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wheelsd avatar image
wheelsd asked

smartSolar 100/20 output drops to OFF state

HI, I have a smart controller Mppt 100/20 controller in my caravan. Since installation I have noticed that when connecting any item , by either a connection to a 12v lighter connection or installing fuses, that the 12v output from the controller drops to OFF state for a period of about 1 sec then turns on again. With the solar panels , 2 x 180w outputting about 20v, disconnected this does not happen. In this state I can see from the app that when the TV for example is connected to a 12v power that the surge current is about 300ma. This would seem to be too low to trigger short circuit protection levels. The controller is set for loadcontrol of smart battery and no links inserted. The problem is not load dependant, that is the load output drops to OFF with all lights , fans etc on or off when a TV is connected to 12v point.. Max load with everything running is about 8amps which is well within the specs for the unit. Measuring battery voltage at BAtt connection points shows no drop in voltage. Any help appreciated.

smart solar set-up help
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marcv avatar image marcv commented ·

Hi all, I had the same problem. This evening I figured out a solution, which worked for me. I put a 12V transformator after the load output. It appears not only to stabalize the LED lights connected directly to the output of the transformator, but also the complete load connected to the SmartSolar. To illustrate, I made a simplified diagram:

I hope this helps you too!


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Paul B avatar image
Paul B answered ·

How is the charger connected to the Battery connections, as it should be connected directly to the battery, then see if you have the same problem

Also instead of measuring the 300ma what is the spike voltage occurring at that same time, and work out why you are having that spike


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wheelsd avatar image wheelsd commented ·

HI Paul, Controller is connected directly to the battery. Can see some voltage disturbance but its not clear if its due to the load output turning off. The issue occurs on two different 12 v feeds. One is with 12v cigarette lighter type connections which is the one where the TV plugs into and the other feed powers the Radio. The TV is just connected and goes into standbye mode so not a lot of power being drawn. The radio starts and also goes into standby mode. Again not a lot of drain. I dont know how the controller works. Does the solar panels provide the 12v load if possible and the controller swith over to battery if the solar panels cannot supply the load. This may account for the approx 1sec disconnect of load output. If I use a 10mtr battery extension lead to power the TV the problem is not there. Its definitely seems to be some surge issue.


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Paul B avatar image Paul B wheelsd commented ·

Again until you do your voltage measurements and advise with how its connected I cant help sorry

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wheelsd answered ·

HI Paul,

the controller has a direct connection to 2 x 12v batts connected in parallel.

The solar panels are hardwired to the controller.

The load is connected to the controller via a switched relay. ie the 12v mains switch in the RV operates a relay to connect 12v to a small fuse distribution box.

With a multimeter across the load terminals the voltage drops to 0 when the TV is plugged in. It is not possible to see if anything else as its not a recording voltmeter.

Installed the above mentioned 12v extension fridge lead between the 12v cigi lighter RV connection and the TV 12v plug I can see the voltage goes from 12.45v to 12.43v when the TV is connected. The 12 volt output from the controller remains ON.

The above symptoms are consistent across 3 different 12v feeds.

Feed 1 - 12v outlets

Feed 2 - a radio ( that goes into standby mode when power is connected, a tank water meter which is off and ceiling lights which are also off.

feed 3 - exhaust fan / light combo and gastop lighter. All off.

The fuses can be removed from any two of the above the issue will remain with the 3rd.

I cannot give you any more information apart from that the fault does not exist with a prostar solar controller. If your wondering I swapped over so I could use the remote temp/voltage sensor and the App.


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JohnC avatar image
JohnC answered ·

Hi Wheels. If your 12V loads are connected to the LOAD terminals of the mppt, then this is likely your issue. And of course it's understandable if you have done it that way. But those terminals aren't suitable for surge starts or inverters.

Wire your 12V loads directly to the batts, and if you need the 'low V' protection of those terminals, just drive a relay using them to trigger it. Maybe your existing relay could fit easily into that scenario?


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wkirby avatar image wkirby ♦♦ commented ·

Yes, I'm certain that the TV is presenting a high inrush current which is tripping the Load Output momentarily. The long extension lead provides enough resistance to limit the inrush current to the TV.

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wheelsd answered ·

HI Guys thanks for the answers. I do find it hard to understand how a 24inch tv or a car radio has sufficient surge current at startup to trip the output control of the solar controller. Especially when the load output voltage measured at the controller changes by millivolts when the TV is connected. I am afraid I have wasted my money as this thing is just too sensitive so will try and return it.

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