Hi all, just refitting a yacht and want to limit my batteries charge to around 80% while they are not being used much and I don’t require the full capacity (rather than leave them at 100% for Months). I only have MPPT solar chargers connected currently and I know I can change the charge profiles in them to achieve my goal, however when the system is all linked up through the GX, the DVCC is forced on and it seems like no changes can be made. So without disconnecting the MPPT controllers from the GX/BMS system and running them as stand alone, is there any way I can tell the system that I only want it to charge the batteries to 80% or alternatively to a set adsorption/float voltage? Thanks in advance.

Yes Victron everything aside from the Alternator regulator. Chat GTP has the following comments, but in practice may be very different. Why Charging to 100% Can Reduce Lifespan Increased Cell Stress At higher voltages (near 100% SoC), lithium-ion cells experience higher internal stress. This can accelerate cell aging or degradation over time. Elevated Rate of Side Reactions When a cell is held at 100% SoC—especially if it’s also exposed to higher temperatures—side reactions inside the cell become more pronounced. These reactions can permanently reduce capacity and increase internal resistance. Long Dwell Times at 100% It’s not just reaching 100% that matters; how long the battery remains at or near 100% also impacts degradation. Frequent, brief excursions up to 100% (e.g., daily cycles) are less harmful than storing the battery at 100% for days or weeks on end. Still Benefits from Partial SoC Even though LiFePO₄ is more forgiving, you’ll still see increased cycle life and reduced capacity fade if you operate it in a partial SoC window (e.g., 10–90% or 20–80%) rather than fully charging to 100% on every cycle.

Chat GPT is still in baby stages and definitely great for code, but i disagree with its ‘reasoning’ based on experiential use. [image] Kiwirob: Increased Cell Stress Yet on a system 100% SOC is not the cells full range of voltage use. Also on a victron system it is not held at the higher voltage. It drops to float (still considered 100% SOC) so using soc is not valid. Cycle life is not increased or reduced. Lifepo4 is energy in and energy out. Whether you do that end to end or sipping up and down, it is energy in and out. [image] Kiwirob: e.g., 10–90% or 20–80% The bms already hovers the cells between percentages of its range. So yes correct but also not correct. I am not the only one with these thoughts though. Again, you may do what you like, it is your kit. I don’t agree with chat gpt based on what i have seen and experienced. Is chat gpt going to back up your warranty? When the manufacturer refuses based on the installer or user not following guidelines?

Discussion with the Pylontech technical department… Question: Is there any problem if, after they reach 100% SOC, I will keep them constantly at 52.5V (3.5V/cell) ? Response: This is not a problem and will not cause battery damage. QED.

Cycling near the top of charge (75%–100% SOC) is detrimental to LFP/graphite cells. Our results show a correlation between the average SOC of battery operation and capacity fade rate, meaning that the lower the average SOC, the longer the lifetime, in these 2500 h of testing. The average SOC was found to be the most critical factor influencing capacity fade for LFP cells, over the factors of temperature, depth of discharge, electrolyte salt choice or graphite choice. Cells cycled in the conventional 0%–100% SOC window showed capacity fade rates intermediate to 0%–25% and 75%–100%. Therefore, the time spent cycling at high states of charge is critical to minimize. https://iopscience.iop.org/article/10.1149/1945-7111/ad6cbd/pdf

Nice and recent article. Thank you ! :+1: They are talking about the fact that 0-25% is better than 75%-100%. True, because 75%-100% will be at a higher temperatures. And temperature is detrimental. They are saying: “At higher SOC, there is more exothermic heat flow produced from faster SEI growth and electrolyte reduction”. So higher wear on 75%-100% because higher temperature. They are talking about 40-60 deg.C temperatures. Lets see… All LiFePO4 manufacturers say that in order for the warranted cycles to be honored, the following must be respected. I am picking below the most restricting ones: Less than 80% DOD, so no less than 20% SOC. Less than 0.2C (C5) for charging / discharging. Battery temperature around 25 deg.C +/- 2 deg.C From the start, their choices: 0-25% SOC - out of the SOC range 0-100% SOC - out of the SOC and temperature range 75%-100% SOC - out of the temperature range (over 40 deg. C) Not to mention that their 100% SOC is 3.65V/cell. The 3.45V-3.5V/cell like many manufacturers are keeping / limiting the cells are another matter. In normal usage (my case) didn’t see temperatures more than 28-30 deg.C, SOC less than 20%, currents more than 0.2C and voltages more than 3.5V/cell. So, I am still waiting a test for normal life usage, not extreme tests like theirs. And another thing… Their entire study is based on a study of SEI (solid electrolyte interphase) growth for the NMC cells. That study is stating that “The experiments show that time and temperature, not cycle count, are the dominant contributors to the growth of the SEI.” In this new current study we are talking here, the authors admit that “To ensure that SEI growth is the primary degradation mechanism, it would be beneficial to have similar studies on LFP cells, modelling the effects of SOC and temperature on SEI growth”. So, in a way, is kinda of “on LFP is probably the same” type of study… But, in the end, each to his/her own. :wink: Only time will tell… :slight_smile:

