Hi all… new here…probably been talked about before, but I’m struggling to figure out why my SOC slowly keeps dropping over the course of a couple of weeks or so….. I have fiddled with settings A LOT but still can’t nail it….
3x300 aH Lipo NG smart (24volt) with LYNX NG BMS, T-class in, distributors and Cerbo GX….. Batteries are remaining balanced and voltage settles on 27 volts everyday. It’s just the SOC slowly dropping I can’t work out
any tips very appreciated 
FAQs pinned to the top of the section:
The SOC often sees a small accumulating error everyday and the float charging voltage of 27.0V will not get the pack back to 100% to synchronise. If you have the default settings for SOC threshold and absorption interval of 70% and 30 days and do not trigger an absorption then you can build up a drift until the next absorption. This really is not an issue, it is only the displayed figure, the batteries are getting charged. If it bothers you reduce the absorption interval or increase the SOC threshold to get daily absorption. You could set the battery charged voltage to 27.0V and 1% tail current but this could then result in false reading of 100% if you have solar. Personally as an NG user, they work well and you get used to the drift.
Additionally, it is hard to get the amphour counting absolutely 100% accurate, it is safer for any drift to be downwards rather than upwards.
Cheers mate for info
Yes my system is standalone with 6 kw of solar….. one more question…. How can I ‘access’ the settings (apart from the basic ones) in the bms1000 ng? Or are they a given ? I see ‘BMS controlled’ on my mppt’s and also the presets ….. is the ‘smart lipo ‘ preset ok to choose as is for the NG setup even considering it is BMS controlled? It gets a bit confusing 
VictronConnect on a Smartphone should connect to the BMS by Bluetooth to get to the settings. When connected to the BMS you should see a cog icon in the top right to get to the settings. However, there are few user configurable options, see the manual.
For any other chargers which are under BMS control make sure you set a suitable charge profile in case BMS comms is lost so the charger work properly. Start with the lithium Smart setting but adjust the absorption and float voltages to 14.0 / 13.5V to match the NG voltages and set the max absorption time to 15 mins as you will get daily absorption cycles.
Cheers mate
So set to daily absorption for 15mins with those voltages?
Yes, that is what I have done.
Thank you…. I have done that and now the individual cells are holding steady at 3.5 volts apiece (28 volts) fully balanced…, what is strange is that even after 15mins is staying in absorption and not dropping back down to 27 float…. Hmmmmm
Even though I have changed to 15mins absorb in BMS and the MPPT’s
Would it not take a little while for the batteries to drop to float voltage, particularly if there is no load?
Gidday @Clark ….. I’m totally offgrid so there is always a load of varying amounts on my system…. I have set my absorption time to 15mins (daily) so I guess what I’m struggling to figure out is why it stays at that voltage (28 volts) after the 15 mins has elapsed…. 
Thanks for the reply 
If the cells are not balanced, the BMS will override the 15 mins absorption setting in the BMS and continue until the cells are balanced. Absorption ends when the SOC reaches synchronisation to 100%, the tail current is reached AND the cells are balanced. The 15 min I told you was for the MPPT in case the BMS fails so you could mot get long absorption when not required on a daily basis, not for the BMS which looks after everything properly.
Ok thanks…. The cells are balanced however
I will change the BMS setting tomorrow and keep the mppt settings as is. Thanx @pwfarnell
The solution is getting the settings in the BMS correct. I had a similar issue and by adjusting the Battery Monitor settings I was able to fix the issue. These settings are accessible from Devices, then your BMS, then the BMS settings, then Battery Monitor settings. Setting Charged Voltage to 27.0v, Tail current to 2% and Charged Detection time to 3 minutes may fix your issue. I hope this helps.
Thanx Stephen….. I’ll have a look now
