Morning, I have 2 x 5kw = 10kw Sunsynk batteries installed. Lately I've been noticing a faster than expected drain at the lower end of SOC.

See attached for example this morning:

In 10 minutes the SOC went from 38% to 16% i.e. 22% drop on a 2500w load.

In my mind a 10 minute load at 2500W should mean roughly 400w or 4% of the battery?

So what could be causing the faster than expected drainage, battery health?

Thanks

 

 

 

 

 

 

How old are your batteries btw?

 

On 2024/02/27 at 7:42 AM, SiriS said:

So what could be causing the faster than expected drainage, battery health?

The problem here is who/what is determining the SoC, what inverter are you using and what is reporting the SoC? Some BMS' seem to thumbsuck a figure based on cell voltage, same with some inverters, when really coulomb counting should be done, the BMS should know the cell capacity and thus based on energy in/energy out, determine a SoC, but if the battery never gets full properly and has time to do balancing, then the SoC can be a useless figure, BSL's can do this, they, via a SunkenSynk inverter claim 100%SoC, which is bull, since if you have energy available they will continue consuming many Amps/Watts for maybe even an hour or more after claiming to be at 100% SoC.

So, you batteries probably need to be charged properly by your inverter, until they will not consume any more energy, then they should be at 100% SoC and then you can see what they would do, but if the BMS determines charge level based on Voltage, then the provided figure will always something that is of dubious value.

On 2024/02/28 at 3:48 PM, Vana said:

How old are your batteries btw?

 

installed about a year ago

On 2024/02/28 at 4:43 PM, Kalahari Meerkat said:

The problem here is who/what is determining the SoC, what inverter are you using and what is reporting the SoC? Some BMS' seem to thumbsuck a figure based on cell voltage, same with some inverters, when really coulomb counting should be done, the BMS should know the cell capacity and thus based on energy in/energy out, determine a SoC, but if the battery never gets full properly and has time to do balancing, then the SoC can be a useless figure, BSL's can do this, they, via a SunkenSynk inverter claim 100%SoC, which is bull, since if you have energy available they will continue consuming many Amps/Watts for maybe even an hour or more after claiming to be at 100% SoC.

So, you batteries probably need to be charged properly by your inverter, until they will not consume any more energy, then they should be at 100% SoC and then you can see what they would do, but if the BMS determines charge level based on Voltage, then the provided figure will always something that is of dubious value.

Txs, inverter is Sunsynk and I definitely do not have enough technical knowledge to comment on BMS capability and whether SOC is actually 100% (interestingly enough, inverter/app always shows 99%, never 100%).

I was wondering if it is a battery health issue, as the 40-20% SOC is often induced in the morning when the main geyser goes on. But my understanding is that discharge is non-linear so doesn't impact the same particle cell(s) all the time? 

My installer did a firmware upgrade yesterday, so I will keep monitoring. According to the installer, a year ago Sunsynk was the best thing ever. Now he says they're absolute 💩 🤦‍♂️.

6 hours ago, SiriS said:

I was wondering if it is a battery health issue, as the 40-20% SOC is often induced in the morning when the main geyser goes on. But my understanding is that discharge is non-linear so doesn't impact the same particle cell(s) all the time? 

Probably not, I'd think, but its likely to be SoC misrepresentation probably by the battery to the Inverter, can you see how much discharge there was, by the time the HWC switches on? Maybe you find you did actually get nearly 80% out already and then the HWC switches on and then the real SoC starts to actually be displayed...

Sunsynk is not the worst product around, by far, but not retaining competent support staff in this country has pretty much caused them to shoot themselves in the foot, lots of unhappy customers, since the failed inverters are not repaired/sorted out within a realistic time frame, when things go wrong... but also, why are there so many failures and specifically during the Lightning season in the north-eastern part of the country, is this maybe more an installation related problem, rather than a product failure? I don't know, but it should be trivial to look at number of SunkenSynk inverter in Transvaal (encompasing GP, MP, NW etc.) and how many in the Western Cape, for instance and then look at the failure %ages based on location... I'd be interested to see what the outcome of this would be... and could tell a story that might prescribe a way to install with all surge protection in place etc. that may well reduce the amount of failures...

Morning, after a firmware update...no change.

Happened this morning again.

On 2 x 5kwh batteries, my SOC went from 38% at 4:46 to 18% at 5:06.

In other words dropped 20% SOC in 20 minutes at average 450w load. According to my calc I should have only dropped 1.5%.

Voltage remained around 52, which according the LifePo4 voltage charts indicate a SOC of 40%. This morning for the first time though I noticed the battery lights are out of sync, right (Master) battery) 2 green lights and left (Slave) battery on 4 lights (inverter indicating 35% SOC).

I've run out of technical expertise...so would this indicate a BMS issue or a faulty cell issue in perhaps the Master battery?

Unfortunately I'm at the stretched limit of my tech knowledge here...  🙃

 

 

 

 

 

 

 

 

Better voltage graph. 

1 hour ago, SiriS said:

I've run out of technical expertise...so would this indicate a BMS issue or a faulty cell issue in perhaps the Master battery?

When the  battery gets charged, is it from grid (it would appear so) or from solar?

LiFePO4 batteries usually report 100% SoC well before they are really full, then they would still consume lots of amps to balance and actually get the cells full, look at my charge for yesterday, the BMS reported 100% at 15:03 app. but the batteries still took current until an hour later, by which time they were pretty much full...

Edited March 13, 20242 yr by Kalahari Meerkat
typo & forgot to attach screenshot...

Hi, no this morning was an exception as SOC dipped below minimum due to load shedding, so grid charged back to minimum SOC. Generally batteries are fully charged by solar in the morning around 10/11am and then stay 100% until at least 6pm in the evening.

It could be a bad cell best have someone  connect there laptop up to the battery to monitor individual cell to get to the root of the problem .

An question how are those 2 batteries wired to each othere and to the inverter .