Saturday, September 3, 2016

holy exploding batteries Batman!

Holy exploding batteries Batman!

My laptop had one of those Sony recalled exploding lithium ion batteries back around 2002. Fortunately, it works fine without a battery (just works like a very light weight desktop and always has to be plugged in to work)

Unfortunately, Samsung smartphones and hoverboards don't work at all if you remove their batteries, and in the case of phones, most are hard wired in such a way that you can't remove the batteries at all.

Now comes a short physics lesson.

The faster you charge or discharge a battery, the hotter it gets... And the hotter it gets, the quicker it dies  and the shorter its overall life. This is nearly a universal law of physics and thus far has never been violated.

I'll give you an example. Take a car battery. We call it dead when it can't start a car anymore. But more often than not, even if the battery is too dead to start the car, you can still listen to the radio while waiting for the tow truck to pick you up. In general, a 'dead' car battery will continue to start a riding mower for years after it's worthless for a car.

If you try to recharge an old battery too fast, you'll kill it for sure. But, if you trickle charge it, generally it'll live a few extra years.

If your car is 'out of tune' or hard to start, that'll probably take a year or two off of a typical battery's life. If it starts almost instantly, it'll add a few years to the battery's life. This is because of the near universal law of resistance. Ohm's law. Basically, the harder you work something, the hotter it gets, and the shorter it's life.

Back to the exploding phones.

All phone companies are racing to get the 'fastest' recharge and the longest battery, both for good reason. But the faster you charge (or discharge) a battery, the more 'explosive' it gets, as per the laws of physics.

Cordless drill motors and other power tools solved this by upping the voltage. This sounds counter intuitive so let me explain.

All rechargeable batteries are made up of smaller batteries, in this case 1.2volt batteries, generally 'C' sized. By going from 5 (1.2x5=6 volts) to 15 (1.2x15=18volt) you triple the overall power, but keep the same charging time, thus, you never burn-up the batteries.

You can even cut the recharge time by 2/3rds by keeping the original wattage, essentially switching from 'C' to 'AAA' ..IE, a 6volt drill (5x C sized) that takes an hour to recharge will work as hard as an 18volt (15x 'AAA') drill that charges in 20 minutes, or, the 18volt (15xC) drill that takes an hour to charge will work 3 times harder than a 6volt(5xC) drill that charges in an hour) but in neither case do they try to charge a cell made up of the larger C sized batteries in the quicker time it takes to charge the wimpy AAAs.

This is the same cell-sizing trick they use in the Tesla and the Volt and why they have insanely dangerous 400-600 volt battery packs, it's in an effort to reduce recharge time without melting the batteries.

Unfortunately, this trick does not work with phones... yet.

So, with phones, they are adding bigger batteries (at the same voltage) and trying to cook them faster in an effort to bend the laws of physics... long enough to get the phone out of warrantee. In essence they are going from AAs to Ds and trying to charge them faster than AAAs. There are ways around this, but they are very inefficient or dangerous.

Once, I left jumper cables on a car too long, I got lazy and ran inside for a cup of coffee and to warm up. Both batteries in both cars exploded. This is the inherent danger in one of the 'solutions' phone companies might choose.


If you have a 2 amp fast charger and a 1 amp slow charger, your phone battery will last longer (the number of years you can keep your phone, not actual talk hours per charge) using the slower one. But, if you just can't wait and buy a new phone every year anyway, go ahead and use the 'lightning' cable.

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