Hi,
I have a Multiplus II with Pylontech batteries (1 x US2000 and 1 x US3000) and MPPT with solar
I am struggling to find out which mode should be used. It is currently configured with BatteryLife but I have seen some users saying it should be configured without BatteryLife?
Can anyone confirm which option should be used?
Sorry, but that is not 100% correct @Alexandra .
Solar will always be used to supply the loads first and surplus solar energy is used to charge the battery.
The difference between the two modes is that with Batterylife the system will increase the "activate SOC limit" by 5% each day the battery doesn't get to 100% SOC. That is done to ensure that the battery is getting to 100% to let the BMS balance the cells.
Example: You have set your SOC limit to 20% and you discharge the battery to that point (day 1), the next day (2) the battery only getting charged to 60% due to bad weather (or the PV array is to small), for the next day (3) the GX device will increase the activate SOC limit to 25% so you only can discharge to that point during the night. Because the weather is bad for a few days the battery never gets to 100% so the GX device will increase the activate SOC limit by 5% each day up to 95% if needed. If the weather gets better and the battery gets charged to 100% every day the activate SOC limit gets lowered by 5% day by day until the original set limit is reached.
Without Batterylife all this doesn't happen and the battery can be in a low SOC for a long time during winter and the BMS never can balance the cells this can lead to cell imbalance and cut offs.
We always recommend to use Batterylife. If I remember correctly some battery manufacturer also recommend it and only give you warranty if you do so.
I was just confused because at night I would notice that it would keep charging and then discharging the batteries (due to no solar being available)... is that OK for the batteries?
Because the weather is bad for a few days the battery never gets to 100% so the GX device will increase the activate SOC limit by 5% each day up to 95% if needed.
Slight correction:
When ESS Battery Life is on, the ESS BatteryLife dynamic (active) Minimum SOC can be increased up to 80% (or maybe 85%). Each time the SOC reaches 85% when charging, the increment for the day is canceled.
I have an issue with my current setup where I want grid to only charge my Lithium batteries when soc falls below 35% , but its not doing as it should do.
for testing I turn on grid and even tho my batteries were higher than 35% like 40% something, still the grid started charging batteries. any idea how can I change this behaviour? , also from all this discussion I think no Batteries life is going to work for me
You have "Optimized with battery life" selected and the "active SOC limit" is 65%.
In that situation, when battery is below 65%, system will slowly load battery up to the SOC of 65%.
also when does it stop charging then?
When "optimized without battery life", battery will discharge down to "minimum SOC setting". SOC will go below that setting only when grid is not present.
When grid comes back and SOC is below "minimum SOC setting", battery will be charged from grid only if PV is not present. It will charge battery from grid up to the "minimum SOC setting". Further charging will be done from PV sources.
I think I havent understood you clearly . that min SOC (35%) in pic means that grid will only charge once battey goes below 35%? and at what soc it stops charging it ?
SOC will go below that setting only when grid is not present.
why is that the case tho? I want to leave grid always available (mcb always on) but want the inverter to accept grid feeding based on soc value , so no manual interaction at all . how can it be achieved?
Let assume that "minimum SOC setting" is set at 35%.
SOC will go below 35% only when grid is missing.
If grid is always present SOC will not ever go below 35%.
If grid is missing and SOC goes below 35%, than at the grid return, battery will be charged from grid only if PV is not available.
If PV and grid are available battery will be charged from both up to 35% SOC. Above 35% SOC battery will be charged only from PV source.
If PV is not available, grid will stop charging the battery at 35% SOC and stay at that level until PV is available and there is more PV power than the load.
If there is more load than PV, power from PV will go to load and grid will provide the rest. In that case SOC will stay at 35%.
You can force grid to charge battery to full if you select "keep battery charged" option.
you can see at 35% soc setting grid is still chariging my batteries , partly supplying loads too . why didnt it stopped as you said earlier?
Your battery is still in ESS #1 low SOC state.
If you use MP-II as a SOC meter the accuracy of SOC measurement is +/- 1%.
in case of mmpt (PV power ) available ,still you can see grid is trying to go bulk and also supplying loads , shouldnt now it be off and go standby? already there is surplus pv power available , whats going wrong here?
Battery is in the "bulk" state not a grid.
Battery is charged by MPPTs.
That 60W "coming" from the grid could be just calculation uncertainty.
You need a grid code if you want to use ESS assistant.
As for not feeding a grid, you just tell your system not to do it.
Set minimum SOC to 30% and grid setpoint above 0W.
Because you have only MPPT chargers they will be used only for loads and battery charging.
