s****. 5800 Power button Red Blinking

Question

Hi,I have used my s****. 5800 for a few months. Last night, I try to recharge the battery (Power charge plugs into s****. 5800), but the power button turned red blinking. I did reinsert a few times to ensure the battery sitting on the s****. properly, still red blinkingKindly advise what's happened? How can I check the battery is still in good condition or die down already? Any way to verify the s****. charging circuit is ok? by measuring the Voltage readings on the battery connections on s****.?Any possibility cause red blinking? Bad contact somewhere in the circuit?Thank you very much for any suggestionEdmund