I have a Grid Connected EP760 with 2 x B500 batteries that is AC coupled to an existing Solar System.
I would like to know if charging to 100% and discharging to 15% everyday is going to negatively affect the lifespan of my batteries?
I understand that in order to maximise the lifespan of Lithium Iron Phosphate batteries, the approximate recommended maximum charge level should not be over 90% of the battery’s capacity and the approximate recommended minimum discharge level should not go below 20% of the battery’s capacity. Are you able to comment on this statement?
Furthermore, does the Battery Management System in the EP760 already implement these recommended charge/discharge levels invisibly in the background, or is it necessary to manual change the Working Mode - SOC Setting to “20%-90%” to achieve these recommended levels?
Note that within a day, my EP760 could also be discharging/charging in smaller cycles based on current solar generation and load changes but post sunset, the battery discharges overnight while supplying night time loads.
i cant fully answer your question, since i dont know about the invisible limits, but there is one important thing about the “Not 100% Charge”. In general its right that batterys dont like to stay at 100%. But Lithium Phosphate batteries actual sometimes need to be on 100% for cell balance. So never charge them to 100% would be also wrong.
Hi @Lyndon_S, Based on your needs, we recommend setting the SOC to 20-90%. Once it reaches 90%, the solar energy will charge it up to 100%. This is similar to how we charge our phones.
Thanks to @Selfmadestrom for the insight, it was very helpful.
Hi @BLUETTI_CARE,
Thanks for the quick response. Can you please clarify what you mean by “Once it reaches 90%, the solar energy will charge it up to 100%”?
I would have thought that if I set the maximum SOC to 90% - doesn’t that stop the battery from being charged above this 90% level?
Note that on my system I have disabled charging from the grid so all charging on my batteries is from solar generation.
Finally, can you confirm that the battery management system does not automatically implement any strategies to prolong the life of the batteries???
Curiously,
Lyndon
Yes, thats correct. Like BLUETTI_CARE mentioned, the SoC Setting just defiened how much of the SoC is filled by grid power and how much by solar. Its not a real limiter. If you set your SoC to 80%, that just means that between 80% and 100% only solar power is used.
Im with you. You buy the product and you should be able to limit the SoC like you want.
The good thing is, the EP Series often get new functions. Maybe this is one of them in the future.
Hi @Lyndon_S, Thank you for your additional information.
Since your EP760 is not connected to the grid, setting the maximum SOC is not necessary.
Please continue to charge and discharge it daily as you did before. Rest assured, the app has a battery maintenance feature.
To extend the battery’s lifespan, please manually recalibrate once every six months, and charge the battery as soon as it runs out of power.
Thank you to @Selfmadestrom for the response, this makes perfect sense.
Hi @Lyndon_S, We recommend that you upgrade both the firmware and the app to the latest version.
We have attached a screenshot for your reference.
I hope it does help.
It is a common recommendation for lithium batteries. However, bluetti does not offer this option in case solar charging to customers for some reason. The only way to limit the SoC level to 80% is to charge from the grid.
@BLUETTI_CARE, @mvadim, @Qwerty, @Selfmadestrom
It appears that the “battery maintenance” feature is to address the issue of mismatched levels in parallel attached batteries.
The battery maintenance function does not address the fact that currently, for a grid connected EP760 that charges only from solar, it is not possible to set upper and lower charge/discharge limits to allow a user to maximise the lifespan of the batteries.
Is it possible for this functionality to be considered for a future firmware release - or alternatively - are you able to provide an explanation as to why charging the B500 batteries everyday to 100% (then discharging to the lower SOC value) is not going to affect the life of these batteries?
Hi @Lyndon_S, Thank you for your feedback. The off-grid charge/discharge limits setting you require is in the planning stages. Please stay tuned.
Similar to charging a mobile phone, the B500 guarantees more than 4K cycles.
There are different chemistries of lithium batteries….
LiFePo4 - from my understanding do not have an 80% SoC recommendation
NMC - are recommended to remain between 10 and 80% SoC to maximise their lifespan…
The Bluetti batteries are LiFePo4 from what I understand.
Also don’t forget the BMS in the EP760 knows exactly what the batteries are, and it should be setup to maximise their lifespan… and we as consumers shouldn’t have to worry about it too much…
I am interested to hear what Bluetti state, maybe update an FAQ?
“Also don’t forget the BMS in the EP760 knows exactly what the batteries are, and it should be setup to maximise their lifespan… and we as consumers shouldn’t have to worry about it too much…”
You would hope so, but I get the impression that this is not the case given that @BLUETTI_CARE added this comment“The off-grid charge/discharge limits setting you require is in the planning stages. Please stay tuned”.
@Aphere, this is not a new topic. I just found this post from September 2022 on the same subject. Introduce an option for a 80% charge limit
So the likelihood that Bluetti engineers genuinely intend to implement charging limits in future releases is probably a fantasy.
