How to wake up a "sleeping" battery (of micro battery models like ULTRA series)?

To achieve extreme light weight, ULTRA series and some customized NANO models (like NANO M1 lite) use micro rechargeable lithium battery. Sometimes, after long-time shipment with zero light, a micro battery naturally drains (an herent quality of lithium battery) and may enter "sleeping" mode, which requires stronger light to wake it up for further battery charging.

You have 2 options to wake up the battery:

• Direct sunlight wake-up (for very strong sunlight)
  Place the device under direct sunlight of around 80000 lx for over 30 minutes. Then the battery will wake up and keep on charging until it is fully charged.

• Using a convex len (for weaker sunlight)
  

  1. Keep the convex len (diameter: 7cm) vertical to sunlight. And sunlight is focused at the focal point.
     Note: If the focal point is too small, it will damage or burn the device. Keep the diameter of the focal point at around 2 cm.
  2. Place the solar panel at the focal point, vertical to the focused sunlight, for about 10s. The battery will wake up. Please immediately move the device away from the focal point after wake up.
  3. Keep on charging the battery under regular sunlight until it is fully charged.

Improper maintenance may also lead to "sleeping" battery. Please maintain the device properly.

Note that "sleeping" battery won't happen after deployment as there won't be long time of zero light after deployment.