Topic: Reminder: Li-Ion Fire Hazards

[Chilly Brioschi]

I know it's been covered, but just a reminder post about inspecting your battery packs.
You may remember my post about a varnished-insulator "magnet wire" connection from an RC pack that I used for my recorder.
The pack fell from a shelf in closet and when I picked it up to re-shelve it, noticed it smoking.
The magnet wire was under the shrink wrap of the pack, and not expected or noticable when I built the soft-pack battery case.

The fall has caused the lacquer insulation to fail, a short occurred, and things got very hot quickly.
I threw pack out the window into a rain-soaked grassy lawn and retrieved it hours later.

Why the re-post?

A similar, but much worse occurrence in today's news:
https://www.cnn.com/2023/11/14/us/brooklyn-fire-family-killed-lithium-battery-scooter/index.html

Inspection and careful maintenance are important.
Storage in safe spaces that are fire-resistant also makes sense.

[fanofjam]

Thanks for this PSA.  Never can be too careful.

I don't want to minimize the general message here, but the short you experienced with your li-ion pack can happen on any battery chemistry.  When the insulating material goes bad on any battery, shorts will happen.  Li-ion's probably get most of the news since there's so much DIY going on and li-ions have the best power ratio which makes them perfect for portable applications.  Anyway, the other things is that alot of the scooters, RC, etc type things come with batteries put together by cheap Chinese battery company's (both cheap battery cells and lousy quality control on the soldering/insulation jobs).

Anyway, my point is that the danger isn't limited to li-ions.

I think the take-away for these types of articles is that it's a best practice to consider any battery charging operation an 'at risk' activity.  Some general rules of thumb that I can think of (note this is just MY brain dump...please consult an official battery website for an exhaustive list)...

- Don't leave charging batteries unattended, or if you're gonna leave the room, at minimum check them for the first ten or 20 minutes after you put them on the charger.
- Keep flammables a reasonable distance from charging batteries. 
- Charge batteries with the batteries resting on a fire-proof surface.
- If possible, recharge your batteries away from living areas...for example, out in the barn or shed.
- Do a heat check on batteries shortly after you start charging.  If they're overly hot, stop charging.  (Note that all battery charging will generate some heat, but for this we're talking VERY hot to the touch.)
- Make sure the right battery charger is used for the battery being charged
- Remember that as batteries age, their internal resistance gets higher and higher.  When internal resistance starts to increase the battery is in the process of going bad. 
- Just because your battery charged fine last time doesn't mean it's not going to overheat this time.  I've had batteries charge fine today and tomorrow they melted probably due to high internal resistance.

I'm sure there are others, but this list is a start.