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mcintosh avatar image
mcintosh asked

DVCC and Pylontech Battery

I recently had my system upgraded and settings set as per your "Victron & Pylontech US2000B and Phantom-S" manual dated 2019-01-22 14:42.

System has following devices and firmware ;

Color Control GX v2.23.

Multiplus 48/5000/70-100 v433.

BMV-702 v3.10.

BMS Pylontech with 4 x US2000B Plus batteries.

BlueSolar Charger MPPT 150/100 v1.39.

On running with DVCC for 3 sunny days, I got the following ;
Note : During "Absorption" phase, System Battery Voltage reached 52,29 V and SOC 98%.

Switched off DVCC and after a few days system stabilised as follows ;

Note : During "Absorption" phase System Battery Voltage reached 53,19 V and SOC 100%.

During "Float" phase System Battery Voltage drops to 52,98 V and SOC 100%.

I have also noticed the values of "Blue Solar Charger MPPT 150/100 - Networked operation - Charge voltage ; are 52,40 V with DVCC on, changed to 54,40 V when DVCC was switched off, and is 57,20 V when system is stable and fully charged. Where does this value come from ?

Any assistance to resolve this problem would be appreciated.

Thanking you,

Tim Mc Intosh




DVCC
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7 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hello Pylontech owners,

Everything I see here is normal and expected.

A managed lithium battery like the Pylontech does not have a bulk, absorption and float stage like a lead acid battery.

Instead there is a max target voltage (set by the battery BMS), and a charge and discharge current limit (also set by the BMS).

When DVCC is enabled, as it should be for these batteries, the GX device takes over the charge control of the inverter/charger and MPPT solar chargers, and then co-ordinates them to best deliver the power that the battery wants, without exceeding the limits specified by the battery, as well as the best performance for our systems based on information from Pylontech and our own infield testing.

You can read more about DVCC and how it works in this DVCC section of the GX manual.

The variation in voltages you see across the devices is to optimise the charging source. Specifically, we want the solar to always push when it can, it will adjust it's charge current dynamically based on instructions from the GX device.

98%, 99% or 100%.

Battery state of charge for managed lithium batteries is quite different than for lead acid and BMV. It is not counted Ah, and reset to 100% when tail current drops to near 0A, but reported by the BMS.

The Victron settings are designed to be stable and reliable. It is likely that the batteries COULD be pushed harder, but there is the risk that the battery life is shortened or the battery would disconnect itself in some circumstances. For example if there is a flash of sun that comes out from behind the cloud, on a nearly full battery, it could spike the charge current and the battery voltage.

So you may not see 100% regularly. This is not a fault, it is a conservation and a compromise for a more reliable system.

DO NOT DISABLE DVCC

Disabling DVCC is forbidden, and likely to void the warranty for your battery. If DVCC is disabled, it is possible for the system to ignore the specifications of the battery from the BMS and push excessive current that the battery does not want (due to cell imbalance or cold temperature for example).


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Pat Davitt avatar image
Pat Davitt answered ·

"I have also noticed the values of "Blue Solar Charger MPPT 150/100 - Networked operation - Charge voltage ; are 52,40 V with DVCC on, changed to 54,40 V when DVCC was switched off, and is 57,20 V when system is stable and fully charged. Where does this value come from ? "

With DVCC turned on the Pylontech BMS is controlling the charging parameters. See Section 5 in the Pylontech compatibility document found here:

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

Pat

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mcintosh avatar image mcintosh commented ·

Hi Pat,

I have checked Pylontech battery - Parameters ;

Max Charge Current 100.0 A

Max Charge Voltage 53,2 V

Max Discharge Current 100.0A

Seems correct for 4 x4 x US2000B Plus batteries.

Thank you

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dennis avatar image
dennis answered ·

I have the same: Charge voltage is 52,40 V with DVCC on. Why should the Pylontech BMS report 52,40 V? Any ideas?

