Doyle's correct, except...
The 60 CT1 has been in the Metz line for a long time. Depending on how old the unit is, it may be configured to take one, two or three types of batteries:
1) a nicad battery;
2) a dryfit battery (similar in many ways to a nicad, but with no problems with memory effect; and/or
3) a lead acid cell.
I haven't seen or used a lead acid cell for decades, but both of the battery housings I have (one of which came with my 60 CT2 and the other of which came with my 60 CT1) have a 3 position switch in the battery compartment that allows you to set the type of battery you are using, and there is a spot on the switch for lead acid (marked "Pb").
Each type of battery will respond differently to lack of use, but it certainly isn't good for any of them.
The flashes are great - they are powerful, flexible and accurate, they recycle quickly and they give a lot of flashes on a charge, but the batteries are neither light, nor cheap.
If you are buying a new one, I like the dryfit batteries best. I believe that the part number referred to by Doyle is the Nicad version.
This link is to the Metz website page listing current accessories for the flash:
Originally Posted by Doyle Thomas