First HoverBoard Battery Failure

https://photos.app.goo.gl/Vv9VwnXDbMuWwchZ6

I've had three ammo boxes of HB batteries in a little used golf cart across the road, in the "party shed".  In cleaning up the area, I decided to move the ammo boxes to the house where I can easily keep them them charged and use for PowerWall augmentation.  To transport, I hooked them to the similar ammo boxes being used to power a golf cart that I was driving and use frequently.   When I hooked one up, with an SB50, I heard a little snap and thought it was due to a low battery being connected to the higher charge in the golf cart.  When I got back to the battery storage/charge area, I heard some crackling.  I found one ammo box with one or more hot and smoking HB batteries.  I pulled all eight HB batteries out of the ammo box.  All HB batteries appeared damaged; most were whole but one was falling apart and obviously still smoking.  I found a little liquid in the bottom of the ammo box.

Most of the batteries had been stored for about two years until, about six months ago, I put them in service for PowerWall augmentation.  Other blog posts can be found on that project.  Coming out of the ~2 years of storage, a small fraction of the batteries were at zero voltage and would not accept a charge.  Perhaps 3 or 4 out of more than 50.

This is the first HB that has threatened fire.  I have had other LIPO batteries from other sources burn.

My PowerWall augmentation cache of batteries numbers about 10 ammo boxes of either 8 or 10 HB batteries each.  All paralleled together and regularly charged to about 40v; I've avoided charging to the full voltage of 42v.  So, I need to consider relocating those ammo boxes to a place where a fire would not be very damaging.

The last three photos show the golf cart charging and PowerWall augmentation area.  The next to last photo shows a wall mounted collection of grid tie inverters that can be used to feed into the PowerWall island.  Using both 12vdc and 36vdc power sources.  The third from last photo shows the collection of ammo boxes that can be either put into golf carts or used to power the grid tie inverters.  I will likely move those to a more remote location, probably into a new garden shed installed for that purpose.