Solar Panels....

Discussion in 'Ham Radio Discussions' started by KB4MNG, Jun 23, 2019.

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  1. KC5KHR

    KC5KHR Ham Member QRZ Page

    I have had the Renogy 100 watt panels up for many years. They have survived hail and wind storms and still give full output.
    If noise is not a concern AND you just want one panel the cheap PWM controller works great (I also have a single panel used in this configuration), but with multiple panels a MPPT controller is the only way to go with the panels in series.
    I also have a few of the notebook style fold out panels that work extremely well for keeping the phones and USB battery packs charged. Those are in the 18-28 watt range.
  2. K7WFM

    K7WFM Ham Member QRZ Page

    I'm using a 100w 12VDC panel to a MPPT charge controller. The cable is ~23 ft from the panel to the controller. The controller also is fed by two additional panels in parallel with 10ga cable that are less than 11 feet from the controller.
    KC8VWM likes this.
  3. KC8VWM

    KC8VWM Ham Member QRZ Page

    I use 32 volt solar panels which reduces voltage losses through the cable length. For these reasons, it's best to keep the controller connections closer to the battery side of things.
    K7WFM likes this.
  4. KF7YED

    KF7YED Ham Member QRZ Page

    I've been following this thread with interest. Last week I lucked into a deal from another ham on three 100-watt Siemens SR100 panels. I also just got a new deep cycle battery for my camper, (
    but I haven't installed it yet. (Waiting on a new battery box to come in.) It sounds like I should pull the trigger on the Genasun GV-10 in my Amazon Wish List and use that to charge the camper battery off of just one of the SR100 panels. Originally I bought them for my Field Day and camping radio setup thinking I could use my Buddipole PowerMini ( controller but that only accepts 10A on the solar input. My thinking now is to just use the PowerMini and one panel to keep my 12V 18AH SLAB topped off. Actually, I have two, and I could swap them in and out of the radio setup while one charges on the PowerMini if necessary. Am I on the right track?

  5. KF5LJW

    KF5LJW Ham Member QRZ Page

    At least the right Train Station. I do see 1 issue. You have 18 AH batteries. Are they AGM or Gel?

    Either way with a 100 watt panel using a MPPT controller means 8 amp of charge current. That is a lot on on 18 AH battery with 8 Amps is the roughly a C/2 charge rate. You wanna be No more than C/6 and no less than C/12 leaving C/10 perfect charge rate. Well C/10 would be an 80 AH battery. You can charge 4 of those batteries with a 100 watt panel.

    Battery you have only requires a 25 to 50 watt panel. Charge both at once.
  6. KF7YED

    KF7YED Ham Member QRZ Page

    So if I use the Genasun GV-10 to charge the camper battery-- ( [​IMG] would that be Would that be okay? It's AGM, 12V 100AH.

    And the Genasun site says the GV-10 will accept up to a 140 watt panel... ??

    One radio battery is AGM: ( The other one I'd have to check. It came out of one of my 4-wheelers and I thought I'd keep it as a backup.
  7. K4AX

    K4AX XML Subscriber QRZ Page

    I have 4 100w flex panels from Windy Nation, EPever MPPT 30a controller with remote head, and a pile of lithium iron phosphate 40ah 512 w/hr batteries. I seem to average about 6 or so amps per panel at 14.6v, and I have enough batteries to easily run the rig as much as I want. I ran my 7300 at FD this year, calling cq non stop and working a lot of digital and cw with little breaks, never had a issue with batteries, the 4 panels topped off quick when I swapped. Nice thing about LiFePo4 batteries is they soak in a charge quick due to low internal resistance com paired to SLA or AGM batteries, and will last for thousands of cycles at the full discharge rate or just under it.

    Edit: testing at Field Day this year and at home, I could not detect RFI with the Epever controller, I had 30 ft of cabling between it and the panels.
    Last edited: Aug 6, 2019
  8. KK6NOH

    KK6NOH Ham Member QRZ Page

    Careful. DC cabling gets lossy the longer it becomes. That's why our national power grid is AC, because of the natural characteristics of DC. It's an interesting story that, about the great battle of DC (Edison) and Tesla(AC).
  9. KF5LJW

    KF5LJW Ham Member QRZ Page

    Factually incorrect on all points. Both AC and DC suffer from voltage drop as the length and currents increase. AC in fact has the highest losses of the two. With DC, only pure resistance of the conductor determines how much voltage loss there will be. AC also has the same pure resistance losses as DC experiences. plus reactive resistance created by the Inductance of the wiring.

    As to why AC won out is stupid simple to answer. Edison was an idiot letting Tesla go. Tesla knew AC is much easier to generate, regulate, control, distribute, and significantly lower cost. Edison picked DC to sell light bulbs he invented. Example is transformers are very easy to step up or down voltage. No expensive active components used.

    However back to the earlier point, Utilities use DC big time for Transmission over long distances using Bipolar High Voltage DC. They run up to 1,000,000 volts DC L-G or 2,000,000 volt L-L. They do it that way because it significantly reduces line losses vs using AC. The added equipment cost more than pay for itself with cut in line losses. At each end you have Inverters and Rectifiers to convert to and from AC for distribution which is all AC.

    So DC is not the issue. The issue is LOW VOLTAGE using 12 volt power. You need to keep line losses to 3% or less, and that is done by sizing cable correctly for the distance and maximum load current expected. 3% of 12 volts is only 0.36 volts. That is not much to work with. Does not matter if it is AC or DC. 12 volt AC would have higher losses than 12 volt DC.
    W0FS likes this.
  10. KK6NOH

    KK6NOH Ham Member QRZ Page

    Sorry but that's wrong.

    Edison lost because AC was able to be generated at high voltages and transmitted great distances before easily reduced down to usable voltages in the home by cheap and easy to make transformers. At the time there did not exist an easy way to change DC voltages, so Edison was forced to generate DC at voltages directly usable in the home. That meant the DC power plants had to be about a mile or two apart or the losses were too great. Edison wasn't an "Idiot" as you say. He was actually quite intelligent. But he was stubbornly stuck on DC and refused to adopt AC which was his downfall.

    So yes, typical 12v DC is lossy. Home 120v AC is nowhere near as lossy. I am correct in my statement of "Be aware of loss."

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