Scary. A home battery hobby project gone very wrong. There are no doubt hundreds of similar rigs around the country. I hope this video gets widely viewed by those of us who might be tempted to DIY solar.

I'm looking forward to becoming a firefighter when I'm 18, I hope I help and save many lives

Ok but what kind of system was set up to charge these batteries? Nothing unsafe with rigging up your own charger if you know what you are doing or just buying a CC CV charger online. I'm going to guess by the dodgy looking solar setup that we had a "powerwall" that lacked most if not all safety features. Would love to know what charge controller they were using for the solar, what BMS they were using if any at all, and if they had other safety features in place on their system. I'd bet this was someone charging used cells past 4.10V and probably taking them down below 3.0V. Anyone that's done a little reading knows its best to keep used cells between 3.00 and 4.00 for cycle life and safety reasons. Further you shouldn't discharge the cells past 1A per cell so build large P groups. Charging current should be limited to similar rates as well.

The thing is that building a power saving rig to save on bills doesn't work because the maths don't add up. Once you have decided on whether you want a 12 volt o r 24 or even 48volt system and necessary BMS and Solar controllers and solar panels and inverters you'll be paying a huge amount of money hoping to recover it back from saving on electricity. But the fact is that Electricity is about 30c per KwH and if you build a 5000 to 10,000 Kw system you'll take a very long time to get your money back....and to top it off those Lithium ion batteries can only discharged 10k times and you'll need to replace the whole system again. Top Quality cells cost $25 per single cell... you'll spend thousands to build a decent pack with the required electronics....

This is wise advice at a time when people are looking for ways to save a buck on their electricity.