The lead acid technology has advanced to get more AH/kg as well as becoming more environmentally friendly and in the process the charging parametres have become more critical. 20 years ago a transformer and a resistor and a diode was the standard for charging lead-acid and as in the process of charging by that method some acid evaporated, you just unscrewed the caps and replaced what was lost.

Now we have learned that eveporating acid is not a good idea and thus todays batteries do not have removable caps but still have vent holes to prevent explosion. This, of course, means that if you evaporate acid by overcharging there is no way back.

So: yes, the resistor diode "works", but you will gradually lose capacity.

The real point here is that when one part of technology (the battery) moves forward the other part (the charger) must follow. Go get the blasted maxim chip and do it RIGHT.

Erik