SOC drops slightly every 7 hours

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sdc88 asked May 09 2023 at 7:47 AM

SOC drops slightly every 7 hours

I recently install 3 x 4kw new BYD LVLs to an existing system on grid that had 3 x 4kw BYD LVLs so a total of 6 (two towers of 3) with a Victron Quattro 48/10000/140. I since I installed the 3 extra batteries my system as been slightly dropping SOC to 99.5% every 7 hours without any change in load or mains loss. What settings can I check to see why this is happening all of a sudden? Let me know if you need further screen shots of any parameters.

Update: I have fully bypassed the inverter so there are no loads and it still dropped SOC slightly on the 7 hour mark and went into bulk charge.

Update 2: did a discharge test all worked ok, went down to 20% SOC, charged back up to 100% and it went back to every 7Hrs issue again. At a loss.

battery charging VictronConnect SOC BYD

victron-1.png (85.6 KiB)

victron-2.png (72.6 KiB)

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Answer 1 · 2023-05-09T07:50:29Z

nickdb answered · May 09 2023 at 7:50 AM

Probably just the new batteries trying to balance.

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sdc88 commented · May 09 2023 at 8:24 AM

I probably should of mention the new batteries have been in for over a month now.

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nickdb ♦♦ sdc88 commented · May 09 2023 at 8:53 AM

Some batteries can take a while to sort themselves out, depending on use.

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sdc88 nickdb ♦♦ commented · May 09 2023 at 9:13 AM

Yeah will see, basically just sits there as a UPS, I might discharge them and have them charge up again to see if this helps.

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nickdb ♦♦ sdc88 commented · May 09 2023 at 9:29 AM

It sometimes helps to run them down nicely and bring it back up to charge.

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sdc88 nickdb ♦♦ commented · May 15 2023 at 6:53 AM

@nickdb no luck

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Answer 2 · 2023-05-09T11:38:41Z

thanar answered · May 09 2023 at 11:38 AM

What is the "repeated absorption interval" value set to, under "Cherger" tab on VE.Configure 3?

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Answer 3 · 2023-05-10T12:05:57Z

sdc88 answered · May 10 2023 at 12:05 PM

@Alexandra seems like you might know what’s happening here?

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Alexandra ♦ commented · May 10 2023 at 1:01 PM

@SDC88

Are you running ESS. are you on keep batteries charged? Or set at 100% in case of grid faliure?

Do the drops coincide with solar day start/end? And as guys have mentioned cell balancing? It is a strong candidate here.

Do they all discharge ok and charge up ok as a bank?

BYDs BMU uses the lowest battery SOC, so it may just be one or two sorting themselves out.

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sdc88 Alexandra ♦ commented · May 10 2023 at 8:06 PM

Not running ESS

Drops are happening every 7 hours but not exactly, sometimes at 3am in the morning, and even without any load on the inverter.

Currently performing a discharge it’s been 12 hours will report back once it’s charged but it’s looking ok at the moment, anything in particular I should be looking at?

If it’s just the batteries balancing, how long can this take? It’s been happening for over a month since the second bank was installed?

Appreciate your support.

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Answer 4 · 2023-05-19T12:16:45Z

sdc88 answered · May 19 2023 at 12:16 PM

@WKirby you have any idea what is happening?

Answer 5 · 2023-05-23T10:13:32Z

sdc88 answered · May 23 2023 at 10:13 AM

@BYD_serviceyou have any idea what is happening?

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byd-service commented · May 23 2023 at 10:35 AM

Both the batteries and Venus device consume energy to stay on, as you can see the consumption is really low. As soon as the voltage decreases below the absorption voltage then it goes into bulk.

On the other hand, in order to have the most accurate SOC it is recommendable to cycle the batteries. If you´re using them for UPS you might want to still set 10-20% for self-consumption and leave the rest as backup.

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sdc88 byd-service commented · May 23 2023 at 10:55 AM

Thanks for replying @BYD_service, so you’re saying in absorption with no loss of mains the battery voltage will still drop?

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byd-service sdc88 commented · May 23 2023 at 12:16 PM

One the battery reaches soc 100% it will change CCL to 0. So even if it is in absorption charging will stop until soc decreases below 100% and it sends a CCL different from 0.

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sdc88 byd-service commented · May 24 2023 at 12:29 PM

So my concern is null and void, it’s basically operating as it should be. @BYD_service

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nickdb ♦♦ sdc88 commented · May 24 2023 at 12:31 PM

It is how the BYD's balance, have a new one that does exactly the same. The more it is left to balance the more it settles.

You can correlate the behaviour to the max cell voltage, CVL and CCL.

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sdc88 nickdb ♦♦ commented · May 24 2023 at 8:34 PM

@nickdb yeah ok, I was just concerned because it keeps getting a high voltage alarm

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SOC drops slightly every 7 hours

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SOC drops slightly every 7 hours

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