Also
for CTEK from me. I have the MXS 10 which gets worked pretty hard keeping the fleet charged
The fixed battery monitor socket is very handy for trickle charging. I install them in the fuse panel cover on the right of the boot in D2s so handy to get to, and no permanent hole if you want to remove it later - just replace the cover. I think there's a pic near the end of Vera's 'What's in the workshop thread'.