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In an DVCC/ESS controled system using Lifepo4 batteries it is not good to charge the cells over 90% SOC in daily operation (you should just do it for top balancing).
As the voltage does not reflect the SOC in a wide range of lifepo4 charge curve, it would be usefull to have a configurable value in the ESS menue for the maximum SOC. As soon the SOC is reached the CVL should be lowered to a configurable value. Charging shall be stoped.
Having a max SOC feature is the simplest change in Victron ESS settings with the highest customer value.
I cannot change every summer the BMS settings for each customer to make them happy. I am an installer an I know what the customer wants.
I can think of one whose specs are based on 3.4V per cell and others who are much higher.
Most well known brands are already taking this into account long before the usage profile of an ESS is considered.
Derating it further isn’t helpful considering the other factors affecting battery life.
Different story if you are DIY’ing.
With a 10 year warranty being fairly common these days, why muck with it?
@nickdb : your battery might have 10 years warranty, however according to legislation it is your part to prove that granted parameters are not delivered anymore.
Good luck by engaging an expert witness to show the restriction to the manufacturer ;-)
In the meantime there are many scientific studies showing in particular for LiFePo batteries the impact of regularily charging batteries to 100%. Even Samsung implemented in their recent smartphones a fetaure to prevent full charging.
From my point there is sufficent evidence in going into that direction!
Personally I trust these studies (had recently also personal contact a scientist for renewable energies) and I will be glad to use these batteries any time beyond 10 years.
Other people can still believe that earth is a slice and go their way ,-)
Cell voltage does not reflect SOC. BMS is in place anyway limiting max cell voltag, thats not an issue and also not the usecase. it just needs a device (cerbo) stopping charging at a specific SOC. My Tesla can do this. It would be quite easy to implement but most likely I have to do it by myself with node red
Why not? Recommended SoC Window is 10% to 90%, regardless if the cell is used in a car or ess
SOC is a relative measurement of capacity based on how a battery is charged. If it has been derated to begin with, to make the guaranteed number of cycles/life, lowering it further is meaningless. An ESS battery has a different use case to an EV and the BMS/specs are configured to reflect that.
Most solar batteries want you above 10%, that low down you’re unlikely to get the performance you are expecting.
Driving it that low will have a worse effect on lifespan than not shaving 10% off the top.
Lifetime is based, beside other parameters, on the used soc window. Charging the battery every day to 100%, regardless if the cell voltage is 3,45 or 3,65 is not favourable. A lot of commercial vendors are interested in maximum capacity and fast charging and not a long lifetime.
But I see Victron is still to much in the lead acid worl of thinking and not reflecting all aspects of LFP usage so I have to solve it by myself
Hi Baxter,
I fully see your point and agree with your requirement. I covered almost the identical requirement in this thread.
In addition to the fixed Min-SOC I implemented a forecast dependent dynamic Min-SOC approach preventing a long term discarge.
The max-SOC feature (inclusive periodic balancing) is currently in beta test, however it showed quite good results recent weeks so far.
Here is another practical example why regularily loading the battery beyond 80% SOC cannot be valuable to battery life. Mentionable is the peak increase after 80% by additional ~10°C. That can't be healthy to battery chemics.
