Last night, we went for a drive into the city as my wife wanted to visit a couple of friends from China. My car had been parked outside in the sun and my GPS mount had come off the windscreen. As I was remounting the GPS, I found that the GPS was bulging where the battery is situated – not a good sign, as it means that the battery is failing and could explode any minute.
Ok – maybe not necessarily, but it is possible – it didn’t explode on the way to the city and it didn’t explode on the way home, so after getting home, I took the GPS back into the house with me. It was a Mio C520 GPS which was bought in December 2007 before our family holiday driving down to Melbourne for the new year. I had replaced the battery in June 2009 after its capacity went very low, like a few minutes.
This is the original battery.
This is what it looks like now. Lithium battery can swell up, due to increase in gas pressure – which can happen due to over charging or due to internal failure. Most reputable lithium batteries come with an overcharge protection circuit – the problem is that over time, and due to heat, that this protection circuit may fail to be effective and the end result is a battery that starts to swell up like a balloon that can eventually pop with disastrous results.
Normally there is no metallic lithium in these batteries, however during overcharging, the metallic lithium may accumulate on the anode faster than it can be dissipated – and can anyone remember high school chemistry where the teacher cuts off a piece of lithium metal and drops it into a pan of water? If not, I will remind you – lithium reacts intensely with water, forming lithium hydroxide and hydrogen gas – the result means a bright flame if the amount of lithium is small – that is why you don’t want to puncture the battery – even though you can feel that it is like a balloon, there is a reason why it is sealed to avoid ingress of humidity, i.e. water in air.
Ok – after removing the battery, this is what it looks like – before I put it somewhere safe in my garage.
What should I do? Order a replacement battery or get a new GPS? This battery lasted more than 6 years, whereas the original battery only lasted 1.5 years. This Mio C520 GPS does not have upgradeable maps, so there are places in Western Sydney that I cannot navigate to because it doesn’t have the street maps. The cheapest replacement battery I can get is from Netherlands for $15 or from China for $18. There are a number of GPS’s like Garmin, TomTom and Navman available with free lifetime maps for under $200, so question is new battery or new toy?