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Steve avatar image
Steve asked

Four Smart Solar Controllers Have Different BAF Charge Times

Searched but have not found an answer ... So have a question.

I have no grid connection.

Have a BMV 712 and 4 150/35 Smart Controllers all talking to each other via bluetooth on VE network. Firmware is up to date on everything. All pieces have identical battery and charge parameters and thus to absolute best of my knowledge are programmed identically. All properly tied into same bus and should get identical feedback and sense the same thing.

So as I understand, when linked like this, they are supposed to act as one big single controller ... correct ?

Here is my problem .... when I look at the histories, on any particular day, none of the chargers have identical Bulk, Absorption or Float or Total Charge Times (adding up BAF) on any day.

If they act as one then shouldn't all four be identical time with the only variation being minute rounding ?

There does not seem to be a pattern either.

Controller One isn't always the shortest Bulk charge time. That idea can be followed through in all combinations and permutations for each charger and type of Charge (BAF)

Total Charge Time for the day varies for controller 1 to 4 (adding all the times up for each charger). Sometimes one is longest and sometimes 3 etc

Time variation can be 15 to 20 minute in a BAF individual cycle or for the day. (Seems like a significant variation to me)

If they all act as one, then they should all show same times within minute rounding variance would they not ?

And if there is a master then shouldn't the same controller consistently kick out first in each phase and for the day ?

Is this normal ? Is there something not synced correctly. Is there some simple piece of programming that I forgot to enter ?

I would really expect them to have tighter tolerances if acting as one.

Thank You For Your Help

Steve

MPPT SmartSolar
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2 Answers
Michelle Konzack avatar image
Michelle Konzack answered ·

Victron Energy products are very excelent but nothing is perfect.


If you do not use the VE.Can versions, which syncronise the Output Voltages ofvthe MPPTs (up to 25) the a small manufacturing tolerance of 50-100mV can produce a significant difference. Also the contacts could get humid and corrode. Only mili Volts each, but they add, hence you will never get same results on your 4 MPPTs.

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Steve avatar image Steve commented ·
New Installation and contacts are fresh. No difference in temp at any connection. Everything with torque spec is torqued to spec. No voltage drops in any connection or wire run. Wires have more than sufficient capacity.


It's not voltage differences between them that I can't figure out.

As for Voltage between them all ... they are very consistent and especially averaged over time. So I do not question the voltage.

It's the time they stay on a charge cycle .... bulk mode for example.

Is Charger Y staying on bulk mode 20 minutes longer than Charger Z considered to be normal ?

To me, that seems to be pretty significant variation and hence the question.

If they talk to each other, what should be the time difference be for them all to switch from Bulk to Absorption (for example).

Charger x is still in bulk mode while charger y is reading everything like its in absorb because y is in absorb.

Is My description and thought process making sense ?

Steve

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Michelle Konzack avatar image Michelle Konzack Steve commented ·

Do you have GX device installed, which control the charging?


You write:

If they talk to each other,

If you do not have a VE.Can version, then the do not communicat to each other.

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snoobler avatar image snoobler Michelle Konzack commented ·

@Michelle Konzack

Please read the OP's post. Clearly indicates communicating over a VE.Smart network. VE.CAN isn't the only way to coordinate MPPTs

https://www.victronenergy.com/media/pg/VE.Smart_Networking/en/synchronised-charging---further-details.html

"Connect multiple SmartSolar charge controllers together in a VE.Smart network to make them charge the battery as if they were one large charger. The chargers will synchronise the charge algorithm between themselves, with no further hardware required. They will simultaneously switch from one charge state to another, for example from bulk to absorption."

@Steve

I would triple check that all settings, including Expert, are truly identical across all four units.

Are you certain this is real? Minutes in each phase may not be comparable to VE.Smart networking status. While you may see discrepancies in times in various phases of charge, do you actually observe the MPPT in different phases? Per the linked doc, each MPPT regulates its own output. While the master may be dictating the phase of charge to all attached units, the individual units may be reporting the phase they would report in standalone mode.

So please, take the time to watch your chargers' behavior and see if they truly report different phases of charging.

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Steve avatar image Steve snoobler commented ·
OK... I will do those things.

I'm highly confident that they are all programmed the same way BUT I do know that sometimes there is some little forgotten part in obscure corners that makes everything work.

The the observations for time differences are from review of data found in the history section for each charger.

How do I figure out which is the master that tells the other ones ? I see no consistency as to the same charger always going from bulk to absorb first (for example). one day x will be first, next day y, next back to x then next day it's z charger. (make sense ?)

Thx

Steve

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snoobler avatar image snoobler Steve commented ·

Again, I want to emphasize that you're assuming something should be a certain way based on historical data. The manual doesn't indicate this. The networked chargers may be logging individual data rather than network data. I don't know. I also come from the perspective that coordinated charging is of very limited value. You won't charge faster or better in the vast majority of cases. Multiple chargers are only beneficial in the bulk phase. Once absorption is reached, the batteries can't accept peak current, so chargers will fall to float randomly as each is no longer able to deliver current to a nearly full battery. IMHO, this is mostly a novelty where the only benefit is a spreading of normal "wear and tear" across the connected chargers.


The first logical step is to see if the chargers behave as the documentation describes, i.e., they are all reporting the same state and transitioning from one state to another. The documentation doesn't indicate that they will report the same times in the same states.


I'm assuming that you can see all four of your chargers and the shunt in the VictronConnect device list. This list should also include the state of each charger. I would expect to see these reporting the same state. However, also worth noting that voltage, power and current are also reported. If these are relatively proportional to each other and their respective arrays, I would say the chargers are behaving as intended regardless of the reported state.



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albert-legrrand avatar image
albert-legrrand answered ·

@Steeve

There is one thing that you ignore or forget: when an electronic system reads a voltage or a current, it's a component called an analog to digital converter (ADC) which takes care of it. The result is discrete, that's to say that it's made up of a certain number of increments, steps if you like, and between each step, there is....nothing. For example if the exact value of the voltage is 4.094V, sometimes you can read 4093 steps and other times 4095 steps. But never you'll read 4094.365212365894325 steps. Because there is noise, that is what causes the time "difference of one step" that you notice. Nothing serious. Sleep peacefully !

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Steve avatar image Steve commented ·
time difference is beyond one step


I understand minute rounding and hence why I tried to describe it. Steps works and based on your explanation, I would expect to see all my numbers to be within 3 minutes of each other. Essentially correct ?

There is percentage not step variation. I would not consider up to 20 minutes difference in time to be a result of step rounding.

20 minutes of recorded variation in 120 minute run time looks fairly significant

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albert-legrrand avatar image albert-legrrand Steve commented ·
Yes, i'm ok for some minutes bulk's jitter regarding noise in voltage mesurement, but 20' or more are too long. There's another problem. I'm reading Snoobler with a certain interrest....
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Steve avatar image Steve albert-legrrand commented ·
yes ... i didnt know if my description made sense but you understand what im talking about now ?


... it just seems not right


I'm going to do more investigating based on Snoobler thoughts and ideas

Steve

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