Help with PV wiring

System
System Posts: 2,511 admin
in Off Grid Solar & Battery Systems #1
Hello all,
I have 2-Kyocera KC-130 panels that I have been conencting to a small 12V inverter for temporary use. I am thinking about building a 24V system with 8-T125RE (Approx. 440 amp hous) by connecting these two KC-130 panels in series and possibly adding more panels to meet charging requirements. I was wondering if conecting two 130's would work and also if I wanted to beef up the charging what other panels could I use that would be compatible to the Kyocera panels. Thank you in advance,
Regards,
Nihar
· Share on Twitter

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Help with PV wiring

    Trojan gives the 20-hour rate on these as 240 Amp hours, so that would be 480 Amp hours @ 24 Volts. In short, two 130 Watt panels is not going to do much for recharging them. On a 24 Volt system those two panels would likely put out around 8 Amps max, which is far short of the minimum 5% (24 Amps). You'd need at least 3X as much panel, and more if you want to meet Trojan's recommended 10% plus be able to accommodate concurrent loads.

    Really you're looking at closer to 1500 Watts of PV if you want to do full charging on 480 Amp hours @ 24 Volts.
    · Share on Twitter
  • System2
    System2 Posts: 6,290 admin
    #3
    Re: Help with PV wiring

    Thanks for the response. So, then to augment the panel needs, what panel combinations could I use to get closer to 1500 W? Could I use Kyocera's or other panels that are 270 W each with the current KC 130s?
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Help with PV wiring
    nmohanty wrote: »
    Thanks for the response. So, then to augment the panel needs, what panel combinations could I use to get closer to 1500 W? Could I use Kyocera's or other panels that are 270 W each with the current KC 130s?

    There you run in to the all-too-familiar problem of mismatched panels. For connecting panels in parallel it is recommended that the Vmp rating of the panels be within 10% or closer if possible. For serial connections the number that matters is the Imp. I don't have the specs on the K130's handy, but they are similar to the K135's and pretty far from the higher Wattage panels: Example:

    K135 Vmp 17.7, Imp 7.63
    K245 Vmp 29.8, Imp 8.23

    There's no easy way to get panels that dissimilar to connect without significant power loss.
    The other issue is the type of charge controller used. The smaller panels like the 130/135 are designed for 12, 24, or 48 Volt systems with a PWM or MPPT controller as their Voltage specs can be used directly through a PWM controller with those systems: one for 12 Volt, two in series for 24, et cetera. The newer panels are often designed for grid-tie systems and thus have "oddball" Voltages like 29.8 or 26.6 etc. These don't match up with standard system Voltage and need to be used with an MPPT controller in order to get proper charging Voltage. For instance the K245 with its 29.8 Vmp is obviously too high for a 12 Volt system without an MPPT to down-convert the Voltage, and it's a bit too low for a 24 Volt system which would ideally have a Vmp of 35 or so.

    Your two K130's in series will have a Vmp around 35. If you go for higher Wattage panels look for ones with similar numbers. One example (but not the only one): http://www.solar-electric.com/co180wamopa.html
    · Share on Twitter

Categories