See here:


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dennis avatar image
dennis answered ·

Here some more Infos:

System overview. Battery hanging around 98% and 99%. Maximum 52.4 Voltage. System never going into Float.


Pylontech Battery Parameters getting via bus.


SmartSolar MPPT Charger getting this Settings via DVCC. The Charge Voltage is only 52.4V but should be 53.2V in my opinion. Why is it like this?


It never gets more than 52.4V and therefore it is never goint into float.

Any suggestions?

Need help to get this fixed or to understand the behaviour.

Any Infos welcome.





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dennis avatar image
dennis answered ·

i found the answers!

see here: https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom#my_system_only_charges_the_battery_to_52v

My system only charges the battery to 52V

When DVCC is enabled, the battery (via the CAN-bms) is responsible for the charge voltage. The Pylontech battery requests a charge voltage of 53.2V. We have however found that in practice this is too high.

The Pylontech battery has 15 cells in series, so 53.2V equates to 3.55V per cell. This is very highly charged and makes the system prone to go overvoltage.

It should also be noted that a LiFePO4 cell stores very little additional energy above 3.45V.

For this reason we opted to override the BMS and cap the voltage at 52V. This sacrifices almost none of the capacity and greatly improves the stability of the system.

The battery won't charge to 100%

Also see the question above. The state of charge of the battery is estimated based on the overall voltage and on how well balanced the internal cells are. Because we cap the battery voltage at 52V, the state of charge will sometimes rise very slowly once it reaches the mid-90s. This is normal and usually resolves over time.

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ commented ·

Nice work Dennis,

We posted the same info at the same time.

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stratanet avatar image
stratanet answered ·

Hi guys,

Just wondering if any of you have seen the Battery Over Voltage alarm described in this post? https://community.victronenergy.com/questions/16064/battery-monitor512-alarm-high-voltage-alarms-victr.html

We're also seeing the same alarm - although I haven't seen it for 2 days. The site has only been active for less than a week; I'm HOPING the batteries just needed a little bit of time to settle. Today has been a good day; full sun and no alarms has brought my SoC up to 99%. FYI this site has 4x Pylontech US3000 batteries.

I'll probably reach out to my distributor if I see the error again.

Cheers,
Richard.

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particle avatar image
particle answered ·

Hi all

With 2x Pylontech US3000, DVCC on, my SOC is stuck at 91% daily. Too low for comfort and nowhere near mid-90s. My new system has been running otherwise well for three weeks. I'm guessing US3000 is not quite the same as US2000 in this respect.

Someone thinks 52V is too low for US3000: https://github.com/victronenergy/venus/issues/536


Any ideas?


By the way, secretly overriding the charge voltage against all parameters visible in the various parameter pages is bad user interface engineering. Just about every new installer will waste a few hours researching the issue. The CCGX should indicate on screen that the Pylontech voltage is being overridden.


2x Pylontech US3000

MPPT 250/85 rev 2

Multipus 48/5000/70-100

Color Control GX

6x 290 W panels (60 cells) in series


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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @particle

did you set the system to 'keep batteries charged' for a while? if so, for how long?

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particle avatar image particle Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Thank you Daniël

On the Color Control under ESS I get "No ESS Assistant found", assuming that this is where I should have set "Keep batteries charged".

I had forgotten to mention that the installation is off-grid.

Sorry for my rant about not showing 52V. It is shown under the MPPT - Networked operation.


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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ particle commented ·

Ahh off-grid, than it should get fully charged for long enough to get the batteries fully balanced.

just to be sure: Pylontech battery is selected as 'battery monitor' in the settings?

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particle avatar image particle Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Sorry for the delay and thanks for the help. Selecting Pylontech battery as battery monitor helped immediately. It was set to automatic before. I get 100 percent state of charge now and 52V on the advanced diagram in VRM. Before, it was 91 percent and 51.75 V max. estimated from the diagram.

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Related Resources

DVCC chapter in GX manual