I was working in my shop trying to tame my CNC, when the Missus crashes in and hollers FIRE, I dashes outside and there close to the house is my Electric Garden Tractor with flames shooting about 5 ft in the air, from the rear mounted metal battery box. Told her to turn on the hose which fortunately was nearby, she did that and I played the hose on the fire, the result shocked the living shyte out of me.
But first let me set the scene, About three years ago I got a super deal on a Nissan Leaf Battery, which I disassembled into 48 modules and a bunch of bus bars, BMS leads and other miscellaneous bits of hardware. I took 10 of the modules and built a 5s by 2p battery with a high quality BMS that had balancing leads as well as high and low temp sensors. Bolted it up between two pieces of 3/4" Baltic Ply with compression plates as needed. Put a 42V charger on it with fuses as needed.
That took care of the traction motor, which previously had been running at 24 volts so was now quite happy to have more volts.
The winch operated forklift on the tractor ( the dear little tractor had been a massive help over that last 11 years as we built our home) was a 12 volt Harbor freight special, soooo I put two of the modules together skipped the BMS and used a variable voltage supply to charge it. fused but otherwise not protected, after all what could go wrong, I only had to charge the 2 module battery once or twice a season.
Well I forgot it was on charge while fighting with the CNC, which is where the wife called the alarm.
The purpose of this windy tale is to describe how the fire was dealt with.
The door of the battery box was already open so I started to spray water into the box, saw that the fire was mainly at one end and concentrated the stream there.
The flames were pretty much gone within 30 seconds but there was quite a bit of insulation emitting smoke so I kept the water trying to cool the wires.
An interesting note is that because the insulation had been burned off the balance wires, they were arcing on the module cases on the big traction battery, I kept spraying them as they burned away until the wires were no longer long enough to reach the module cases. once the fire was right out, less than 5 minutes after we started with the hose, I pulled the modules out, the bank of 10 Was sooty and had the balance wires sticking out all over the place but was otherwise intact, I tested the 10 modules a week or so later and they seem to be fine.
The other two module cases were burned through on three of the four edges with holes about 4" long by 3/4" wide. these were not tested but were taken to the land fill.
The lesson here is obvious so don't bother with the lecture, the reason for the post is that if you can get water onto the individual modules of the battery it is quite easy to extinguish a fire. The problem of course is that in a car or other big battery array the cells are often encased in a strong sealed steel case and therefore inaccessible. Hope this helps if you ever need to put out a rather frightening and very hot fire.
But first let me set the scene, About three years ago I got a super deal on a Nissan Leaf Battery, which I disassembled into 48 modules and a bunch of bus bars, BMS leads and other miscellaneous bits of hardware. I took 10 of the modules and built a 5s by 2p battery with a high quality BMS that had balancing leads as well as high and low temp sensors. Bolted it up between two pieces of 3/4" Baltic Ply with compression plates as needed. Put a 42V charger on it with fuses as needed.
That took care of the traction motor, which previously had been running at 24 volts so was now quite happy to have more volts.
The winch operated forklift on the tractor ( the dear little tractor had been a massive help over that last 11 years as we built our home) was a 12 volt Harbor freight special, soooo I put two of the modules together skipped the BMS and used a variable voltage supply to charge it. fused but otherwise not protected, after all what could go wrong, I only had to charge the 2 module battery once or twice a season.
Well I forgot it was on charge while fighting with the CNC, which is where the wife called the alarm.
The purpose of this windy tale is to describe how the fire was dealt with.
The door of the battery box was already open so I started to spray water into the box, saw that the fire was mainly at one end and concentrated the stream there.
The flames were pretty much gone within 30 seconds but there was quite a bit of insulation emitting smoke so I kept the water trying to cool the wires.
An interesting note is that because the insulation had been burned off the balance wires, they were arcing on the module cases on the big traction battery, I kept spraying them as they burned away until the wires were no longer long enough to reach the module cases. once the fire was right out, less than 5 minutes after we started with the hose, I pulled the modules out, the bank of 10 Was sooty and had the balance wires sticking out all over the place but was otherwise intact, I tested the 10 modules a week or so later and they seem to be fine.
The other two module cases were burned through on three of the four edges with holes about 4" long by 3/4" wide. these were not tested but were taken to the land fill.
The lesson here is obvious so don't bother with the lecture, the reason for the post is that if you can get water onto the individual modules of the battery it is quite easy to extinguish a fire. The problem of course is that in a car or other big battery array the cells are often encased in a strong sealed steel case and therefore inaccessible. Hope this helps if you ever need to put out a rather frightening and very hot fire.
