Hotrod flashlights and battery safety.

[Frostcream]

Fellow enthusiasts, I hope you’re all well.

I’ve read posts stating to be careful not to overdraw from your batteries. Example, pairing emitters that can pull 20 amps with a 10 amp battery.

Is there any truth to the belief that you can over-pull from a battery and send it into thermal run-away? Anyone with first-hand experience of a thermal event in a hotrod flashlight?

[ryansoh3]

Thermal runaways are very rare, but can get dangerous because the flashlight is a tightly enclosed space, and pressure can build to dangerous levels.

Explosion in a charger: My 14500 battery explosion, with pictures
Trustfire X6 explosion while off: Trustfire X6 SST-90 EXPLODED
Imalent DX80 driver failure: My Imalent DX80 caught fire, vented smoke, almost exploded (replacement head arrived)
Solarforce L2T, shorted out car battery: Exploding flashlight kills man

None of the cases above are due to shorts or over-currents however.

Name brand li-ion cells have a safety test that checks for fire and explosion during a dead short:

INR21700-50E.pdf

9.2 External short-circuit test

Test method: Fully rated charged cell is to be short-circuited by connecting the positive and negative terminals of the battery with a circuit load having a resistance load of 80 ±20 mΩ. The battery is to discharge until a fire or explosion is obtained, or until it has reached a completely discharged state of less than 0.2 V and the battery case temperature has returned to ±10°C of ambient temperature. The return to near ambient of the battery (cell) casing in an indication of ultimate results. Tests are to be conducted at 20 ±5°C and at 55 ±5°C. Criteria: No fire, and no explosion. External short-circuit test shall be performed with the UL1642 standard

So while thermal runaways are rare, they can be deadly, so reasonable precautions should be taken.

[Frostcream]

Yes, exercising caution is a given. I was thinking that if it was a substantial issue to be concerned about, there would be people here who have actually had it happen.

I have a D4V2 that I push very hard every day, lots of turbo, purposefully delayed stepdown, etc. I’d hate for that to become a pipe bomb, but it just doesn’t seem to care and the battery doesn’t get too hot.