This is coming from a thread drift of the battery
I believe that some 3 stage chargers are 3 stage due more to wording than to fancy electronics
CharlieJ posted this 3 stage chargers graph in the vent thread:
(Actually I believe that the current
graph in the bulk stage is wrong. It should be a flat line at the max current
This graph indicates to me that there is a voltage setpoint. As long as the voltage is below the setpoint the current output is maximum. Once the voltage setpoint is reached, the current output is throttled as needed to maintain that setpoint. This is the transition from bulk to acceptance. This is no different than how a dumb car regulator operates.
In this sense you would call your car regulator
a 2 stage regulator. What is different is that the voltage setpoint is higher than what you would normally set your car regulator to. And since this would eventually overcharge your battery
the smart regulator has a transition, it changes the set point after a suitable time transitioning you from the acceptence to the float stage.
From an electrical
standpoint, a battery has an internal resistance that increases with increasing state of charge. Using Ohm's law this means once the battery reaches a certain state of charge there would be no way of maintaining full current output without raising the voltage above the acceptance voltage.
I'm not saying that these chargers do not charge faster, they do because the setpoint before the cut back is higher, but if you set your car regulator to that same voltage it would behave exactly the same. The additional electronics
that you are getting with the 3 stage charger
turn down the voltage set point to float at a later time.
There are what I would consider true 3 stage regulators. Balmer and Iota
are two examples.
The Balmer defaults to 0.2 volts higher on the bulk stage than the acceptance. It also decides how long to stay in the bulk stage by estimating how full the battery is by looking at the fraction of time that the alternator
is turned on to maintain the voltage.
3. Bulk Charge - The most aggressive of the charging stages. Voltage is held at a pre-set level, specified by battery program
selected, for a set time period. Factory-set bulk time is 30 minutes.
4. Calculated Bulk Charge - Holds voltage at bulk level for six minutes, then calculates battery condition by comparing
existing voltage, time at voltage, and field percentage to target values. If values are met, the regulator advances to the
next stage. If values are not met, the regulator extends the bulk charge time by an additional six minutes and compares
real-time to target values. This will re-occur until all values are met.
Iota's IQ also has a higher bulk voltage set point than the acceptance, but they don't go into how the stages advance.
IQ Smart Charger for DLS Series Battery Chargers from IOTA Engineering