If you've got a Bangalore Broadside Model C (Solar Panel version), the solar panel keeps your battery charged up during daylight hours.
The blue LED on the end of the solar panel indicates that solar panel is charging.
However, sometimes this LED can fail. But it doesn't necessarily mean that it's not charging.
The easiest way to tell is to use a multi-meter across the terminal from the solar panel.
Make sure the solar panel has line-of-sight to the sun to make sure it's getting as much light as possible.
Connect the multi-meter terminals across those of the solar panel and check the voltage it's supplying.
If the solar panel is working, you should see a voltage of between 2 and 17V, depending on the light level.
Note that, ironically, if the blue LED has failed, the solar panel will charge your battery more efficiently as it doesn't use some of the power to light the LED.
Note also that if the blue LED is still flashing and you try and measure the output voltage, you'll see it vary up and down (a digital multi-meter with some lag may have trouble keeping up with it). Again, this is because it draws some power from the solar panel to light the LED.
If you measure no voltage at all, it may need replacing with a new solar panel.