Does the red battery indicator mean the battery is charged or discharged.

You may want to look for the manual but it is mostly caused by a bad battery. The battery may be discharged far and many chargers are not capable to charge batteries being even close to full. Green means charging and red is fail. It keeps trying. A broken and useless battery may show the same indicators flashing. Inspect the battery to make sure it is in a good condition, like acid at about the right level and no traces of melting on the container or visible loose/bent plates. Put a voltage or multimeter on 20 Volt at its terminals and determine the battery has any voltage to begin with. 11Volt indicates an empty battery and 12,8 to 13,2 is probably full. An empty 12 Volt battery is charged with a 12 Volt ~ 1 Amp power adapter (maximum 1/10 of battery Amp but not until fully charged) and preferably a 1 Amp fuse in the + line. This is "attended charging," meaning things must not get hot and charging is stopped before the battery is full. Then try the charger again, always the 12 Volt clamps attached first and next the plug in the mains. Disconnecting is in reverse order.
Bad batteries often have sulfur on their plates and can be revived by fast discharging but the success rate is low. Meaning a battery can be better but not good enough. Batteries have a life of 5 years and closer to 10 when always charged. When charging was low and often not, the battery could have died after two or three years. This apart from a limited number of charge-discharge cycles. The test is with all lights on and then not dimming in the first minute or after ten seconds. Good batteries must hold charge for a week and not much less every day.

What does the red light mean on irobot Google Search ,,try this link

Hi,

The yellow light means that there still is an amount of charge on the battery, meaning that it isn't fully discharged. The red light means that it is partly discharged and you can charge it up.

Hope this helps. If it does, I'd appreciate a 4 thumbs up. Thanks,

Handie Andie

Hi.

If the red light is solid, that means that the Roomba is near to full discharge. If the light is flashing red, then the Roomba is completely out of charge.

If the Roomba is fully charged, then there may be a fault.

Here full list of light codes:

Pulsing Amber - Charging
Green - Fully Charged
Amber - Partially Discharged
Red - Almost Fully Discharged
Flashing Red - Fully Discharged"

Here manual

See also
Roomba DISCOVERY MODELS' DIAGNOSTIC TESTS

It sounds like you have an intermittent connection. When an internal power connection is lost, it will cause the charge indicator to indicate discharged. Check your solder connections, particularly the solder connections that hold the batteries in place

If both yellow and green LEDs come on, this indicates
a deeply discharged or defective battery pack.
Allow the battery pack to remain in the charger for 15
to 30 minutes. When the battery pack reaches normal
voltage range, the red LED should come on. If the
red LED does not come on after 30 minutes, this may
indicate a defective battery pack and should be
replaced.
n After normal usage, a minimum of 1 hour of charging time
is required to fully recharge battery pack.

I still have the manual for my mouse.  Model number 64321.
When this mouse was manufactured it used NiCad batteries which developed a memory much more than the newer batteries.  The older NiCad batteries needed to be conditioned occasionally so Kensington provided a way to do that with the charging base. 
The red light is for indicating discharge status of NiCad batteries.
The red light will flash quickly when you press the battery discharge button on the bottom of the base.  This indicates that you now have 5 seconds to place the mouse in the charging base for battery discharge.
The red light will flash flash more slowly when the battery is being discharged.
After the battery is fully discharged, the base will then charge the batteries.
It should be noted that very few manufacturers of products that utilized NiCad batteries provided a "battery conditioning" feature.  Kensington was unique in this regard.  Battery conditioning allowed NiCad batteries to have a longer useful life.

Now maybe you can help me....  I lost my power supply that plugs into the USB connector.  If you have yours, can you tell me what the output voltage is and what the polarity is of the inner pin.  This will be marked right on the power supply base.  
I plan to just get a generic power supply from Radio Shack, but I need the voltage value and polarity.  Until then, I can still use the mouse, but it won't charge.  FOr now, I'm just using standard AAA batteries.
Thanks.
[email protected]

the steady red light showing when in charger shows that
it is charging. the blinking red light when taken out of
charger or turned on and off means it is not fully charged.
leave it in charger till red light turns green.

Tips for battery Indentification: A charge mark is provided on the battery pack to help you remember whether it has been charged or not. Two colors are provided (red and grey) - you may choose which one indicates charged and discharged.