Efficiency of combined PV and alternator charging.

[svsagres]

Ah yea, thats a pretty fancy and spendy system! Definitely the Lamborghini install.

I mean, there are other ways to achieve it to. Some of the cheaper FET based BMSs have communications abilities that can be integrated, and you can run Victron’s VenusOS on a Raspberry Pi if you want.

I mostly wanted a system that I could build and forget about, and, well, it’s worked beautifully over the past 8 months since we finished it.

 

[hwse]

First, you will need a DC to DC charger between your alternator and LiFePO4 battery.
You can set the charging parameters to control the interaction between them.

It is very common to have multiple charge sources, know the charge profiles of each will explain how they behave/interact.

Your statement is true if we are talking about a dumb internally regulated alternator. The OP said Balmar so it will be controlled by an external regulator. It is perfectly fine to charge LFP with an externally regulated alternator as long as the regulator is set up to limit the output based on the alternator's temperature.

 

[hwse]

Smart regulators can be set up to charge lifepo4.

This is for a cruising powerboat with no shore power. Efficiency is important; therefor according to Balmar alternator efficiency suffers with solar input.:
Quote from Balmar:
The problem with multiple charging sources is that they tend to fool one another. Say your solar panel (or wind generator) is charging the battery at 14 volts and pushing in 10 amps. You start the engine/alternator up and it sees not the true State of Charge of the battery but 14 volts from the solar panel. The alternator thinks the battery is fully charged and puts out the minimum current (only a few amps). The result is the alternator is not doing anything and the solar is putting in only 10 amps. This condition isn’t damaging to the charging assets, but it is inefficient charging."

FAQ - Balmar

I am convinced of the benefits of external regulation. Will my (Non-Balmar) alternator work with your MaxCharge (external) regulators? It depends. If the alternator is internally regulated, it needs to be converted to work with an external regulator. See the next FAQ below to learn more. If...

balmar.net

Your regulator will only limit the total output if the LFP cannot except the total of all charge sources which probably will not happen. More likely it will need to throttle the alternator output to limit the alternator's case temperature. You should not expect to get the rated maximum output because that will certainly overheat the alternator which is why you need alternator temp control. The Balmar 614 will do that for you.

 

[hwse]

Does that regulate the voltage and/or amps? Is there any concept of bulk/absorb/float or ??
Trying to understand how it works.
Are any of these programmable or made for different battery chemistries?

EDIT:
Found this Aims regulator for lithium. Not sure i want to charge that high. At this price i think i would want a DC to DC charger.
>>
The regulator continuously monitors the input voltage. If the voltage is within the operating range of 9.4 – 14.4V, power will be supplied to the output terminal allowing power to the loads. If the voltage drops below 9.2V or is over 14.6V the power is cut off at the output terminal preventing power to the loads.

All charge sources controls the voltage by regulating the current. The voltage is the input to the regulator (in an alternators regulator or a solor NPPT controller or a mains charger, it does not matter) and based on that voltage, it will control the current output so that the voltage does not go above the set-point. If the voltage is below the set-point, it will put out as much current as it can (CC). Once the set-point is reached, it will limit the current output to prevent the voltage from being driven above the set-point (CV).

So, it regulates the current. The voltage is the result of the current to the battery and state of charge.

 

[wholybee]

All charge sources controls the voltage by regulating the current. The voltage is the input to the regulator (in an alternators regulator or a solor NPPT controller or a mains charger, it does not matter) and based on that voltage, it will control the current output so that the voltage does not go above the set-point. If the voltage is below the set-point, it will put out as much current as it can (CC). Once the set-point is reached, it will limit the current output to prevent the voltage from being driven above the set-point (CV).

So, it regulates the current. The voltage is the result of the current to the battery and state of charge.

You have this backwards. All chargers regulate voltage. Say you have a 10A charger. You set the voltage to 13.8V. The charger will attempt to put out 13.8V, but because of the SOC of the battery and ohms law, that would require more than 10A. So it puts out as much voltage as it can without exceeded the max current. As the battery charges, the voltage rises, and once it gets to 13.8 that the charger is trying to achieve, current can begin to fall.

 

[squowse]

Can victron DC-DC and MPPT be linked so that they co-operate on charging voltage?

 

[squowse]

You have this backwards. All chargers regulate voltage. Say you have a 10A charger. You set the voltage to 13.8V. The charger will attempt to put out 13.8V, but because of the SOC of the battery and ohms law, that would require more than 10A. So it puts out as much voltage as it can without exceeded the max current. As the battery charges, the voltage rises, and once it gets to 13.8 that the charger is trying to achieve, current can begin to fall.

