Assembling a simple system. Which charge controller?

DIY
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1

Have a panel w following specs
250 watts
VOC 37.3 v
Operating volts. 30.1
Operating current 8.31 A
Max fuse. 15A

Battery. 100 ah lifepo4

Is the smart solar. MPPT 85/15. The one I want to use?

Will initially just be loading a 60watt. 12 VDC
Mini fridge.

Thanks

2

250W to 12vdc is 20A.
[You can pop you panel spec here] for a recommendation (MPPT Calculator - Victron Energy) or use the dtabase list and pick out your model if it is a known manufacturer.

Otherwise off the top of my head a 75/15 will work or a 100/20

3

Good info thanks
Unfortunately I don’t have a victron panel
250 watts. 30 volts

Want to use w lifepo4 12.8 volts

So maybe the 100/20 controller?

4

You don’t need a victron panel. The database in the calculator has jinkos and others.
If you don’t want power clipping the 100\20 is the better choice.

5

I think I’ll go w the 100/20
Can you explain power clipping

Thanks

6

Alot of it depends on installation circumstances.

But the basic math is 15A x battery voltage.

250W ÷ 12v is 20.83A. but your battery will rise to around 14v. So the same equation you will have a potential of 17A

If you use a 15A mppt for example anything above 15A of charge can not be used. So it will be clipped as it cannot be used. So you can loose a few watts.

However that being said, in real world conditions during most of the running you hardly see the full power out of a panel because of either irradiance or temperature. (Or at least we don’t because of location)

The choice i have seenalmost always come down to purchase cost anyway.

7

So I have assembled the above system and am pretty much loving life.
One issue I am having is whenever the charge controller switches to float (green light) the inverter trips out. If I turn inverter off and back on it works again. Don’t know if this is damaging inverter or how to stop this from happening.
Any input will be appreciated.
Thanks

8

Perhaps I should mention that inverter is hooked directly to battery not thru load terminals. I had read something once that mentioned maybe not to do that?
Plus I am using much heavier cables going from battery to inverter.

9

The way You connected the inverter is the right one: load output is not the best way to connect serious loads (it’s ok for LED lights and such).
As for cables from battery to inverter: the heavier they are, the better (within some common sense, of course) - the resistance is less and so is the loss of energy.

Does the inverter show any error when tripping? One thing I could imagine is that the transition from absorption leads to voltage drop - maybe inverter treats it as fault?