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tiannasins asked

150/70 MMPT not fully charging batteries and staying in bulk mode

Hello!

19 days ago my system started only bulk charging and only charging up to 13.56-13.59. It will not go into float or absorption. The only thing different I have done is updated the firmware when alerted to do so. The charge controller has had these symptoms once before and resetting the controller fixed the issue.

There are currently no significant energy draws on the system and I've had a full day of sun to test. My feeling is it's a faulty controller. Does anyone have any other recommendations on what could be going on??

Actions taken:

Reset charge controller on 3 occasions

Tested batteries - Good

Tested solar panels - Good

Disconnected battery sense - no change

Checked all fuses - no blown fuses

Reset charge controller to factory defaults - no change


System Details:

(2) 24 volt 320 watt solar panels wired in series

(4) 100 ah 12 volt batteries

150/70 Smart solar Victron MPPT

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MPPT Controllersbattery chargingMPPT SmartSolarsmart solar charging behaviour
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snoobler avatar image snoobler commented ·

I doubt it's the BMS. You don't indicate use of a GX, and standalone 12V with BMS can't throttle current. They can only disable charging cutting current to 0.

IMHO, your battery is at a pretty low state of charge (50%-ish), and

Recommend you go to user type and configure as follows:


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"Smart Lithium" are victron batteries, and you don't have those.


The vast majority of LFP battery charging occurs between 13.2 and 13.8V. Assuming you get perfect sun maxing out your panels to their 320W rating, you're going to need over 8 hours of full array output charging. That's likely going to take you 2-4 days depending on solar conditions.


If you're in the Northern hemisphere, the sun is about as far South as it gets, so your daily kWh is going to be notably less than ideal.


You have 5.12kWh of battery capacity, and based on your array performance, it's going to take you > 5 days to fully charge.

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tiannasins avatar image tiannasins snoobler commented ·

Great info Snoobler! I have smart lithium batteries from Renogy and this was the previous setting when it was working correctly. I have two 320 watt solar panels for a total of 640 watts. 20 days ago the weather was not as sunny and I was reaching a fully charged battery state.


Today during testing regarding the BMS (which wasn't the issue as you had indicated), I was watching my charging like a hawk. My volts went up to 13.48 (it's a mostly sunny day) and then it starts to drop. It goes back down to 13.28 for some reason even when it's receiving 110 watts of solar. I've turned off all 12 volt and there is nothing drawing power currently. This is the behavior it's been exhibiting over the last 20 days. :(

I will try your custom setting and see if that helps at all. Thank you for your suggestion!

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Alexandra avatar image Alexandra ♦ commented ·
Could be the temps we are seeing there the battery bms affecting the charge.
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tiannasins avatar image tiannasins Alexandra ♦ commented ·

Thank you for your suggestion! I will investigate and report back once I've followed directions to reset the BMS.

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tiannasins answered ·

It does seem to be the BMS malfunctioning. I'm working with Renogy right now to fix the issue. Thank you for everyone's help! I'll reply back with the solution once I find out.

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