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tweetybird avatar image
tweetybird asked

MPPT 100 30 only charging at 13.2 volts

I have 4 100 watt panels in parallel into a 100 30 controller, I have it hooked to 1 100 amp hour lithium phosphate battery, and the rotary switch in that mode. I went out today and had 19 volts coming from the panels to the charge controller, but only 13.2 volts going from the controller to the batteries. It was in the bulk mode. Shouldn't it charge at higher voltage?

mppt charging
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5 Answers
randy-putnam avatar image
randy-putnam answered ·

Is this a smart MPPT, and if so, can you check the settings on your iOS or Android device? If not, be sure the rotary dial is set to LFP battery profile, and finally is your BMS limiting the voltage to what would be float voltage even though the MPPT is set to bulk?

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tweetybird avatar image
tweetybird answered ·

I am new to this. I do have the rotary dial set to LFP profile. I looked back thru history and the last 5 days is all i saw, it showed 0 watt yield and 0 watt P Max and the battery has been losing voltage every day.

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randy-putnam avatar image
randy-putnam answered ·

OK. I’m confused. You know you have measurable voltage from the panels into your MPPT and out to your battery, and you have 5 days of history showing no watts from the panels, which says to me that you have a smart solar MPPT (same model as mine) and a way to look at its performance via your iPhone or android device. When I have no results showing from my panels into and out of the MPPT it‘s usually because my shore power battery charger is on and charging the batteries, which will override the MPPT.

The fact that you are losing voltage every day says there is no charging going to your LFP battery. What it is the brand? How old is it? Do you have any loads running off it when you measure the voltage?

My Battle Borns have a 13.9V charge profile and the MPPT absorbtion/float parameters are 14.4/13/5.

Hope some of this helps.

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tweetybird avatar image
tweetybird answered ·

I will run out tomorrow and have a better look


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seb71 avatar image
seb71 answered ·

Check (with a multimeter) the polarity of PV wires at the MPPT PV terminals.

So check if "+" PV wire is connected to "+" PV terminal and "-" PV wire is connected to "-" PV terminal.


What is the VOC of your 100W panels?


If you do not have any shading issues, you should make 2 strings of 2 panels in series and then conect those 2 strings in paralel.


Depending on the VOC of your panels, maybe you could connect all 4 panels in a single string (all 4in series). But only do this if 4xVOC is smaller than 100V (with a safety margin).


Also, you can tweak the LFP charging settings (and make a custom profile).

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