Panasonic WX-ST400 Operating Instructions Manual page 17

Important
⿟ When recharging Ni-MH batteries, only use the original charger
(WX-SZ200P). The charging time depends on the battery type and the
specific use situation, but at longest it will be around eight hours.
⿟ Some batteries may not perform well with this product. If possible, use one
of the recommended batteries. The recommended batteries are as follows.
Rechargeable battery: BK-3MCCA Panasonic Ni-MH AA-size battery
Dry-cell batteries: LR6PA Panasonic alkaline AA-size battery
LR6XE Panasonic alkaline AA-size battery
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