LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[mat jam]

Delphin,

I was only planning on posting the video and a summary of its contents in the quest for a better understanding of something many of us are interested in. When you attempted to pull a fast one, I felt compelled to find the truth. It is in my nature since the bulk of the work I do in my profession is research. With a healthy dose of curiosity. But now I understand your position and dependence on the product.

[Q Xopa]

Originally Posted by mat jam

I posted the EXACT same question on that forum as I did on this forum. I received help on this forum and anarchy on the other forum which likely explains why this forum is more popular. Again you have not been forthright in your desire to belittle me because you are unable to qualify your position. So rather than provide the data you resort to attacks which explains why people no longer trust comments or product reviews.

You waffle by first attempting to say they are different chemistries, then to admitting the video is correct, then again to, no they are different. You are acting like a child in the playground and prone to group mentality. When someone kicks someone you jump right in and start kicking right along. You have shown your true colors. I am sure you are are nice guy.

If possible can we get back to the topic please? If we wanted a slanging match we would turn on reality TV.

[Delfin]

Originally Posted by Q Xopa

If possible can we get back to the topic please? If we wanted a slanging match we would turn on reality TV.

Good advice, thank you.

[newhaul]

Originally Posted by Q Xopa

If possible can we get back to the topic please? If we wanted a slanging match we would turn on reality TV.

here's my attempt
I just got done with an ev guys video where he has been keeping specific records over the last several years on a set of Winston cells and has come up with a number for degradation of the cells capacity . With 3 years of full cycle and capacity tests have according to him shown a capacity loss of 15mAh per cycle for his 90ah cells.
https://youtu.be/N7scKCQlfYs

[Delfin]

Originally Posted by newhaul

here's my attempt
I just got done with an ev guys video where he has been keeping specific records over the last several years on a set of Winston cells and has come up with a number for degradation of the cells capacity . With 3 years of full cycle and capacity tests have according to him shown a capacity loss of 15mAh per cycle for his 90ah cells.
https://youtu.be/N7scKCQlfYs

I'll repeat the question on this thread, as it will have wider interest here, so does that seem like a lot to you? Haven't watched the video yet...

[newhaul]

Originally Posted by Delfin

I'll repeat the question on this thread, as it will have wider interest here, so does that seem like a lot to you? Haven't watched the video yet...

Here is my reply from the other thread

no its not that much. The math says 1.5ah per 1,000 cycles per 100ah capacity.
( approximately) just remember that was with the cells used in an ev
So high C rates both ways

[weavis]

OK
We have removed some posts. They were rude and arrogant and dismissive.

The easiest way to get along with folk is to NOT RESPOND to any commentary you find offensive, childish or inflammatory. The second a post is made in a derogatory manner, it is there for all to see and will be moderated accordingly and infractions added if required.

But then, you know this.

[john61ct]

Jehu is a fantastic DIYer resource, especially for assembing packs from those little cylindricals.

But yes, his use case is high-C-rate propulsion, and he generally uses vendor charge profiles in line with that usage.

Thus getting only a few thousand cycles would be considered a very long lifetime, whereas here as House bank usage, that's just past getting broken in if cared for properly.

In that context the mAh loss per cycle should be immeasurably low.

[Delfin]

Originally Posted by newhaul

Here is my reply from the other thread

no its not that much. The math says 1.5ah per 1,000 cycles per 100ah capacity.
( approximately) just remember that was with the cells used in an ev
So high C rates both ways

Ah, I thought you had written 15 milliampere, not 1.5. 1.5 makes more sense, and as you say, isn't much at all/1,000 cycles. In a marine application, one would think it would be a fraction of that.

[newhaul]

Originally Posted by Delfin

Ah, I thought you had written 15 milliampere, not 1.5. 1.5 makes more sense, and as you say, isn't much at all/1,000 cycles. In a marine application, one would think it would be a fraction of that.

with the way we use them and the actual ah that a new bank tests out with ( mine showed 108ah ) stop to stop it will take a while just to degrade down to the manufacturer spec of full capacity for the battery.


I wouldn't be surprised if in house usage and not traction usages the loss rate would be to small to measure .
Last test Maine sail posted about in August last year over a thousand cycles and 0 measurable loss of capacity.

[john61ct]

Originally Posted by newhaul

with the way we use them and the actual ah that a new bank tests out with ( mine showed 108ah ) stop to stop it will take a while just to degrade down to the manufacturer spec of full capacity for the battery.

And AH capacity can **increase** after breaking in period, compared to fresh from the factory.

That is why best practice is to establish a good initial baseline benchmark for 100% SoC, using the exact same equipment and protocols you will use for future years (hopefully decades).

[sparrowhawk1]

Thank you weavis. I actually learn as much from the people that are learning and asking questions as from the gurus. And the biggest problem with rude people is it stops other people from commenting because they don't want to be attacked.

[Delfin]

Originally Posted by newhaul

here's my attempt
I just got done with an ev guys video where he has been keeping specific records over the last several years on a set of Winston cells and has come up with a number for degradation of the cells capacity . With 3 years of full cycle and capacity tests have according to him shown a capacity loss of 15mAh per cycle for his 90ah cells.
https://youtu.be/N7scKCQlfYs

Interesting video. His figure of 15 mAh per cycle comes, I believe, from the manufacturers spec sheet, and that would be 15 amps per 1,000 cycles, and that is a fair amount. He supplies a whole lot of numbers in the video, so it is hard to keep track, but on reflection, his usage pattern in an EV doesn't look much like a marine application. He mentions he has run the cells down to less than 1 volt 10 times or so, but routinely takes them down to 2.7 volts per cell. Additionally he says he is discharging at a pretty fast rate.

I got pretty much the full capacity out of my 600 Ah bank and stopped at just over 3 volts per cell, and for most people, if you recharge after drawing out 75% of capacity rather than 100%, you aren't likely to go much below 3.125 volts per cell. Point is, while I think we can learn from EV, usage of LFP house banks on boats is going to be significantly different and give much different life than one might experience in a car. Lithionics publishes a graph of their own data that shows that if you discharge their packs to no more than 50%, they project 5,800 cycles at a 1C charge and discharge rate, which is 3 times the charge rate and 10 times the continuous discharge rate what I will ever use. I doubt most people could use the battery that much before some other reason for getting rid of the boat presented itself.

[nebster]

Yes, I think Jehu's charge pattern yielding ~1300 cycles to 80% SOH is pretty believable. That certainly comports with the longer lifecycles other folks are estimating (or experiencing in real life).

I'm actually surprised his ten deep discharges didn't do more (and more immediate) damage.

[rgleason]

Originally Posted by senormechanico

That's a better one than I had found. As part of the rules, we must be curtious, eith each other. We don't necessarily have to all agree.