Laptop batteries have a limited lifetime. After this they no longer hold charge. Once they have expired there is no alternative but to replace the cells. The easiest way to do this is to buy a new battery pack. None are available for the CR-48.
Your choices are limited to
- discard* the dead batteries and always run from the power adapter (charger)
- discard* the dead batteries and purchase a suitable external battery pack that provides power through the external power connector.
- break open the dead battery pack and replace the cells inside with like-for-like industrial replacement cells.
- buy a new laptop/netbook
* take them to your nearest household waste recycling facility
Standard advice from Google is
If your battery won't charge, follow these steps:
- Unplug the power adapter from your Chromebook.
- Remove the battery from the bottom of the Chromebook. Push the slider on the bottom to the right to release the battery.
- Re-insert the battery.
- Plug the power adapter back into the notebook and a power outlet. See whether the battery is charging by checking the charge indicator light next to the power port.
- If it's unlit, unplug the power adapter from your notebook and plug it back in. You may need to repeat this step six to 12 times until the indicator light comes on. For best results, do this in two second intervals -- plug the power adapter into your Chromebook for two seconds, unplug it for two seconds, and repeat.
- Once the charge indicator light appears, leave the Chromebook charging for at least 24 hours to make sure it's completely charged.
On the support forum, one user (midnitewolfy) suggested this variation
I believe the problem has something to do with a badly made charge socket, or maybe there is some kind of wiring that works with the positive and negative connections in the charge plug that disables charging if it makes contacts badly? I'm not sure... but this is what I did:
I found that when I ran off the wall charger and shut down, i would see the smallest flash of light on the battery charge indicator when I pulled the wire out. Holding the laptop very comfortably and paying very close attention to the light, I CAREFULLY eased the plug in and out of the laptop as slow as possible to find the flash again, and when i found it, so long as my hand was steady, it remained on. From there I just pushed the plug in completely and it seemed to fix whatever the problem was.
You've already done this so the only remaining option supported by Google is presumably to report the fault
Otherwise you're probably into the realm of electronics.stackexchange.com.
I'm not familiar with the CR-48 but if it is the connector that is at fault, you may be able to replace the plug on the charging cable. Alternatively, try a replacement charger. Replacing the connector in the CR-48 is presumably possible if you are willing to open the case, are unworried about any warranty and have some basic electronics skills.