By this point we have all we need for a basic charge, and I do actually need to charge some batteries. I can build a simple current regulator with an LM317 and a resistor, which will be good enough for now.

No Termination

The simplest thing would be just to charge some batteries and log to the computer. There’s a marvellous thing out there called FeedGnuPlot which makes graphing realtime or static data so easy one has to resist the temptation to graph everything. But before we can do that, we need to be able to read analogue values and throw them over USB.

There are lots of ‘smart’ chargers out there. Most of them boast that they can charge your batteries quicker than the competition, and that a ‘smart’ algorithm will somehow prevent packing as much current as possible into a cell in the shortest time from having deleterious effects. Slow chargers are harder to come by: there are the cheap constant-current things you run for a certain amount of time—but if your batteries are not absolutely dead they will overcharge, and probably overheat and explode, as mine did. So not ideal. A few vacations ago, as a break from reading, I converted an old analogue ammeter into a basic adjustable-current charger with current and voltage read-off. The current regulation is not particularly clever. It uses the ’trick’ I devised for my AS Electronics coursework