Battery charging

i have bought a military battery at a yard sale and i want to use it as a backup battery, i have successfully discharged from it using the positive and negative holes but i cant seem to charge it using the same method can anyone try to help me?

thanks



the positive is the upper hole and the ground is the bottom hole, does anyone know whats the hole next to the negative is for?

Any markings that might indicate the type of battery, or a part number?

Is it very heavy (lead acid) or relatively light (lithium ion)?

A lot of batteries have protective circuitry built right into the battery case. It's pretty hard to tell without opening the case.

What a unusual mystery battery ? If it’s lithium you may have scored on a great deal but it might have protective circuitry inside as mentioned. How heavy and what size is it??

Its definitely a lithium ion, and it had a sticker that said this:

Discharge:
Max. voltage 16.8V
Nom. voltage 14.8V
Min. voltage 10.5V

Charge method (CCCV):
Charge voltage: 16.8VDC max.
Recommended charge current: 5A max

so i tried just plugging a dc 12v charger to the positive and negative and it didn't worked. maybe it has to do with the middle hole

In general, lithium batteries are always charged with what is called a "Battery Management System" or "BMS" for short.  That's because lithium batteries need to be charged very, very carefully under strict control.  Otherwise, some can rupture, catch of fire, and have killed people!  Airplanes have crashed because of lithium battery fires.  I suspect that third connection is for monitoring the charge being given.  Don't just try to jumper some 12V charger wires to it and expect it to work properly.

Please don't try to actually use/charge this battery until you've contacted the manufacturer to find out exactly HOW this battery should be charged.