Small PV For Convenience. What Can Be Improved Upon?

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  • Soulearner
    Soulearner Registered Users Posts: 18
    Re: Small PV For Convenience. What Can Be Improved Upon?

    One last question please.
    We decided to take the hit and get 4 100w panels, wire 2 sets in series, then wire the sets in parallel.

    Are we still OK with this Renogy 30A charge controller?
    Thank you!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Small PV For Convenience. What Can Be Improved Upon?
    Soulearner wrote: »
    One last question please.
    We decided to take the hit and get 4 100w panels, wire 2 sets in series, then wire the sets in parallel.

    Are we still OK with this Renogy 30A charge controller?
    Thank you!

    If I recall correctly the panel Imp is 5.3, so four in parallel would be 21.2 on a 12 Volt system.
    On a 24 Volt system two panels in series gives the needed Vmp and then you have two strings in parallel so the current would total 10.6.
    What you can't do because it is a PWM controller is run the higher Voltage array configuration on a 12 Volt system.
  • Soulearner
    Soulearner Registered Users Posts: 18
    Re: Small PV For Convenience. What Can Be Improved Upon?

    ...I think that's a 'yes'. :-)
    We will end up with 34 volts @ 10.6 to the PWM controller, then out to 2 12 volt batteries wired in series.
    So I guess we're good to go. I'll order everything later if I don't hear you say I've got it wrong.
  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Small PV For Convenience. What Can Be Improved Upon?

    Just install all the panels in parallel. It allows each panel independence against any shade variables.
    you will need MC 4 parallel clips.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Small PV For Convenience. What Can Be Improved Upon?
    Just install all the panels in parallel. It allows each panel independence against any shade variables.
    you will need MC 4 parallel clips.

    Well, no; if he's going to a 24 Volt system the panels need to be two in series to get the Vmp high enough. Then parallel the two strings.
  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Small PV For Convenience. What Can Be Improved Upon?
    Well, no; if he's going to a 24 Volt system the panels need to be two in series to get the Vmp high enough. Then parallel the two strings.
    If the system size is under 3500 watts of power, 3.5kWh OP is better with 4 panels
    working independently to charge for 12v system. Utilizing more panels in string to configure 24v systems under 3500 watts is pointless on charge efficiency, and the more independence from each 12v panel increases harvest, just as what is proven from micro inverter systems. BMS is no different, building to the correct system demands will offer optimal harvest efficiency, and the constant battle with peukerts law only regognizes that individual panel harvest will improve charge optimization, at least for 12v up to 3500 watts. My recommendation is if OP choses a demand in power between 3500~5000watt should the system be 24v for better optimization. Just my 2 cents dealing with engineers for 10 years.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Small PV For Convenience. What Can Be Improved Upon?
    If the system size is under 3500 watts of power, 3.5kWh OP is better with 4 panels
    working independently to charge for 12v system. Utilizing more panels in string to configure 24v systems under 3500 watts is pointless on charge efficiency, and the more independence from each 12v panel increases harvest, just as what is proven from micro inverter systems. BMS is no different, building to the correct system demands will offer optimal harvest efficiency, and the constant battle with peukerts law only regognizes that individual panel harvest will improve charge optimization, at least for 12v up to 3500 watts. My recommendation is if OP choses a demand in power between 3500~5000watt should the system be 24v for better optimization. Just my 2 cents dealing with engineers for 10 years.

    That is a load of nonsense.

    If you are charging a 24 Volt system the Vmp of the array must be high enough to charge the system. Period.
    Micro inverters are not involved: they do not use batteries.
    BMS is not involved: this is a very small off-grid system using lead-acid batteries.
    3500 Watts is not involved: we are talking about four 100 Watt panels here.

    I don't know what engineers you deal with, but if that's an example of their thinking they aren't very practical.
  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Small PV For Convenience. What Can Be Improved Upon?
    That is a load of nonsense.

    If you are charging a 24 Volt system the Vmp of the array must be high enough to charge the system. Period.
    Micro inverters are not involved: they do not use batteries.
    BMS is not involved: this is a very small off-grid system using lead-acid batteries.
    3500 Watts is not involved: we are talking about four 100 Watt panels here.

    I don't know what engineers you deal with, but if that's an example of their thinking they aren't very practical.


    So let me clarify I'm speaking in terms of harvesting optimization. I'm implying 24V for the size and panels used is pointless for OP with less charge efficiency, a 12V system is better under this circumstance.

    A 12V system will optimally perform if each panel per meter square has its own independence.
    Plugging in 2 panels in series for 24v system will increase the chance and probability of not only soiling degradation, but as well shading, so there are power losses that start from the panel.

    While for 24V systems can optimize charging using smaller conductor wires, panels are more prone to being affected to soiling/shading per meter squared.

    That's no different than the scenario of a string inverter system operating at 80% VS a micro inverter system which operates at 86.5% or higher because of panel independance and the use of that surface area per meter squared.

    Any PV system plugged into a series as a string, is more prone to deficits of power production because of the effects of soiling and shading, per metered squared.

    So "building to size" as long as the battery system and bussing of the inverter allow, is better to build to that size for HARVESTING OPTIMIZATION. To make the the surface area of the panels less prone to vmp/imp losses. 12V systems due to inverter bussing usually max out at about 3500 watts, then the systems have to step up to 24, 36, 48, volt etc, only because the inverter doesn't have the allowable bussing, nore is there a conductor size large enough to make 12V acceptable for higher wattage outputs.