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simon-bernin asked

[solved] SmartSolar 75/15 overload protection / on/off pulse

Hi,

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. :)


Best regards


Simon


EDIT:

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.

Solutions:

-GreatScotts's board

- 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.


MPPT Controllers
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2 Answers
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simon-bernin answered ·

I have contacted Victron directly. They say, that this is normal behavior for overload and my capacitive load is not suitable even though it stays way below the 15 A of discharge current. I'm supposed to use it on the battery or with a relay. There will be no change in the timeout for overload...

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adev avatar image adev commented ·

similar issue here..

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simon-bernin answered ·

Hi,

I contacted Victron again and mentioning the overload of less than 5 ms seen in the video, they said:


"At the moment they are looking at improving the DC load output.

In the manual at section 3.6 and picture 5 we show how to deal with inverter loads and the MPPT, for bigger DC loads the Battery Protect was invented."


@adev

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adev avatar image adev commented ·

Nice response. Presumably that means changes to the hardware, so no help for existing systems.

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simon-bernin avatar image simon-bernin adev commented ·

Yep, I guess so. Reading other posts, they already lowered the max amps a few times with each generation. I got it to work with 20 cm of coiled 0,2 mm^2. Literally not cool for 15 amps, I know, but it works for the max. 3,5 A the psu needs when running. In fact, there is a visible electric arch when you connect it without the coil.

I also purchased a miniature 25 A relais from Fujitsu ( FBR51ND12-W1), and might use it for the trolling motor to disconnect it from the battery in case the voltages drops to much.




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