The ess manual describes the difference in the settings between with battery life and without.
In my own words however i can tell you the difference though.
With battery life will ensure that you batteries get to the 100% charge everyday despite how you have set your soc in case of grid faliure. This means that first thing when the sun comes up, the solar being produced will go to direct charging, but it means the loads will run from grid if it is there, until the solar becomes great enough to do both.
Without battery life, solar will run your loads and use excess to charge batteries, you may or may not get back to 100% depending on your systems excess solar production. It will keep your grid set point untill you hit sustain or the soc in case of grid faliure set.
Either is acceptable for lithiums. It really does depend on how you want to run the system and take care of the batteries.
It looks like Without BatteryLife will work for me as my batteries keep getting charged and then discharged throughout the day now and even at night.
LiFe batteries can run low, so if there is poor solar for a period then let it do that.
At least then you don't have to fight with Batterylife (which can be dimwitted) when the Sun shines again.
It probably makes more sense in European/British regions where they get excited about sunshine, but in brighter climates my recommendation is to leave it off.
If I recall correctly, if the SOC does not reach 95% then it removes 5% from the active charge. If it exceeds 95% it adds back 10%. Or something to that effect.
Regarding with/without Battery Life, in my opinion Battery Life is best suited for Lead-Acid batteries, which must be fully recharged as soon as possible. Keeping lead-acid batteries partially discharged for a long time will damage them.
For LiFePO4 there is no damage if they are not fully charged even for weeks, if not months.
If the battery has a BMS which does balancing, this cell balancing only happens when the battery is very close to full. So you want them to get full from time to time, at least, even in the case of LiFePO4.
But after the initial period after putting them in use, once the cells get to a very close charging state at the top, they should not badly drift out of balance (if they do, either the cells are not well matched in capacity and internal resistance, or one or more cells are bad). You just have to limit the discharge at a point where no cell reaches lower than 3.0V (you can set this limit higher if you have plenty of capacity). This is set by Minimum SOC value in the first place and by the dynamic cut-off voltages in the second place. The third "line of defense" is the battery BMS. So set these 3 limits taking into consideration this sequence. In normal use with ESS, you want the discharge to be only stopped by the Minimum SOC.
With BatteryLife not enabled and a relatively low Minimum SOC value, you use more energy from the Sun over time. For instance you always take advantage of a day with full Sun which follows a streak of cloudy days. With BatteryLife enabled, in such a case the Minimum SOC would have been maybe 80% or close to it and you have no capacity to store lots of energy. Also the LiFePO4 battery takes a higher current when it is discharged than when it is close to full.
If there are weeks of cloudy and short (winter) days, you can manually rise the Minimum SOC temporarily if you think is necessary or temporarily enable BatteryLife (once the SOC is above the dynamic Minimum SOC, to not charge the battery from the grid).
Also, if you have frequent blackouts (for a few hours at a time) you should rise the Minimum SOC.
Close but not quite there.
The difference between the two modes is that with Batterylife the system will increase the "activate SOC limit" by 5% each day the battery doesn't get to 100% SOC. That is done to ensure that the battery is getting to 100% to let the BMS balance the cells.
According to this info:
https://www.victronenergy.com/media/pg/Energy_Storage_System/en/controlling-depth-of-discharge.html
With Battery Life, SOC does not have to get to 100% each day for active SOC limit not to be increased by 5%.
85% daily SOC level is high enough to keep active SOC limit unchanged.
When, during the day, SOC gets to 95%, the active SOC limit is lowered by 5%.
When, during the day, SOC will not get to 80%, the active SOC limit is increased by 5%.
My experience is slightly different.
When, during the day, SOC will not get to 80%, the active SOC limit is increased by 5%.
When daily SOC level gets over 80% and less than 85% active SOC limit is unchanged.
When, during the day, SOC gets over 85%, the active SOC limit is lowered by 5%.
As a result, when Sun is scarce, the SOC stays at around 80% when grid is present, and will newer get above that level.
Here is a graph of last 90 days.
I noticed today that Active SOC is decreased by 5% when 85% is passed. Not necessary to reach 100%. It was at 30% after several cloudy days and it dropped to 25% after reaching 85%. Experienced today.
Don't know if this has been mentioned (or if that I have go tit right) but one big difference between the modes that I have notice is:
With Battery Life the system will dedicate the Solar Charger output to the batteries until they are charged exclusively, and not add to mains power loads until they are charged
But w/o battery life, mains loads will get Solar Charger current and balance will go to the batteries. In the systems I maintain, this generally makes a big difference in utilising total PV output during the day.
Change modes and see for yourself! thanks to VRM
