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pmcsurf1 avatar image
pmcsurf1 asked

4x100 watt Renogy panels on a Victron 100/20 mppt controler 12 volt

I have 4 panels in series and I've not had any issues yet.

I had 3 x 100 panels using the 100/20 mppt controler but my output seemed very low and my house back wouldn't charge well. Seems like I'd get around 7 or 8 amps changing. My soc panel never showed anything close to 20 amps. I added another 100 watt panel hoping to get more amps charging.

System seems to be working bit now I understand I'm over powered? My 400 watts rarely come up to 300 watts in direct sun so I didn't see the harm in having 400 watts on a 100/20 mppt.

Will the controler be damaged in the current setting or will it limit the out put automatically? Downsides?

Would a 30amp mppt be that much better?

Thanks

Paul

MPPT Controllers
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8 Answers
Alexandra avatar image
Alexandra answered ·

@Pmcsurf1

With 400W you should be able to see 20 amps full out of the mppt. As 400w ÷ 12v is 30Amps.

What is the VOC of the panels all added together? If you disconnect them from the mppt and check the voltage of all the panels connected do you read the correct (added) voltage there?

If they are fine, then it may be possible the connection in the MPPT is not great?

Your battery does not need a charge or is in poor condition and cannot take a charge, are other reasons for low amps.

What battery do you have?

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pmcsurf1 avatar image pmcsurf1 commented ·

I have six 6 volt flooded lead acid batteries. They are Trojan T105. Using the Victron Bluetooth app I've NEVER seen 20 amps going onto the batteries. Maybe half that. I dont know how to use this site so I'll share what my victron app was reading.

Been at a marina for several days plugged into shore power so batteries are charged.

App read:

Solar, 40 w, 81.87 v, current 0.5

Battery, 13.44 v, 2.90 A, state is float.

I'm assuming the mppt controler is limiting the panels to 40 w. It was a sunny day in Florida when this was checked.

I've heard that panels will only give you 75 percent of their rating. Is that why I never see 400 watts? Is that why I never see 20 amps?

Should I split my 4 panels from series to parallel?

Oy vey

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pmcsurf1 avatar image pmcsurf1 commented ·

Batteies les than 1 year old.

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pmcsurf1 avatar image pmcsurf1 commented ·

screenshot-20220315-161755.jpg

Sreen shot

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screenshot-20220315-161755.jpg (377.8 KiB)
pmcsurf1 avatar image pmcsurf1 commented ·

Update. Looks like an update. screenshot-20220316-135929.jpg

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screenshot-20220316-135929.jpg (537.4 KiB)
pmcsurf1 avatar image
pmcsurf1 answered ·

Does anyone's 400 watt rated panels actually put out 400 watts?

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Alexandra avatar image Alexandra ♦ commented ·
Yes in perfect operating temperatures.

They can even over perform when they are cold that is why the mppt calculator also has you set the mimimum temperatures for the area you are installing in.


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kevgermany avatar image
kevgermany answered ·

Starting from basics, the 20amps max output from your MPPT at 12V is 240W. In reality you can work on 14V, closer to 300W.

Your app shows the controller is in float mode, i.e. it sees the batteries as fully charged.

It might be the controller settings. And there is an exclamation mark over the cog wheel. Please open that up, tell us what you see there and also what the battery settings are.

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pmcsurf1 avatar image
pmcsurf1 answered ·

screenshot-20220316-140111.jpg

Today's screen shot.


screenshot-20220316-140111.jpg (389.7 KiB)
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Alexandra avatar image Alexandra ♦ commented ·
@Pmcsurf1

Check your rebulk offset as well.

You wont see 400W out of a 20Amp charger as @kevgermany mentioned. The charger is limited to 20Amps.

Another factor affecting output is panel temperature. If you check your panel specs you will see they are rated at 25°C. No panel is ever 25°C in the hot sun. So there will be derating there as well.

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pmcsurf1 avatar image pmcsurf1 Alexandra ♦ commented ·

Check your rebulk offset?

Really? I'm a noob.

Let me splane something to you. I'm thinking about paralleling 2 panels and series 2 panels. However, I've got 4 panels in series now with 10 awg from panels to mppt. Maybe 25 feet. Could I parallel 2 and series 2 and keep my 10 awg?

Bulk offset. Hmm

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pmcsurf1 answered ·

After update this is what happened. screenshot-20220316-140626.jpg


screenshot-20220316-140626.jpg (419.6 KiB)
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pmcsurf1 avatar image
pmcsurf1 answered ·

My soc shows 14.1520220316-141130.jpg


20220316-141130.jpg (3.6 MiB)
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kevgermany avatar image kevgermany ♦♦ commented ·
Sorry, but voltage isn't SOC. What it's saying is that you have 14.15V at the battery. That seems to be a good bit better.


If these two shots are at the same time, you have a wiring problem between the charge controller and the battery/master volt unit. There's also maybe some current bleed off, either due to DC loads, or wiring. There's about 13A going somewhere.
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pmcsurf1 avatar image
pmcsurf1 answered ·

After the reboot from the update things have leveled off some. Went back to float. screenshot-20220316-165334.jpg


screenshot-20220316-165334.jpg (384.1 KiB)
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kevgermany avatar image
kevgermany answered ·

Keep an eye on it. But it looks good from that.

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