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Drew McIntyre avatar image
Drew McIntyre asked

Charging Rate is Restricted by MPPT Controller

Greeting,

I have been successfully RVing with my trailer that has 2-100 W PV panels, 1- MPPT 150/30 charge controller (with Smart Battery Sense wireless V and T sensors) and 2- 12 V lithium batteries.

During our last RV camping trip I needed to run our portable 2200w generator due to trees shading the PV panels. The batteries were at 66% capacity.

The problem:

With a generator producing anywhere from 180 to 100 W over a 2+ hour period the battery charge went only from 66% to 70%. The trending feature shows that a small charge occurs in very short intervals and then flat lines for about 20 minutes and then repeats the same pattern. When graphed it looks like stairs.

Any ideas on what might be causing this problem would be greatly appreciated.

PS: I noticed the same stair step trend when I went back to PV charging.


Drew





MPPT Controllers
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klim8skeptic avatar image klim8skeptic ♦ commented ·
@Drew McIntyre what are you using to determine Soc?

Might be worth mentioning battery voltages, and post a few screenshots from the mppt and SBS.


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Drew McIntyre avatar image Drew McIntyre klim8skeptic ♦ commented ·

Thanks for your suggestion. I have included some screenshots below. Also, what does Soc stand for?


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kevgermany avatar image
kevgermany answered ·

SOC - State of Charge.

What's the capacity of your batteries?

Is the vertical line in the first graph when the generator started charging?

A graph of current Vs state of charge for the same period would really help.

Are there other loads during the period of the graphs.

Screenshot please of the BMV settings (from cogwheel, top right in you screen shots) as well as the ones previously requested.

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Drew McIntyre avatar image Drew McIntyre commented ·

I have 2 12.2V, 120Ah Lithium Batteries

Yes, the vertical line was when the generator was plugged in

Sorry, I didn‘t screen shot % charge vs amps

There were no other loads during charging

Addition screen shots below- thanks for your help!

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pwfarnell avatar image
pwfarnell answered ·

Isn't the stair steps just the rounding of the SOC value to whole numbers, so the graph is showing 66%, 67%, 68% etc even though the SOC is steadily increasing. The steps are very uniform and I am sure if you measured them against the 66% to 79% lines you would find that they are 1% steps. The charging power remains continuous. I do not think this is anything of concern.

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Drew McIntyre avatar image Drew McIntyre commented ·

Greetings, maybe the stepping pattern is typical but it took 2 hrs of generator running with no RV loads to charge batteries from 66 % to ~ 70%. In the past I could fully charge the batteries in this time or less.

To add some intrigue, see the below snapshot which is when my RV returned from the trip and fully recharged the next day in the sun using the PV panels. It looks like it went from a regulated stepping charge to unconstrained charging at about 72% SOC.


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