You cannot fully charge four Ni-Cad cells in series from a 5V cell phone charger because as I and Tony showed, each cell needs as high as 1.55V which is 6.2V for four cells in series.

 

A word of caution.

NiCd battery chargers were not designed to charge other battery chemistries. Lithium ion batteries will not tolerate abuse and will leak, explode, and/or catch fire if not charged properly.

A NiCd battery charger cannot detect charge termination for lithium ion batteries.

 

A word of caution.

NiCd battery chargers were not designed to charge other battery chemistries. Lithium ion batteries will not tolerate abuse and will leak, explode, and/or catch fire if not charged properly.

A NiCd battery charger cannot detect charge termination for lithium ion batteries.

Thanks Dennis,
Another poster (which I can't seem to find now) suggested I post images of the 'guts' of my charger(s) in order to help determine the proper 'surgery' to fix the high voltage issue with the recently purchased ebay charger, and/or the low voltage issue with my original charger.
I'm attaching images of both my original charger, which has a miniscule 0.47 VDC output and the one from ebay with 12.5 VDC output. Notes are added to the images. Hope this helps inform suggestions re: solution(s). Also, per milwaukee data, open circuit voltage on these chargers is 1.9 VDC. My orig charger is CAT# 48-59-0180; later model (ebay charger) is CAT # 48-59-0300.
Much obliged.