Yep

 

[wholybee]

Can victron DC-DC and MPPT be linked so that they co-operate on charging voltage?

Yes. The "best" solution is to install a victron smart shunt or BVM. Then, both the DCDC and the MPPT will use the voltage and current from the shunt. Not only will the be in sync, but they will use the actual current charging the battery, which might be very different from what is measured at the MPPT or DCDC if you have a large load.

This only works if you get the "smart" versions of the DCDC and MPPT.

 

[hwse]

You have this backwards. All chargers regulate voltage. Say you have a 10A charger. You set the voltage to 13.8V. The charger will attempt to put out 13.8V, but because of the SOC of the battery and ohms law, that would require more than 10A. So it puts out as much voltage as it can without exceeded the max current. As the battery charges, the voltage rises, and once it gets to 13.8 that the charger is trying to achieve, current can begin to fall.

Sorry but your understanding of cause and effect is backwards. The voltage is the effect of ohms law. V=Ir. The regulator cannot change the voltage that is being produced. Its purpose is to control how much current is being produced (I). The resistance is the total present at the time due to all wiring, connections and (most importantly) the internal resistance of the battery.

When the battery is at a low SOC it has very low internal resistance so a large current will not drive the voltage up to the set point, so the regulator creates as much current and the charge source is capable of. As the battery nears it max capacity, the internal resistance rapidly increases which causes the voltage to rise precipitously to the point where starts to exceed the the set point. At that time, the regulator restricts the current that is being produces which based on ohm's law prevents the voltage from being driven above the set point. Once the battery is completely full, there is no amount of current that can be added to it without driving the voltage above the set point and the regulator will stop all current outflow.

The voltage is sampled (input) and the regulator controls the current generated (output) which by means of Ohm's law regulates the voltage. The voltage is the effect of how much current is being sent to the battery. A charger cannot "put out" voltage. It only produces power (watts) and the voltage is the results of the current and resistance.

 

[hwse]

Can victron DC-DC and MPPT be linked so that they co-operate on charging voltage?

The simplest way to get them to cooperate with each other is to select one charge sourse to be your primary final charge source. Then set the others to 0.1v - 0.2v lower for absorption charge voltage. If you have enough solar, I would use that as my final charge controller.
That way during the time that you are bulk charging all sources will be putting out as much as they can. Then when you get to the top of charge, all but one will stop producing current and let the final charge controller add the little bit needed to fully top the battery.

 

[wholybee]

The simplest way to get them to cooperate with each other is to select one charge sourse to be your primary final charge source. Then set the others to 0.1v - 0.2v lower for absorption charge voltage. If you have enough solar, I would use that as my final charge controller.
That way during the time that you are bulk charging all sources will be putting out as much as they can. Then when you get to the top of charge, all but one will stop producing current and let the final charge controller add the little bit needed to fully top the battery.

Victron controllers will talk to each other via Bluetooth. The only reason I would set one at a different voltage is if it is not Victron. For example, the alternator should be set lower.

 

[hwse]

Victron controllers will talk to each other via Bluetooth. The only reason I would set one at a different voltage is if it is not Victron. For example, the alternator should be set lower.

This is correct for all Victron smart products, but Victron is not true for Victron products that do not have Bluetooth connectability. I have two IP67 30-1 chargers for my shore power charging and they do synchronized charging. I am planning to add a Phoenix 121200 inverter which does not have Bluetooth and will need to connect it to a CarboGX or add a Bluetooth module.
Also, Victron is a new player in the market. The problem is that many of us have charge sources from many different manufacturers. I have owned my current boat for 25 years and the alternator regulator was on it when I got her. I suggested my method as a hack to get multiple charge souses to play nice even with they cannot talk to each other.

 

[wholybee]

Sorry but your understanding of cause and effect is backwards. The voltage is the effect of ohms law. V=Ir. The regulator cannot change the voltage that is being produced. Its purpose is to control how much current is being produced (I). The resistance is the total present at the time due to all wiring, connections and (most importantly) the internal resistance of the battery.

When the battery is at a low SOC it has very low internal resistance so a large current will not drive the voltage up to the set point, so the regulator creates as much current and the charge source is capable of. As the battery nears it max capacity, the internal resistance rapidly increases which causes the voltage to rise precipitously to the point where starts to exceed the the set point. At that time, the regulator restricts the current that is being produces which based on ohm's law prevents the voltage from being driven above the set point. Once the battery is completely full, there is no amount of current that can be added to it without driving the voltage above the set point and the regulator will stop all current outflow.

