Low drain vs high drain cells


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Jamenhaut

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Hi, I started working again on my 7s40p battery.

Most of my cells have been harvested from ebike battery pack, but for my build Im gonna use only cells from ebike packs.
I rode several times on this forum that it's better to work with laptop cells but I didn't understand why.

Is it about high and low drain cells?

From ebike packs Im having cells rated from 0.4 to 8A discharge current.
Does it mean that there is high and low drain cells? Or so, how to difference them?

And my last question is, what’s the disavantage about high drain cells, because it’s nice to have high discharge rates but it should be a negative point that I didn’t get.


Greetings,
M.
 

Oberfail

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Its not better to work with laptop cells.
Its just generally reccommended to stick to one set of cells because different kinds of cells have different charge / discharge characteristics.
If you for example have a 40p pack with 30 ebike cells and 10 laptop cells, you cant just draw 40 times as much current as a ebike cell is rated for, you have to take the weakest cell, most likely the laptop cell, into consideration aswell.
 

floydR

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An Ebike cell with a .4A discharge current? What cell is that?
later floyd
 

OffGridInTheCity

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Hi, I started working again on my 7s40p battery.

Most of my cells have been harvested from ebike battery pack, but for my build Im gonna use only cells from ebike packs.
I rode several times on this forum that it's better to work with laptop cells but I didn't understand why.
Is it about high and low drain cells?
It's about availability, quality, price to meet the design of your battery. ebike batteries are generally limited in size - so high drain cells (e.g. hi amp) cells are needed to deliver the required current.

Powerwalls are generally large and are designed for significant capacity. This leads to using many, cheaper, low drain cells that add up to the needed current and capacity.

And my last question is, what’s the disavantage about high drain cells, because it’s nice to have high discharge rates but it should be a negative point that I didn’t get.
High amp cells are generally more expensive. If you don't need high-amp then why pay more.

There's no right answer - design your battery and acquire cells you need to achieve the design goals.
 

Jamenhaut

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An Ebike cell with a .4A discharge current? What cell is that?
later floyd
LDAME11865 https://baterie18650.pl/wp-content/uploads/2020/04/Product-Specification_2Ah_ME1_LGC-1.pdf
got 40 of these
that's the only cell that i have in these ranges, the next ones are between .5 and .6A

High amp cells are generally more expensive. If you don't need high-amp then why pay more.

There's no right answer - design your battery and acquire cells you need to achieve the design goals.
Ok, it looks like I can just keep on harvesting theses cells,
So theses cells will be still working well into low drain application like powerwall?


Thanks for your answers guy!
 
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floydR

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2.7 max. discharge current 10000mA 10A sometimes listed a max. continuous discharge and max pulse discharge.
Yes these cells will be fine in a powerwall as long as they pass IR (internal resistance) check,capacity test, self discharge test,
later floyd
 

Jamenhaut

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2.7 max. discharge current 10000mA 10A sometimes listed a max. continuous discharge and max pulse discharge.
Yes these cells will be fine in a powerwall as long as they pass IR (internal resistance) check,capacity test, self discharge test,
later floyd
so in the ebike pack where they are drawing current above the standard discharge current and more near to max. discharge current?

So me when designing packs, should I care more about the standard or max. discharge current to define the currents I allow the pack to let it go?
 

floydR

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E bike battery might come close to the max discharge rate.
Neither standard or max discharge somewhere in between.
Remember You are having a bunch in parallel so if you draw 40A(1kw) from a 7s40p battery pack that is 1A per cell. @80p that drops down to .5A per cell. design. I would design packs for use at or below what I tested the cells at.
Later floyd
 

Wolf

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LDAME11865 https://baterie18650.pl/wp-content/uploads/2020/04/Product-Specification_2Ah_ME1_LGC-1.pdf
got 40 of these
that's the only cell that i have in these ranges, the next ones are between .5 and .6A
I think you mean LGDAME11865
1643492520380.png
Fairly decent cell designed for Light Electric Vehicle.

