The 475VA and the 475VAA were designed for slow current drain and, are also used in standby and emergency battery packs.
FAA Approved Model List
If your airframe is not shown on the list below, it is recommended a FAA form 337 should be filed with the local FSDO.
M475VA INSTALLATION ELIGIBILITY - Schweizer Model 269D
M475VAA INSTALLATION ELIGIBILITY - Waco Models Classic Waco F5 and Classic Waco F5C