The voltage is sampled (input) and the regulator controls the current generated (output) which by means of Ohm's law regulates the voltage. The voltage is the effect of how much current is being sent to the battery. A charger cannot "put out" voltage. It only produces power (watts) and the voltage is the results of the current and resistance.

Sorry, but yes, I am 100% right on this, and yes it is driven by ohms law. Chargers are a voltage device. Disconnect the battery and measure the voltage of the charger output. It will be exactly what you set the charger voltage to, with zero current, and zero watts. And whatever resistive load you put there, it will stay at that voltage as current increases due to ohms law. The voltage is regulated to the set voltage, while the current is free to change to whatever it will be due to ohms law. Until the current exceeds the capacity of the charger, at which point the charger gives all it can, and the current stays maxed out and voltage reduces, because any more voltage would drive current too high. Throughout all of this, the charger is regulating and adjusting voltage, not current.

 

[wholybee]

This is correct for all Victron smart products, but Victron is not true for Victron products that do not have Bluetooth connectability. I have two IP67 30-1 chargers for my shore power charging and they do synchronized charging. I am planning to add a Phoenix 121200 inverter which does not have Bluetooth and will need to connect it to a CarboGX or add a Bluetooth module.
Also, Victron is a new player in the market. The problem is that many of us have charge sources from many different manufacturers. I have owned my current boat for 25 years and the alternator regulator was on it when I got her. I suggested my method as a hack to get multiple charge souses to play nice even with they cannot talk to each other.

True, not all Victron products support this, only the smart ones, as my first response said. The question was specifically asking about Victron.

 

[hwse]

Sorry, but yes, I am 100% right on this, and yes it is driven by ohms law. Chargers are a voltage device. Disconnect the battery and measure the voltage of the charger output. It will be exactly what you set the charger voltage to, with zero current, and zero watts. And whatever resistive load you put there, it will stay at that voltage as current increases due to ohms law. The voltage is regulated to the set voltage, while the current is free to change to whatever it will be due to ohms law. Until the current exceeds the capacity of the charger, at which point the charger gives all it can, and the current stays maxed out and voltage reduces, because any more voltage would drive current too high. Throughout all of this, the charger is regulating and adjusting voltage, not current.

Disconnect the battery and measure the voltage of the charger output. It will be exactly what you set the charger voltage to, with zero current, and zero watts."

Sorry but in this case, the multimeter is the (very high) resistance and the charger puts out a corispondingly very small (mostly unmeasurable current to produce a voltage that matches the set point. The voltage is sensed, and the current required to hold it steady at the set point is produced.
the voltage is sampled (sensed) and the current is adjusted to keep the voltage at the level that is desired. If voltage could be regulated, then the battery voltage would immediately go to the set point when charging a low battery, but this is not the case. The current is max until the voltage is sensed to be where you want it at which time, the current is reduced to prevent the voltage from being driven too high.

 

[hwse]

Sorry, but yes, I am 100% right on this, and yes it is driven by ohms law. Chargers are a voltage device. Disconnect the battery and measure the voltage of the charger output. It will be exactly what you set the charger voltage to, with zero current, and zero watts. And whatever resistive load you put there, it will stay at that voltage as current increases due to ohms law. The voltage is regulated to the set voltage, while the current is free to change to whatever it will be due to ohms law. Until the current exceeds the capacity of the charger, at which point the charger gives all it can, and the current stays maxed out and voltage reduces, because any more voltage would drive current too high. Throughout all of this, the charger is regulating and adjusting voltage, not current.

Another way to think about this is to take the concept compleatly away from electricity. We are talking about power and losses or basic energy system.

When you are driving in your car and you want to go 60-mph, you press the gas pedal down and the car accelerates. As you approach 60-mph you lift your foot partially off the petal until the steed stabilized at the desired 60-mph. If you come to a hill or have a change in wind speed, you need to move the pedal to compensate for the increase or decrease in drag/resistance. By changing the pedal position, did you change the speed, or the power produced by the engine. The only thing that you can control is how much power is produced, the speed is a result of the power vs drag.

In this example, the engine output (HP) is equivalent to the power output of the charger (Watts). FYI, 1-HP is = to 745.7W. The speed of the car is equivalent to the voltage in our charging system. the rolling resistance of the car, hills, wind... is equivalent to the total resistance of the in a charging system.

 

[wholybee]

Another way to think about this is to take the concept compleatly away from electricity. We are talking about power and losses or basic energy system.

