LAPTOP BATTERY ISULATION BREAK-DOWN:
About 40 years ago, Black & Decker discovered that cardboard tubing makes the best insulation material for Ni-Cad batteries, since they become extremely hot in some circumstances, during rapid charging, near the “full” point.
And, if the ambient temperature in your automobile reaches 150 F, then the internal battery temperature could reach 300 F or higher, while being charged.
However, most NiMH and Lithium Batteries, made in China or Japan, save space and look better, if insulated with plastic sleeves, which are colorful and are about as thin as a Wal-Mart shopping bag.
Therefore, in my opinion, most Laptop Battery fires are due to the ?thermal breakdown? of the thin, vinyl or Mylar insulation material, which causes rapid heat, if two adjacent cells short-circuit together, and which will ignite the battery case.
So, one solution for a better laptop battery pack is to insert thin strips of business cards between each cell, if you can find enough space without changing the soldered connections. But, most battery packs have no air gap between the AA-size cells.
HOW TO INSPECT OR REPARE AN OLD $100 LAPTOP BATTERY PACK,
by any qualified Electronic Technician:
1. Discharge or bleed the battery pack for 8 hours with a 10-ohm, 10-watt resistor inserted between the outer pins, 1 & 5.
2. Use a strong knife blade or a wood chisel to crack the seam at one corner of the plastic covered battery pack by gently tapping the knife or wood chisel with a small hammer. And, if you ruin your first, bad, battery pack, don’t worry, since you might improve, next time. CAUTION: If the knife blade is inserted too deeply, the battery cells, wires, or the printed circuit board might be damaged.
3. Pry, gently, along the battery seam until you circumnavigate the battery pack.
If careful, you can reassemble and seal the battery pack with silicone rubber, after inserting some thin, business card strips between each, AA size, battery cell.
4. But, be sure to replace all circuit boards and thermal sensors in the exact same position as they were, before resealing the battery pack. Or, take a picture, if needed, with you new digital camera, before disturbing any component!
5. Generally speaking, any good NiMH or Lithium battery cell can be used for other projects, like miniature racing cars or LED flashlights, if other cells show damages from leakage, short-circuits or overheating.
Several cellular telephone manufactures have also had similar problems with thin, plastic, shrink-sleeve insulators on their battery cells, if being recharged on an automobile dashboard in desert climates, like Lake Havasu City or Phoenix, AZ.