I just bought the SmartSolar MPPT 75/15 and wanted to use it with a 12 V battery and 200 Wp solar setup. I connected a load: 12 V / max. 120 W notebook charger with its own 15 a fuse. The load keeps switching on and off in a pulse pattern, as it has been described before here in the forum. Directly connected to the battery (or to a 10 amp $3 pwm controller) it works fine.
The battery was fully loaded, the charger was in the floating mode. I had the jumper removed and set the load to always on via bluetooth. Firmware versions were the latest available today.
I suspect the device's electronic over load protection to be responsible. For what ever reason it might be reconnecting the load after 2 seconds...
However, the device should be able to handle it according to the device's specifications. I know the instructions say that some loads might a have too high starting current, but then the timeout for the overload disconnect is definitely too low. And why is it reconnecting instantly? Or is it just the 12v switching power supply it can't handle? Has somebody experience with inductive loads? I want to connect an electric boat trolling motor with also 15 A max and I fear that it won't be able to handle it.
Also, I know I could also use a relay or keep it directly connected, but what's the point of spending a sunday afternoon looking through specifications and then buy a product, when it doesn't do what was promised? Especially in this price category...
The rest of the charger seems to be neat though. :)
A video from GreatScott on youtube (thanks to adev for linking it down below) shows how capacitive loads can cause a current of more than 15 A for less than 5 ms, which causes the overload protection to trigger a bit early.
- Around 20 cm of coiled 0,2 mm^2 wire at the load output (good for less than 5 amps, I guess)
- Miniature 12 V relais with more than 15 A, e.g. Fujitsu FBR51ND12-W1
tip for the relay: Invert the power output via the app, and use the relay's standard connection to save the power for the relay's coil.