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Laptop Battery Insulation Failures

By micro.sleuth ·
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.

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.

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Majority of failures

by mjd420nova In reply to Laptop Battery Insulation ...

Over 95% of the failures I've seen regarding the battery failures of the Lithium Ion battery packs have been from shorts across the terminals, both on the battery and on the connectors inside the laptop. This really forces the temperatures to escalate and melt that flimsy insulation, making the problem even worse. The mfgrs haven't corrected the problems as I see it, only a redesign of the current carrying connections away from each other will eliminate the failures. You can make the batteries from any material and a short will still make smoke and flames.

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High Heat causes leakage.

by micro.sleuth In reply to Majority of failures

High Heat during the charging or the discharging of batteries will cause higher internal pressure or boiling to occur within the battery cell and leakage of the battery chemicals.

Your observations also ageee with my observations of Ni-Cad battery failures, which were correctly charged by GE and Black & Decker, with a pulsating DC current, but failures were caused by the assumption that they could remain "plugged-in" for weeks at a time.

The "memory effect" occurred, afterwards, when new, voltage sensitive circuits were added by Radio Shack to "walkie-talkies". Therefore, voltage sensitive charging circuits developed a memory, not the Ni-Cad batteries.

But, why has Underwriters Labs not been involved, nor has been asked to approve any new, consumer, battery packs, that may explode or burn, if overcharged?

Are failures planned to sell more batteries with flimsy, plastic insulation materials?

My orignal paper, "Laptop Battery Cover-Up", (above) has a new patenable approach to calculating "Power In = Power Out, minus heat losses", which is needed to determine when any type of battery is fully charged, even Alkaline Batteries.

And, major experiments should be conducted at Research Centers to improve the efficiency of any battery system by minimizing the heat losses.

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