question

A cascade is not going to provide you with much benefit. The 48V Multiplus is going to be permanently charging the 24V one's batteries. If you take 1600W off the 24V Multiplus the 48V one will have to supply that power plus losses. I can see what you are trying to do though, keep good equipment working. You'd be better off running them independantly for different purposes. Naturally this would mean splitting up MPPTs and solar strings, it starts to get complicated.

48V is the way to go though, would you not consider selling your old Multiplus to fund new kit instead? Which brings us to the question about monitoring your old Multiplus. Probably not if it has 18xxxxx firmware, then no, not at all, 19xxxxx firmware, yes with limitations. The limitations will annoy you next to your new shiny 26xxxxx firmware in your 48V Multiplus.

Hey!

Thanks for your reply. I am bound to the 24V system by a 24V wind turbine. I left that out as the question was getting long already. I would love a 48V system but it would mean selling everything and starting all over. Waste of money. I'll consider running two separate systems. Sad I cannot find a good use for the AGMs.

The reason I thought about this is that the 1600VA from the 24/1600/40 from PowerAssist plus the 3600W pass-through from the 48V system would give me a nice powerboost, without stretching any of the two battery systems. During the day this wouldn't be a problem if I feed in enough solar to the 48V system. At night would be different as I would just drain the 48V system trying to recharge the 24V system. Maybe I could install a switch to switch off the AC connection between the 2 at night?

On more thing, would the 24V system try to charge the 48V system through the AC-out of the 48/5000? Thought I read this somewhere in connection with AC-coupled Fronius inverters. That would be an option too to get more power...

Hello,

I have a similar plan myself!

I currently have a 24V system with 3kva Multi and OPzS 500Ah battery bank. The system if off-grid, but I can charge from grid if necessary, so the AC-in is connected to my grid supplyer.

The house is divided in several circuits, each with its own MCB. I diverted many circuits (lighting, IT, TV, etc) to my offgrid system, while maintaining higher-load circuits still on-grid (whasing machines, motors, etc).

I intend to get another Multi, this time 48V, new battery and have its own MPPT and Venus device. The AC out of this new system would go to a new MCB board, but one circuit would feed the older Multi.

Now, the important thing is how to program the behaviour using the "ignore AC" switch of each multi and also make the second one (in the cascade) work sometimes in passtrough (not charge bank, just let AC flow in to out). So, during sunny days, each Multi would have no AC on its input. In the night, I could make the first work from grid (charger enabled) and pass AC to second (charger disabled). After 1st bank charged, I could enable 2nd unit charger and charge the older bank. I could also not enable the AC in of first and charge the 2nd bank from the 1st, but seems rather silly...