I bought it double, with the idea that if the battery breaks or runs out, I will continue my work manually on the field. In the end, it is easier for you to get tired and stop than the machine. So buy it single, only with the battery, and I think it is more than enough, at least for the way I work. It looks very high quality as a material externally, although all the internal components are the same everywhere, from China. It has been used for almost a year in 14-acre kiwi farms and everything still works correctly. The manual pump has been removed and the weight has dropped to 4.6 kg empty. I don't know, maybe I would have bought it, although my first thought would be a 16-liter lithium for less weight. Not that you save much... 800 grams.
Edit: In the second year, the pump started to have a small leak, resulting in not reaching the required pressure to stop working. For now, it works like this until it is replaced. Cost 15-20€