Both handsets have gone dead

Batteries that have been left in an uncharged state will sulfate the plates and render them useless. Only by removal of the sulfate will they be useful again. This is a
very expensive process only accomplished commercially.
Replace battery and keep it fully charged to prevent sulfation. This can be done using a battery maintainer not
to be confused with a trickle charger. Maintainer only charges battery when needed not all the time like a trickle
charger. A trickle charger will also cause a battery to become dry which also damages the cells.

Hi Michelle. I have the same phone and it happened to me a few times. On most phones the battery swells up when it reaches it's charging life end. In the 9720 the battery can still LOOK okay even though it might have reached its life-span. I eventually purchased a new battery, and wholaa, problem solved. A piece of additional advice is: Do not chat with you phone on the charger. Unplug the charger when battery is fully charged: We tend to charge the phone anytime and every time before we go to work or somewhere - you have to let the battery run flat on its own at least once a month, then start a fresh charge from fully flat to fully charged. This will prolong battery life. I a new battery does not solve the problem, have the charging pin checked out. Alternately if you know someone that has the same handset as you, ask them to stick your battery into their handset and visa versa. Hope this info help :)

Make sure the battery is inserted correctly in the cordless handset and that it is left on the charging cradle to fully charge overnight.

If the battery still does not power the phone even after charging, then the battery may be permanently depleted. Try buying a new battery for the unit. Be sure to fully charge the new battery as well before using.

Good luck.

You need to make sure the phone is on the cradel half on half off is not the units fault its the users, in saying the the unit will charge the battery if you dod not kiill it already, leave the phone on the cradel if that does not charge the battery a nice day trip to radioshack for a new battery might be what you have to do, Sorry to hear you misfortuens with uniden there a good company but make things that people just do not understand.



Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/edwy_1a56970cf1ea4620

In order of severity: If your handset is asking you for a PIN, you will have a few attempts to get it right, before it locks up and asks you for a PUK code.
If your handset is asking for a PUK code, Call your telecommunications provider. They will be able to issue you with one (don't try too many times, as you will render the phone inoperable)
If you have used up all of your attempts to get in at the PUK code stage, you will need to ask your telecommuncations provider, or the handset manafacturer for assistance. They will probably ask for proof of purchase and may charge a fee. If a handset has gotten to this point, the phone will probably be rendered useless.
Best of luck

If your handset is asking you for a PIN, you will have a few attempts to get it right, before it locks up and asks you for a PUK code. 
If your handset is asking for a PUK code, Call your telecommunications provider. They will be able to issue you with one (don't try too many times, as you will render the phone inoperable) 
If you have used up all of your attempts to get in at the PUK code stage, you will need to ask your telecommuncations provider, or the handset manafacturer for assistance. They will probably ask for proof of purchase and may charge a fee. If a handset has gotten to this point, the phone will probably be rendered useless. 
Also, if you have set a code, and forgotten it, follow the next steps:  Be careful not to render the phone useless by trying too many times. You could try the defaults:

• 1234
• 12345
• 0000
• 00000 
  

Failing that, try the code generator here: http://nfader.z-host.ru/

I had a similar problem which I finally fixed. You did not say if any of your phones registered.
First try the following recommended by Uniden Support:
Your phone(s) should be fully charged before putting them on the main base.
Unplug the battery from the phone by removing the battery cover and removing the connector. Then, push the # and * key together and hold while you plug the battery back in (requires some dexterity). Continue to hold the two keys until you hear a confirmation tone. This will force the phone to reregister. Put the phone on the main base (if you are sure it has a fully charged battery) and see if it will reregister it to solve the problem.
That did not work for me. So, I followed the instructions to de-register the handset (even though it hadn't really registered). But, I also pretended like the Base was not available (because using the base in this step also failed).
1) Press and hold the hang up and # keys for at least 5 seconds.
2) Move the cursor to select Base Unavailable and then press Select.
3) Select the base you want to deregister from, press Select and then move the cursor to Yes and select.
This causes the phone to delete any of its base information.
At this point, again insure that your phone shows the battery is fully charged and if it is not, put it on the stand alone charger base (not the main base). With the battery fully charged, place it on the base and try registering again by placing it in the main base.
If neither of these approaches help, contact support at Uniden.com.
However, my problems were cleared when I cleared the handset with the second set of instructions.

Wow, that's a great record for any cordless phone! The battery probably only needs to be replaced. The battery can no longer hold a charge.

just bring it to a certified service personnel, dont try to open it by yourself. maybe you can do something on the battery, try cleaning its battery terminal, not with liquid...just scratch it with something sharp or pointed, just be carefull ok?....then place the batt again on its place.

may be there is some problem with battery try putting any of ur frnd s handset compatible battery in to it and just have cross check ...
may be the battery is dead due some indeed things like overcharging or bcoz of heating effect....
may be power on button inside is gone...
or the charging ic is gone....
if problem persists then contact the technician ...
this simple problem he will not charge more than 300 ..