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Does an MPPT solar controller, turn excess voltage into Current/Amps?

PaddyHaig

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Does an MPPT solar controller turn excess voltage into Current/Amps?

If my solar panels create 21V @ 7Amps and my battery only needs 14.2V to charge. What happens to the excess voltage? Is it just wasted away by dumping into a heatsink or is it converted into additional current/charge?
 
Does an MPPT solar controller turn excess voltage into Current/Amps?

If my solar panels create 21V @ 7Amps and my battery only needs 14.2V to charge. What happens to the excess voltage? Is it just wasted away by dumping into a heatsink or is it converted into additional current/charge?
An MPPT solar controller can be imagined as a specialized DC-DC converter that feeds the battery its desired charging voltage. By lowering the output voltage, a higher current can be drawn by the battery, so in a way, voltage is „turned into current“. However, there is no „waste“ in the sense that energy is purposely converted to heat, it is merely a side effect of the process that is not 100% efficient.
 
Does an MPPT solar controller turn excess voltage into Current/Amps?

If my solar panels create 21V @ 7Amps and my battery only needs 14.2V to charge. What happens to the excess voltage? Is it just wasted away by dumping into a heatsink or is it converted into additional current/charge?
The mppt will use the excess voltage to boost the charge current when available.
Higher voltage panels will work more efficiently than a lower voltage panel using an mppt instead of a pwm
Controller. Here is two examples using a 100w panel similar to yours thru the Victron mppt smart solar and a 96 cell 327w 60v panel on a clear 40deg day.
 

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The mppt will use the excess voltage to boost the charge current when available.
Higher voltage panels will work more efficiently than a lower voltage panel using an mppt instead of a pwm
Controller. Here is two examples using a 100w panel similar to yours thru the Victron mppt smart solar and a 96 cell 327w 60v panel on a clear 40deg day.
There is NO excess Voltage with a MPPT controller , the controller seeks the most efficient working point to get the max amp into the battery.
Important is that your string (s) must be equal and the VOC just under the max VOC of your MPPT controller.
Most MPPT controllers wake up (adjustable) at 70% VOC
 
Instead of volts/amps, think in terms of power, it's pretty straightforward. If your controller is getting 100 volts at 5 amps from the panels, that's 500 watts of power. It converts those 500 watts into 12.5 volts at 40 amps. (for example), still 500 watts of power, but in a different form.
 
So, from what I have read from the replies to my query and from the pictures posted above. (Which I am so very grateful of)
It would seem rather clear that the excess voltage generated by my solar panels (That being voltage over and above what the MPPT solar controller, has been programmed to use when charging the battery/batteries, whilst charging in bulk mode, in my case 14.2V, will be converted into additional current/amps, being pushed at the battery/batteries. If that is, the MPPT controller, believes that the battery/batteries should be in a position to accept this additional current. Naturally, if the MPPT solar controller senses that the battery is near full, 80-90%. it will reduce the current being fed to the battery to a lower trickle rate of charge, whilst maintaining a steady charge voltage, as the battery charge cycle comes to completion? Am I right?

I hope so, as I have a german mechanic and a Norwegian retiree trying to browbeat me into believing, that it is not possible for a solar controller to convert excess Volts into Amps. :)
 
So, from what I have read from the replies to my query and from the pictures posted above. (Which I am so very grateful of)
It would seem rather clear that the excess voltage generated by my solar panels (That being voltage over and above what the MPPT solar controller, has been programmed to use when charging the battery/batteries, whilst charging in bulk mode, in my case 14.2V, will be converted into additional current/amps, being pushed at the battery/batteries.
Current is not "pushed", it is "drawn" or "pulled". It is the complete circuit that determines the maximum current that can flow: an empty battery draws a higher current which gradually gets lower as the battery approaches a fully charged state. The voltage is not "in excess", it is merely higher than the optimum required for charging the batteries without damaging them. In order to protect the battery and to optimize output power (which is the product of voltage and current), the controller lowers the voltage to let a higher current flow when the system draws it.
 
Current is not "pushed", it is "drawn" or "pulled". It is the complete circuit that determines the maximum current that can flow: an empty battery draws a higher current which gradually gets lower as the battery approaches a fully charged state. The voltage is not "in excess", it is merely higher than the optimum required for charging the batteries without damaging them. In order to protect the battery and to optimize output power (which is the product of voltage and current), the controller lowers the voltage to let a higher current flow when the
 
It just seems that I'm struggling to get a straight answer to my original question. I do apologise for my limited understanding of electrical current flow and exactly how Volts/Amps/Watts work.
However, I've done my best to get some understanding of DC electrical theory. But I sit here and ask myself, why can't what I though was a simple question be answered simply? Is it me, and the way I am presenting my question?
So, I'm going to try again to pose the question?

It would seem that my 100A LifePo4 battery, when 50% SOC, according to it's BMS, technically can suck up to an optimal charge current of 50A, however it can suck as much as 300A (3C).
The gauge of pure copper stranded wire, from my Solar controller to my 100A LifePo4 battery at 2 metres in length, is 10mm2 . All the above I believe to be fine. The wires from the Solar panels to the Solar controller are the wires they came with.

