the International Rollei Club

It has been some time since you posted your request about the Rollei 140 RES battery. But, since again, I recently replaced the battery on my "legacy" flash unit, I thought it best to post a reply. If not still pertinent for your purposes, it may be of interest to others. Firstly, I must admit that my 140 RES is my preferred flash unit on many occasions, and has received considerable use over the many years. I am presently using it with my Sony a7R mounted with my collection of various Canon FD lenses.
I consider it somewhat easy to replace the battery. But it may be considered difficult by others depending upon your skill sets.
The battery is a 4.8 Volt, 700 mAh ( 3.36 Wh ) sintered NiCd rechargeable battery. This is basically 4 x 1.2v cells mounted together and shrink-wrap sealed, and sold as one battery. Depending upon who you purchase this battery unit from, it should cost you between $9.00 to $15.00 (U.S. dollars). I most recently obtained my battery for $12.95 US from BatterySpace out of Richmond, California. I do recommend this company, but there are many others to choose from. It is very important to obtain the correct battery. I am aware there is conflicting information about the proper battery for this unit on the internet. However, I can assure you the information I provided is absolutely correct. I have done this before, and always with success.

Regards, Stan