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

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easy-rooster asked May 28, '23

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 Controllers BMV Battery Monitor smart solar charging behaviour

img-2414.png (308.7 KiB)

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Modifications Space

Node Red Space

Answer 1 · 2023-05-28T22:52:21Z

klim8skeptic answered · May 28, 2023 at 10:52 PM

@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 commented · May 28, 2023 at 11:51 PM

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 ♦ easy-rooster commented · May 29, 2023 at 12:28 AM

@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 klim8skeptic ♦ commented · May 30, 2023 at 02:42 AM

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 ♦♦ easy-rooster commented · May 30, 2023 at 03:02 AM

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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Answer 2 · 2023-07-13T23:58:20Z

easy-rooster answered · Jul 13, 2023 at 11:58 PM

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 ♦ commented · Jul 14, 2023 at 08:32 AM

@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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easy-rooster klim8skeptic ♦ commented · Jul 14, 2023 at 01:01 PM

It's a Honda EU2200i, so 2200 watts maximum. I limit the input to anywhere between 12 and 14 amps (been playing around with it, I limit the power to take it easy on the generator and not run it ragged) which at 120 volts would be 1440 to 1680 watts.

I can trick the system into momentarily giving me full power by turning the AC off and then back on, the surge load will get the Inverter to pull the full 1500+ watts but only for a few moments before it settles back to drawing 1000 watts.

Charging the battery yesterday evening as solar power diminished to zero, it continued to pull that same 1000 watts +/- ~100 until the battery was charged from 41% to 90%

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klim8skeptic ♦ easy-rooster commented · Jul 14, 2023 at 06:47 PM

Do you have Charge Current Limit enabled?

CCL will limit the charge current into the battery. Solar charge gets limited last, mains/genny gets limited first.

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easy-rooster klim8skeptic ♦ commented · Jul 14, 2023 at 08:54 PM

To protect the batteries sure, I remember setting up a charge limit but it's probably like 50 amps or something. Right now the battery is just taking an amp or less, when the sun starts to go down it'll start draining the battery. The generator is just stuck at ~1000watts, and it's not the generator. I plugged in another appliance to it and using the Honda app I could see it pull the 250 extra watts and deliver ~1250 watts.

And it's behaving inconsistently. When I got back to the RV this afternoon and fired up the AC and the generator, it pulled the full 1500 watts I had it limited to. It fully charged the battery and started limiting solar current and ran the AC (and the rest of the rig) with the 1500 watts and a little bit of solar. So I shut the generator off and let the AC run on the batteries for about 45 minutes, got it down to about 60%, turned the generator back on and it's back to this 1000 watt behavior.

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easy-rooster easy-rooster commented · Jul 14, 2023 at 08:58 PM

The inverter is currently in power assist mode, not sure if it was in a different mode earlier.

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1689368225100.png (107.1 KiB)

easy-rooster easy-rooster commented · Jul 14, 2023 at 09:28 PM

OK, I think I understand what's happening. When the inverter goes into Power Assist mode, it stops trying to charge the batteries and just uses solar, battery if needed, and the generator, to run the house loads and it seems to prioritize the grid last, which is why as the sun goes down the battery will start to drain.

I turned the AC off, let the battery charge up a little and made sure the Inverter went back into whatever mode it's normally in when it allows charging, then fired the AC back up and the generator is now giving up its ~1500 watts and charging the battery again.

It seems like just charging the battery draws so much current that it flips the inverter into Power Assist mode and stops trying to charge the battery, causing the weird shore power behavior.

Does that sound right-ish?

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easy-rooster easy-rooster commented · Jul 14, 2023 at 09:36 PM

Why won't it just charge the battery slower and stay in bulk charge mode? If it would just charge it at 15 amps instead of the 43 or so it wants to do it would all be fine.

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