Solar panel regulator output voltage

Discussion in 'Mech Tech' started by pkrboo, Apr 4, 2016.

  1. And my lash-up.

    Obviously not as proud a house keeper as the Pop-Top kitchen crew:oops:
    Razzyh and sANDYbAY like this.
  2. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    Mine will involve a certain amount of hose pipe :D I'll stick some pics up when it's done.
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  3. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    I've decided that I'm going to have a Solar Array because it sounds much posher than Solar Panels.
    First up the controller, I didn't want a wardrobe at the back and the instructions warned against installing it next to a battery.
    I made a couple of shaped batons so I could bolt the controller directly to the wall in the van. Out of the way but easily accessible so I can see what's going on.
    Then I took a 'brass rubbing' of the contacts so that I could mirror them for the cable entries.


    Drilled only the holes for the panels and battery as I won't be putting a direct load onto the panels, everything will be fed from the leisure fuse box


    I started the wiring with the two battery cables


    And tucked a fuse in nice and close to the battery


    I stripped out the roof lining and insulation so I could work out how to feed the cables and also drill the holes to mount my new tailgate hinge covers.


    You can see where the two panel cables will go through and then run down inside the vent to re-enter below the controller.
    The two battery cables go through into the vent and travel down and across the roof of the engine bay.

    I need to wash all the pencil marks off but this is what I'll have in the van.


    I've got two baby girls to look after tomorrow but if they have a kip I'll start sorting out the panels themselves.

    Sent from my iPad using Tapatalk
  4. That is super neat @sANDYbAY :thumbsup:
    Here's a thought....
    See the output with the little lamp symbol on it on the right?
    Well it's a timed (or I guess simply on/off) 12v feed direct from the battery. These controllers all seem to have them.

    I've wired mine directly to a 12v accessory socket for the rear. I plug in the shower & compressor etc here & it gives me good access to the rear wheels.

    Just an idea coz. with all that 12v available, you may as well use it;)

    Rear facing controller mounted on the back of the wardrobe...

    ...and the ungainly black box beneath is a surface mounted 12v female socket. Surface mounted coz I didn't want it in the wardrobe space.
    sANDYbAY likes this.
  5. BTW, love the way the screw heads line up on your controller :eek:
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  6. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    It did occur to me that I might be able to get a 12v water heater to run off that power supply to give me a tank of hot water each evening, obviously I'd need to fit a bathroom in somewhere as well. :)
    theBusmonkey likes this.
  7. Tempting....

    although we just boil a kettle & run the shower off that :p
  8. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    Moving on a bit more. I've finished the connections and cable route from under the Poptop and today the solar array has been stuck on.


    Sent from my iPad using Tapatalk
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  9. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    My starlight collecting panels live. :chewie::chewie::chewie:

    With a bit of scattered cloud in the sky which occasionally obscured the energy given off from our nearest star I was getting;

    PV - 19 v - 2.2 A
    Batt 14.5 v - 2.8 A

    and about half an hour later

    PV - 20v - 1.3 A
    Batt 14.5 v - 1.6 A
    theBusmonkey likes this.
  10. Yay @sANDYbAY , solar off;)

    17.32 on 16th May. Van facing north, roof down:

    4.3 amps from the panels, but only 0.37 going into the batteries which are on float. The rest is dumped through the heat sink.
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  11. All I can add is that I've been unplugged for 5 days on one 100w panel / 115ah battery and the fridge is still working. But I'm going to finish unloading it and switch it off for a bit tomorrow.
  12. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    So, can anyone help me understand the figures I've put up?
    Is the actual useable outlet from the panels effectively the amps?
    Does the amp figure from the panels go down as the battery gets more charged?
    Why has thebusmonkey got more amps than me?
    Is it because he lives on a hill and is nearer the sun?
    Are my amps getting stuck because I'm squeezing all my amps through thin 2.5mm cable?
    Why is there only one monopolies commission?
  13. Bus monkey has less than 1a going into battery, so less than you. Your figures indicate your battery is getting charged up. If you could press a button to show the amps from the panel, you'd see higher figures. :)
    theBusmonkey and pkrboo like this.
  14. The most useful measure of the solar panel output is the power, which is amps times volts. Your solar panel works at around 20 volts, which is way too high for charging a lead-acid battery, which would start bubbling and gassing. The charge controller regulates the voltage sent to the battery, to be a maximum of 14.5 volts or so so the battery charges as fast as it can. The power going into the battery is this lower voltage times the battery current.

    So your first figures work out as:

    PV - 19 v - 2.2 A = 41.8 Watts
    Batt 14.5 v - 2.8 A = 40.6 Watts

    Meaning the regulator is putting 97% of the panel output into the battery :)

    You're generating enough power for a small compressor fridge to be cooling constantly :)

    Later on:

    PV - 20v - 1.3 A = 26 Watts
    Batt 14.5 v - 1.6 A = 23.2 Watts

    So now the panel is producing quite a bit less power, and 89% of the panel output is making it into the battery. You're now generating enough for a compressor fridge to run normally, only actively cooling half the time.

    A smart battery charger will put as much current into the battery as it can when the battery is discharged, and the battery voltage will slowly rise from 10 or 11 volts to 14.5 volts when around 80% full. At that point the charger will prevent the voltage rising any higher by slowly reducing the current. When the battery will only accept a very small charging current without the voltage rising above 14.5 volts then it's fully charged.

    On the other side of the controller, it will be optimising the voltage and current (which, multiplied together equal the power) from the PV panel to get as much power out of the sunlight as the panel can.

    I'd be interested to know what happens when the battery is fully charged. The battery voltage should be 14.5 still, and the battery current close to zero. Not sure what the panel output will be: perhaps a higher voltage but very low current, to avoid wasting power in the controller.
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  15. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    Thank you for that @Fonant the mists of my ignorance are slowly clearing. My second figures then were telling me what the controller was putting into the battery and not, as I'd thought, a measurement of the battery itself.
    zedders likes this.
  16. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    Finished, well almost, I just want some insulating tape to replace the masking tape on the X strut.

    I fitted a fuse into the roof so I can isolate the panels if I need to remove the leisure battery.


    I bought two versions of bulkhead glands and didn't like any of them so I did a bit of plumbing instead. I'm 5'7" and I can't see them from the ground even with the top down so they're nice and stealthy.


    A bit of messing around with offcuts of hose pipe gave me this route for the cables from the roof. There's plenty of room under there so that's where I joined the cables from each panel.

    Bertiebot, rickyrooo1 and zedders like this.
  17. Super neat as always @sANDYbAY !!
    However, you've raised the bar again. You appear to have a genuine 80 kph sticker on your roof instead of low budget stick-on vinyl numbers.
    You'll be doing weddings & entering show'n'shines next...;)
  18. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    Entirely based on your thread and recommendation I assure you. Hopefully my 99p sticker will protect me from all the big bad scary European lorries. :)
    theBusmonkey likes this.
  19. Top job @sANDYbAY really nice install

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