Why DIY ?? Stop with Eve or Lishen or aluminium terminal cells without factory build stud/thread.

[curiouscarbon]

If It it's about cooling the battery casing in tropical temperature environment....

Yes indeed, primary interest is sub-ambient charging temps. Not high-C-rate charging. (that’s secondary hehe)

Fighting elevated ambient temperatures, not self-heating from fast charge.

Basically, insulate battery compartment and regulate temperature to prevent cycle degradation… nothing too exotic ? but maybe tropical

After reading that LiFePO4 experiences more cycle degradation when charged at only 30 celsius, I began designing cell material regulator for myself..

Important to note that peltier come in different grades, similar to battery cells. 40x40mm but 3amp,6amp,9amp,15amp ratings.. inversely related to resistance, 15amp modules are 0.75-0.9ohm AC resistance when tested with cell resistance meter individually. I am using 15amp rated modules (TEC-12715) stacked. This means that individual module has lower delta T and higher efficiency. If delta T per module is <10 C and voltage per module is <3 V then efficiency can actually begin to approach R-134a refrigerant based systems with arguably significant responsiveness and maintenance benefits. (using H-bridge heat flow can be reversed in realtime, no delay for heat pipe valve rotating) (solid state heat pump element, much less prone to failure than compressor in my opinion) (still requires rotating pump for water/glycol coolant)

I’m anxious about having the liquid coolant near the batteries, due to possible conduction… so I would use air to take away the heat.. no high-C rate so no need for high thermal conductivity of direct contact of coolant or cooling plate maybe.. just insulate a bit.

Will document more soon.. soldered some IC today, slow brain..

Still learning about ideal charging temperature for LFP..



This is the paper I am referring to when I say 30 C degradation for charging.

General LiFePO4 Degradation vs Temperature

Concerned about your LiFePO4 batteries ♨️Overheating♨️ or ❄️Freezing❄️and losing ability to hold charge due to operating temperature? This is a research paper that carries out charging and discharging at set temperatures, and evaluating the...

diysolarforum.com

 

[Frank in Thailand]

I've been playing with peltier since the pentium 120mhz..
1995?

I'm not worried about keeping charge in solar system setup.
it charges and discharge every day.
the few micro Ah it would keep extra by cooling it below 30c, time, materials and energy (from that same battery) needed to cool..
most situations not beneficial.

time and costs involved better just buy 280Ah instead of 200Ah cells
probably cheaper also

Obviously there are circumstances where that's not so relevant.

Like I have 4 X 800watt wind turbines in a location that seldom have wind... Or enough wind to start the turbines.
Absolutely not cost effective.
But... When there is rain, often it's combined with wind, strong enough to produce electricity.
And rain usually is absence of enough light to solar charge.

At the time I "developed" that setup..
I had 200ah lead acid, 16*.
That was hardly enough to live a few rainy days.
We all know how much lead acid s*cks compared to lithium..
But 2019.. LiFePO4 was crazy expensive, 4 times the price of...

Now.. it's there.
And now I would not make this choice to buy and build them, but use the funds for additional solar and LiFePO4.

Peltiers can be really successful.
Stacking them, I've never tried.
I know units that are in service many many years.
As long as you can get away without fans...
But even those can reliable.
Silent wings 3, liquid bearing, really low power consumption, good static pressure and under 24/7 use, roughly 25 years before they fail.

I won't be using any peltiers in my setup soon, but please make a new thread about it.
I'm curious about it.
And do have peltier, heatpipes, etc. For different projects tinkering
Because it's fun!

 

[nonoceb]

I would like to see a real AC IR mesurement, easy to say new harder to have a video of real mesurement

 

[nonoceb]

Peltier can be efficient with low voltage like 3.3V instead of 12V, i was thinking remplace dump balancing resistor by peltier module and activate balancing at 3.4V to keep them cold for charging

 

[Frank in Thailand]

Please explain, what is AC IR ??

Found it

Sadly, I don't have this equipment or know anyone who has.

I do have this one:YR 1035+
My experience with it is limited to measure Internal resistance and high accuracy voltage.

Happy to do some tests, if you can tell what steps to take with this meter.

 

[nonoceb]

Please explain, what is AC IR ??

Found it

Sadly, I don't have this equipment or know anyone who has.

I do have this one:YR 1035+
My experience with it is limited to measure Internal resistance and high accuracy voltage.

Happy to do some tests, if you can tell what steps to take with this meter.

View attachment 57825

good, test these cells vs your EVE cells, accuracy isn't very important

 

[Frank in Thailand]

Obviously also have multimeter:
and ampere meter.

I'm not an electrician, most of my tools are used only with their basic functions while they can do so much more.

Step by step (or link to website that has) on how to use them to get the accurate information you like..

A few minutes is easy to make YouTube.
10 hours... That's problematic

 

[Frank in Thailand]

Internal resistance is easy enough.
One cell Vs 8, will have difference.

