now that is of course pretty expensive incomparison to the cheap lead acid battery,but then again Li-Ion batteries offer a waybetter volumetric and gravimetric energy densitywhich means the final battery pack will bemuch smaller and lighter.But as I was about to order, I noticed thatthe cells do not perform well in cold conditionswhich is a problem because temperatures inGermany can go down to -20 degree Celsiusin winter.That is why I started searching for a moredurable battery type alternative and foundLiFePO4 batteries or Lithium iron phosphatebatteries.This battery chemistry is known for not onlybeing able to handle lower temperatures butalso for being safer which you can easilysee for yourself by just searching for themon YouTube.Another difference is that LiFePO4 offersa slightly different nominal voltage whichactually makes it more suitable to be a leadacid replacement and also the charging voltageis a bit different, but a constant current,constant voltage method is still recommendedfor charging.However the only reasonable LiFePO4 cellsI found were these, with a capacity of 19.2What a price of 9.19€ if I order 63 of them,which I would require.That would equal around 580€, which wasa bit too pricey for my taste.Thankfully though I found those 100Ah LiFeYPO4cells at a price of 114€.The Y by the way stands for Yttrium that isadded to the cathode to allow this batteryto work down to -45 degree Celsius.4 of those cells in series should not onlygive me a voltage range between 14 and 11.2Vbut also a capacity of 1.28kWh at a priceof 457€, which seems acceptable.Once again this battery technology is notas cheap as lead acid, but lies with its bettergravimetric and volumetric energy densityright between lead acid and li ion.So naturally, I ordered 4 of those cells alongwith suitable terminal connectors and a fuse.After receiving them, I inspected them tomake sure that they were not damaged and thencontinued by connecting the cells with theterminal connectors according to this diagramin order to create the 12V battery pack.As soon as I was sure that all the voltagesat the battery pack were correct, it was timeto choose a suitable BMS which should at leastfeature an overvoltage, undervoltage and overcurrent protection along with a balancingfeature to keep all the batteries at the sameenergy level.Now of course I could have used one of those4S Chinese BMS which you can find all overEBay.But it just didn’t feel quite right andsafe for such a big amount of stored energy.So luckily after I searched the web for quitea while and only found pretty expensive BMS,I finally discovered the company Energus PowerSolutions which offer the Tiny BMS for a morereasonable price.It works with 4 cells of LiFePO4 and basicallyoffers all the features that I have been lookingfor and even more by for example offeringtemperature measurements, Analog and DigitalInputs and partly Outputs and also loggingof the battery activities.So after receiving my board along with allthe required wires and temperature probes,I added a fuse to the plus terminal and anotherterminal connector to the minus terminal whichI then used to connect the BMS B+ and B- solderpad to the battery pack through thick 12AWGwire.Next I removed all the wires from the BMSbalance connector expect the 5 upper oneswhich I then either soldered to the terminalsor locked them in place with the used screwsaccording to this scheme.Afterwards I plugged the balance connectorinto the BMS and continued by preparing thetwo temperature sensors, securing them inplace at the right and left side of the packand then hocking them up to the BMS as well.And as soon as I was done securing the BMSin place and tidying up the wiring, the hardwareof the battery pack was basically complete.So I hooked up the included USB UART converterto the BMS and a computer and started thegiven Battery Insider software.There I am able to define all the max andminimum voltage, current and temperature valuesand whether I want to use the dual port orsingle port mode.Dual Port basically means that my chargerand load circuit are not the same and thusI want to cut them off separately.But since I am using an MPPT Charge controller,which offers a load output on its own, I havecharger and load circuit combined and thusI need the Single Port Mode which thereforemeans I have to connect the charge controllerto the B+ and C- solder pad.Of course you can also find all those informationin the 76 pages long manual of the BMS whichwas actually quite an interesting read.To finish the software part however, I setthe voltage and current values according tothe LiFePO4 profile that my MPPT charge controllercame with.And with that being done the battery packwas ready for installation inside a housing.So after measuring the dimensions of the batterypack, I chose a slightly oversized electricalcabinet.As you can see it is not only made out oftough steel sheet and thus weighs a ton butit also fulfills all kinds of safety standardswhich is always nice to have.And of course the battery pack fits effortlesslyinside it, which means it was time to drilla big hole in the bottom lid of it in orderto mount a cable feedthrough and then I continuedby drilling 4 holes for the cabinet into mygarage wall and then securing it through thehelp of plastic anchors and big screws.Next I prepared two conduit pipes which throughthe help of pipe clamps I then secured tothe wall.Last but not least I guided thick wire intothe electrical cabinet, placed the batterypack inside it, and hooked the B+ and C- padsup to the wire which I then connected to thecharge controller.And with that being done my rather crude Powerwallwas complete.According to the appliances used in my garage,it also seems to work without a problem whichwas also confirmed by my solar charge controllerapp as well as the BMS software.Now granted, my solution is a tiny bit moreexpensive in comparison to the tesla Powerwallwhen we look at the kWh per €.But then again I can easily modify it by addingmore batteries to not only increase the capacitybut also change voltage up to 51.2V.And with that being said, I hope you enjoyedwatching my unique take on the DIY Powerwallproject.If so don’t forget to like, share, subscribeand hitting the notification bell.Stay creative and I will see you next time.