Yeah, basically you want to optimize the voltage to have a "reasonnably low" current in order to avoid too much copper.
- 12V system, typically up to max 1-2 kW
- 24V system, typically up to 4-5 kW
- 48V system, typically 10 kW -> this is the maximum nominal battery voltage that is usually considered safe to touch, as it goes close to 60V when fully charged.
- 300-600V system : typical for up to a100-200 kilowatts, like big UPS, powerful EVs,
It's simply limited by physics. 100-300A continuous is a current that is quite OK to handle with serious copper, over that, the switching, protection, and cabling elements become too expensive, and you should go up in voltage.
Also, requirements differ wildly. An EV for example, has to provide short peaks at maximum power, solar storage has rather to be efficient for continuous power, very very different designs !
Usually, battery systems don't go to kilovolts, that's too dangerous because High voltage DC loves to creep and spark, while batteries love to burn down to the ground in a smelly firework when in presence of sparks. Not a good combination.
you rather parallelize smaller <1kV systems. Not sure how Telsa does it in Australia.
There's also not much systems inbetween 48V and 300V, as you have the hassle of protecting against those crazy humans coming in contact with the high voltage, you may as well go up in voltage. Some electric forklifts run off 96V perhaps.
10 Megavolt storage caps?
Forget it.
Look page 22, Fig. 5.4.1-2, that's a microfoarad range smoothing cap, good for 50ms.
https://www.energy.siemens.com/ru/pool/hq/power-transmission/HVDC/HVDC_Proven_Technology.pdfAnd that's only a ridiculously small 0,5 MV !