Solar charge controller QRM mitigation?

Discussion in 'General Technical Questions and Answers' started by KB7KJY, Oct 10, 2019.

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  1. KB7KJY

    KB7KJY Ham Member QRZ Page

    I have not purchased the 24-12v converter yet. Discussion of QRM on one of the solar discussion got my attention and I am not moving forward until I answer some questions.

    If you have suggestions for a better alternative to running a 100watt HF rig from my 24v battery I would much appreciate it.

  2. KB7KJY

    KB7KJY Ham Member QRZ Page

  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Wrong criteria for your operation.

    There is no need to limit current, that only robs you. With 1800 watts of panels into a 24 battery at most will only deliver 65 amps and that would only be a few minutes around solar noon after a cloudy morning with no sun. Two points here to make

    1. You will never see 65-amps, and even if you do, 65-Amps on a L-16 battery is a C/7 charge rate which is just fine. C/4 rate (105 amps) is max and you are not even close to 105 Amps of charge current.

    2. Disable current limit, not needed and the looser is you by limiting harvest to something less than maximum possible.

    I have no clue what you meant when you said:

    Charge Controller has nothing to do with how much current the load uses. All the Loads are connected directly to the battery. It can be pitch black dark outside with ZERO solar power and the batteries will deliver any current demanded by the load.

    Midnite Solar is an OK product, but not my favorite for 2 reasons. They are noisy (mechanical with annoying fan), and inefficient. Thus why they need a fan to cool it off.

    It just does not meet your needs, and if you had done a little research you would have found out pretty quick they are prone to EMI/RFI generation.

    Here are some things and in order to try to minimize the noise. You will never get rid of it.

    1. Use tightly twisted wires from panels and batteries. This tightly couples the circuit conductors to magnetically balance out common mode current and adds inductance aka low pass filter.

    2Keep battery wires as short as possible.

    3. Use Ferite Toroid rings to wind panel and battery conductors around as close as possible to Controller. Start with panel wires as they are the largest offender.Use low frequency mixes.
    Last edited: Oct 12, 2019
    K0UO likes this.
  4. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Your Big refrigerator probably has a 1000 to 1200 watt inverter on it alone, I see where you need so much power.
    Big appliances and boondocking don't mix. I've seen this a hundred times with my other RVers friends, everybody wants a big home refrigerator (XYL) and then they want to go off grid for a week!!!
    KP4SX likes this.
  5. KB7KJY

    KB7KJY Ham Member QRZ Page

    When used in conjunction with the Whizbabg Jr. It does.

    I have done significant research. Primarily on sites that are very solar specific. What was lacking there was discussion of RFI. That's why I am here.

    My best understanding is that I don't want to exceed C/8 to avoid boiling your batteries.

    Thanks for the input. Whichever controller I wind up using, the tips on chokes and wiring will be of value.
  6. KB7KJY

    KB7KJY Ham Member QRZ Page

    Looks to me like I don't want to exceed 54 amps to stay below C/8.
  7. KF5LJW

    KF5LJW Ham Member QRZ Page

    That is a good general rule for lead acid batteries being charged with commercial power chargers when a Constant Current of C/8 can be applied for hours upon hours. Solar is not a hard source and can only supply peak power for a few minutes around solar noon. Secondly you indicated you use L-16 batteries which are a hybrid Traction Battery made for floor machines and lifts. Hybrids can deliver and take much higher currents, thus being hybrid can easily handle up to C/4 charging currents on commercial power for hours. Solar cannot do any of that as it is not capable of delivering enough current long enough to worry about in your application.

    What you should be focused on and fuss about is do you have enough panel wattage to replace what you use in a day. Any good design has more than enough capacity to replace what was used the day before and then some. It is counter productive to do otherwise like limiting charge current when there is no reason to do so. Funny since you mentioned you have been on a solar forum they did not tell you if you reside in the Pacific Northwest to consider using AGM batteries due to the extra high charge rates required for the area. AGM's can take up to C/2. That is what Sunking would tell you if you asked him.

    Seriously given what you have now will work fine without handicapping the system. The Controller is the RFI issue you now have to deal with. Good Luck.
    Last edited: Oct 12, 2019
    K0UO and N7EKU like this.
  8. KB7KJY

    KB7KJY Ham Member QRZ Page

    I had planned on 1800 watts of panels. I can squeeze 2400 watts up there if I get creative with roof vents I may be able to fit 2400 watts.

    I don't expect anything aproaching nameplate ratings as they are flat mounted on the roof.

    I am having trouble understanding why you are suggesting AGM's. I have looked closely at AGM and found FLA to be the best bang for the buck. I don't mind checking SG and topping periodically.
  9. KF5LJW

    KF5LJW Ham Member QRZ Page

    FLA's are the best bang for the buck, but they are not always a good fit for the application. AGM's have their place like:

    1. Applications requiring very high charge and discharge rates like a solar system in the Pacific Northwest where the sun does not shine and when it does requires the panel wattage to be very high and exceed a C/6 charge rate. Another example is say a small battery with a large load requiring a high discharge rate in excess of C/6. AGM internal resistance is extremely low, and thus can handle the high rates. You fit in this category and number 2.

    2. Mobile application where spills cannot be tolerated. AGM was invented for military aircraft.

    3. Unusual mounting/installation orientation like on their side.

    4. Extreme cold climates where you cannot tolerate a frozen battery.
    K0UO likes this.
  10. KB7KJY

    KB7KJY Ham Member QRZ Page

    I am putting 1800 watts of panels on the roof.

    I am not understanding your reason for recommending AGM over FLA? Space and weight are not a big issue.

    I have found that FLA's are the best bang for your buck.

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