question

Higher voltage = smaller cables and copper is not cheap...

Have you considered putting the inverter in the bunker? Short DC run, longer, but way smaller AC run.

Have you considered charging the 24V from the AC output of your main system, That simplifies things and gives you stable battery backed control voltage.

I am about to run a new 24V control supply bus/loop but it will be derived from a 12V battery system, via a boost converter, or two. The 12V will be on continual float, suppyed by by the main AC output. No as efficiant but way easier than a bucket full of high current relays.

MPPT on a turbine, wind or water, needs to be a very slow loop so that the decion to change the terminal voltage on the turbine, and thus the speed, is based on an average output over several minutes, if not tens of minutes for wind.

You may be better measuring wind speed, again an average, and setting the terminal voltage from a lookup table.

You may want to think about installing a small PLC to manage this stuff, again something I am about to do.

Al

Bunker is built, has 7x 70mm2 2core cable to power room, bunker is damp not good place for inverter. Major headache is space in barn conversion, battery systems are bulky, can produce noxious gasses, so bunker was solution, FLA battery boil less at 2 to 5C.

I think 48v battery is just better, same 96 cells in 4 strings. But do I need 23 cross links, or can I rely on 4 separate strings to share current. 24v just doubles issues here.

I do accept 240v 24v charger could be simple, not in spirit of design.

Monitor mid battery volts is good idea, which BVM does well, but which string? Or add 4 way selector switch, use my voltmeter.

Think 2nd BVM channel could be more useful to monitor wind turbine current, color control will record this value, until I can buy a Victron MPPT to do wind turbine job.

Will watch web, Victron pride their ultra fast response of MPPT, light changes fast too. You are right time lag on wind turbine should be longer, maybe 1min, it still needs to respond to gusts, but time response is simple variable in MPPT app, just add it in next version update.

I work with PLCs and AC drives every day, be nice to keep this simple. So use less power in January, do washing up by hand - and enjoy view, run wood stove alot, simple off grid existing!

Hi Doc. 96 large cells? You're in 48V+ territory now, please forget 24V. One saving grace is your mppt's now have double their 24V capacity.

I hope they come with auto-watering. With 4x strings, take care balancing your wire lengths to each too.

Monitoring them could be onerous, and you could consider batt balancers. For those (in Victron blue) you'd need 3x units (12V blocks), all the cross-wiring, etc.

https://www.victronenergy.com/battery-monitors/battery-balancer

https://www.victronenergy.com/upload/documents/Datasheet-Battery-Balancer-EN.pdf

Call me a doomsayer if you will, but this isn't worth doing any way but properly. This is a substantial batt system, and deserves good treatment.