According to Correctional Service Canada National List of Personal Property for Men Inmates can have 8 - Batteries (rechargeable and charger).

• Easy-to-read LED displays charging status:
  Red = Charging, Green = Good to Go!

• Includes 4 rechargeble batteries

• “Bad battery” indicator light

• Overcharge protection limits battery damage from overcharging

• Automatic safety shut-off when charge is complete

• Recharges 2 or 4 AA or AAA NiMH rechargeable batteries in 5 hours