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Solar question

Discussion in 'Off Grid Living' started by Falcon15, Jan 14, 2015.

  1. Falcon15

    Falcon15 Falco Peregrinus

    All right, here goes:

    I have two (2) one-hundred twenty (120) Watt solar panels. My charge controller is showing 0 Amps (caveat, it has been overcast - however, I should be seeing something register on my controller). I replaced the old charge controller, as I thought the board went bad because it was showing 0 Amps from the panels. It now seems that I was incorrect (leaving me with 0 Amp output from the panels, and a spare charge controller).

    Using my multimeter, I checked the amperage output from the panels at the terminals on the back of the panels. They are rated at 16.5 AMPs, and each one, at the terminals registers 16.5+/- 0.1 (in overcast conditions). The feed (the cable that runs directly from the panels to the charge controller - a 4 foot cable) registers less than 6 amps at the controller.
    Could the cable connections at the terminals be corroded (visually, they are slightly oxidized - ever so slightly - they are dull rather than shiny silver) or in some way could the cable be compromised and as such restrict the flow?

    Last edited: Jan 14, 2015
    sec_monkey likes this.
  2. sec_monkey

    sec_monkey SM Security Administrator

    Do you have the tools to desolder and resolder the cable?

    Could be wrong on this, please follow all safety rules.
    Is the cable damaged or corroded ? Have you measured the resistance ?
    Some types of cable have been known to fail and sometimes start fires, cable of Chinese or other iffy origin may be a suspect.
    If there is no improvement, replacing the cable with one of larger gauge could be the thing to try next.

    @BTPost is one of our experts in the field. He is currently recovering from injuries. Get well BT! :)
  3. melbo

    melbo Hunter Gatherer Administrator Founding Member

    If you have amps at the panels but significantly less on the other end of the cable, I'd say that something is wrong with the cables. One could be broken internally or the ends are corroded. I wonder if your controller has a cut-in amp rating which would prevent it from doing anything at 6 amps.

    Also, are you using an 'amp clamp' to measure amperage?
    Last edited: Jan 14, 2015
    Yard Dart, azrancher and sec_monkey like this.
  4. azrancher

    azrancher Monkey +++

    OK, 120 watt panels, putting out 16.5 amps, would make them 7 volt panels, that would be an unusual panel voltage. Are you sure you are measuring Amps and not Volts, 16 Amps is a lot to measure on a regular multimeter unless you are using a shunt. I'm thinking the cable is bad, disconnect it from the panel and measure the resistance from the connector on the panel to the controller, also disconnected.
    Yard Dart and sec_monkey like this.
  5. Yard Dart

    Yard Dart Vigilant Monkey..... Moderator Site Supporter++

    Is the cable the one provided with the panels or the controller, if not, what type/gauge of cable is it? I assume you have checked each end of the cable and made sure the ends are crimped properly and secure. And that you have checked all connections to ensure nothing is loose in any manner. I would also suggest inspecting the cable jacket for any nicks/cuts that may be grounding out.
    sec_monkey likes this.
  6. sec_monkey

    sec_monkey SM Security Administrator

  7. sec_monkey

    sec_monkey SM Security Administrator

    @Falcon15 OPSEC first. Can you post some edited pictures please ?
  8. Falcon15

    Falcon15 Falco Peregrinus

    No, standard old school multimeter, interrupted (positive) circuit measurement
    sec_monkey likes this.
  9. azrancher

    azrancher Monkey +++

    Well if there is 16 Amps and the controller is disconnected, it's going somewhere.
    Dunerunner, Yard Dart and sec_monkey like this.
  10. Dunerunner

    Dunerunner Monkey

    sec_monkey and Airtime like this.
  11. Dunerunner

    Dunerunner Monkey


    Are you measuring between the controller and the panel? If so, you may have a ground fault bleeding off 16A before power gets to the controller.
    Since the run is only 4', I'd just run another cable and test again.
    kellory, Yard Dart and sec_monkey like this.
  12. Airtime

    Airtime Monkey+++ Site Supporter

    AZ had the same reaction I did, I was suspicious if volts and amps are being confused here. Two very different things and measured in two different ways.

    For measuring amps, Dune's pic is perfect. (the meter is in series with the load)

    To measure voltage the meter is connected with the + connected to the + of the voltage source and the - connected to the - of the voltage source. If the load (charge controller, or light, or whatever the needs power to operate) is disconnected you should still read a voltage. (the meter is in parallel to the voltage source and load). This is called an open load voltage.

