Building my own powerwall

First off, I just want to say a huge thank-you to three places on the internet:

  1. Jehugarcia on Youtube – he kinda started or at least popularised the whole “DIY powerwall” thing on the internet.
  2. Pete (aka HBPowerwall) on youtube – An aussie vlogger who built several impressive systems and inspired me to make my own
  3. Finally, the secondlifestorage forum where many people discuss their own homebrew DIY powerwall (myself included)

Anyway, as you may (or may not, since it’s an new blog) be aware, I fitted solar power in my home in 2015. I have two separate arrays. A 4kWh “main” array on my roof that provides grid-tie power, and a separate, isolated 1.5kWh array on another roof (I’m fortunate to have 3 roofs for my solar).

Solar is great, it has reduced my cost of electricity in half, literally 50% of what it used to be. Combined with that reduction in electricity costs, I also earn about £500 per year entirely tax free. My solar panels paid for themselves this year (2020) and from now on, anything they generate is entirely profit based and again a back-of-the-napkin calculation tells me that for the £4,000 I paid for my solar power, I stand to make another £4,000 back over the life of the system (assuming nothing breaks) and the life of the system is considered to be around about 20 years (meaning I have 15 left).

The 1.5kWh array makes on average about 4-5kWh per day during the spring/summer/autumn and about 0.5-1kWh per day during winter, and is used to charge a bunch of 18650 lithium ion batteries that I assembled myself into 48v packs of various capacity and now I have around about 5KWh of battery. If I need to I can also charge the batteries of the independent solar system during winter using any excess power from the main grid-tie array. I do that using a custom raspberry pi / relay setup that looks at my grid export and can use it to power things / charge batteries if needed.

I use an Iconica (as far as I can tell, a re-badged PIP4048) inverter which has an MPPT charger as well as an automatic transfer switch. The transfer switch means that if my batteries go flat, it will swap instantly to AC power instead of battery. It swaps so fast in fact, that none of my computers turn off (however, they are also on a UPS which would deal with a momentary loss of power).

Overall the system works great, it took me around about a month to build it and that was mainly waiting for parts to arrive from China or the EU.

Anyhoo… here are some images

Inverter, fuses, circuit breakers, and the automatic fire extinguisher. At the moment it’s not connected to the grid, so that’s why there’s no AC isolator if you were wondering.
80A DC circuit breakers, 100A DC fuses.

and here are a few battery packs I assembled from 18650s…

18650 48V pack with balance wires for BMS
One finished battery pack (if you are wondering why negative is brown, simple, the shop ran out of black and it was an extra 3 weeks for black)

This setup now powers the following equipment in my home

My NAS (linux ATOM box that uses ~ 50W power) – also the webserver serving this website

My TP-Link PoE switch (about 10-15W)

My desktop computer + monitors (uses about 100W)

CCTV NVR (10W)

Router (10W)

Cable Modem (8W)

The whole system (excluding the actual solar panels) cost me in the regions of £800 and gives me about 5KWh of power with the ability add more batteries whenever I like.

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