Minimal I can test is 2 BYD cells 6.4v

 

[Frank in Thailand]

Testing with my YR 1035+:

One Eve 280 is 00.18 m ohm
That is a cell that wasn't installed during the fire
Other Eve152Ah, also not installed during the fire 00.32

Both have had that reading since the start. Or actually, the 152Ah where 6 months old before I got the meter.

The BYD dances a little, probably because it's getting charged.
Between 00.12m and 00.22 m ohm

I don't understand how this can give you information.

As new Lishen 152 was 32, "old" Eve 152 was 32, and new Eve 280 18

The BYD (2 cells)" with 12-22 right in the middle.

In a few hours solar is about the same as we use for power, and battery isn't really charged or discharged.

I can make new reading then.

 

[nonoceb]

high IR mean old used cell. As IR AC tester is doing fast discharge charge at 1khz for mesuring it's better doing this without external current.
0.2mOhm (280Ah) at 1C discharge = 2% heat loss, and as you can double IR AC for continous DC discharge, in reality it's 4% heat loss

 

[Frank in Thailand]

I don't have AC-IR, just my YR 1035+
And willing to make any test within its, and my capacities.

The AC-IR machine looks nice, no idea for the costs.

And for "one time use", the $40 for the YR 1035+ is already high.

 

[nonoceb]

YR 1035+ is fine for our application and it's a low cost AC IR tester

 

[Frank in Thailand]

Leaned something new today!
I did not even know it was AC -IR
In a few hours, when it's stable (not 20-40A charge per set) I'll measure again.

What value are we looking for?
And does 2 cells measure influence the IR?
I guess it does, 2 X the battery, is 2 X the internal resistance, yes?

So if I measure 12, one cell has 6?

 

[Frank in Thailand]

I measured with a few A charge, more stable bit not yet great.

Tomorrow I can make some different settings in my setup, run it a few hours "battery less" so the LiFePO4 cells rest and should give stable reading.

To be continued

 

[Frank in Thailand]

Took little more time, but now I have stable readings.

Battery charged to 60% 0.001 voltage difference between the cells.
(What is absolutely normal at 60% for all LiFePO4, of you have more...like 0.01v or higher...
You have a huge problem)

2 cells 35-38
4 cells 71-74

Average 17-18 m ohm
To place the numbers correctly

00.17 to 00.18 m Ohms

Whole pack (8 cells) 01.40m ohm
00.175m ohm

I did some further investigation, and it seems like that the cells didn't reach the C rating within temperature range

Signs of mounts
Seem to be from this testing phase.

Without any real evidence..
I can't say for sure.
The batteries work now nice and stable.
That's for sure

 

[stienman]

You're spending about $97/KWH, while I'm spending $130/KWH.

It's a 30% markup for known new, traceable cells from a reputable seller with reasonable support and at least some warranty.

But even that's a big savings compared to the commercial market in the US. Consider the following, not including shipping or installation:

Tesla Powerwall - $778/KWH
Renogy - $708/KWH
BigBattery - $396/KWH
GYLL - $312/KWH

Notice that there's approximately a 50% drop between each tier. (why renogy is "competing" with Tesla, though, when its quality and support put it in, at best, the middle tier, I'll never know)

DIY, slow boat cells from overseas is, again, a 50% drop to $100-$150/KWH.

The problem is that your cells are essentially within that tier, but don't include any traceability, guarantee, warranty, or support.

So yes, while there is a 30% savings, it's still pretty close to what others spend on DIY packs, but they're getting significantly more in terms of support.

All that said, if you can somehow get the to my door, DDP, for $100/KWH I'd gladly buy a few.

 

[Frank in Thailand]

If you are talking about you spending $130 on "Eve" or "Lishen"..

Absolutely worthless (some of them) with only warranty, if they don't show you might get some refund.
Just look at my "high quality" 152Ah cells and the long long list of trouble.

If you are on the forum long enough you see the pattern where buyers from China just have actually no warranty at all.

Probably why the USA sellers of the same cells need to minimal tripppe the price, to compensate for this risk.

Where Eve and Lishen is known as "sub quality" , BYD is as top quality.

The cells available from Lishen and Eve via Ali express or Alibaba are almost certain drop outs for EV builds, did not match QA tests.

For that matter...
The eve, lishen and BYD we are able to buy all have the same "black spot"

Please..
Don't think you can buy real quality Eve, Lishen or BYD via Alibaba or AliExpress.
Just dropouts, that are still absolutely great for solar, our low C rating, for many, many years.

 

[stienman]

I'm happy you've found a solution that meets your needs, but to proclaim that everyone else is stupid for choosing a path that failed for you is unproductive.

You asked why some are still choosing this path, and I explained why, yet you keep suggesting that I'm wrong for continuing down my path.

I have two battery packs with 32 cells each of decade old LiFePO4 cells that I only recently revived and sorted. Using diyBMS I can see the voltage of each cell and find runners long before they become a problem. I have a torque wrench specifically for these cells. All my cell terminals are flexible. I've compressed them according to the manufacturer's instructions (instructions which have been around for over a decade - so I'm not sure why you claim cell compression is a new thing). I'm using the appropriate conductive antioxidant.

These are all things you obviously had issues with, and so yes - for you I'd strongly recommend a path where experts have taken care of those aspects of your system for you.

