The Manson PV Charge Controllers, series SBC-71-- are not worth the money, and it is better to pay a bit more and get a Plasmatronics regulator.
I have a Manson SBC-7130 PV Charge Controller, and I have found limitations in its design which make it inferior to the Plasmatronics Solar Charge Controllers.
The Manson unit claims to have a 3-stage charging system, with "bulk", "absorption" and "float" modes of charging. However, when the Manson unit is showing that it is in "float" mode, there is actually no charging happening. A look on the LCD screen will show that the current during "float" is "00.0" amps. The way the Manson controller works, is that the unit stops the flow of current to the battery when "float" is being displayed. The voltage in the battery then drops down to some level, and then the charging cycle commences from the start, with "bulk", "absorption" and then "float". What this means is that more current is flowing through your battery than you would want in the course of a sunny day, which results in excessive loss of electrolyte, particularly in summer. This requires frequent checks of the electrolyte level, and topping up when necessary. Recently, I found that the plates of my battery were "high and dry".
The Plasmatronics regulators, such as the PL series or the new "Dingo", when in "float" mode, maintain the battery voltage at the programed level by pulse-width modulation (PWM) of the current.
Unlike Manson, Plasmatronics does provide support to the consumer from the Australian manufacturer (Manson does not bother to respond to emails sent via the "contact" facility on their website), and the advanced user manuals are written by someone who is fluent in English and knows how to communicate the information to you that you need to know.
31st August 2012: I had the Manson PV Charge Controller maintaining a Century GC2 battery, but the battery failed, I would say prematurely, and I suspect overcharging was the cause (a cell shorted out). I now have the "Dingo" by Plasmatronics, and I'm very happy with it.