Thursday, February 11, 2010
Tips for RTLS/RFID Battery Life
Tips for RTLS/RFID Battery LifePhysics cannot be changed; from the moment a battery comes off the production line it starts its life cycle degrading to a dead state where no more power is available. In my observations even the newest high tech rechargeable batteries never seem to match their fresh off the production line capacity after a few discharge / charge cycles. The newest battery designs offer high power and great performance, but when they get to a midpoint in voltage they drain quickly and die abruptly. What is the number one question asked by customers; “How long do the batteries last?” Now the standard answer given to that question by, I would say ninety percent of RFID/ RFID RTLS vendors is two to five years. Wow what a spread, three years, the max life is 250 percent higher than the minimum. Problem is as customers we only hear the five year projection and then wonder why our batteries are dying so soon. Now this is not exactly the vendors fault, you see today’s business climate and operational demands require ROI in Months not Years. This business model puts pressure on the price side of any deployment and focuses more on short term return on investment rather than on the total cost of ownership over as little as a two year period. When you take these figures out over five and ten years the results can be disastrous. (I have real world deployment cost comparisons available if you would like them.) So what happens; the vendor (at the request of the customer) designs the system with the minimum number of tags, locators, and readers required just to cover the read area. Naturally Power Levels on tags, locators, and readers are set as conservatively as possible to save power and extend battery life as well to meet customer expatiations. (Side Note: I just was at another customer last week where this was the problem. After adding a few locators and turning up the transmitting power to a level that would get over the interference and cover the distance of placement the deployment is working flawlessly. Meeting afterwards with the customer describing the issues and resolution action taken the first question asked was; “If you turned up the power how long will the batteries last now? My answer; not as long as they would have in the non-functioning configuration.) So with that out of the way what do you need to do to make that battery last. 1. More tags, locators, and readers, must be added to a deployment to keep communication power levels low enough to stretch battery life. 2. Chose tags to meet your expectations. The smallest tag you can find also means it has less room for the battery system. In most cases regarding batteries, size is directly related to capacity. 3. Tag cost is way down the list when compared to business needs and performance requirements. Lowest cost tag price equates in most cases to not having the newest battery technology onboard, giving you high performance batteries and battery management systems. 4. Balance the business process. In other words only do tag location when it is required by your business. In most tags the “communication scheme” is adjustable. The more talking a tag or locator does the faster the battery drain. 5. Have a Plan, batteries do die. Some vendors offer warranties up to five years (if you pay the maintenance contract) that even cover the battery; others offer a one year warranty that covers everything at no additional cost. Any good vendor should offer a systematic plan for the inevitable battery demise and replacement of these batteries or tag in non-replaceable battery models. 6. Work with a good vendor which will think outside of the box. There are a lot of them in the market and when they run into situations outside of their normal deployments they call me and I blend in other technology to cover the gaps. Over just the last couple years we have used; solar, parasitic power and many other options to extend or eliminate the battery power parameters. Chose wisely and go locate something.
Posted by Byron Blackburn at 9:24 AM