Unanswered Questions in design

Have a 200watt panel on the roof and a Victron 15amp charge controller with two 24 group lead acid batteries. Looking to upgrade to eventually run the whole camper and the roof ac unit. It’s a 30 amp trailer. Not sure where to start. I’m trying to learn as I go. I would Imagine adding a 30w charge controller/ inverter would be a great place to start? I currently don’t have a inverter installed. Suggestions on how to proceed with upgrading ?

Hi,

Still designing, came onto an approach which seems to me almost to good to be true (in my case), so I have the suspicion I make a mistake. Can you enlighten me?

The engine of my truck exists with 24V 35/55/80A alternators, so I assume that on the 80A model I could use about 50A (so roughly 1000W) without impacting the core of the truck.

I would prefer to run my "ESS" on 48V as it makes technically and financially most sense.

Now I could run 24-48 DCDC convertors, but to get to 25A on 48V takes 3.

But I could also run a 24V inverter and use it to convert my 50A spare of 80A 24V alternator in a 1000W 230V generator, which I connect to the ACin of the multiplus. In order not to stretch my alternator, and leave my truck stater batteries alone, I need a multiplus where I can set a very low limit on the ACin, only the 48/3000 model with limit minimum of 4.3 A stays in the 1000W ballpark (5000 is 6A). If I put a Cyrix 230A between alternator/starter battery & the inverter which I can program a bit, I should be able to make sure the invertor only kicks in when the engine is running. As the inverter can be rather simple, the 24 1000W (or let's say 1500W to be safe), can be a more plain (cheaper) brand as Victron. Or do you see a benefit of using a Phoenix

Fringe benefit, I can boost the AC out 2400W of the multiplus to 3400W (or about) by running the engine, and while I drive my base equipment runs on the alternator, only using the mutiplus/battery/solar for powerassist , and for charging my living batteries with whatever is spare of the 1000W.

When connecting to a landline (or other 230V source), I disconnect the inverter and replace it with the landline, the UPS function makes this transparent on the ACout side.

Eventually I can add a low power 230V 24V charger to AC out, and use that to maintain the truck starter batteries during longer stops (e.g. think parked 6 Months between holidays). I don't risk to make a loop as when the engine runs, the charger will detect high voltage on the starter side, and quit charging.

I would put a CerboGX to tie stuff together, and it seems to me I could use that to eventually add a temperature sensor on the alternator which the GX could use to kill the inverter, e.g. by opening the cyrix.

Looking forward to your views, spend many hours reading, but only experience makes a master, and that I lack.

Many thanks

Nicolas

UPDATE: A potential weak point (to be checked in real life) could be the alternator overheating when having to deliver the 1000W with the engine @ idle => low rpm => low cooling => it gets too hot and brakes. In the this setup it seems the throttling of the 1000W could only be done, by cutting ACin (4.3 A being the minimum limit) on the multiplus or switching the inverter on-off (limit it to e.g. 500W makes no sense it seems to me, as this gets below the multiplus threshold) . This would be beter manageable in a charger based system, where you could throttle.

Hi,

I'm currently planning my ac coupled 30kWp pv system.

I think about buying
2x 20kW Fronius 20.0-3-M with
3x Multiplus 2 5000VA inverter (one on each phase).
One fronius will be connected between grid and ac-in, the other (with max. 15kWp pv attached) to ac-out of the multis.

Will this comply with the factor 1.0 rule?
Will BOTH of the fronius inverters feed back to the grid, when the grid is available and the battery is full?

thank you!

Best regards
Thom

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