OK, here's some more of this. There is a second battery monitor position. So I've ordered a 32V-12VDC converter and will use that to monitor the 32V system. It won't tell me the actual value of course but I can establish what the normal reading is with the 32V battery charger doing it's thing. If it goes below that I know the power supply to the bilge pumps is compromised.
Then there is a high water monitor which is simply a float switch to ground. Easy peasy.