    With the load then connected to the voltage source (+ to + of voltage source and - to - of voltage source) you generally will see the voltage on the meter drop a bit. This is the loaded voltage.

    If there is no voltage on the meter with the open load test (no load connected) then you have a problem at the panel (bad fuse, bad diode, bad wire, etc.)

    If the voltage is say 16-20 volts but drops to way way down almost nothing when the load is connected, then you have either a short or problem in the load or there is a poor connection in the panel.

    If you measure the current with the meter in series (as in Dune's picture) you will see the amperage the load is drawing from the panel. This should vary up and down as the panel moves in and out of the sun. If this is zero, then no electricity is flowing from the panel to the load.

    If the current measure stays fixed at a non-zero value as the panel moves in and other of the sun, then there is likely something wrong with how you are measuring current or with a setting on the meter.

    Many panels (especially the ones not intended for permanent installation with fancy charge controllers) can be connected direct to a battery to charge it without a charge controller. This works fine for panels that are small relative to the battery size and the battery chemistry along with the impedances between the panel and battery works as its own simple charge controller. However, when the sun goes down, these set ups can drain the battery so there is generally a diode in the circuit to prevent this. A diode is a device that allows current to flow one direction but not the other. In the vernacular of the plumbing trades (just hiked my pants up so the backside cleavage didn't show) it is just a simple check valve for electrons. These have amperage limits and if the panel was in the sun, generating some healthy juice and the wires accidentally shorted, the current flow could exceed the diode's current rating and fry the diode and you'd get nothing out of the panel. Some also have a fuse that will hopefully blow before the diode but yours may or may not have that. Just a couple things to check.

    Give it all revisit and check back in or PM me if you wish.

  13. sec_monkey

    sec_monkey SM Security Administrator

    Last edited by a moderator: Jan 25, 2015
  14. azrancher

    azrancher Monkey +++

    I think what Falcon said by interrupted means that the meter was in line with the current coming out of the collector.

    SM, those meters only measure AC current, the panels put out DC unless they have an Enphase type converter which converts to AC, and they there would be no need for a converter.

    I believe they do make clamp on DC current meters, but I don't own one.
  15. sec_monkey

    sec_monkey SM Security Administrator

    Thanks @azrancher :)

    Yep there are DC versions, sorry should have linked the DC version.
    Last edited: Jan 14, 2015
  16. sec_monkey

    sec_monkey SM Security Administrator

    Last edited by a moderator: Jan 25, 2015
  17. melbo

    melbo Hunter Gatherer Administrator Founding Member

    The meters I use will do both AC and DC amperage: Here's a good picture with explanations of the dial settings on a fluke 115
    sec_monkey likes this.
  18. melbo

    melbo Hunter Gatherer Administrator Founding Member

    I use a Fluke 381 with clamp and iflex cable clamp and also the Fluke wireless suite that has a bunch of voltage, amperage and temp sensors that all talk back to the 3000 mm or a laptop running Fluke software.

    Its all pretty heavy duty stuff but my job has me around 230kV/34.5kV and amperages of up to 1780 or so on my LV windings. My clamp will do 2500A AC with the flex cable
    sec_monkey likes this.
  19. sec_monkey

    sec_monkey SM Security Administrator

  20. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Solar work from DC panels / batterys / ANYTHING before an inverter (makes AC from DC) you need to walk into Sears and buy a 60.00$ DC amp clamp MM . I have 2 , Plus many more that offer different readings for different tests .
    I own Fluke / PICO etc, but here were just 101 - electricity ..

    120watt panels will not put out 16 amps , there is a hope & a prayer , 5-7 MAX & VOC is ?
    Back of most panels have there data , & are these 2 panels joined ? If so how ? Series Or parallel ?
    Who CC you using ? PWM or MTTP

    NOW I know lots of questions , Don't worries My 9K system is the same as yours right now , 2 weeks of fog & rain , Zip in harvesting .
    Do NOT play with amps while the panels have sun on them UNLESS you can shade them off to nothing while connecting & disconnecting leads. one arc or spark will kill control's & damage MC4 type of connectors . Without SUN were all hoping .You need sun to test.
    If ya had sun , voltage from both leads should match the sticker on the back .

    We have a way also to test the amount of power that a panel can produce , but B4 I spill that , we need to know the system numbers & type.


    I'll edit with the Pimps& queens link

    Craftsman 82369 - Digital Clamp-On Ammeter

    Craftsman - 82369 - Digital Clamp-On Ammeter | Sears Outlet
    Last edited: Jan 14, 2015
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