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Need Help with Solar Panels & Renogy DCC50S MPPT

Flashman

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Aug 25, 2021
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Newbie here, so this is hopefully obvious to others.

I have two Newpowa 12v 160w solar panels wired in parallel.

My math using the solar panel specs shows that the maximum I would get out of these panels should be: (Vmp) 16.77V, (Imp) 18.6A, for a total watts of 312 watts. Not the "320" advertised, but close enough it seems.

They are plugged into a Renogy DCC50S MPPT charger w/ BT2 Bluetooth adapter.

First day of testing, the Renogy DC Home App (what a crappy app btw) informed me that it maxed out at 17.59 Amps and 236 watts. I attributed this to "well it wasn't that sunny, so that's fine". However, the second day of testing, Renogy DC Home App again said it capped again at exactly 17.59 Amps and 236 watts. Now that sounds like I'm hitting a hard limit of some sort - I'd expect to see variations between the two days. I went and verified my parallel wiring, that seems good. The vehicle was turned off during this time, so there was no competing alternator input. But even then, I think I am well within the DCC50S limits.

Thoughts, ideas? Stupid things I missed?

So new at this, I can make dead wires spark,
Rick
 
Thoughts, ideas? Stupid things I missed?

Any chance the app display isn't updating/refresting automagically? Controller output tends to fluctuate constantly as solar conditions and loads vary. I would bet heavily against getting identical readings in real life.

A battery monitor shunt before the house battery might be helpful here if the app is unreliable. Renogy makes one and there are cheaper unbranded ones out there.
 
Well, disconnect a panel and see what it says after a couple days, then swap panels. You might have a dead panel, or your batteries are full and it was only needing 17.59a to top them off and stop charging. Try throwing a heavier load on there and see if the numbers come out the same?

Also, the panels are rated by VoC x Max amps so I'd guess your VoC is 17.2?
I'm pretty sure I don't have a dead panel, as I am pulling 236 watts (and each panel is only 160 watts). Now the battery being close to full, hmm; if the battery BMS is capping its draw at 17.59a - that could explain two-days being identical. So I will attempt a heavier load on it and see if it increases the pull. Good idea.
 
Any chance the app display isn't updating/refresting automagically? Controller output tends to fluctuate constantly as solar conditions and loads vary. I would bet heavily against getting identical readings in real life.

A battery monitor shunt before the house battery might be helpful here if the app is unreliable. Renogy makes one and there are cheaper unbranded ones out there
The DC Home App refreshes whenever you pull it down, and in any case I was looking at previous day 'peak' values - so no real-time data is necessary. It is just a terrible app, not for data reliability (haven't seen any comments saying anything about) - but for interface and 2-screens of advertising and sales crap - and one tiny screen of useful data.
 
The BMS should not be "capping" the input current, that isn't what they do. The BMS will either allow current to flow or not.

Another test you might try is changing the angle of the panels or throwing some partial shade and see if the numbers change. You could also do a short circuit test on both panels as quick as you can after reading the the current through the system.
 
The BMS should not be "capping" the input current, that isn't what they do. The BMS will either allow current to flow or not.

Another test you might try is changing the angle of the panels or throwing some partial shade and see if the numbers change. You could also do a short circuit test on both panels as quick as you can after reading the the current through the system.
So you think it is possible to get identical peak values on different days with different levels of sun/rain/coverage? That is what seems like red herring to me that something else is going on.
 
So you think it is possible to get identical peak values on different days with different levels of sun/rain/coverage? That is what seems like red herring to me that something else is going on.

No, I agree it is strange. But the tests outlined could show that you have something else going on for sure. By eliminating some causes definitively you are moving towards the answer.
 
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