RV Voltages too high while charging
I have a problem and have been wrapping my head around this for a few days. I have four 100w Solar panels, and a Morningstar RJ-45 programmable charge controller wired to batteries. I have Four In...
Forum Discussion
There is a difference in the way the "smart charger" does Bulk with constant , current-limited amps, and the "other" chargers.
Barre, in his 2002 book, "Managing 12 Volts" goes into this quite a bit. His terminology for the different types of chargers may not be universal, but you can translate.
He compares them by how they do "voltage regulating" He explains how the voltage regulator works with the alternator in a car. The initial high current is cut right back to maintain the voltage and this "constant voltage" charger has a tapering current profile from the beginning.
The problem with that for fast charging is that the charger causes an initial "spike" in battery voltage, but there has been no time for the battery SOC to rise. The voltage regulator sees this spike and cuts the current right back.
A "multi-stage charger" uses a different regulation, that Barre says has an initial "constant current" regulated stage that produces a fixed amount of current. The battery will accept this high constant current while in the mid-SOC range but at some point this has to be changed and it goes into a voltage regulation stage with tapering current.
(He does not get into "regulated constant current" vs "current limited" which confused me greatly back when we had threads on this. Eventually I think I got it straight that there is no current regulator, just a current limiter)
So the whole thing for fast charging is to keep the current high despite that initial "spike" in battery voltage when you turn on the charger. Only let the current taper later on when it has to once the battery has reached a "gassing voltage" or what we call Vabs for this.
Barre also mentions how they add a "smart" regulator to a cruising boat's alternator so it can do the fast charging with constant current in the Bulk stage instead of suffer the big taper you get with an ordinary voltage regulator. Mex has posted about those too.
Barre, in his 2002 book, "Managing 12 Volts" goes into this quite a bit. His terminology for the different types of chargers may not be universal, but you can translate.
He compares them by how they do "voltage regulating" He explains how the voltage regulator works with the alternator in a car. The initial high current is cut right back to maintain the voltage and this "constant voltage" charger has a tapering current profile from the beginning.
The problem with that for fast charging is that the charger causes an initial "spike" in battery voltage, but there has been no time for the battery SOC to rise. The voltage regulator sees this spike and cuts the current right back.
A "multi-stage charger" uses a different regulation, that Barre says has an initial "constant current" regulated stage that produces a fixed amount of current. The battery will accept this high constant current while in the mid-SOC range but at some point this has to be changed and it goes into a voltage regulation stage with tapering current.
(He does not get into "regulated constant current" vs "current limited" which confused me greatly back when we had threads on this. Eventually I think I got it straight that there is no current regulator, just a current limiter)
So the whole thing for fast charging is to keep the current high despite that initial "spike" in battery voltage when you turn on the charger. Only let the current taper later on when it has to once the battery has reached a "gassing voltage" or what we call Vabs for this.
Barre also mentions how they add a "smart" regulator to a cruising boat's alternator so it can do the fast charging with constant current in the Bulk stage instead of suffer the big taper you get with an ordinary voltage regulator. Mex has posted about those too.
