Converter vs. Charger, Whats in a name?
I read over and over again the misconceptions that exist out there regarding the converter systems in RV's and Travel Trailers. Most people are under the assumption that their converter is a battery charger or somehow has a separate battery charging function. RV's and Travel Trailers have a 12 volt DC system that requires 12VDC be supplied to it to operate those appliances and systems. This is what the converter is for. The converter is designed to supply a range of voltage safe enough to operate the 12 volt system and also adequate enough to charge battery if one is utilized in the RV or trailer. Most commonly you have a 55 amp converter, which creates 55 amps of available current (Amps) in a voltage range of 13.2 to 14.5 VDC. There is also most likely a battery tied in series with the 12 volt system. Not parallel, but in series, meaning whatever the converter produces, the 12 volt systems and battery see simultaneously. A converter is not a battery charger. It just so happens that whatever is not being consumed by the 12 volt systems, out of the 55 amps it creates, is available for a battery to take in the event it needs current to charge.
Now, without getting overly technical, because it can get very technical, a battery will always accept some amount current to offset natural internal discharge or any sort of parasitic drain. Even though your converter creates 55 amps, your battery isn't accepting all of that. As a battery charges, it develops resistance to current, the higher the charge level of the battery, the higher the internal resistance. This internal resistance pushes back or blocks the flow of current going into the battery until it reaches that point of equilibrium where it is only allows in mere milliamps of current to offset that internal discharge/parasitic drain. For this example I use the typical car battery and alternator.
The average alternator in a car creates anywhere from 90 to 130 amps. From what I hear and see from RV and trailer owners regarding the converter system, you would also assume that they would think the battery in their car would over charge from the massive amounts of current being supplied from their alternator. But again, no matter the amount of current being created, the battery regulates the flow of incoming current.
Now let’s talk about voltage, this is where "3 stage" or "multiple stage" charging comes into play. Bulk, Absorption, and Float are your typical charge stages. The output voltage per stage is where I think most people get confused. A converter creates a range of voltage between 13v and 14-14.5 volts that is capped. Converter manufacturers set the parameters at a no load scenario and a full load scenario. Meaning that with nothing that requires 12 volts operating in the system, the converter will output no more that 14-14.5 volts, but with a full load (everything that requires 12 volts) operating, it will output no less than 13-13.2 volts. This range is established to safely operate the 12v system. When batteries became more and more common in RV’s and travel trailers, the need to safely charge them came into play. Battery chargers have been around forever and they are designed to do one thing; charge a battery. They are not and were never intended to operate a 12v system.
With that in mind, battery charger manufactures can manipulate the output voltage to the battery into distinct stages. Bulk stage is where massive amount of amps is flowing into the battery, the low resistance of the battery allows this. The high rate of amps allows for a higher voltage to the battery. During the Absorption stage, the batteries internal resistance is starting to increase and the amount of current flowing into the battery begins to taper off and thus the voltage being supplied to the battery begins to taper off. The final stage or Float stage, is where the battery is only accepting in a very small amount amps. Typically it is only accepting in the milliamp range at the point to offset internal discharge and parasitic drain. At this point the voltage being supplied is only adequate enough to maintain the charge level of the battery.
What may be great for charging a battery may not be so great for operating a 12 volt system. When it comes to a converter, the set voltage range of 13-14.5 volts DC fluctuates depending upon total system load, It will be higher with less total system load and lower with more total system load. A converter being a converter, and not a battery charger does not “see” that there is a battery hooked up to it. All it “sees” is another load, or something that is requiring current (Amps) and voltage. A converter cannot distinguish between a battery and an LED light, they are viewed only has loads on the system.
I mentioned earlier that the battery is in series with the entire 12 volt system. Converters do not charge the battery independent of supplying voltage and current to the entire 12 volt system. There is no isolated function or feature that exists in a converter to do this. In a “3 stage” charger or converter, as some converter manufacturer now claim multi stage “charging” in a converter, the output voltages during these stages are designed for proper charging of a battery. The charger phases into and out of bulk, absorption, and float based upon detected amp draw from the converter. Typically at 4 amps or less a 3 stage charger would enter float mode. This is all fine and dandy for a battery, as a battery is the only thing hooked up to a battery charger, in an RV you have multiple systems drawing current from the converter. What happens when total system load is greater than 4 amps? The converter simply never enters float mode. How can you claim you have 3 stage battery charging, when the device you manufacturer is being used in an electrical environment that is not designed for what 3 stage charging of battery is supposed to be able to accomplish? Now do not get me wrong 3 stage and multiple stage charging is a great function; for battery charging.
