Guess he is really using an AI to pretend as "knowledgeable" person.......what makes him think it will end well?And just like that....He (or it) was gone....
Now our lives will go back to normal..... Ahhhh a breath of fresh air.....
Ahh yes!! Salem in 1692! The good ole' days!
REAL LIFE IN THE REAL WORLD !... oh... there's something more enjoyable than the DIY solar forum ?
Hi Sverige,Welcome to the forumIt’s nice to get a different perspective on LFP batteries.
Just about every LFP ESS cell datasheet specifies charge termination at 3.65V and 0.05C tail current and just about every DIY battery user and 100% of solar power YouTubers interpret this (wrongly) as “charge up to 3.65V all the way down to zero current”.
In what I regard as the danger zone, 3.65V and under 0.05C, how much damage is done? What I mean is when people continue to trickle charge a large capacity bank of paralleled LFPs at currents which represent a tiny fraction of C, it is (according to cell manufacturer specs) an overcharge, but how damaging to cycle life is this? There are some people who will say that lithium plating of the electrode is occurring in this region of overcharge, but this seems unlikely. What do you say about this?
Edited to add: in EVs with small capacity cells stacked in series to high voltages, perhaps charging into the region below 0.05C is not likely to occur as the current involved would be quite small. In DIY ESS setups where people parallel connect large capacity cells, 0.05C can be a large current. In my case with a 4S4P setup, 0.05C is 58A and charging CV to 3.65V below that current is pushing the cells to a higher SOC than the cell manufacturer says is the charge termination point. Charging to 3.45V at 5A could even be a higher SOC than 3.65V at 58A!
Nice to see you back here.
Generally speaking, for prismatic cells, you don't need to stack atop another. Just do your layout like what CATL does. If we ignore the pressure difference cause by different stacking. The most important factor becomes free electrolyte inside battery can. Normally when a cell is been developed all the testing and electrode jelly-rolls is been optimized under the assumption of a flat layout. Electrolyte will deplete through-out its cycle life, designers will try to avioid any hetergenity in the rate of decay across all the battery electrode. If you look at the jelly-roll, its normally perpendicular to the terminals. If we put it horizontally, the electrode layers on the bottom will have way more acess than regions on the top. Also, in a vertical condition, the capiliary force in the seperator will be easier to draw electrolyte more uniformally to the electrode.Thank you for answering too
Very interesting about sodium. Considering sodium cells cost slightly above LFP with the few sellers that do sell them I see no point for them on the market right now. I actually think having them "fail a market test" may be bad for the development of the tech until as you said lithium prices go up(which none of us wants, but at the same time we want more cheaper options for ESS).
Regarding my "cell position" question from page 2 post #39 of this thread. If you had some input it would be greatas I'm about to rip my already commisioned pack apart in next few days... We had a moderately long heated debate about cell position here few weeks ago at the end of which I concluded I see no scientific evidence for harm caused by them being stacked atop another as in my photo (or on the short edge as another poster said), but based on another person's experience of failures happening seemingly because of it I decided better safe than sorry. There is an idea that when lying on its side (long or short) parts of the jelly roll are above the electrolyte and get starved. I posit capilary action should take care of that, but what is the truth I don't know.
Very good question. Beginning at 30% SOC and top at 80% SOC% will make your cycle life significantly longer by a factor of almost 1.5 to 2. That means its not 0.5 cycles and its more like 0.25 or 0.3 cycles. Jeff Dahn even published a paper on NCM been cycled at a middle SOC range and it can cycle for a very long cycle life. See the link: https://iopscience.iop.org/article/10.1149/1945-7111/ac91ac
And just like that....He (or it) was gone....
Now our lives will go back to normal..... Ahhhh a breath of fresh air.....
Glad you didn't get scared away, your definitely an asset to the community.
Being cycled once a day for solar, is calendar age more of a factor than cycles?
Thanks for your answer! People generally set their charge termination voltage higher than 3.42V as cell balancing needs to be accomplished in this upper region of the charge curve and only when the voltages of out of balance cells diverge can the balancing begin. With ESS cells being usually huge capacity relative to the balancing current available, you need time to bleed off the extra energy as our cells are likely not as well matched as EV cells.
Not to get off topic but...I find it very interesting and scary that we live in a world that has progressed AI technology to the point now where it is very difficult to tell if we are conversing with a robot. We can tell immediately if we are talking with someone in person or even over the phone, but when talking over forums, it gets "dicey". There needs to be better AI detection software developed to flag this type of thing, perhaps a good tech start up?? Flagging and banning potential AI chat bots.... I was told years ago that if you think of it, it most likely already exists!!
Just pass a law that AI's have to identify themselves. How do you send an AI to jail if it breaks the law?
