Should I Change My WFCO Converter?
Opinions have often been expressed, both on this and other RV forums, that most stock RV converters are inadequate to properly charge and maintain batteries and are often of poor quality. It is frequ...
Forum Discussion
Mike,
To re-iterate what BFL said, I prefer to think in terms of "constant current" and "constant voltage". Let's say your bank is at 50% state of charge (SOC), so about 12.2v, and you're using a 40a charger, set at say 14.8v (just one setting). The charger is "limited" at 40a max output. This is called current limiting. When you turn on the charger, the amps will immediately rise to the charger's current limit (40a), but the charger's voltage will start out somewhere in the low 13's, just enough above the (12.2) battery voltage to compensate for resistance (R) in the circuit, and will begin to rise. At some point, as the batteries are getting charged up, their voltage will rise, and so will that of the charger, in order to maintain a charge. This stage is called "constant current" (cc), and is often called boost or bulk stage. Current is held steady at the unit's limit, while volts rise.
Once the battery voltage nears your 14.8v setting, minus R, things change. The voltage will now hold steady at your 14.8v setting, and amps will begin to taper. They will continue to taper until such time as they will appear to level out or go static. (I find on a pair of my 6's, that happens at about 2.5a at 14.8v). This stage is called constant voltage (cv), seeing as the voltage now holds steady, while amps taper. This is also called Absorption stage.
So, essentially, a 3 stage "smart" charger is just a cc/cv power supply, (just like a megawatt, meanwell, etc.) but with an added float stage. "Smart" chargers monitor the process, and switch to float once it is determined the battery is "full", according to factory preset parameters. Likewise, the voltage settings for each stage are factory preset. So, for example, most converters with a built in 3 stage charging feature, will continue in cc/boost mode until their factory preset of say 14.4v is reached, but then, instead of continuing at 14.4v, they drop down to another factory preset, of say 13.6v, or 13.6 "Vabs" (absorption stage voltage / cv voltage). But now this is also called "normal", because it is what the converter usually runs at while simply converting... in "normal operation".
Now, using an adjustable unit, you are the one who decides on the voltage setting (Vabs). Once the batteries reach near to your setting, and cc switches to cv, the unit will continue at your setting, in cv, until either you turn it off, or a timer does. Once you become familiar with what constitutes FULL for YOUR batteries, you can either monitor their status, and turn things off manually, or, if you know how long it generally takes to get them to full, from any particular SOC, you can set a timer and walk away. Likewise, you may wish to do a 50-80%soc charge, so same thing. Set the timer for how long it takes to get them to ~80%. For example, a 55 amper on your bank will take roughly 2 hours to do a 50-80%.
Hope this helps clarify things.
To re-iterate what BFL said, I prefer to think in terms of "constant current" and "constant voltage". Let's say your bank is at 50% state of charge (SOC), so about 12.2v, and you're using a 40a charger, set at say 14.8v (just one setting). The charger is "limited" at 40a max output. This is called current limiting. When you turn on the charger, the amps will immediately rise to the charger's current limit (40a), but the charger's voltage will start out somewhere in the low 13's, just enough above the (12.2) battery voltage to compensate for resistance (R) in the circuit, and will begin to rise. At some point, as the batteries are getting charged up, their voltage will rise, and so will that of the charger, in order to maintain a charge. This stage is called "constant current" (cc), and is often called boost or bulk stage. Current is held steady at the unit's limit, while volts rise.
Once the battery voltage nears your 14.8v setting, minus R, things change. The voltage will now hold steady at your 14.8v setting, and amps will begin to taper. They will continue to taper until such time as they will appear to level out or go static. (I find on a pair of my 6's, that happens at about 2.5a at 14.8v). This stage is called constant voltage (cv), seeing as the voltage now holds steady, while amps taper. This is also called Absorption stage.
So, essentially, a 3 stage "smart" charger is just a cc/cv power supply, (just like a megawatt, meanwell, etc.) but with an added float stage. "Smart" chargers monitor the process, and switch to float once it is determined the battery is "full", according to factory preset parameters. Likewise, the voltage settings for each stage are factory preset. So, for example, most converters with a built in 3 stage charging feature, will continue in cc/boost mode until their factory preset of say 14.4v is reached, but then, instead of continuing at 14.4v, they drop down to another factory preset, of say 13.6v, or 13.6 "Vabs" (absorption stage voltage / cv voltage). But now this is also called "normal", because it is what the converter usually runs at while simply converting... in "normal operation".
Now, using an adjustable unit, you are the one who decides on the voltage setting (Vabs). Once the batteries reach near to your setting, and cc switches to cv, the unit will continue at your setting, in cv, until either you turn it off, or a timer does. Once you become familiar with what constitutes FULL for YOUR batteries, you can either monitor their status, and turn things off manually, or, if you know how long it generally takes to get them to full, from any particular SOC, you can set a timer and walk away. Likewise, you may wish to do a 50-80%soc charge, so same thing. Set the timer for how long it takes to get them to ~80%. For example, a 55 amper on your bank will take roughly 2 hours to do a 50-80%.
Hope this helps clarify things.
