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bilmcla asked

SmartSolar 75/15 low voltage under load

Hi There

first off thanks for reading my question, and thank you in advance for any answers that come through.

What was working perfectly fine now is not, and any attempt to run load from the “Load” terminals on the SmartSolar controller fails. Without any items turned on, the available voltage is 13.4v. As soon as you turn on something; a light, usb charger, etc; the voltage drops to 9v and renders the available power useless. I have a 12v 90w laptop charger. Plug that in and voltage drops to 4-5v.

the setup is as follows:

  • I’ve converted the kids cubby house to an outdoor office
  • 200w solar panel
  • SmartSolar 75/15
  • OMP 12v, 25a circuit breaker for each circuit. PV - Battery - 12v Load - 240v/500w inverter
  • Everything is cabled with Narva 50amp rated cable
  • 50Ah LiFePO battery
  • 12v load consists of 3 LED lights, usb charge ports, and 12v power sockets. This is connected to the Load output on the smart controller
  • Inverter has its positive connected directly to the battery, with the negative connected to the 12v load circuit so that in the event of the low battery, the circuit will cut out - as per the instruction manual.
  • Inverter is for a 32” Samsung Smart monitor.
  • 12v load and inverter are connected to a common ground bus.
  • As per instructions, PV is not on the common ground
  • Inverter power is not affected as it’s powered directly with battery
  • PV charging seems unaffected suggesting it’s specific to the Load component of the controller
  • Peak amperage is around 13amps

troubleshooting tasks already undertaken

  • Charge battery with mains powered car charger.
  • Swapped OMP circuit breaker from load with Inverter circuit breaker. No change
  • removed positive wire from load terminal on the controller and connected directly to battery. All other wiring unchanged. This resolved the problem and suggests a problem with the controller. Am currently running this setup for a number of hours and seems to be fine
  • Reset controller to factory defaults
  • Disconnected and reconnected all power to controller several times
  • According to the app, I have the Latest firmware versions installed v1.59
  • Battery setting set to always on
  • Jumper removed

Keen to hear of any other troubleshooting I should do or if you think the controller has a fault.

thanks again.

MPPT Controllersvoltagefaultlow power
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Please post some screen shots from Victron connect of the readings with no load and load.

And please don't connect load to the battery again.

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bilmcla avatar image bilmcla kevgermany ♦♦ ·

Hi @kevgermany

thanks for your response. The app only shows load amps, so doesn’t show any changes when you turn load on.

Below is load and battery voltage.


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png-image.png (164.2 KiB)
What are the panel readings?
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