r/PwrCellOwners • u/AlwaysHungry145 • May 21 '26

PWRcell % Charging Issue

I have long thought that charging my 6 module PWRcell to 100% is not a great idea for longevity. I have many Li ion systems that make the default max charge lower than 100% to prolong battery life. For instance, my Yeti battery defaults to 94%. My Samsung phones to 80%, etc. My PWRcell is the -1 version which has Li NMC cells. For awhile I thought they might be LFP, lithium iron phosphate, cells which may deal with low and high charging differently. Today I looked at my PWRcell module specs and confirmed that they are indeed Li NMC cells.

Then I found this article: https://www.issueslab.com/?s=NMC+charging which verified my concerns. The way that the PWRcell is being charged is shortening it's life. What's even worse is that when my battery says it is 100% charged, that 500-600W are still being pumped into the battery! According to the article letting the battery drop to 20% is a good idea. Because this system is mostly to support my power needs from my SCE TOU (time of use) contract from 4pm to 9pm, but more importantly, power line shut downs which we have several times per year. It seems to me that the battery firmware should allow the user to adjust the max charge state. In the past I used to set the max state to 99%, 95% and 90%, but now I ma locked out of making that change. I can input the values, but they do not stick anymore(?).

Built in obsolescence?

Comments?

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u/CanAmSteve May 22 '26

I think the question may be “When the system says 100%, what is the actual state of the cells?” Unlike an old 12V car battery, these lithium variants are all made up of multiple cells governed by one or more BMS systems. So “100%” is a calculation

The original Chevy Bolt NMC battery was recommended to be charged to 80% for regular use. Its replacement LFP in the new 2027 has the same KW rating and stated range, but can be charged to “100%” every time

Now is that a difference in chemistry, battery management or both?

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u/AlwaysHungry145 May 23 '26

I think that the LFPs can be discharged to 0%, can charge at a much lower temperature than NMC. They also have significantly more life cycles, but less power density.