question

mikedf avatar image

Mppt 75/15 doesn't charge thought the load terminal

Hi there,

I'm having some issues with my smartsolar, that doesn't provide enough current through the load output. Everytime a load tries to push/start to operate, the mppt voltage on the app goes up and down like something is wrong.

Any way I can find how to fix this or what could be the reason?


MPPT - Solar Charge Controllermppt smart solar
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4 Answers
mikedf avatar image
mikedf answered ·

I'm using the smart controller with a 110w solar panel to power just a fridge and charge some appliances...the mppt is also connected to the car battery...been using this way for a while, but only the past few days came up with this issue. At the moment basically can't power more than a phone, and the mppt cuts off...tried to connect the fridge straight to the battery, but then the mppt doesn't charge the battery enough and fridge cuts off.

The only different thing I notice now is through the victron app that the voltage goes up and down fast and just doesn't do its job.

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seb71 avatar image
seb71 answered ·

Some PV voltage drop under load is normal.

But how big is the load?

Any difference if you power the load directly from the battery?

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michelg avatar image
michelg answered ·

Hi Mike ! How many panels do you have connected on your system, and also what kind of loads are using on the mppt ? (Watts / Amps consummed would be interesting to know).

Also, the size of your cabling to the battery ? Also, from the manual :

Some loads with high inrush current can best be connected directly to the battery. If equipped with a remote on-off input, these loads can be controlled by connecting the load output of the controller to this remote on-off input. A special interface cable may be needed. Alternatively, a BatteryProtect may be used to control the load.

Michel

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Thanks for your comment Michel.

Any chance my mppt is broken? And not charging properly?

Anyway to test it?

Cause my issue is that even with the load connected to the battery, the fridge doesn't start, and the battery is good because it starts the ute. Seems that the mppt doesn't get power from the solar to charge the battery.

Thank you

Cause my issue is that even with the load connected to the battery, the fridge doesn't start


I hope that in the above by "load" you mean the fridge.


And not the Load output of the MPPT.

Yes the fridge

Do you know how many Amperes does that fridge draw?

When you power the fridge directly from the battery, does it work for a while or it does not work at all?


A car battery is not good to be used as a storage battery. It is designed for a large current draw (for engine start), but for a very short time. After which it is immediately charged back to full.

The fridge draws around 5amps when is working...that's what I used to see on the victron app.

Connected to the battery it used to work for a few hours, but last time I used didn't even started...also the fridge has a cut off battery protection at 12.5v.

Cann you test your system with some other load?

Maybe the fridge is defective now.


Or test the fridge somewhere else.

The fridge works when I turn the car on. And attempts to start when connected to the load output. But not even the phone can charge from the load output.

Well, it seems that the transistor or relay is burned. Two options : either replace the mppt, either connect directly everything to the battery. I'm not sure if there is a fuse, that could have protected the load output. Try asking here to someone from Victron Staff.

Michel

Thanks Michel.

I believe more that's what's happened.

Anyway to test for a burnes transistor? How can I found out? How does that happened?

At this point, better contact the seller.

Thanks a lot for the comments guys

Make sure that you check the fuse in the bottom of the mppt plz.

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mikedf avatar image
mikedf answered ·

Also I'm using a 15amp cable from the battery to the mppt with a 20amp circuit breaker.

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Protecting a 15 amp cable, with a 20 amp circuit breaker is bad news.

seb71 avatar image seb71 klim8skeptic ·

Maybe he means a DC switch rated for 20A.