[image] Alex Pescaru: Not to mention that their 100% SOC is 3.65V/cell. The 3.45V-3.5V/cell like many manufacturers are keeping / limiting the cells are another matter. Voltage alone does not tell you the SOC. This is a common beginner mistake when working with LiFePo4. There are three significant parameters that affect the final SOC when charging LiFePo4 batteries: the charge current during the CC phase the charge voltage during the CV phase the cutoff current Let’s take a 100Ah LiFePo4 cell. Case 1: Charge with 50A up to 3.65 V and cutoff when current drops below 5 A (this is the definition of 100% charged from most cell manufacturers). Case 2: Charge with 20A up to 3.5 V and keep it in absorption for 1 hour. The cell will be charged to 99.99% of Case 1, with the same degradation. So the apparent “limiting” imposed by the manufacturers is not real in PV systems where we have variable charge current and cannot cutoff the batteries at the end of the charge. Looking at it another way, when our 100 Ah cell reaches 3.5V, it has a higher SOC in Case 2 than in Case 1. [image] Alex Pescaru: not extreme tests like theirs. If you do a little research, you will find that using higher temperatures is a scientifically accepted method to speed up processes in long-term battery cell tests. As long as you keep using the same temperatures when varying other parameters (e.g. SOC range), the results will show the impact of the other parameters (average SOC in this case). This is a scientifically accurate peer-reviewed paper that comes to this conclusion: The average SOC was found to be the most critical factor influencing capacity fade for LFP cells

@MondeoMan thanks for the information. Do you have any practical suggestions to the application of this information in the context of Victron equipment or is the purpose of the information to simply reinforce the assertion of the original poster?

And also for re iteration, if the manufacturer of the battery being used says to do things a certain way, then do it. It is on them if it is incorrect. No one needs to lose a warranty over internet articles and chat gpt. I do know from experience/experiment a battery pack that never is allowed to balance does not do well.

Hi LX, I would also like to re iterate that nobody has suggested that they use the batteries in any way that does not comply with the manufacturers recommendations. You do not need DVCC or a Cerbo or a smart BMS or a shunt to comply with manufacturers specifications on battery management. My friend, one of the best professional offshore sailors in the world, has two Victron lithium batteries, a small BMS and a solar controller. If someone does not wish to charge their batteries to 100% each and every time and leave them at 100% for extended periods, this is fine. It may not be advantageous, but it is not going to void a warranty. As long as the batteries are charged and blanched according to the levels and frequencies specified then all is well. ChatGTP is simply finding and summarising all of the knowledge that humanity has acquired. It might be far more accurate than someone’s anecdotal experience and very limited experiments.

[image] Kiwirob: ChatGTP is simply finding and summarising all of the knowledge that humanity has acquired My problem is this. (And its not with chat gpt) Too many internet articles (which is chat gpt’s source) vomit out copycat information which is incorrect/unverifies or half baked. And somehow through the sheer number or repetitions it has become ‘truth’. [image] Kiwirob: someone’s anecdotal experience and very limited experiments There is an entire community of people who take and test ideas found on the internet. As well as battery manufacturers who develop management systems for cells they have specific chemitry combination chosen. (And there are many lifepo4 vairants). Al i am saying is be careful. I have seen warrenties being voided in the real world.

Deliberatly Limiting batteries charge

Q&A and troubleshooting

Topic		Replies	Views
Target SoC is 100%. I want to lower it to 80-85% DIY diy , ess , dess , cerbo_gx	36	2659	13 August 2025
Victron: please create a default LFP profile DIY beginner , lithium_battery	25	1079	22 February 2026
How to stop MPPT from charging battery to 100% daily? DESS diy , ess , dess , mppt_rs , cerbo_gx	62	1775	3 July 2026
Limiting LiFePo4 battery SOC to 60% for winter storage while retaining shore power for heat Q&A and troubleshooting marine , beginner , lithium_battery	16	861	12 December 2025
Setting charge percentage for LiTime battery DIY beginner , mppt_controllers	19	1548	18 January 2026

Deliberatly Limiting batteries charge

Related topics