Batteyr charging in an RV
Here's my rant for the day. I have heard so much outright misinformation, misnomers, and just flat out uninformed individuals passing off their opinions as gospel regarding maintaining their batter...
Forum Discussion
Well ..... I'll take a shot at rounding off some of this rhetoric ... in general terms. IMHO, the original post contains truth in it ... irrespective of whether or not it came from a trolling motive.
Regarding the OP's statement No. 1: This appears to me as true.
Regarding the OP's statement No 2: When loads are "in parallel" - as they are when both the RV's general 12 volt electrical system plus it's battery(ies) are connected separately to a stock converter's output terminals - any current from the converter will be shared between the loads, depending upon an easy math equation showing how current divides between parallel loads depending upon the size of each load. What this means in the RV world is if, to the converter, the partially discharged battery appears as a low resistance when compared to the resistance of any other 12 volt items that happen to be turned on, the battery will get most (per the equation) of the converter's current - if the battery will accept that much current relative to the voltage that winds up on it's terminals. Of course what voltage winds up on the battery's(ies') terminals in turn depends upon the converter's output voltage value -> after being reduced by the voltage drop from the current flowing through the wiring between the converter and the battery(ies).
Regarding the OP's statement No. 3: A qualified statement, but probably true 99.X% of the time .... depending upon how the RV's manufacturer installed a converter and integrated it into the RV's 12 volt system.
Regarding the OP's statement No. 4: This appears to me as true.
Regarding the OP's statement No. 5: The first three sentences very well might be true - but the information that these three sentences are trying to is convey is subtle, and would require some careful study of charging curves and an understanding of how to interpret the areas under the curvers. In the engineering world areas under curves are very important and are part of the information that's intended for them to convey. However the remainder of statement No. 5 could have been worded more clearly and qualified a bit ... I myself would be concerned about voltages above 14.8 volts appearing on my RV's entire 12 volt system.
FWIW, my (somewhat unusual) RV battery power situation agrees with what is implied in the OP's statements: My dual 100 amp hour 12 volt true deep cycle AGM coach batteries both safely float, and charge, mostly on only the RV's stock 45 amp single voltage converter. Their recommended float voltage exactly matches the converter's nominal output voltage, and .... since AGM batteries have much lower internal resistance than that of wet cell batteries .... if needing charge they also bulk charge "well" from that same nominal converter output voltage. So the fact that a converter is basically just a "power supply" works well in my setup.
I may be wrong, but I think that for decades lead acid batteries in many applications have been charged and kept charged by a single-output power supply. As far as I can tell, the main reasons for use of muilt-stage chargers in RVs are for: Squeezing longer service life out of the bulk of wet cell lead acid batteries (via a proper floating voltage) and putting more charging current faster (using a boost voltage) into both wet and dry lead acid batteries so that generator run times can be reduced. Multiple voltage levels from a charger optimize these two goals - but are not necessarily required in all situations for creating happy batteries and happy campers.
Regarding the OP's statement No. 1: This appears to me as true.
Regarding the OP's statement No 2: When loads are "in parallel" - as they are when both the RV's general 12 volt electrical system plus it's battery(ies) are connected separately to a stock converter's output terminals - any current from the converter will be shared between the loads, depending upon an easy math equation showing how current divides between parallel loads depending upon the size of each load. What this means in the RV world is if, to the converter, the partially discharged battery appears as a low resistance when compared to the resistance of any other 12 volt items that happen to be turned on, the battery will get most (per the equation) of the converter's current - if the battery will accept that much current relative to the voltage that winds up on it's terminals. Of course what voltage winds up on the battery's(ies') terminals in turn depends upon the converter's output voltage value -> after being reduced by the voltage drop from the current flowing through the wiring between the converter and the battery(ies).
Regarding the OP's statement No. 3: A qualified statement, but probably true 99.X% of the time .... depending upon how the RV's manufacturer installed a converter and integrated it into the RV's 12 volt system.
Regarding the OP's statement No. 4: This appears to me as true.
Regarding the OP's statement No. 5: The first three sentences very well might be true - but the information that these three sentences are trying to is convey is subtle, and would require some careful study of charging curves and an understanding of how to interpret the areas under the curvers. In the engineering world areas under curves are very important and are part of the information that's intended for them to convey. However the remainder of statement No. 5 could have been worded more clearly and qualified a bit ... I myself would be concerned about voltages above 14.8 volts appearing on my RV's entire 12 volt system.
FWIW, my (somewhat unusual) RV battery power situation agrees with what is implied in the OP's statements: My dual 100 amp hour 12 volt true deep cycle AGM coach batteries both safely float, and charge, mostly on only the RV's stock 45 amp single voltage converter. Their recommended float voltage exactly matches the converter's nominal output voltage, and .... since AGM batteries have much lower internal resistance than that of wet cell batteries .... if needing charge they also bulk charge "well" from that same nominal converter output voltage. So the fact that a converter is basically just a "power supply" works well in my setup.
I may be wrong, but I think that for decades lead acid batteries in many applications have been charged and kept charged by a single-output power supply. As far as I can tell, the main reasons for use of muilt-stage chargers in RVs are for: Squeezing longer service life out of the bulk of wet cell lead acid batteries (via a proper floating voltage) and putting more charging current faster (using a boost voltage) into both wet and dry lead acid batteries so that generator run times can be reduced. Multiple voltage levels from a charger optimize these two goals - but are not necessarily required in all situations for creating happy batteries and happy campers.