1643492951024.png

The IR spec is the key here ≤40mΩ which for an "ICR" cell brings it extremely close to a high drain "INR" cell.
If you can get all your cell within ±7mΩ and ±250mAh of each other than you will build a reasonably good battery.
7s40p with average cell of 2000mAh equals an 80Ah battery. A 20A draw on the battery will give you theoretically 4 hrs of run time with a 500mA draw on each cell. Quite acceptable for high or low drain cells. Just keep the IR and mAh close between cells and you will be successful.

Wolf
 

OffGridInTheCity

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E bike battery might come close to the max discharge rate.
Neither standard or max discharge somewhere in between.
Remember You are having a bunch in parallel so if you draw 40A(1kw) from a 7s40p battery pack that is 1A per cell. @80p that drops down to .5A per cell. design. I would design packs for use at or below what I tested the cells at.
Later floyd
People often use 1000ma (1a) for their discharge test as this is what OPUSs and similar charge/discharge capacity testers offer. In my case I use 500ma (0.5a) because my OPUSs get too hot and shut-off. A strong recommendation is to design your battery to use <= what you use in your tests to validate your cells. So you know going in you're cells can handle the draw on the battery.

For example, a 14s100p at 1a/cell = 100a@48v = 4,800watts of continuous power. If you do 200p (or 2 x 14s100p in parallel) it will go up to 200a @ 48v = 9600w you can safely draw.

My home powerwall is large enough that I average <200ma (0.2a) / cell - so 500ma discharge testing works for me :)
 
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Jamenhaut

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I think you mean LGDAME11865
View attachment 26857
Fairly decent cell designed for Light Electric Vehicle.

View attachment 26858

The IR spec is the key here ≤40mΩ which for an "ICR" cell brings it extremely close to a high drain "INR" cell.
If you can get all your cell within ±7mΩ and ±250mAh of each other than you will build a reasonably good battery.
7s40p with average cell of 2000mAh equals an 80Ah battery. A 20A draw on the battery will give you theoretically 4 hrs of run time with a 500mA draw on each cell. Quite acceptable for high or low drain cells. Just keep the IR and mAh close between cells and you will be successful.

Wolf
Ahaa! I based my packs on the cells that have the higher standard discharge current. and so have theses cells:
89x INR18650-35E ~3300mAh (tested SOH)
163x NCR18650GA ~3400mAh
28x US18650NC ~2800mAh

So it would be better to replace the US18650 by another higher capacity cells that draw lower discharge standart current but with a maximum discharge current suiting with my spec of 40A for each parallel pack?
Would it be better to replace it with the LGEBMJ11865?
All my cells are IR tested with the RC3563 and are under 30mΩ (thanks to you for posting a lot about IR)

People often use 1000ma (1a) for their discharge test as this is what OPUSs and similar charge/discharge capacity testers offer. In my case I use 500ma (0.5a) because my OPUSs get too hot and shut-off. A strong recommendation is to design your battery to use <= what you use in your tests to validate your cells. So you know going in you're cells can handle the draw on the battery.

For example, a 14s100p at 1a/cell = 100a@48v = 4,800watts of continuous power. If you do 200p (or 2 x 14s100p in parallel) it will go up to 200a @ 48v = 9600w you can safely draw.

My home powerwall is large enough that I average <200ma (0.2a) / cell - so 500ma discharge testing works for me :)
Yes, i was testing under LiitoKala that only allow 500ma discharge current, but i just ordered 3 Opus, to test them faster and be OK to drive higher current from the cells. Looking forward to build a fan cooling system for them ;)

Thanks guys
 
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vicriz

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I think you mean LGDAME11865
View attachment 26857
Fairly decent cell designed for Light Electric Vehicle.

