Places where I buy batteries:

AA, AAA Alkaline Batteries


9V Alkaline Batteries

$1.19/ea for 8



12V Auto Batteries

For basic low cost replacements: Walmart or Home Depot

Ni-MH Low Discharge Rechargeable Batteries

Amazon Basics or Sanyo Eneloop from Amazon

18650 Batteries

AliExpress Liitokala Batteries (best price for value/will take a month for delivery) (one of the best performance batteries) (trusted site for li-ion cells)

Walmart EBL 18650 Batteries (low cost option within the States)