Observations on different solar panel performance / DC-DC charger performance





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  1. #1
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    Default Observations on different solar panel performance / DC-DC charger performance

    Been experimenting with a few different panels and DC-DC chargers, sharing some observations.

    I have:

    2x 130w FlexoPower Tacoma panels (max volt 19.1, open current volt 24) mounted to caravan roof.
    1x 220w FlexoPower Mojave flexible/portable panel (max volt 18.1)
    2x 120w AcoPower flexible/portable panels (max volt 20.8)

    In the caravan, a 40A national luna DCDC

    For RTT camping, a WRND.

    All connected to BlueNova 104ah 1300w LIFEPO4 batteries.

    ...

    Some observations:

    The two Tacoma panels on the roof - in early and late sun - do not charge well with the NL 40A DCDC. Putting a volt meter on them with them not connected to the 40A DC-DC shows a voltage of around 22.91 on a sunny day, with the sun about two fists above the horizon. Once connected to the 40A DC-DC, the voltage starts to fluctuate as the charger tries to draw power, a cycle dropping to about 18v, back to 22, every 2 seconds or so. The charger outputs some amps - 1-2, in a similar cycle, and the charger display cycles between charging and not charging. This stops when the sun gets to about three fists above the horizon, and the output is a steady 10A, and increases to 12-13 as the sun continues to rise.

    Connecting the same panels to the WRND, there is no voltage cycling, and the output is steady at about 5 amps.

    Connecting either the 220w FlexoPower panel or one or both Aco Power 120w panels (in parallel), placing the panels on top of the Tacoma panels (to achieve same orientation to sun, with Tacoma panels disconnected), the National Luna DCDC has no voltage fluctuation, and both configurations produce about 5 amps when the sun is two fists up, and increase to 10-12 as the day goes on.

    So I'm led to the conclusion that the two Tacoma 130w panels (which are a different panel type, as far as I can tell) struggle a bit more in low light, before coming into their own - but - what throws me is why the WRND has no problem with them. I guess there are some differences in the MPPT algorithm between the two controllers, which makes the WRND a bit better in the earliest and latest hours.

    I set the WRND up with Brad Harrison connectors on it, and it is what we use when RTT camping. Has a lead to the dual battery with a BH plug, so just plug and play. Can also carry it in the caravan on longer off-grid trips as a spare.

    Remain very impressed with the 40A NL, despite its struggles in low light with the roof-mounted panels - consistently get 40.5A from the alternator. I have plugged all 5 solar panels into it as well, in parallel, and got nearly 40A. Realize this is not optimal because the 220w Flexopower panel is a few volts lower than the others, which brings the whole system down a bit, but it still works well.

    The BlueNova LIFEPO4s are simply amazing pieces of kit. They use Bluetooth LE to output SOC percent, charge, discharge, and temp - which is quite handy. I have two installed in the caravan (Conqueror Companion), and added a 16mm wire pigtail with BH plug to be able to connect a third in a battery box, as needed. The battery's BMS system coupled with the NL 40a DCDC regulates the charge going into each very well.

    FWIW.

  2. The Following User Says Thank You to heyyahhey For This Useful Post:


  3. #2
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    Default Re: Observations on different solar panel performance / DC-DC charger performance

    Thanks fot your results with the different panels and controllers. It just goes to show how different configurations can give results far removed from each other and how the time of day affect them.

    For sure there are great and fast controllers working better than perhaps the cheaper versions.

  4. #3
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    Default Re: Observations on different solar panel performance / DC-DC charger performance

    Thanks a lot for this. I am contemplating buying the NL 40A controller for my Comfort trailer. I am thinking of going to around 280-320W panels at this stage, with the possibility to expand later on. I installed the Victron 15A smart charger and would have liked to install victron dc-dc also, but then I need another unit for solar input. Thus considering the NL 40A single unit for dual purposes.

  5. #4
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    Default Re: Observations on different solar panel performance / DC-DC charger performance

    Quote Originally Posted by Bassfisher View Post
    Thanks a lot for this. I am contemplating buying the NL 40A controller for my Comfort trailer. I am thinking of going to around 280-320W panels at this stage, with the possibility to expand later on. I installed the Victron 15A smart charger and would have liked to install victron dc-dc also, but then I need another unit for solar input. Thus considering the NL 40A single unit for dual purposes.

    Another point with the NL 40A is it has a third charging input. This was very helpful to me, because when I upgraded I also changed to LIFEPO4, and the Ctek AC battery charger that was in there was not recommended for them, so I needed to replace the charger.

    Rather than buying a lithium smart charger, I bought a 600w, 24V DC power supply. This I wired into the A/C supply from the distribution panel, to this third DC input on the NL.

    It will charge at the full 40A. There is a big "but" though - the fan in the power supply runs when it is at this output, and it's louder than I would like. The fan shuts down when the output drops below about 10A, so running regular loads, etc..., it does not run. In theory in a caravan application if you were towing to the campsite, the batteries should be charged - so should not be an issue - but something to keep in mind.

    Another factor is that the cables running back to the trailer need to be hefty - 16mm is recommended - to avoid excessive voltage drop, which will cause the NL unit to throttle back the charge. I actually needed to increase revs on my engine from idle in order to generate enough power - but only to about 1,400 - 1,500 - so in a normal driving scenario it would be fine. The vehicle had been sitting, plus has a dual battery itself, so the alternator was working hard.


    EDIT - sorry - did not register initially what you said about the Victron smart charger --- so my point about the additional DC input on the NL isn't really relevant to you anyway :-).
    Last edited by heyyahhey; 2020/06/03 at 06:09 AM.

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