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Dyness BX51100 batteries won't charge past 48% (Deye 8K Inverter)


Marcodp

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Hopefully someone has experienced a similar error or has and idea/knows how to fix this issue?

A friend has a Deye 8K Inverter (SUN-8K-SG01LP1-EU) with 3 x Dyness BX51100 batteries with 20 x Canadian 550w panels.

The whole installation has been running well for about 18 Months - about a month ago when we noticed the 3 x batteries will not charge past 48%.

We checked for errors and there are none (nothing listed since mid 2023).

We have checked the BMS (see pics below) also checked various battery settings (and adjusted just in case) without any joy.

We have now also turned off using System work-mode just in case but still no joy (the pic still shows on but that was before we have subsequently turned it off) 🙂

Just in case, we have requested a firmware update from Deye which we are waiting for (Deye are very good so hopefully it should be completed in the next few days)

I have included pictures of the settings...

Has anyone experienced this issue and is there any ideas/suggestions to overcome the issue?

Additional info: The batteries are installed as per manufacturer specs (page 18/19 of user manual below) and all cable lengths are the same

Dyness-5-12kWh-BX51100-Lithiumion-Battery-UserManual.pdf (sunkissedsolar.co.za)

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Edited by Marcodp
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2 hours ago, Marcodp said:

Hopefully someone has experienced a similar error or has and idea/knows how to fix this issue?

A friend has a Deye 8K Inverter (SUN-8K-SG01LP1-EU) with 3 x Dyness BX51100 batteries with 20 x Canadian 550w panels.

The whole installation has been running well for about 18 Months - about a month ago when we noticed the 3 x batteries will not charge past 48%.

We checked for errors and there are none (nothing listed since mid 2023).

We have checked the BMS (see pics below) also checked various battery settings (and adjusted just in case) without any joy.

We have now also turned off using System work-mode just in case but still no joy (the pic still shows on but that was before we have subsequently turned it off) 🙂

Just in case, we have requested a firmware update from Deye which we are waiting for (Deye are very good so hopefully it should be completed in the next few days)

I have included pictures of the settings...

Has anyone experienced this issue and is there any ideas/suggestions to overcome the issue?

Additional info: The batteries are installed as per manufacturer specs (page 18/19 of user manual below) and all cable lengths are the same

Dyness-5-12kWh-BX51100-Lithiumion-Battery-UserManual.pdf (sunkissedsolar.co.za)

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Although you have grid charge on for 24hrs a day and only 1 period below 48% have you tried unticking grid charge for all periods and check if batteries charge above 48% from PV. 

Allow the batteries to discharge to 25% and then recharge via PV and keep the house loads low to speed up charging. 

Another tip would be to start the 1st timer block at 00h00 and end at 00h00. Current settings are spread over 2 days. 

 

Edited by Scorp007
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@Marcodp,

Maybe not entirely related to you buddy's problem, but I would like to know how the "20x 550W CS's" are connected to the inverter.

If 10+10 (10 panels per string), that is dangerously close to the max Voc (496V). And that is at STC (Standard Test Conditions a la 25 Deg C). That will increase quite a number of volts at 0 Deg C, if you are in a cold (e.g. highveld) area. And that is smoke signal territory! 

I hope I'm wrong about my assumption. 9 of those 550W panels max. per string.

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🙂 good eye for picking this up 🙂  .... there are 4 strings ... each facing a different direction and paralleled at the inverter (he has an interesting roof design which was a challenge to ensure he received maximum sun throughout the day), so the voltage is all well within range (PV input Voltage (V): 370V (100V-500V)) however if you add up the wattage (20x550w = 1000w), this actually exceeds the max PV/DC recommended solar wattage of the inverter (Max. DC Input Power (W): 10400W), but there is absolutely no chance of that based on his panel placement even if one wanted to consider cloud edge (edge of cloud effect).

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17 hours ago, Scorp007 said:

Although you have grid charge on for 24hrs a day and only 1 period below 48% have you tried unticking grid charge for all periods and check if batteries charge above 48% from PV. 

Allow the batteries to discharge to 25% and then recharge via PV and keep the house loads low to speed up charging. 

