where does this charge voltage come from

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wedgehog asked Jun 11, '22

where does this charge voltage come from

My victron system has a 250/85 and a 250/100 MPPT and a 500 amp shunt and multiplus 2. I have the ESS software installed. I understand that the two MPPT chargers are now controlled by the ESS. I set the 100% charged voltage in the shunt to 54.50 but I notice that it is stopping at 54.00 volts. Surprisingly I noticed that in the NETWORK section of the MPPT's it states Charge Voltage 54.00 volts. Strange it should be in the networking menu, but where is this information coming from? My BMS is not linked to the network.
Does the ESS system have it's own charging parameters? are they editable? is there anywhere Victron publish them?

battery charging ESS SmartShunt

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Answer 1 · 2022-06-11T18:17:03Z

seb71 answered · Jun 11, 2022 at 06:17 PM

The "Charged voltage" from the SmartShunt/BMV does not control the battery charging. It is just one of the parameters used for SOC synchronization to 100%.

When using ESS, the battery charging voltages are those set in the inverter. But you should also set them (same values) in the MPPT chargers, too (for instance if the communication cable is unplugged, then the MPPT will still use correct voltage values).

You mention "Networking". Do you mean VE.Smart Networking? You should not use that for ESS. Connect the chargers with cables to the GX device.

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wedgehog commented · Jun 11, 2022 at 06:48 PM

Hi Seb 71, I just added a bit below. Ok I agree the Charge voltage and the shunt charged voltage are not controlling exactly what the battery is charged to, so my question still stands, What does?

Yes the two MPPT chargers are connected to the Cerbo with VE direct cables.
There is nowhere to set the "Charged voltage" in the MPPT chargers. or the Inverter charger, only Absorbtion and float, the battery voltage which is set to 48volt is not the actual voltage a fully charged 48 volt battery would be.

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seb71 wedgehog commented · Jun 11, 2022 at 08:30 PM

What does?

I already answered:

"When using ESS, the battery charging voltages are those set in the inverter."

There is nowhere to set the "Charged voltage" in the MPPT chargers.

"Charged voltage" is only a SmartShunt parameter, as I wrote.

Start by reading the manuals of all your devices. And the ESS manual.

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wedgehog seb71 commented · Jun 11, 2022 at 09:33 PM

You are not quite grasping this are you, When I say "Charged voltage" I am not referring to anything in any menu, I am referring to the voltage of the battery when it is fully charged. Something is setting mine to 54 volts and it is not a setting in the inverter charger, that only has settings for Absorption and float as I said already

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seb71 wedgehog commented · Jun 12, 2022 at 06:57 AM

You have to read into batteries and battery charging, too. Some aspects of these are explained in MPPT, inverter and ESS manuals.

"Absorption voltage", as used in Victron equipment (and other) is the voltage at which the charging switches from Bulk/Constant Current phase into the Absorption/Constant Voltage phase of battery charging.

For LiFePO4 batteries, those are the most relevant charging stages.

In ESS, the charging voltages are those set in the inverter, as I keep saying.

If your battery has a BMS and the charge is stopped at lower voltage than that set in the inverter (while you still have Sun), it might be that the charging is disabled by the BMS (because one or more cells have too high voltage). But you haven't gave enough details about your system.

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wedgehog seb71 commented · Jun 12, 2022 at 11:31 AM

Hi Seb, I understand exactly what you are saying, I don't know why people on forums always assume the person asking knows nothing or is an idiot. The last part of your statement is the helpful and relevant part and I thank you for reminding me of that, At 54 volts the cell voltage would be 3.375, unless as you say it is reached by one or more cells being much higher than the others, in which case the BMS should discharge them until they balance, The balancing start is set in my BMS at 3.4 volts but you are correct the cells are not balanced, they were top balanced before the get go. I am starting to think this 250 Daly is crap and I see it only has a balance current in the milli amps. I have ordered an active balancer which goes up to 2 amps balance current, will see if that's better,
You are wrong by the way, with lipoly the bulk charge is 98% or more of the charge and the Asorb. is kept short, Lipo do not gass like lead acid.

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Answer 2 · 2022-06-11T18:43:16Z

wedgehog answered · Jun 11, 2022 at 06:43 PM

My bad, I see that the charge voltage in the "Networked Operation menu changes with solar, so obviously it's showing the "Charging voltage" not the charge voltage as such, it was fixed at 54 when I wrote the question because there were clouds and little solar, so just showed the battery level. But the question still stands, the battery won't charge above 54 so where is it being told to stop there?

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Answer 3 · 2022-06-12T12:36:30Z

Maybe this helps

MPPTs show two voltages, Panel and what they see from the battery connection. Assuming good wiring, this is battery voltage to within a few hundredths of a volt.

Shunt shows battery voltage as measured.

Charging is three phase and four phase on the MPII.

First phase, bulk, is simply pump as much current in as the batteries will take, limited by the max current setting (under ESS/DVCC control). During this phase the battery voltage increases.

Second phase, absorption, is fixed voltage - once the configured absorption voltage is met, the charger maintains this voltage and the batteries continue to charge, but current will drop as they become more charged.

Third phase, float, is a lower voltage, and keeps the batteries fully charged.

Fourth phase, if configured, is storage. this is an even lower voltage and is to stop the batteries from degradation due to self discharge (most useful for lead acid).

Notice I haven't mentioned your Charged voltage yet. This is only used by the shunt for state of charge (SOC). When Charged voltage is reached AND current drops to the tail current setting for the specified time period the Shunt resets state of charge to 100%. From then on it calculates SOC based on current in and out of the battery. If it didn't work this way, measurement inaccuracies add up and cause drift in the SOC displayed.

The 54V you're seeing is either the actual battery voltage at the time, or the shunt parameter charged voltage. It is set in the shunt configuration.

Sorry to be long winded and cover stuff you mostly know, but I can't identify gaps in your knowledge and it's usually the minor missing point that causes confusion. ;-)

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