I have solar panels, with an open circuit voltage of about 19.5V in full sun.
My batteries, depending on temperature, could require as much as 14V to fully charge although 13.8 would be more usual.
I appreciate that if the panels are delivering less power that the batteries can accept, at any given point, then the resultant terminal voltage will be less than ideal because the charge current will be lower, I am not expecting magic or over-unity but I am looking for a simple efficient way to get the maximum power from the panels.
I don't, at this point, want a circuit suggestion I am looking for comments on my understanding, or lack of it for that matter, with regard to power conversion.
I may be making assumptions here that are simply wrong but then that is why I am asking the questions.
Firstly I am assuming that capacitors store energy and that the voltage, assuming there is enough to work with, is of little importance.
For simplicity lets assume that the batteries are not fully charged and effectively capable of holding the panel voltage down at 13V when connected directly.
If I charge capacitors with the panels and use PWM and a choke to control the battery charging current which is modulated to maintain the optimal capacitor, and hence, panel voltage will I gain anything as a result of operating the panels at a higher voltage?
Taking this a step further, if the panels are arranged to output say 30-50V, dependent on irradiation, can I use the same system to generate a charging current that would result in a much lower battery terminal voltage without inuring huge losses?
The reason I ask about this extreme situation is that useful power may be available at low light levels if some of the panels are connected in series.
I will be using a small PLC, or possibly a PIC, to manage things and I appreciate that I have not addressed a charging strategy but for simplicity I would like these questions treated in their simplest form.
In short … Using PWM and a choke to generate a current into some load is the following possible:-
Panels at 18V delivering 5A into the capacitor bank (90W)
Current drawn from the bank, via PWM switch and a choke, to hold the bank at 18V
I need to take out 90W right?
Assuming 5% losses in the choke and switch my target load must be recurving circa 85W, which, if we work on a terminal voltage of 13V, would be about 5.6A, far more than would flow if the panel were connected directly to the battery.
Will that work or am I just missing the point somewhere?
My batteries, depending on temperature, could require as much as 14V to fully charge although 13.8 would be more usual.
I appreciate that if the panels are delivering less power that the batteries can accept, at any given point, then the resultant terminal voltage will be less than ideal because the charge current will be lower, I am not expecting magic or over-unity but I am looking for a simple efficient way to get the maximum power from the panels.
I don't, at this point, want a circuit suggestion I am looking for comments on my understanding, or lack of it for that matter, with regard to power conversion.
I may be making assumptions here that are simply wrong but then that is why I am asking the questions.
Firstly I am assuming that capacitors store energy and that the voltage, assuming there is enough to work with, is of little importance.
For simplicity lets assume that the batteries are not fully charged and effectively capable of holding the panel voltage down at 13V when connected directly.
If I charge capacitors with the panels and use PWM and a choke to control the battery charging current which is modulated to maintain the optimal capacitor, and hence, panel voltage will I gain anything as a result of operating the panels at a higher voltage?
Taking this a step further, if the panels are arranged to output say 30-50V, dependent on irradiation, can I use the same system to generate a charging current that would result in a much lower battery terminal voltage without inuring huge losses?
The reason I ask about this extreme situation is that useful power may be available at low light levels if some of the panels are connected in series.
I will be using a small PLC, or possibly a PIC, to manage things and I appreciate that I have not addressed a charging strategy but for simplicity I would like these questions treated in their simplest form.
In short … Using PWM and a choke to generate a current into some load is the following possible:-
Panels at 18V delivering 5A into the capacitor bank (90W)
Current drawn from the bank, via PWM switch and a choke, to hold the bank at 18V
I need to take out 90W right?
Assuming 5% losses in the choke and switch my target load must be recurving circa 85W, which, if we work on a terminal voltage of 13V, would be about 5.6A, far more than would flow if the panel were connected directly to the battery.
Will that work or am I just missing the point somewhere?
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