Sterling SMART BMS Max 74%

[powellytvr]

Hi all.. can anyone educate me a little as to why my brand new Sterling Lithium 100AH batteries only ever show max 74% please? I’ve attached some screenshots of the settings I can see in the app

 

[Pausim]

What are you using to charge the battery? It needs 14.4V/14.6V to achieve a full charge. The engine charging from the alternator may not achieve the required voltage, particularly if you have a smart alternator. Many users of lithium batteries find they need to install a B2B (battery to battery charger). Also the standard CBE mains charger might not be set for the required voltage.

 

[powellytvr]

At the moment on the drive 700W of solar through a Votronic controller that we have correctly set to 14.4V. Inbuilt charger is a CBE 16A unit correctly set to Gel, but not currently on hookup. So batteries seem to sit at 70-74% on the drive. I did notice after a drive they show 100% but drop back to 70-74% within an hour... parked up on the drive the resting draw of the van is @ -1.5A

Not very electrically minded so Ive read for hours but can't get my head around it.. am thinking its maybe not worth worrying about tbh!! But it doesn't seem right..

 

[RowleyBirkinQC]

What does the ‘SOC Set’ parameter on ‘Cell Characteristics’ section do/refer to? Given that appears to be set to 71%, could that be a maximum state of charge of the battery?

This thread and/or tagging some of the participants here may help answer your query…

BMS DALY soc problems

hi, i have fully charged my 2 sets of 4 cells, they are all balanced and all cells are at around 3.194. i had them set up in pairs so as to get 400amp hours, i could not set the soc it stayed at 0%, so i changed the cells around to make then 200 amp hours just 4 cells and found i could still...

www.motorhomefun.co.uk

 

[Drexl]

I have 2x 100Ah Sterling batteries with bluetooth, using a Votronic triple 60/40/430 with 2x 175w solar panels and Votronic smart shunt. Having had this system for over a year it works well, however the battery BMS's are not accurate and sometimes throw up some odd SOC readings. Sometimes one battery shows much lower SOC than the other, however I have good confidence they are both charged 100% by looking at the sum of the cell voltages. If you check the battery voltages at rest e..g. not being charged - at night or after disconnection from the solar charger for a couple of hours, if the rest voltage is approx 13.35 to 13.4v the batteries are fully charged. Battery voltage rule of thumb is that 13.3v or above the battery is 80% plus full.
So I tend to ignore the BMS SOC readings and just use the smart shunt readings from the control panel in the van or use the Votronic app.
The settings I have chosen are shown below following the information in this thread on Outandaboutlive.

Sterling Power LiFePO4 (Lithium) Leisure Batteries, Post #31 | Motorhome Matters | Motorhomes Forum

Hi our van at the moment is at RV Installations, Mullacott, North Devon, having *4 x 175 watt solar panels, Victron mttp 60 amp controller • Victron 2Kva

forums.outandaboutlive.co.uk

When the van is between trips on the driveway I remove the solar fuse to stop the batteries charging and run the fridge to discharge batteries to 50% SOC then switch off and defrost the freezer. Then I monitor the SOC a couple of times a week - top up with solar if the SOC drops to 40%.
The solar controller can be tricked into thinking the batteries are 100% charged in spring / Autumn when the solar is weak. It doesn't happen often, however I think that this happens when the voltage supplied by the solar panels is fairly constant at approx 14.2 volts for a period of time - the algorithm in the Triple unit is sensing the voltage and current the batteries are taking and assumes the batteries are fully charged and the SOC zooms up to 100%, when in reality they are less than that. This can be seen from the 24 hour graph in the app. Easy to fix, just plug in the EHU and charge up to real 100% and the smart shunt will re-set to real 100%.
Triple Unit settings
Setting 7 - LiFeP04 14.2v charge / 13.4v float
Battery BMS settings (Password is 123456)
Cell high volt protect 3.65v
Cell low volt protect 3.0v
Sum volt high protect 14.6v
Balance open start volt 3.4v
Balance open diff volt 0.015v

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[powellytvr]

OK thank you, I think looking at the app and the supporting documentation you’re probably right and just focussing on the voltage is where I should be, and evening voltage is steady at 13.4-13.6

Bizarrely, this is the reading from the app now after 2 hours since I wrote this post and checking them every morning/evening for past 2 days.. I dunno, got 2 weeks away mostly without EHU so I will see how we get on as my suspicion all along and as you say is that the pretty pictures in the app probably not accurate