question

easy-rooster avatar image
easy-rooster asked

Trouble getting 100/20 Charge Controllers to fully Charge batteries, enter float before full charge.

(System details at the bottom of this post)

Headlines:

Both 100/20 MPPT charge controllers (configured identically) enter float before batteries are fully charged (set to 28.4 volts by the BMV-712) and even below the float voltage, which is set to 27.2V (Float is being entered around 26.9V, which is about where the BMV and MPPTs settle with a variation of about 0.04V between them, seen in image below)

I've ensured the charge controllers are reading actual battery voltage at night (via history), not just reading 0V

Charge controllers connected via closed breakers, and the solar system is capable of delivering around 700w when I do something like turn the AC on mid-day. I can watch the power flow via the Cerbo GX console window on my laptop

They also will charge the batteries, just not to full capacity.

The batteries will charge to full capacity on shore power (or generator, same thing.)


Additional Information:

I've given the following threads a read, and tried my best to follow along and check off things where I could understand:

https://community.victronenergy.com/questions/83517/batteries-not-being-fully-charged.html

https://community.victronenergy.com/questions/193395/smartsolar-goes-to-float-before-batteries-are-full.html

https://community.victronenergy.com/questions/171324/24v-battery-bank-in-float-before-bulk-charge-volts.html

I've also consulted the online Victron and Battleborn documentation for ideas. Here is the documentation for my batteries (I have 2 in parallel for a 24V 100Ah system)

https://battlebornbatteries.com/wp-content/uploads/2022/10/BB5024-Manual-Edition.PIM_BB5024Rev018_09062022.pdf

Some screenshots:

OK, so only one screenshot, the forum isn't allowing me to upload anything else, just throwing errors. So I'll just dictate.

Second Screenshot was settings from the BMV-712

100Ah

28.4V

0%

4.00%

3m

1.25

95%

0.10A

3m

Third Screenshot was settings from one of the 100/20 charge controllers (Both identical)

24v

Charger Enabled (on)

User Defined

Expert Mode (off)

29.00V

27.20V

28.80V

Equalization - Disabled


Full system Outline:

4x Rich Solar 200w panels, each divided into two strings for each charge controller.

2x MPPT 100/20 Smart Solar charge controllers

Smart BMV-712 w/Smart Shunt

Cerbo GX (connected via hard line VE bus links to BMV-712 and both charge controllers.

2x Battleborn 24V 50Ah batteries in parallel

MultiPlus 24/3000/70

Orion 24 - 12v converter (for RV 12v system)

MPPT ControllersBMV Battery Monitorsmart solar charging behaviour
img-2414.png (308.7 KiB)
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2 Answers
klim8skeptic avatar image
klim8skeptic answered ·

@Easy Rooster Have a look at the Cerbo manual, esp the section Distributed Voltage and Cuerrent Control.

You can get the Cerbo to share the voltage, current and temperature measurements from the BMV to the mppts.

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easy-rooster avatar image easy-rooster commented ·

OK, I gave it a couple reads. What stood out to me was that it turns over the charging algorithm to the Inverter, rather than the MPPTs individually.

I don't have to worry about the batteries since they each have their own BMS/protection, the manual says communication isn't needed or available.

https://www.victronenergy.com/live/battery_compatibility:battleborn

There was a thing in there about configuring the BMV-712 to be a DC meter, but I think I'd rather have it as a battery monitor, and DC loads are pretty minimal usually, so I don't think the loss of charge current would be a problem, the solar system charges the batteries up to 84ish% quite quickly.

After switching the DVCC on, we are now charging the battery in bulk mode, and getting the voltage up now approaching a full charge. The phone app showed we were in bulk, now we are in absorption...and running out of sunlight.

Thanks for the direction, this experiment may need tomorrow to complete.

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klim8skeptic avatar image klim8skeptic ♦ easy-rooster commented ·

@Easy Rooster Your BMV settings need a bit of tweaking also.


Second Screenshot was settings from the BMV-712

100Ah

28.4V

10%

4.00%

3m

1.05

99%

0.10A

3m

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easy-rooster avatar image easy-rooster klim8skeptic ♦ commented ·
This does seem to be working, I was gone most of the day, came back and we were floating at 27.2V


I also updated the BMV values as you suggested.


I made my BMV mad when I did click over to DC meter mode, then back to battery monitor, it has forgotten the SOC and so won't displace that or time left. I suppose when I get home, connect to shore power and let it settle out again it'll fix itself.

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kevgermany avatar image kevgermany ♦♦ easy-rooster commented ·
DC meter isn't going to help.

As you're on solar, you can increase detection time. Clouds cause charge current drops which can trick the system into early float.


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easy-rooster avatar image
easy-rooster answered ·

Would any of this impact how much power is being pulled from the grid(generator)? It's been hot lately so I've been running the AC and using the generator to supplement solar. However it doesn't seem to want to pull the maximum power from the generator to assist recharging the battery, it kinda just stays somewhat level +/- about 100w or so either going into, or coming out of the battery.

I have the current limited to 13.5 Amps, it's only pulling about 8 at the moment. I've seen it pull the full amperage (roughly 1500 watts or so) at times, but right now it's only pulling about 1000 watts.

I'd like to to pull power to charge the battery too, battery is currently at about 62% charged, been pretty steady around there all day.

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klim8skeptic avatar image klim8skeptic ♦ commented ·

@Easy Rooster have a read of the MultiPlus generator FAQ.

You set the AC input limit to 13.5a. What are the specs of your genset?

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