However my difficulty in getting a straight answer on, is this.

If I had one (1) 110W Solar panel.
Vmp: 18V
Imp: 6.11A
Voc: 21.6V
Isc: 6.72A

Wired up to a Votronic Solar controller capable of handling a current of up to 20A

The Solar controller, in turn, wired up to a 100A 12V Nominal LifePo4 battery, using 2 metres of 10mm2 copper wires.

The charge Voltage for the LifePo4 battery set to 14.2V.

The difference between the Solar panels generated Vmp of 18V and the 14.2V that is being used to charge the battery is 3.8V.

What is happening to this excess 3.8V's?
Where is it going?
Is it being converted into Current/Amps by the MPPT Solar controller?

Because from watching my Solar controller LCD panel. It would seem that in full sunlight on a clear sky day, that I am creating more than the 6.11A Imp, on the Solar panel label.
Which leads me to believe that the Votronic Solar controller IS converting excess Voltage into additional current.
 
It just seems that I'm struggling to get a straight answer to my original question. I do apologise for my limited understanding of electrical current flow and exactly how Volts/Amps/Watts work.
However, I've done my best to get some understanding of DC electrical theory. But I sit here and ask myself, why can't what I though was a simple question be answered simply? Is it me, and the way I am presenting my question?
I am doing my best to help you with the theory by presenting my answers in the simplest possible fashion. However, you can also help a little by realizing that not all questions can be answered in a way that fully correspond to the expectations of the person asking.

So, I'm going to try again to pose the question?
...
However my difficulty in getting a straight answer on, is this.

If I had one (1) 110W Solar panel.
Vmp: 18V
Imp: 6.11A
Voc: 21.6V
Isc: 6.72A

Wired up to a Votronic Solar controller capable of handling a current of up to 20A

The Solar controller, in turn, wired up to a 100A 12V Nominal LifePo4 battery, using 2 metres of 10mm2 copper wires.

The charge Voltage for the LifePo4 battery set to 14.2V.

The difference between the Solar panels generated Vmp of 18V and the 14.2V that is being used to charge the battery is 3.8V.

What is happening to this excess 3.8V's?
Where is it going?
Is it being converted into Current/Amps by the MPPT Solar controller?
Let me give another shot. Thanks to the person who made the suggestion - sorry for being too lazy to look up who it was.

In my understanding of theory, there isn't a way to "convert voltage into current" because the two are associated in a relationship. Excuse my joke if you think it is inappropriate, but you wouldn't ask for "owner" to be converted into "dog" or "husband" into "wife". This is why it is better to think in terms of power. Power is the result of the relationship, expressed in the product of voltage and current. Within a circuit, when one parameter is changed, this product still remains. When a source provides an input voltage that is too high for the target application, the DC-DC converter circuit in the MPPT controller outputs a lower voltage. This makes it possible for the input current to be lower than the output current. However, the power stays the same (apart from a small loss due to heat, which can be expressed in the degree of efficiency).

I suggest not to use the term "excess" when converting voltages, because to me this implies that something has to be given up or "dumped". Let me use your numbers for the calculation (assuming perfect conversion with 100% efficiency):

Input:
18V * 6.11A = 110W

Output:
110W / 14.2V = 7.75A

The DC-DC conversion allows a higher current to flow at a lower output voltage. The power remains the same.

Because from watching my Solar controller LCD panel. It would seem that in full sunlight on a clear sky day, that I am creating more than the 6.11A Imp, on the Solar panel label.
Which leads me to believe that the Votronic Solar controller IS converting excess Voltage into additional current.
If this is how you like to express it, feel free to think that way. It is just that the people I know who are used to dealing with electricity experience discomfort at the thought of "converting voltage to current". The solar controller is converting one voltage into another voltage, preserving the total power output and letting the output draw a higher current at a lower voltage.
 
Many people are trying to give you the really technical terms of how MPPT work. I assume that you want it in simple, easy to understand terms.
In simple terms, you can describe MPPT vs PWM as this:
PWM: voltage in -> voltage out. That is, if you have a 24 volt solar panel, you can charge a 24 volt battery with it.
MPPT: voltage in -> voltage out that matches your battery. That is, if you have two solar panels in series (say 48 volts), your battery will still be charged at the proper voltage (say 24 volts). The "excess voltage" you mentioned before (which would be the extra 24 volts) would essentially be used to double the charging current.

You can get really technical and prove that everything I said above is wrong. But in simple terms, this is close enough to how MPPT and PWM work.
 
For the end user that is more interested in getting the most out of their mppt rather than wanting to grasp the engineering details of how they work, the general rule of thumb here is that mppts want a minimum 30% increase of incoming voltage over the nominal voltage of the battery bank they are feeding, as this disparity is where they will usually make the most difference in gains efficiency. Bear in mind that not all mppts are created equal, and you are certainly not going to get the same performance from a $100 mppt or the ones built into the all-in-one units like mpp, growatt, etc as you would from a Midnite classic or Morningstar TriStar (for reasons of proprietary algorithms and much better drivers/FETs and other related components).
 
