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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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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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