If you want something doing well, do it yourself, goes the saying. Toyota’s version might go a bit like this: if you want something doing well, do it yourself and then Matsushita Electric Industrial Co to help you out a bit. And then go and polish your Prius.

Toyota has, according to reports, decided to buddy up with Matsushita to invest some more yen in their joint venture, Panasonic EV Energy Co., which will be responsible for making a shedload of batteries to go with the shedload of hybrid vehicles Toyota plans on making in the next few years.

Investment in the battery building joint venture will cost Toyota and Matsushita 20 billion yen (that’s around £98 million for you currency watchers) and will finance a new nickel-hydride battery factory in Japan’s Shizuoka Prefecture, according to Bloomberg.

Japan’s Nikkei newspaper, meanwhile, indicates the expansion plans are even bigger than that, with another li-ion battery factory to be built in Shizuoka Prefecture, although there’s no confirmation on that one yet.

All of this factory building malarkey, reckons the Nikkei, will lead to one million hybrid batteries a year making their way through the factory gates. Handy number, really, and about the same as the number of Priuses that Toyota has sold to date.

• Plug-in Prius hybrid hits UK roads
• Guess how many people drive a Prius
• Want a hybrid? Now you can update your old banger
• Panasonic household fuel cells coming in 2010
• Sneak peak at the 50m long eco-yacht
• Toyota says the “P” word (as in “peak oil”)
• Solar powered Prius – pie in the sky?
• Honda revs up for hybrid price war
• Build your own hybrid fuel car
• Ikea spends big on clean tech start ups