Keep in mind that you are not charging a battery in an RV, you have to operate the entire 12 volt system. At any given time, the system loads that may be on in an RV may not allow a typical multi stage charger to properly enter or exit any one of the stage. The voltages being supplied during the “stages” of battery charging may not be ideal for operating the entire 12 volt system.
Now, without getting overly technical, because it can get very technical, a battery will always accept some amount current to offset natural internal discharge or any sort of parasitic drain. Even though your converter creates 55 amps, your battery isn't accepting all of that. As a battery charges, it develops resistance to current, the higher the charge level of the battery, the higher the internal resistance. This internal resistance pushes back or blocks the flow of current going into the battery until it reaches that point of equilibrium where it is only allows in mere milliamps of current to offset that internal discharge/parasitic drain. For this example I use the typical car battery and alternator.
The average alternator in a car creates anywhere from 90 to 130 amps. From what I hear and see from RV and trailer owners regarding the converter system, you would also assume that they would think the battery in their car would over charge from the massive amounts of current being supplied from their alternator. But again, no matter the amount of current being created, the battery regulates the flow of incoming current.
Now let’s talk about voltage, this is where "3 stage" or "multiple stage" charging comes into play. Bulk, Absorption, and Float are your typical charge stages. The output voltage per stage is where I think most people get confused. A converter creates a range of voltage between 13v and 14-14.5 volts that is capped. Converter manufacturers set the parameters at a no load scenario and a full load scenario. Meaning that with nothing that requires 12 volts operating in the system, the converter will output no more that 14-14.5 volts, but with a full load (everything that requires 12 volts) operating, it will output no less than 13-13.2 volts. This range is established to safely operate the 12v system. When batteries became more and more common in RV’s and travel trailers, the need to safely charge them came into play. Battery chargers have been around forever and they are designed to do one thing; charge a battery. They are not and were never intended to operate a 12v system.
With that in mind, battery charger manufactures can manipulate the output voltage to the battery into distinct stages. Bulk stage is where massive amount of amps is flowing into the battery, the low resistance of the battery allows this. The high rate of amps allows for a higher voltage to the battery. During the Absorption stage, the batteries internal resistance is starting to increase and the amount of current flowing into the battery begins to taper off and thus the voltage being supplied to the battery begins to taper off. The final stage or Float stage, is where the battery is only accepting in a very small amount amps. Typically it is only accepting in the milliamp range at the point to offset internal discharge and parasitic drain. At this point the voltage being supplied is only adequate enough to maintain the charge level of the battery.
What may be great for charging a battery may not be so great for operating a 12 volt system. When it comes to a converter, the set voltage range of 13-14.5 volts DC fluctuates depending upon total system load, It will be higher with less total system load and lower with more total system load. A converter being a converter, and not a battery charger does not “see” that there is a battery hooked up to it. All it “sees” is another load, or something that is requiring current (Amps) and voltage. A converter cannot distinguish between a battery and an LED light, they are viewed only has loads on the system.
I mentioned earlier that the battery is in series with the entire 12 volt system. Converters do not charge the battery independent of supplying voltage and current to the entire 12 volt system. There is no isolated function or feature that exists in a converter to do this. In a “3 stage” charger or converter, as some converter manufacturer now claim multi stage “charging” in a converter, the output voltages during these stages are designed for proper charging of a battery. The charger phases into and out of bulk, absorption, and float based upon detected amp draw from the converter. Typically at 4 amps or less a 3 stage charger would enter float mode. This is all fine and dandy for a battery, as a battery is the only thing hooked up to a battery charger, in an RV you have multiple systems drawing current from the converter. What happens when total system load is greater than 4 amps? The converter simply never enters float mode. How can you claim you have 3 stage battery charging, when the device you manufacturer is being used in an electrical environment that is not designed for what 3 stage charging of battery is supposed to be able to accomplish? Now do not get me wrong 3 stage and multiple stage charging is a great function; for battery charging.
Keep in mind that you are not charging a battery in an RV, you have to operate the entire 12 volt system. At any given time, the system loads that may be on in an RV may not allow a typical multi stage charger to properly enter or exit any one of the stage. The voltages being supplied during the “stages” of battery charging may not be ideal for operating the entire 12 volt system.
