What would be an appropriate suppression system here? That's a lotta batteries all arranged like a boy scout arranges kindling logs for a campfire.

A roof-mounted water tank with a thousand gallons ready to dump into the shed? A drum of baking soda?

Or maybe rebuild the shed out of cinder block and clear any overhanging vegetation?

Maybe this whole setup is on desert dirt with plenty of clearance. The fire plan is "run away and wait."

A ton of sand, but that's the main issue with those systems and why it's genuinely impractical as anything but a hobbyist project. They need constant monitoring as all of those cells are from laptop and risk thermal runaway at some point. Even with the best matching possible some cell in his configuration will have higher internal resistance and create heat. "Real" large off-grid systems all use LiFePO4 and are unlikely to just catch fire. That being said from the forum post he seems well aware and he probably has individual fuse for each cell.

You could also just bury it so that the worst of the explosion is mostly mitigated. I've also seen small container setup which would probably work better than his (seemingly) wooden shed.

You can see the shelter here [0] and it is apparently 50m from the house [1].

Would be better if the ground was paved around the shed, but it seems to be far enough from other free standing structures.

[0] https://secondlifestorage.com/index.php?threads/glubuxs-powe...

[1] https://secondlifestorage.com/index.php?threads/glubuxs-powe...