Great Expectation Questions

One of the many questions I had was that they used dialogue that not many people use now. Like, when they talked about the convicts were around the battery, or near the battery, I didn't know what they were talking about. Also I still don't know what they are talking about because I keep searching it up and it says that its and electrical cartridge, I don't think they used electricity back in dickens' day. So anyone who can answer and clarify my question please tell me what a battery is.