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MPT-7210A Questions
Hi All,

I've been charging my 48V 1.3kWH pack from a 160W panel in my patio, using an MPT-7210A. I followed some Youtube videos on how to set it up, get it to auto-charge, etc. but I've discovered some odd things about it so far and I can't tell whether I have a defective unit or whether this is "normal".

First, I can't set the fan speed to anything besides 100% power otherwise the output gets unregulated and the screen flickers. I've made a video which I shared with the seller, who is asking me now how much it will cost me to "repair at a shop" so they can give me a partial refund. Otherwise they seem clueless about this issue:

Second, it does not seem able to charge constantly/consistently. Most I've seen it put out is 107W into the batteries, which is fine for me, but after 30s(?) of running at ~100W, it then shuts off the output, "rests" for a while, then slowly ramps power back up to ~100W. Is this a setting issue, is it overheating, is this just normal? This may be why I'm only getting ~110WH on a sunny day even though I should have at least 2 hours of direct sunlight.

Any comments from others who have used this cheapo controller would be helpful, as I'm still just starting out/learning about solar charge controllers.
ramg likes this post
Sounds to me like something is getting hot inside and thermally shutting down. Watching the video, it looks like it's possibly the power regulator is causing an issue with the screen. Or an incorrectly sized capacitor and it's constantly getting drained/recharged, causing the flickering.

Other than that, I'm not sure. Confused
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In parts 3 and 4 he talks about replacing the capacitors both smd and the lager ones on the board.
Mikes DIY Powerwall Update 31 MPT-7210A MPPT Solar Charge Controller Testing Part1/4
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Korishan and cmg_george like this post
Thanks, I'll check those out. Looks like he replaced the fan also in a later video.
Hmm first one seem to be an error. The 2nd can also be related to the set tracking point. What voltage are your panels and what tracking point have you set?
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Still can't figure out the fan issue; tried adding a bigger capacitor in parallel with the fan output but it didn't change anything. Instead I switched to a larger, quieter, and as it turns out twice as power efficient (~82mA vs ~160mA) 80mm fan and 3D printed an adapter for it. At least this way it's quieter and using less power at 100% setting:


File is here if anyone else wants to do this mod, it's not very good for airflow since it's offset and very shallow of an adapter, but it's probably still about the same airflow as the original 40mm fan:

Otherwise, I did the 100nF -> 10nF mod for C22,23,24 as Mike did in his Youtube videos, might help a little, not yet sure. I'll add a pair of 2200uF 50V capacitors on the input from the solar panel also which may help a bit with quick voltage drops like a plane/bird flying by.

I'll also be adding in an ESP8266 (D1 Mini) and current/voltage logger from here: also.

(01-25-2018, 07:54 AM)daromer Wrote: Hmm first one seem to be an error. The 2nd can also be related to the set tracking point. What voltage are your panels and what tracking point have you set?

Tracking point is set to 35.1V, panel is a 160W Pmax panel at 35.1V Vmp and 44.2V Voc.
hbpowerwall and Korishan like this post
Here's some scribbles about the circuit diagram if anyone is interested, I only bothered with the main power path so I can add a logger and some bits trying to figure out what was wrong with the fan: 

The shunt before the battery output is approximately 10mOhms, which gave me 9.64mV/A at 2A load.
Finished adding the logger to the MPT-7210A, data is live here (just charging from a bench supply at the moment, but it'll show live solar data starting this evening, though I won't be charging the battery since I'll be out for work travel the next 10 days:
hbpowerwall and Korishan like this post
Well, got back from vacation and found out I had reversed the polarity of the panel like a dummy, so I only have one day of solar so far. Today it didn't seem to record any data even though it got lots of sun, probably because the MPT-7210A is in a metal cabinet (outdoors) with poor Wi-Fi, even though it's only about 10' away from the access point (indoors). Here's the log it recorded from the bench test charging a battery, then the solar panel voltage log from yesterday:

What are you using for a data logger?

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