question

zetecnology avatar image
zetecnology asked

pylontech 52.4v charge voltage will never allow cell balancing

I have observed reasonably high cell imbalance due to the limited charge voltage surely we should be limiting charge current in combination with voltage ie in my system when the pylontechs call for 14.8a at 53.2v allow them say 5a but with 53.2v to enable cell balancing.

In my opinion limiting charge current as requested by the pylontech would have been a far more effective way to manage overvoltage problems than limiting the charge voltage to 52.4v

As the DVCC settings are forced there is no way for me to experiment, is there a way around these settings without having to downgrade the firmware to a version that did not force the settings?

As an advanced user i really should be able to alter these settings

Thanks

Darren

Lithium Battery
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4 Answers
janieronen avatar image
janieronen answered ·

Hi. That voltage should be enough for pylontech for balancing. How ever you can limit charge current to give a few very long charging periods which gives BMS-cell balancing more time to get all cells to equal SOC. As you can see from documentation that voltage limit is done as special 15s configuration.


Have you looked with pylon tech app that what is cell balance status and does your all batteries have same SOC? If that not enough you can once top up all batteries individually to get full top-balanced. If need support you can share diagram and photos how batteries have cabled.


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

My system only charges the battery to 52.4V

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 52.4V. 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 52.4V, 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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zetecnology avatar image
zetecnology answered ·

Thanks for your reply janieronen i am very aware of the reasoning behind these settings but my point is that even victrons own batteries call for 3.55v per cell for balancing reasons (same chemistry as pylontech) even if i connect one individual pack it will still not allow the bms to enter a balancing state at 52.4v like i said the pylontech charge current curve is what really needs to be limited to avoid the high voltage alarm problems the approach taken by victron is not much more than a band aid fix

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Alexandra avatar image
Alexandra answered ·

@Zetecnology

If you check on the GX you will see the battery using DVCC requests a higher voltage than programmed.

The programming is only there just in case and can't hurt the battery.

If you read the pylon batts own manual, the battery balancing is triggered at 90° SOC. (See section on storage) Pylons are not Victron and are not even the same cell type so you can't compare the two at all.

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zetecnology avatar image
zetecnology answered ·


Alexandra no the battery requests a higher voltage than the victron allows, longer term it remains to be seen if it hurts the battery by getting so far out of balance (at a cost to the end user)

and the cell type chemistry is exactly the same with both pylontech and victron so can be compared

i just wish people will not keep quoting inaccurate information

3 comments
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nickdb avatar image nickdb ♦♦ commented ·

the voltage is fine for conventional pylons.

V3 GX code allows for 16 cell batteries.

There are literally thousands of installs working perfectly.

Prior to v3 batteries pretending to be pylon may have had an issue.

This is a certified and tested solution with Pylontech.

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zetecnology avatar image zetecnology nickdb ♦♦ commented ·
Yes but my point is that it's not the right way to go about solving the original problem of high voltage alarms that seemed to plague new installs, and there is the possibility of incorrect information being used (lost in translation)

what we are being forced to use is making the BMS have no say in managing individual cells, something victron expressly forbids with their own battery

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nickdb avatar image nickdb ♦♦ zetecnology commented ·
Dvcc max charge voltage was expressly introduced for dealing with high voltage/cell imbalances. The CVL does not prevent that nor affect cell balancing,
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