So I want to charge a battery from a pedal-powered dynamo, and use that to power my PC, my screen, and pretty much everything else in my home office. This whole thing is a little project to improve my own health while I'm working; I'm not here expecting to make major miracle savings on the electric bill or anything like that. I'm still thinking about where to buy/how to make the dynamo (and much gratitude to everyone who's already helped me to better understand how they work.) But when it comes to the battery, there's a lot I still need to understand. My reading gives me the impression that charging a battery (whichever type, still not sure what's best) is an awkward task, and a battery charger has a precise voltage/current curve it follows, and if it doesn't, the battery explodes. Or at least, suffers and loses time out of its operational lifespan. Meantime, the current coming out of the dynamo is going to be all over the shop, and cutting out irregularly. (My software/networking background inclines me to "always assume malevolence": ie, imagine that the user of the pedals will be actively TRYING to wreck the battery - therefore I should make that physically impossible to do.) So what do I need in between the dynamo and the battery? At a guess: - something to rectify the current coming out of the dynamo (because I can't see how you'd charge a battery with AC.) - something to buffer it/smooth it out so the battery charger can be as constant as possible. (Batteries take what, multiple hours to charge? Meanwhile I might want to pedal thirty minutes and pootle off to have my dinner. We can afford a lot of wasted effort, since it's only a toy. But still, it would be satisfying to be as efficient as possible.) - something to actually charge the battery, with its precise current curves and shut-off circuitry to prevent overloading. - then presumably something to invert the power coming out of the battery, so I can wire it up to the standard 13amp plugs that everything runs off. (I live in the UK, so that's 240V at 60Hz I need coming out.) I'm a bit naive about all this, so I haven't really got any numbers on how long the battery will last, or how much work it will be to charge it up all the time. (It's only the for office, I'm not going to try running the fridge and washing machine by pedal power.) But all the same, maybe I also need something to automatically switch it all over to the mains once the battery's dead. Can all / any of these stages be bought as off-the-shelf components, or am I building them all myself? (Do things like UPSs already have to do a lot of this already?) Also, are there any important stages I've forgotten, or problems I'm not seeing?