Battery sizes are measured by their capacity to store electricity, but it's important to consider usable capacity rather than just what the total capacity is. That's because you don't want to actually use a battery's entire capacity, as this can damage it. The usable capacity is called. The size of the solar battery you need will depend on the size of your home — specifically, how many bedrooms it has. To work out what size battery you'll need, you can start by. Generally speaking it is better to buy an oversized solar battery, but only as long as your solar panel system is big enough. Otherwise you'll want. You can charge an electric car with a storage battery, but it's typically not worth it because you'll almost certainly need to tap into the grid to. Yes, but there are caveats. You'll struggle to fill multiple batteries without a large solar panel system. There's also the risk of one or several batteries failing in a multi-battery system, which can reduce the overall effectiveness and how much power you can access.