I recharged the battery of Pentax Optio mx. The battery's specification is Pentax Rechargeable Lithium-ion Battery D-L17, 3.7V 1800mAh but after the charging and put it in the Pentax Camera what appeared on the screen of the camera was BATTERY DEPLETED. What does it mean? What do I need to do with this?

You cannot charge the battery using the USB cable.
Here are the battery specs for this camers.
Power Battery Form Factor: Proprietary D-LI8 Usable Battery Types: Lithium Ion rechargeable Batteries Included: Proprietary D-LI8 Lithium-Ion rechargeable Battery Charger Included: Yes

Take out the batteries and clean contacts with alcohol and a Q-tip the long ones like a doctor uses are better. If the batteries are more
than two years old I would replace them. I take it that this camera
probably uses AA. Reg. Alkaline batteries would be alright just to
try it with if you get it working then I would put a set of lithium batteries in it as these last far longer.You can also buy rechargeable AA batteries. If it has a lithium L-Ion rechargeable battery pack and it
is several years old you may want to buy a new one for it. There is
several reasonable sellers on Ebay with the proper battery for your camera. If this don't solve your problem I would say the camera is done. In my experience these new cameras just don't last as long as the old manual film cameras.

No. You can use disposable alkaline or lithium batteries, or rechargeable NiMH batteries, but AFAIK there are no rechargeable Li-ion batteries in that size.

ggentertainment.com/Pentax/Pentax-Optio-50L/
www.shopping.com/xPO-Pentax-Pentax-D-LI88-Rechargeable-Lithium-Ion-Battery-for-the-Optio-P70-39774

What kind of batteries are you using? Make sure they are rechargable. Normal batteries are not strong enough. Try using either rechargable Lithium Ion batteries, or rechargable Nickel Metal Hydride (NiMH) batteries. These are much stronger and should give you a good battery life.
If you are already using these, I suggest you take it back to where you bought it.

Hope this helps,
Gillian

Clean the battery contacts in the camera with a cotton swab lightly dampened with rubbing alcohol.

I would NOT suggest trying to charge the D-LI63 battery, in any other way, than a charger made specifically for this battery. (D-L 'eye' 63) This is a ->LITHIUM ION battery. This battery can be overcharged, and blow up. Connect a Positive, and Negative from a power source to the wrong terminals, (Those brass strips on the battery), and if you get them reversed, it may blow up.

"Li-ion batteries are not as durable as nickle-metal hydride or nickle- cadmium designs, and can be extremely dangerous if mistreated. They may explode if overheated or if charged to an excessively high voltage. Furthermore, they may be irreversibly damaged if discharged below a certain voltage."
Source: http://en.wikipedia.org/wiki/Lithium-ion_battery

I would suggest another affordable charger, specifically made for the Pentax D-LI63 battery, used in the Pentax Optio M40.
From a quick search just now,
http://sterlingtek.com/dh67-trav---ac-dc-pentax-optio-m40-battery-charger.html

Hi,

For my Z712 I'm using since one year CRV3 li-ion rechargeable.
No problems until now, few THOUSANDS of photos.

I've buy it from ebay.co.uk .

Regards.

EINAI SKETH MALAKIA H PSIFIAKI

Yes, the battery that comes with the C-7000 can be recharged. This battery is the Olympus LI-12B Lithium Ion battery and it can be recharged using the LI-10C battery charger. Both the battery and charger are included with the camera.