solar panel sizing question

[goboatingnow]

my understanding of the synchronized charging is that one unit is elected a master and it determines the battery voltage for the others

I will have both controllers in my lab over the winter as Im doing some coding to access the VE.direct port , so I'll know more anyway

Ill have to rig up a solar panel emulator !

[hlev00]

Originally Posted by noelex 77

Thanks for that.

It certainly looks like it is possible exactly as you indicated.

Victron have lots of software updates and I suspect this capability has been added in one of these updates. That is a great feature of Victron controllers. The software updates have significantly improved the controllers‘ charge algorithm and adjustability compared to the units I purchased a couple of years ago.

Has anyone enabled this synchronisation with just the controllers themselves? It would be nice to know exactly what is meant by “basic” synchronised charging. Hopefully that means the controllers will jump to the same charge state. Without the smart battery sense for a single voltage reference, presumably the voltage of one solar controller is used as the reference.

Yes. I have two 75/15 units that make their own network for syncing. It works great.

[noelex 77]

Originally Posted by hlev00

Yes. I have two 75/15 units that make their own network for syncing. It works great.

Thanks for verifying you can indeed have synchronised charging without any optional extras.

Sorry for the mistake, my understanding that the Smart battery sense was needed is obviously incorrect.

The Smart battery sense does provide more accurate battery voltage measurements by eliminating the voltage drop in the cables between the controller and the batteries. It also provides battery temperature at the battery rather than using the internal temperature of the controller (measured at solar start up), so it is still worth the small cost.

[Pete7]

Originally Posted by noelex 77

The Smart battery sense does provide more accurate battery voltage measurements by eliminating the voltage drop in the cables between the controller and the batteries. It also provides battery temperature at the battery rather than using the internal temperature of the controller (measured at solar start up), so it is still worth the small cost.

Indeed, never really worried about battery temperature until I fitted the battery sense a year ago. I have now seen some big temperature changes which weren't expected. Over Christmas, with 8c water temperature the batteries were sat at a similar temperature. MPPT charging voltage rose to 15.1v to take account of the low temperature. 3 hours of gentle motoring home (5 knots) into a bitterly cold wind saw the battery temperature rise to 32c, much higher than I would have guessed.

During the summer after spending a couple of days in Weymouth harbour I noticed the battery temperature was 26c. Surely not, in England Out came the temperature gun widget and showed a reading of 25.5c. Final check there is a thermometer on a RM ST60 and that also showed 26c water temperature and hence the battery temperature. Batteries rose to 32c after we motored to a new location for an hour.

The upshot is I now need to do something about engine room ventilation, but at least the MPPTs are varying the charge voltage depending on the battery temperature.

Pete

[goboatingnow]

Glad we resolved the issue here