What happens to the excess voltage?
There is no excess.
Forget about volts for a moment.
The solar panel can deliver, with good solar energy, 110 watts of electrical power. The MPPT controller circuits collect the power from the panel and convert to suitable voltages and current for the battery, its a power converter.
There are many power converters that convert power at one voltage level to power at a different voltage level, for example your AC powered phone charger, the MPPT is just a specialised type of power converter.

All battery chargers apply a charge voltage suitable for the battery type and the battery state of charge.
Regard voltage as a measure of 'push' and current as a measure of 'flow'. Usefully the product of voltage and current is the amount of energy flowing in a circuit at that moment in time, measured in watts.

Neglecting any losses in the system, 18 volts applied to the MPPT with the panel capable of delivering 6.11 amps, gets 110 watts of energy into the energy 'store' inside the controller.
If we assume the battery needs charging, the charger electronics in the MPPT 'push' amps into the battery. The degree of 'push' will be the difference in volts between charger output and the battery. If, for example the battery needs 14 volts to charge, then the current available from the 'store' will be watts divided by volts, 110/14 = 7.86 amps.
In real life the solar energy falling on the panel wont be at the maximum and will vary due to weather conditions.
The MPPT controller will respond to changing conditions by 'loading' the panel optimally, thus being able to transfer via the conversion process, the maximum amount of power available to the battery. Once the battery reaches full charge the controller no longer 'loads' the panel for maximum power but just enough for the battery needs.

Mike
 
Does an MPPT solar controller turn excess voltage into Current/Amps?
No. The charge controller takes the input voltage and amps (which equals some number of watts) and it outputs the same number of watts (minus any conversion losses) at the battery charge voltage. The resulting amps are simply the watts divided by the battery charge voltage.

I hope so, as I have a german mechanic and a Norwegian retiree trying to browbeat me into believing, that it is not possible for a solar controller to convert excess Volts into Amps.
They are correct. First, there is no excess volts. Second, volts are not converted into amps.

Vin x Ain = W (The voltage and amperage in from the panels gives you a wattage)
W = Vout x Aout (That same wattage is converted into a different voltage and amperage, but it's the same wattage)

where Vout is the battery charge voltage. That's basically it. A simple conversion of watts from one voltage/amperage into a different voltage/amperage.

This is of course a bit over simplified but it's the basic idea.
 
Am I right?

I hope so, as I have a german mechanic and a Norwegian retiree trying to browbeat me into believing, that it is not possible for a solar controller to convert excess Volts into Amps.
Your are colloquially correct but technically (as others have pointed out) incorrect. As rmaddy states:
A simple conversion of watts from one voltage/amperage into a different voltage/amperage.

This is of course a bit over simplified but it's the basic idea.
The watts/in=watts/out is the essence of what you need to know. Your german and norwegian friends are either impatient and very poor teachers, or- if not- are perhaps not competent to give you advice :)
First, there is no excess volts. Second, volts are not converted into amps
technically correct as he pointed out.
He’s competent to give you advice.

I completely understood your colloquial description as coming from a lay person who understands the practical effects and described it in a non-technical lay person’s vernacular.
 
Question: where does the excess power go when mppt is in Float mode? aka battery is fully charged?
 
MPPT controllers do not waste power, YOU waste power. Any successful PV system wastes power because there has to be excess power to recharge batteries from power used on bad days. The charge controller also limits current in order to match a prescribed charge profile. If you don't use it at that time, you loose that opportunity. Your solar panel may have a MPP rating of 18V at standard temperature. That may drop to 16 or 17V when it gets hot in the sun. When you look at the charge control display and it says 19V, you are likely wasting energy. I use this simple fact to use that excess energy to heat water. Looking at that voltage, my controller dumps as much energy into heating water as it takes to lower the panel voltage down to MPP of the panel. Ther is often a lot of energy just not used, enough to fill my hot water needs. This is something many here just don't understand.
 
Question: where does the excess power go when mppt is in Float mode? aka battery is fully charged?
There isn't any 'excess' - the controller only uses what it needs/can use to supply charging energy. If it can use all your panel's output it does, if it can't it doesn't. Similar to your solar panels sitting there in the sun not connected to anything. They have power 'potential', they're just not making any power because there's no where for it to go.
I like the water analogy, it's easy to understand. There has to be a path for current and a voltage discrepancy to the load, for any current to flow.
 
Question: where does the excess power go when mppt is in Float mode? aka battery is fully charged?
When the battery is fully charged, the current drops to zero and thus the batteries are consuming no power. The panels also produce no power when the current is zero, so nothing is wasted. The panels have potential to produce power.

I have long suspected (but never bothered to test) that panels producing power should be cooler than identical panels in the same solar situation that have nothing connected to them. If that is the case, then the answer to your question is that unused potential simply heats the panels. Somebody with an IR imaging system could test this easily by putting two similar panels next to each other in full sun, short one of them, leave the other open, then see if they are at different temperatures.
 
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