Austrian Alps- 24 v System?!

[benzose]

Hi everyone, this is my first post.
I need your support with a problem. I have 2 mountain huts in the Austrian Alps - both off grid. We currently live in a hut in which I have a very simple setup.

200AH- DIY Lifepo4 12 volt
Victron 100/20 charge controller
3x 100 watt 12 volt panels

It is doing pretty fine so far.

So now there is my problem:
The other hut is to be rented out. Since the costs of renovation are very high, you have to look where you can save, of course.
For this I bought used panels:
16x

SUNTAICS STC 135-34M5-P Electrical data Nominal power (Pmax) (Wp) 135
Voltage, max. (Vmp) (V) 26.8
Current strength, max. (Imp) (A) 5.04
Open circuit voltage (Voc) (V) 33.5
Short circuit current (Isc) (A) 5.53
Power tolerance (%) +/- 5
System voltage, max. (V) 600
Temperature coefficient of Pmax (% / 0C) -0.44
Voc (% / 0C) -0.37
Isc (% / 0C) +0.08 Notes: stated values are nominal values

for $ 160


The structure should look like this.

24v 200AH DIY Lifepo4 prism.
Victron 100/50
16x modules in parallel.

Unfortunately, I only noticed afterwards that the end-of-charge voltage was too low.

Is there any way I can use the panels in a 24v system?
If not- which other options do i have?

Thanks for your help

 

[TomC4306]

Absolutely!
Rewire your panels to be 2 in series first, then those 8 pairs in parallel.
Open circuit voltage of 2 panels in series is 67v. Your Victron 100/50 tolerates VOC of 100 volts.

 

[cotswoldstony]

If you are renting out your hut I recommend fitting a LVD to protect the battery bank and combiner box as PV isolator with lightening protection/DC trip to protect the charge controller.

 

[DJSmiley]

I would upgrade the MPPT to a 150/70

That allows you to put 4 panels in series. With 16 panels you can do 4S4P
With 29V you're ending up with about 120V for the string.
The temp coefficient needs to be calculated as well. Assuming -20C (not unlikely in the mountains) you can expect 19% more voltage, thus with 4S perfectly for a 150V controller.

The 50A controller can't handle all those panels: 16x135 = 2160W, thus 90A at 24V. A 50A charge controller will cause quite a significant loss of available power

Not sure if you're planning on an inverter, but you can look into inverter/chargers as well, as eg a MPP Solar or Growatt. Those also have a pretty decent MPPT integrated with a higher voltage input. Saves you also on wiring and connectors.

LVD: I don't think thats needed. An invertor has that already integrated, and the BMS should do the same job. For in the alps, especially if the setup is left unattended, i would look into heating the cells and at least proper working undertemp protection.
Especially on higher altitudes, there is sun, but also low temperatures... Last time I was in the alps in Austria it was like -20 celcius, but clear blue sky and sun.... (While the lower town was completely clouded)

If it's summer-only usage, you can just disconnect the battery (I would recommend that anyway), or take it with you.