You seemed so happy with your choice that I didn't go into the reasons I'd actively choose against your path, but as you're insisting my reasons are wrong, here's the main reason I don't think your path will work well for me:

You can't get BYD packs that are perfect in every way at that price. One of the following, or a similar issue, MUST be true:

1. They are used, or didn't pass QA.
2. Some firm owned them, went bankrupt, and a liquidation sale is providing real value for good product, but it's a deal that won't be around long term.

If it's 1), keep in mind that these packs are irreparable. If one cell in your pack runs, you get to throw the whole pack out. Unless there's a good reason these are on temporary sale, then I doubt you're actually getting grade A, perfect, new, matched and batched packs for this low of a cost, which means that, as a whole, your investment is unlikely to last as long as rated. Even if a cell does go bad, I replace it and move on. You've got six packs. If one cells goes bad you lose 16% of your storage capacity, and by that time the available packs will be sold and you'll be searching for a replacement that doesn't match the rest of your system.

If it's 2), then sure, strike while the iron's hot and grab a bunch of them while you can, knowing that the deal won't last forever.

Just because your path is good for you doesn't mean another path is bad. Be happy with your journey, let us know how things go, but don't actively tell others that they are wrong to travel a path other than the one you've chosen.

 

[Frank in Thailand]

@stienman
Perhaps the information is for over a decade out there.
And I'm happy for you that you where able to find it, 10 years ago.

I do not know your background, for me software third line support.

To me, Lithium battery was something expensive for ebike 10 years ago.
And 3 years ago unaffordable.
Professionals? here?, rural Thailand?
Without bashing, my mother has higher knowledge then any available Thai "expert".
"Professional" construction workers build a wall, take a hamer, make a hole and place the window frame.
Anyone who knows a bit of this Thai professional level, probably smiles in recognition and knows, nope.... That's not an option.
In Bangkok area, there for sure are professionals.
What left me with a long road of trial and error, where availability of simple things as "appropriate antioxidant" already something is that needs to be ordered from the states.
Unless you find vaseline appropriate

I doubt that your capacity 10 years ago was in the area of +500Ah
That's a good thing!

Eve have their lower capacity cells with pre drilled and tapped holes.
Not their 100-280Ah units, 20-30Ah.
And with it, the humongous difference in error margins.
20-30Ah will have way lower capacity to deal with then 280Ah.

I'm happy for you that your setup works great.

Also that you had the opportunity to work with flexible Bus-bars
(not provided by Chinese seller)
And that you gained in depth knowledge before you started.

Me? I watched Will Prowse and Dave Pozz

Became member of this forum and read as much as I could find about LiFePO4.

I'm not trying to stop anyone from tinkering.
Just pointing out that there are (sometimes cheaper) alternatives that have better build quality then we ever can make ourselves.

Also that our 280Ah cells aren't intended to be used as we do.
20Ah perhaps was/is, but that's not what most members are playing with.
And with it the increase of possible errors, and loss of batteries or more.

It's important people understand that we are no longer within Factory specifications, way, way, WAY outside it.
And that there are alternatives who are, without compromise on quality or costs.

As said, if they where Available 18 months ago I would perhaps be tempted to DYI because it's fun, but for the stability, we live off grid, would have chosen pre-build.

Now BYD Box is available long long time. +/- $3000 for 150Ah, S16, 51.2v. (7.5 kWh)
That's already discounted price...
And no, not realistic alternative for me.
$1300 for 13.3 kWh...
That is realistic alternative.

Perhaps "unicorn find", but it's out there!

If anything, I try to inform that we are Walking a dangerous path, the higher capacity builds.
And that there are quality alternative out there.

Sure, losing one cell would mean losing the set.
Not easy to replace (but bypass is really doable)
I doubt that many cells stay around 5 or 10 years to have the same type replacement, and with it, the probelm is the "same".

To my knowledge they have failed QA high (dis)charge test.
(C2 rating) probably got at some location too hot.

They have 260Ah, low internal resistance (00.18 m Ohm) and work at the start, stable.
Something that my 152Ah Eve cells did not.

Many of my issues would not have occurred living in Netherlands, where materials are widely available.
Here? Post order, where Covid made over 50% lost.
(Thai desinfect with alcohol spray.
That does wonders for the address label.. all is black...)

I share my experience and my opinion.

The high capacity(+200Ah) cells with garage drilled and tapped threads...
Aren't easy to use safely in S16 setup.
If it's any way possible, buy with laser welded studs!

 

[iamrich]

Now BYD Box is available long long time. +/- $3000 for 150Ah, S16, 51.2v. (7.5 kWh)
That's already discounted price...
And no, not realistic alternative for me.
$1300 for 13.3 kWh...
That is realistic alternative.

Perhaps "unicorn find", but it's out there!

I paid $850 for my used 24v BYDs (x2) and managed a reliable 6kwh out of them so far. Who knows how long they will last, but I felt they where a good deal (can't find them now). If you are getting 13kwh for $1300, I would consider that a great deal! Wish there was local USA stock at that price.