Wont hold charge. Flashes red for a few secinds then solid green

Mine is an Invacare M51 Pronto Surestep with an onboard Winsunny battery charger. My charging lights are solid red and green/ yellow. Depending on if it is charging or not. What kind of charger do you have?
I have to replace my charger because it is not working. My green light is staying green while charging even though my joystick is showing my batteries are depleting and I just got new batteries. sigh.

according to manualslib type site for the wg540, solid red means charging for the wa3840 and wa3838. After 30 minutes if battery has not reached 10 volts (of 18), the red will begin flashing meaning defective.
Just green? Ready to go. Green flashing? Overheat.
Tangent; sometimes a discharged battery needs a little coaxing - have to get a little voltage into the battery for charger to try to charge. Different company, electric drill. I plead ignorance if this applies for the 3840 since they mention the half an hour time.

Indicator Lights:
1.Headset Status Headset Indicator Light
2.Powering on Steady blue, then intermittent flashes
(changes to standby mode)
3.Powering off Red appears and goes off
4.Standby Blue intermittent flashes
5.Charging battery Red solid light. Light indicator turns off when
battery is fully charged and headset is off.
6.Low battery Triple red flashes
7.Pairing mode Blue/red alternating flashes
8.Missed call Purple flashes. Press the call control button
to cancel flashing light.
9.Incoming call Triple blue flashes when ringing.
Power on and off:
1.Turn on the headset Press and hold the call control button until the
indicator glows blue. You will hear ascending
tones.
2.Turn off the headset Press and hold the call control button until the
indicator glows red. You will hear descending
tones. When power is off, indicator stays off.
If none of this is helpful then it may be that your battery is dead, if that is the case then you will need to replace the whole headset. The battery's are not replaceable.

Good luck from Headsets Direct!

Not familiar with this model but on other camera chargers I have used it flashes red while charging then goes green when it's charged, it should tell you this in the manual about charging the battery

KODAK Easyhare digital camera light status
1. Blinking green light(or blinking blue or white light in some models) - Means camera is performing a power up procedure. Note: Wait a few moments to see if the camera displays a solid green (or blue or white) light or a blinking red light.
2. Solid green light(or blinking blue or white light in some models) - Means Camera has sufficient power
3. Blinking red light - Means camera batteries are weak or need replacement; If battery are new and still red light camera needed to be repaired

For futher assistance contact Kodak support line 1 800 235 6325 (23KODAK)

it doesn't change to green, the solid red light means it is fully charged, there should be a legend on the front of the charger to help you with this. If it flashes real fast the battery is malfunctioning and slow flashing is charging and again solid is fully charger.

Remove the battery anhd replace with a new one. It sounds like the cells have collapsed and cannot any longer charge

This means Battery is low to charge the capacitor.
I suggest you test this with unused new Duracell.