SDR-S15P, SDR-S15PC, SDR-S15PU, SDR-S15PR, SDR-S15EB, SDR-S15EC, SDR-S15EE, SDR-S15EF, SDR-S15EG, SDR-S15EP, SDR-S15GC, SDR-S15GD, SDR-S15GJ, SDR-S15GK, SDR-S15GN, SDR-S15GT - Panasonic Movie Service Manual (repair manual). Page 6

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1. Remove the SIDE R PCB. (Refer to Disassembly Procedures.)
2. Remove the Lithium battery (Ref. No. “B2501” at foil side of SIDE R PCB) and then replace it into new one.

This Lithium battery is a critical component. 
(Type No.: ML-614S/ZTK Manufactured by Energy Company, Panasonic Corporation.)
It must never be subjected to excessive heat or discharge.
It must therefore only be fitted in requirement designed specifically for its use.
Replacement batteries must be of same type and manufacture.
They must be fitted in the same manner and location as the original battery, with the correct polarity contacts observed.
Do not attempt to re-charge the old battery or re-use it for any other purpose.
It should be disposed of in waste products destined for burial rather than incineration.

Above caution is applicable for a battery pack which is for SDR-S15 series, as well.