Using Multiple Battery Charging Methods at One Time

[Country Campers]

With all of the Solar, DC-DC, Multiplus, converters and so on being installed with different system requirements I have a question.

With a Solar Charger, a DC-DC Charger, and a standard Converter installed in an RV, Will all of these trying to charge a battery hurt the battery?

I realize that most that would do a system like this would have a Lithium battery, which would have a battery monitor system built in, but with a stock set up from a manufacture with solar, a standard wet cell battery and maybe the owner wanted to add a DC-DC.

Brian

[howson]

With all of the Solar, DC-DC, Multiplus, converters and so on being installed with different system requirements I have a question.

With a Solar Charger, a DC-DC Charger, and a standard Converter installed in an RV, Will all of these trying to charge a battery hurt the battery?

I realize that most that would do a system like this would have a Lithium battery, which would have a battery monitor system built in, but with a stock set up from a manufacture with solar, a standard wet cell battery and maybe the owner wanted to add a DC-DC.

Brian

Good question, Brian.

The ability to "talk" to each other is one of the reasons (besides the cool factor of the app) I went with Victron equipment. They work together cooperatively. The Victron components are programmed with the same battery type and are "aware" of each other and what they are doing, including charging the battery bank.

The Renogy DC-DC charger in my system is the exception, but that is only engaged while towing and only if I know the batteries need a charge AND I know that the solar output is not enough to do the job due to cloud cover, darkness, etc. I chose the Renogy because (at the time) the Victron option wasn't capable of being networked with the other Victron equipment. (That may have changed by now.)

With a Multiplus (or similar inverter/charger) the OEM converter should be disconnected and/or removed completely from the circuit.

[Jkwilson]

Usually it’s not a problem. Think of it as filling a tank with three air hoses at possibly different pressures. Each hose contributes air until the pressure in the tank reaches the pressure of the highest pressure hose.

With a battery, charging voltage is the pressure, with current into the battery determined by the difference between charging voltage and battery voltage. At first, all the chargers contribute according to their charging capacity, but eventually the one with the highest charging voltage is the only source supplying current. In the event all sources have exactly the same charging voltage, you can see problem since the charging sources are usually designed to reduce charging voltage when they see a draw less than 1A. Three identical sources (unlikely) would shut off while the battery was still accepting 3A resulting in a delay in finishing the charging process depending on how the charging sources are programmed to behave.

[Scott'n'Wendy]

And to throw a little wrinkle in the question - different controller types. A pwm controller and a mppt controller hooked together to the same battery? The higher voltage pulses of the pwm potentially fooling the sensing software of the mppt?

[TucsonJim]

And to throw a little wrinkle in the question - different controller types. A pwm controller and a mppt controller hooked together to the same battery? The higher voltage pulses of the pwm potentially fooling the sensing software of the mppt?

The primary aspect of Brian's question is "will it hurt the battery". The answer is "no". But as John Jkwilson mentions in his post above, it may result "in a delay in finishing the charging process depending on how the charging sources are programmed to behave."

So running a PWM and a MPPT controller will not hurt the battery, but it may take a little longer to finish topping off the batteries as one controller confuses the other.

Jim

[Country Campers]

The primary aspect of Brian's question is "will it hurt the battery". The answer is "no". But as John Jkwilson mentions in his post above, it may result "in a delay in finishing the charging process depending on how the charging sources are programmed to behave."

So running a PWM and a MPPT controller will not hurt the battery, but it may take a little longer to finish topping off the batteries as one controller confuses the other.

Jim

So with your input and Jkwilson John's as well I am guessing that it would be better to allow one item to finish the charge cycle?

It would be not very often that 2 charging items would be used at one time, if on shore power there would be no need for solar to be on for example.

Brian

[TucsonJim]

So with your input and Jkwilson John's as well I am guessing that it would be better to allow one item to finish the charge cycle?

It would be not very often that 2 charging items would be used at one time, if on shore power there would be no need for solar to be on for example.

Brian

Unless you're in a hurry to get it topped off, I wouldn't concern myself with it. That last little oomph to go from 95% to 100% won't make much of a difference at all it it takes 60 or 90 minutes.

[ncitro]

Country Campers I keep all mine enabled, with the exception of disabling the DC-DC charger if I'm closer to full and it's sunny. That's mainly to save wear and tear on the alternator. At any point in time when plugged into generator or shore power I could have solar going, the Multiplus, and a fixed voltage 100A converter I have as a backup from when the charge output of my Multiplus failed. Usually the converter is disabled unless I have a lot of shore power available and need to charge quickly. That said I've never had an issue when these sources were running. I have all of them set to approximately the same fixed voltage (within .1v) based on Lion energies recommendations, and rely on the battery BMS to terminate charging when they're full. In my experience they take whatever I throw at them until about 99% and then taper current until they hit 100%.