HI..
Being new to ESS system and exactly how it operates:- I want it to charge the batteries only when there is excess PV production (Fronius grid-tie inverter on AC-in)... but definitely never charge from the grid when there is insufficient solar and batteries are low.
Will the self-consumption mode ensure this alone, or will i need to change any other parameters?
Hi Lazza
Yes ESS works as intended, it will never use the grid to charge the battery only PV when there is excess power it will power the house loads first then any surplus goes the battery then the grid as excess.
This is how my system works and have zero power bill and a credit as well.
Regards
Rob D
NZ
Hmmm .... i have a ESS System with a Multiplus II. The battery settings are for "battery life". If the battery stays lets say at 70% and the ESS is not able to charge for more then 24 hours, the ESS is using around 100 Watts from the grid to bring the batteries further up to the "Active SOC Limit", which is defind by the venus .....
If your system never uses grid power to charge, you are not using "battery life" settings .... right ? If you are in battery life mode you will see something like #1#2 below the inverter:
If the solar yield is not able to charge this system up to 80 % in the next hours, it will use
grid power to charge up to 80% (which is the highst setting that "Activ SOC Limit" can reach.
-> conclusion: depends on the settings of your battery ! The system WILL use power from the grid if in battery life mode.
Jens
Hi
I am using lithium's so they don't require battery life set, so it never uses the grid at all. i do get #1 when i get below my SOC % setting which i set at 20%.
Regards
Rob D
NZ
Hi Rob,
i think that this statement is not right in all cases. Even lithium batteries don't like it to stay on a low SOC for a long time. They cope with low SOC better then PB, but mostly they like "storage" voltage -> e.g. 50% SOC if they are not used for some time. Mine are lithium type too. Lithium even don't like to stay on 100% SOC for longer periods of time.
So maybe Victron can give us a statement which settings are recommended for lithium batteries in an ESS environment.
Jens
Hi Jens,
This depends on the use of the system type of batteries,
An ESS system usually doesn't have the batteries at the same SOC for long times, only in winter time with little sun it can make sense to set the lower SOC limit a bit higher.
usually lithium batteries already have a lot of 'spare' build in at 100% charge, with the exeption of LiFePO4 batteries, but they have less problems with staying at 100% charge.
How to treat your battery depends on how you use it, as you don't have LiFePO4 you'll probably have defined '100% SOC' at below the max charge (max 4.2V, you'll be using somewhere between 4.00 and 4.10 V?)
Victron cannot make statements on recommended settings, as those are defined by the battery manufacturers.
Hi Daniel,
yes .... i use 4.1 Volts per Cell but also "battery life". Victron can not make statements for the voltages ... thats for sure. But: is it recommended to use "battery life" with lithium ? The battery will stay at ~ 46 Volts (in my case 2sp3 Telas model s). I thought i would be better to have the batteries near storage voltage then to have them at lets say 20 % SOC at winter time.
"Battery life" will increase the usable SOC if the sun comes out more often.
Thx
Jens
Hi (newbie here) have a similar problem. Some days ESS works perfectly using battery overnight (Self Consumption) other nights is goes into sustain mode early in the discharge cycle and uses the grid to slowly recharge over hrs (around 8 hrs).
(I'm using a 5Kva MP IIGX, ESS (min SOC -20%) in 'Non-battery life mode', with 5Kva LifePro4 battery, 15 330w panels.
The two overnight discharge examples (good and bad) are as below, I would appreciate any help.
(sorry I didn't want to start a duplicate post on a very similar topic)
Thansk Alan 
Alan, this is about the third existing post where you seem to be asking the same question, you would be better served opening your own, with a full system overview and configuration.
This is a common newb question.
First, SOC is a relative measure, it can drift for several reasons.
Voltage is king. If you are hitting sustain then the voltage of battery has hit a minimum threshold which would imply the SOC is wrong or the thresholds are wrong - something is misconfigured.
This is how the system will behave if the two don't agree.
Follow the setup of your relevant battery, step by step, from the following link and make sure you are configured correctly.
https://www.victronenergy.com/live/battery_compatibility:start
Thanks, Nick (I was trying not to duplicate this topic afresh) will get a new post going, appreciate the help and advice.
A
Please screenshot all the inverter setup tabs (assistant summary included) from veconfigure.
Do the same for the GX main screen, BMS page and BMS parameter/details page.
Include DVCC and ESS GX pages also.
When you are having issues, screenshots from VRM which show battery votlage/Current, cell min/max and BMS discharge limits.
Some older BMS firmware (such as pylon) may not show cell min/max, in which case you should get your supplier to update the battery firmware for you.
