No capacitor in the AA holder of my 45CL3 or 45CT4. The original owner manual provides no explicit warning against the use of rechargeables in the 45-39 AA holder, although the instructions do say "use only alkaline manganese batteries of size IEC LR 6 (penlight cells size AA)"
The 45-40 Nicad pack from Metz is not one that is designed for the user to remove and replace cells. The Nicads in this holder are factory installed in the pack.
I just rechecked my two battery holders and indeed found a black capacitor in both battery holders, which I neglected to see due to its location.