Lithium Ion Batteries in Medical Devices
There has been a huge growth in portable devices in recent years - everything from wristwatch communicators to mobiles phones and laptop computers. The list grows monthly. The power supply, frequently a re-chargeable battery, has always been a limiting factor on physical size and weight. More recent developments in electronics design and technology at silicon wafer level have had a huge impact on both reducing power consumption and size, with circuits drawing microAmps, where before the same circuit may have needed milliAmps. The pressure on batteries to become smaller and lighter is never ending.
Enter the Lithium Ion battery (Lion or Lithium Polymer LiPo). More power per cubic centimetre than ever before, not just high current capability, but also better stability of output Voltage during the discharge cycle.
It is very tempting to choose a Lion battery and design your medical device around it without considering the relevant standards first. It's only a battery after all...? And millions of mobile phones and laptops use them, don't they?
Beware - there are at least two potential problems here. The Lithium ion battery has had a chequered history so far (reference certain commercial aircraft - and check YouTube too).
Firstly - a medical device will require the battery to be ISO 62133 compliant. There are very few compliant batteries on the market at the moment because the technology is fairly new. No battery supplier wishes to bear the cost of ensuring compliance needlessly. Therefore, you will have to carry out the testing yourself (not advised), or have a qualified test house do this for you. The testing alone is relatively expensive. However, if you check the test requirement in ISO 61233, you will see that a sizable quantity of the batteries will be consumed in the testing. Depending on the cost of the battery - it could easily double, possible triple the total testing cost. Don't forget - if the battery fails the testing, what are you going to do then?
Then there is the second issue to consider. Many airlines and postal systems will not allow Lion batteries over a certain (power) size to be carried through their systems without special provisions, and compliance with their particular regulations. If you are involved with portable medical devices using batteries, none of this should be news to you. But if not...
Fewer costly oversights - let us at Vivitronics Ltd help with the development, minimise the risks, and contribute to your success.