by the way , to try and visualise what goes on imagine this is as a model of
battery charing, it doesn't matter if the
power source is a mains
charger,
solar controller or
engine alternator
The human is controlling the variable resistance and watching the amp and volt meters
Note the
power source is " capable of 20 volts and 10 amps", but its not regulated ( you are doing that ) lets assume the " human" can react as fast as is necessary
Bulk mode
You want the system to provide as much power that it can into the
battery, i.e. all of its 200Watts of power
So, the variable resistance is set to the lowest amount , i.e. the slider all the way left. The voltage you read is set by the a combination of the internal power source and battery resistance, but for all intents is set by the battery chemistry, you will see max amps flowing ( i.e. 10A) and the voltage will be anywhere from 11.5-13.5 and will start to generally slowly increase )
you will also see the
current gradually reduce from its max of 10A
Absorption,
You know that the battery can only tolerate a max voltage that prevents excessive gassing or battery over
heating and or destruction, this say in this case is 14.5V
S0 as your voltage meter reaches 14.5V, you need to prevent any further voltage rise, you will gradually increases the resistance of your " controller" , you will see the voltage stop rising
keep adjusting the resistance to ensure the voltage remains stable at 14.5. What you will howver notice is that your changes will gradually increase the resistance
AT a certain point you will wish to determine the end of absorption mode, typically you have decided that at a amp flow of 2 Amps, the battery can be " regarded" as full. ( usually between 1 and 5% of battery capacity expressed in Amps)
now you want a " float charge "to maintain the battery,
float
to therefore go to float mode, all you can do, is increase the resistance even more ( cause thats all you can actually control). you will find that the
current falls to a low or zero value, and the battery voltage drifts down to 13.5V ( nominally) that its resting voltage , note you dont " pull it down " to 13.V. IN effect the
charger is disconnected from the battery,
What you will then find is that there is a small current flowing and that periodically you will reduce or increase the resistance to " hold " the battery voltage at 13.5V, inreality you are moving from no charge to trickle charge from time to time
This is the basis of all charge control
PS: Sorry the battery is a 12V LA battery