If you read the Starcloud whitepaper[1], it claims that massive batteries aren't needed because the satellites would be placed in a dawn-dusk sun-synchronous orbit. Except for occasional lunar eclipses, the solar panels would be in constant sunlight.
The whitepaper also says that they're targeting use cases that don't require low latency or high availability. In short: AI model training and other big offline tasks.
For maintenance, they plan to have a modular architecture that allows upgrading and/or replacing failed/obsolete servers. If launch costs are low enough to allow for launching a datacenter into space, they'll be low enough to allow for launching replacement modules.
All satellites launched from the US are required to have a decommissioning plan and a debris assessment report. In other words: the government must be satisfied that they won't create orbital debris or create a hazard on the ground. Since these satellites would be very large, they'll almost certainly need thrusters that allow them to avoid potential collisions and deorbit in a controlled manner.
Whether or not their business is viable depends on the future cost of launches and the future cost of batteries. If batteries get really cheap, it will be economically feasible to have an off-the-grid datacenter on the ground. There's not much point in launching a datacenter into space if you can power it on the ground 24/7 with solar + batteries. If cost to orbit per kg plummets and the price of batteries remains high, they'll have a chance. If not, they're sunk.
I think they'll most likely fail, but their business could be very lucrative if they succeed. I wouldn't invest, but I can see why some people would.
1. https://starcloudinc.github.io/wp.pdf