Sony VGN-NR430E - Manual (Page 105)

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Precautions
❑ If you have not used the battery pack for a considerable amount of time, the remaining battery charge may become short.
However, this is normal and does not indicate a malfunction, because the battery pack will gradually discharge over time
even when not in use. Connect the AC adapter to your computer and recharge the battery pack before using the computer
again.
❑ You do not need to discharge the battery pack before recharging.
❑ If, after fully charging the battery pack, the battery power is still low, the battery pack may be reaching the end of its life
and should be replaced.