Battery first or more panels first for a shaded balcony, my answer changed after logging May data
I used to think the obvious upgrade path for balcony solar was add a battery as soon as possible. After tracking a messy shaded setup through May, i am less sure.
Apartment context because it matters. I am renting in Munich, one balcony facing south east, one small side section that gets late afternoon sun for maybe two hours. No roof access. The original setup was two panels on the main rail with a small battery system. This spring i borrowed two extra panels from a friend for three weeks and tested whether more panel area helped more than the battery did.
The battery system in my case is a Jackery SolarVault 3 Pro with the base battery, with feed in set around the normal balcony solar limit here. It has been fine, not really the point of this post. The interesting part was watching what happened when i added panel area in a place that looked stupid on paper.
With two panels only, good days were clean but short. The battery would charge nicely around midday, then the balcony shadow from the building opposite killed production earlier than i wanted. I was still buying power for cooking around 19:00 unless the battery had stayed full.
With four panels, total peak power did not look impressive because the side section is badly angled. But the production window got wider. The late panels were only adding a few hundred watts for part of the afternoon, yet that was exactly when the two panel setup would normally be dropping off and the battery would start covering the apartment load before dinner. Over the three weeks, the extra panels added less dramatic peak numbers and more useful shoulder hours.
My rough takeaway now is this. If your balcony already produces more midday energy than your household can use, battery first makes sense. If your generation window is short because of shade, more panel area or a second orientation may beat more battery capacity, even if the added panels look inefficient by normal roof solar standards. A bigger battery cannot store sunlight you never collected.
The annoying bit is that spec sheets do not help much here. You need a few days of hourly data, not just annual kWh estimates. I would tell past me to borrow or temporarily mount panels before buying extra battery packs. The answer might be different for every weird balcony.
I am returning the borrowed panels next week and will probably buy two of my own once i find mounting hardware that does not anger the landlord. The battery stays, but i would not expand it until i know the summer shoulder hours are actually there.
If you have a weird balcony layout, did you end up prioritising panels or battery first? I feel like the usual advice assumes a clean south facing setup that most renters do not actually have.