WatchGuard’s Very Conservative Battery Charging Strategy
- Li‐Po (lithium‐ion polymer) battery technology is currently the most broadly used, high density battery technology. The lifespan of all Li‐Po batteries degrade after every discharge/charge cycle.
- Li‐Po battery manufacturers typically specify the charge and discharge voltages to product manufactures that will maximize the run time their batteries (i.e. the voltage level to achieve a 100% charge, the voltage level of effective depletion, and the maximum safe charging current level). Most electronics are designed to use the full top and bottom voltage ranges of the batteries in order to maximize the number of hours the electronic device can operate.
- When depleting/charging Li‐Po batteries at their maximum levels, the battery lifespan degradation rating will typically be a loss of 30% of the original capacity after 300 full charge/discharge cycles.
- WatchGuard has done three things that more than double the expected lifespan of the Li‐Po batteries:
- VISTA does not drain the battery below 20% (3.5 Volts),
- VISTA charges the Li‐Po batteries at half of the maximum safe level (4 hours instead of 2 hours),
- VISTA stops charging the Li‐Po battery at 85% of its maximum voltage capacity (at 4.1 Volts).
- Because of the very gentle (conservative) handling of the Li‐Po batteries, VISTA cameras typically will not reach the 30% degradation level until approximately 600 full discharge/recharge cycles.
The Impact of Pooled Deployments
WatchGuard Video pioneered the ability to rapidly checkout a VISTA camera using the “Checkout Kiosk.”
The key advantage to agencies of using the checkout kiosk is that fewer VISTA cameras are required. Agencies running the Checkout Kiosk will often only need about 50% ‐ 70% as many cameras as there are officers using the cameras. This can be a substantial cost savings.
One drawback of pooling VISTA cameras is that each camera will get significantly more use than a camera that is individually assigned to a single officer.
If a camera is assigned to a single officer, over the course of a single year, the Li‐Po batteries would likely be cycled about 245 times (5 times a week for 49 weeks). After 245 charge/discharge cycles, the degradation of the Li‐Po battery would be estimated at about 10%.
In a pooled deployment, depending upon the ratio of cameras to officers, shift lengths, etc., a pooled camera could see up to 730 charge/discharge cycles in a single year (2 times a day for 365 days). After 730 charge/discharge cycles, the degradation of the Li‐Po battery would be estimated at over 30%.
Li‐Po battery degradation is a fact of life with modern electronic devices, and replacing batteries needs to be factored into the plan for operating a fleet of cameras over numerous years.