Genuine Savi W440, Savi W440-M, Savi W740, Savi W740-M OEM Replacement Battery or Spare Battery. It is so easy to install, just slide the old one off and snap new one on. It will give you up to 7 hours talk time on a full charge which takes 3 hours (charge approximately 20 minutes prior to the first use). Approximately 1 1/4″ x 7/8″ x 1/4″ thick.
Important note: You can replace the battery mid-call, without losing the call, as long as a charged battery is reattached in the next 5 minutes. This allows for unlimited talk time.