Product: Maymom Battery Holder Compatible with Medela Pump in Style Advanced Breast Pump (9V) with Microfiber Bag; Replaces Medela Pump in Style Battery Pack 9 Volt; Made by Maymom
Brand: Maymom
The battery pack for pump in style advanced uses 8 AA alkaline or rechargeable batteries. Provides up to 1 hour of pumping time. Please note using battery pack might not have the same suction power as using the AC adapter because battery will drain down as it is used. Adjust the power setting on the pump to fit your comfort or replace old batteries with new batteries.  Pump in Style comes in two types in terms of input voltage, 9V and 12V. You can identify its voltage by looking at the faceplate of your pump. This battery pack is designed to be used with the "9VDC" pump. If you have a 12VDC pump, DO NOT buy from this listing.   Authentic Maymom spare parts are engineered, tested and approved to work specifically with the intended breast pumps. Satisfaction guaranteed or your money back. 
The battery container identification of 12V is referencing total voltage of 8 pc of alkaline batteries. The reference to use with the 9V pump is reference to pump's using the 9 V AC adapter having an output of 9VDC. You can find this "9VDC" mark on the faceplate of your pump.
Uses 8 AA UM-5 batteries (not included). For more consistent pumping performance, rechargeable batteries are recommended
Serve as a battery hold for general purpose 8x AA batteries with an ON/OFF switch.
Perfect for pumping on the go, no need to worry about finding an outlet

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