When you are driving in your car and you want to go 60-mph, you press the gas pedal down and the car accelerates. As you approach 60-mph you lift your foot partially off the petal until the steed stabilized at the desired 60-mph. If you come to a hill or have a change in wind speed, you need to move the pedal to compensate for the increase or decrease in drag/resistance. By changing the pedal position, did you change the speed, or the power produced by the engine. The only thing that you can control is how much power is produced, the speed is a result of the power vs drag.

In this example, the engine output (HP) is equivalent to the power output of the charger (Watts). FYI, 1-HP is = to 745.7W. The speed of the car is equivalent to the voltage in our charging system. the rolling resistance of the car, hills, wind... is equivalent to the total resistance of the in a charging system.

I will trust my formal electronics education and 40 years of experience.

 

[hwse]

I will trust my formal electronics education and 40 years of experience.

That is fine and you are not the only one who looks at it this way.
I actually had this same discussion with the TA in the Physics lab when I was in college. We ended up going to the Dr. Gibbs the Dean of the Physics Department and he explained to the TA that in colloquial terms we talk about "controlling" the voltage but based on cause and effect the voltage is the desired outcome and result of controlling the amount of power being generated.

 

[wholybee]

A BJT is a current device. With that device and in that sense, then yes, you are controlling current, and based on a voltage measurement after the device adjusting current at the base of the transistor which will change the voltage across the load. However, that is true of a BJT, but *not* of an FET which is a voltage device. And in the case of a package like an LM317, we don't care about how it works inside, whether it uses BJTs or FETs. An LM317 as a discrete device is a voltage device, not a current device. Any specific charger could be built with BJTs, FETs, an LM317, or similar, or a combination of those. In many cases it is via PWM, and you are not controlling current or voltage, but pulse width. We don't care, the charger as a device is a voltage regulator, not a current regulator. In any case, we say we are regulating voltage, because that is what we care about, and that is what we hold to a specific value as the resistive and current components in circuit change. We are not regulating current, because while whatever technique we might use to change voltage (which is by current with a BJT or by voltage with an FET, or by pulse width with PWM), voltage is what we are monitoring and holding to a specific value. And that is what a charger is doing, holding a specific voltage. Only when it is incapable of holding that voltage because of excessive current will it allow the voltage to change.

 

[hwse]

A BJT is a current device. With that device and in that sense, then yes, you are controlling current, and based on a voltage measurement after the device adjusting current at the base of the transistor which will change the voltage across the load. However, that is true of a BJT, but *not* of an FET which is a voltage device. And in the case of a package like an LM317, we don't care about how it works inside, whether it uses BJTs or FETs. An LM317 as a discrete device is a voltage device, not a current device. Any specific charger could be built with BJTs, FETs, an LM317, or similar, or a combination of those. In many cases it is via PWM, and you are not controlling current or voltage, but pulse width. We don't care, the charger as a device is a voltage regulator, not a current regulator. In any case, we say we are regulating voltage, because that is what we care about, and that is what we hold to a specific value as the resistive and current components in circuit change. We are not regulating current, because while whatever technique we might use to change voltage (which is by current with a BJT or by voltage with an FET, or by pulse width with PWM), voltage is what we are monitoring and holding to a specific value. And that is what a charger is doing, holding a specific voltage. Only when it is incapable of holding that voltage because of excessive current will it allow the voltage to change.

I think I am beginning to understand where you are coming from. Your whole frame of reference is electronics which by their nature are control devices. They are instrumental in our charging systems, but their usefulness is in controlling the power creation we need to charge our batteries.
A BJT takes changes to a tiny current to control the magnitude of a much larger current but it in itself creates no current or energy. that is provided by another DC source. The same is true for FETs using a voltage to switch on and off a much larger power supply. The PWM creates pulses of energy at the full nominal voltage to reduce the power delivered to whatever it is connected to but in and of itself, it creates not power. It controls the power produced by another DC source.
My reference on the other hand is power generation. Without adding energy to a battery, its voltage will never increase. Without limiting the power put into a battery the voltage will increase without limit until it goes up in smoke. The cause of increases in voltage in a battery are the addition of energy. The purpose of a "voltage regulator" is to limit the current put into a battery to prevent an increase in voltage above the set point.
To say that the electronics that you mention are setting (to cause) the voltage is equivelent to saying that the ECM computer on a car is causing the car to travel at any given speed. The ECM is not capable of moving a car. That is the job of the engine which produces the power to move. The ECM samples all of the data and changes the things that cause the engine to make power. It is all about cause and effect. The engine power is the cause of the speed. The chargers power output is the cause of increase in voltage.