It may seem unbelievable, but in the midst of the microcontroller era, taper battery chargers are still on the market. They are basic, very robust, and charge lead-acid batteries quickly, but they have drawbacks, like an uncontrolled charging cycle, an end-of-charge current that is far too high, and they don't tolerate polarity reversals. If you own one, you can upgrade it with one of the designs presented in this article series. Here, we describe how to set up a basic protection circuit. In the second installment, we add a charge control feature, in both a full-analog version and a “luxury” microcontroller-based option for the demanding ones.