Another tip would be to start the 1st timer block at 00h00 and end at 00h00. Current settings are spread over 2 days. 

 

Thanks @Scorp007, let me try ....will feedback on outcome

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Great, I supposed that PV config makes some sense, even though not ideal. 

And going parallel inverters to increase the MPPT count is sometimes not ideal - other than roof layout. In my experience, Inverters in parallel behave somewhat different (and strange) compared to a single inverter.

Maybe also try and run the inverter/battery combo in Voltage mode (i.e. disable the Lithium function) to see if that makes a difference.

 

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PROBLEM SOLVED! 

Hindsight is 20/20 😀 and thanks to all for the input / suggestions (all part of the learning process).

I must admit, the issue did not make a lot of sense because there were Zero errors (nothing in the log and no indicator on the batteries other than not going past 48%). The installation had existed for 18+ months without any issues and Work-Mode was now turned off.

While driving to my friend's house last night to continue looking into this issue (he's an old guy in his late 70's), I was thinking of the possibility that he may have changed something unsuspectedly (i.e. place a tick somewhere it should not be) as the touch screen can sometimes be finnicky and his eyesight not so good anymore 🙂 (don't tell him I said this 🙂 ), so I decided to Reset the Inverter back to Factory Default as a starting point and work from a clean slate as they say.

Arriving on-site, that is exactly what I did and almost immediately after resetting the Inverter to default, a BIG message appeared across the screen saying: NO BATTERY

This was NEW and forced me to check everything Battery related (cables, connections, fuses etc.) and I found it - the Battery Fuses had melted inside the holders

I know there are those that would say you should have checked that first, and in hindsight possibly, but there was no visible indication that the battery connection was the issue or that there was a problem with the fuses (only when I eventually tried to open the holder and could not). Looking at the Pics is that voltage was flowing and the BMS was working (sort of 🙂 .... check the first 3 pics attached) and the batteries would charge up to 48%.

If I had not Reset the inverter, the message may never have appeared .... I have no doubt we would have got there eventually, but this did save us a lot of hours 😅

So, what caused the Fuses to Melt? - before Resetting, I recorded the previous, settings and the reason for the fuses melting looks to be because the installer (or he) had changed the Max Charge & Max Discharge to 150A while he had 100A fuses installed, which is now so obvious - as I said, hindsight is 20/20 😂

Anyway, thanks to all for your valued input/suggestions (all part of the learning circle).

 

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2 hours ago, Marcodp said:

the Battery Fuses had melted inside the holders

Hi @Marcodp

Would be nice to see a photo of the fuses. Or maybe just explain fully.

Did the fuses "blow", as in open circuit, or did the surrounding fuse holder melt and therefore the fuses where not making contact anymore? I suspect the former.

Any idea what had caused this? (not the setting, but charging/discharging to 150A)

I've had instances where customer has 150A fitted, yet draws 200A+ without blowing.

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Posted (edited)

@Sidewinder, I am really not sure what could have caused this other than the Charge/Discharge setting set to high - any ideas?

I have attached some pics, but I could not open the holders for love or money - they are fused shut. 

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Edited by Marcodp
Corrected the wording
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8 hours ago, Marcodp said:

@Sidewinder, I am really not sure what could have caused this other than the Charge/Discharge setting set to high - any ideas?

I have attached some pics, but I could not open the holders for love or money - they are fused shut. 

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Heating in an electrical circuit is always caused by current flowing through a resistance. If there is significant resistance in the contact between fuse and fuse holder, a current well below the fuse rating can cause enough heat to melt an fuse holder.

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1 minute ago, TaliaB said:

Heating in an electrical circuit is always caused by current flowing through a resistance. If there is significant resistance in the contact between fuse and fuse holder, a current well below the fuse rating can cause enough heat to melt an fuse holder.

Another install using AC rated fuse holders. 

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May I suggest that you get a decent couple of fused isolators with correct rated DC fuses, like a Keto / Jean Muller.

The way I understand is that every battery must have its own fuse isolator and then 1 where all the batteries combine. 

What size and length is the battery cables?

Edited by Vaal
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