View attachment 26858

The IR spec is the key here ≤40mΩ which for an "ICR" cell brings it extremely close to a high drain "INR" cell.
If you can get all your cell within ±7mΩ and ±250mAh of each other than you will build a reasonably good battery.
7s40p with average cell of 2000mAh equals an 80Ah battery. A 20A draw on the battery will give you theoretically 4 hrs of run time with a 500mA draw on each cell. Quite acceptable for high or low drain cells. Just keep the IR and mAh close between cells and you will be successful.

Wolf
Hi Wolf,

How to categorize between high or low drain battery...?
I mean the 'minimum requirement' of high drain battery. Maybe if the battery have 5C (min) then we can call it high drain?
 

Wolf

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How to categorize between high or low drain battery...?
High drain cells generally are a different chemistry than low drain cells, for high drain it is usually IMR and INR . These cells have a very low AC IR readings usually in the sub 20mΩ range allowing high amps to flow without generating massive amounts of heat. These cells are mostly found in power tools. The "low" drain cells are generally ICR chemistry and some hybrids usually in the >30mΩ range. Max discharge capability of a cell is not necessarily the deciding factor in identifying a "high" or "low" drain cell.

Here is an example from my database of all the cells that have a 10A max discharge which included ICR, INR, NCR, and CGR chemistries.
Wolf

1652589517863.png
 

italianuser

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How to categorize between high or low drain battery...?
I mean the 'minimum requirement' of high drain battery. Maybe if the battery have 5C (min) then we can call it high drain?
A high drain battery will be sold as "Power cell", while the other type is called "Energy cell". From my research cells at and above 10Ah discharge capacity are usually power cells. And some energy cells (ICR chemistry) do reach 4 or 5Ah discharge capacity.

Here's a table I keep as a reference:

18650_chemistries.jpg
 

OffGridInTheCity

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@Wolf and @italianuser - very interesting!

I've had a sense of the power vs energy aspect just from working with so many cells but the detailed comments have brought it in focus today :)

Battery 1 in my powerwall is high drain cells (LGDAMF11865 and ICR18650-22P have 10a discharge) but I don't see the chemistry specification in my data sheets - where does one find this?

The rest are modem (laptop or energy cells). Battery 1 is fairing well but at <160ma / cell I wonder if it will make a difference in the long run in a powerwall context between power and energy cell types. Time might give some anecdotal info to share.
 
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italianuser

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Battery 1 in my powerwall is high drain cells (LGDAMF11865 and ICR18650-22P have max 10a discharge specs) but I don't see the chemistry specification in my data sheets - where does one find this?
I learnt from you all! :)

They are both ICR cells (the name itself or the datasheet sometimes give the info or some sort of a hint), the LG is a MF1 series and the datasheet says:

Lithium Ion ICR18650 MF1 2150mAh
1.4 Model name: ICR18650 MF1
2.6 Standard Discharge (Refer to 4.1.2) Constant current 0.2C (430mA)
2.7 Max. Discharge Current 10A

So, I suppose, it's life is longer when using normal discharge at 0.2C and that 10A brings it at maximum stress level (maybe heats up a lot, too? or maybe, only good for a limited amount of time / peaks)
 

OffGridInTheCity

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I learnt from you all! :)

They are both ICR cells (the name itself or the datasheet sometimes give the info or some sort of a hint), the LG is a MF1 series and the datasheet says:

Lithium Ion ICR18650 MF1 2150mAh
Ah - so obvious! But ICR in the chart above is marked *low drain....

2.6 Standard Discharge (Refer to 4.1.2) Constant current 0.2C (430mA)
2.7 Max. Discharge Current 10A
These ICR18650 MF1(s) were from 20cell ebike packs from BatteryHookup and eBay a few years ago. As ebike packs the 10a might have provided some amount of surge capability.
 

vicriz

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High drain cells generally are a different chemistry than low drain cells, for high drain it is usually IMR and INR . These cells have a very low AC IR readings usually in the sub 20mΩ range allowing high amps to flow without generating massive amounts of heat. These cells are mostly found in power tools. The "low" drain cells are generally ICR chemistry and some hybrids usually in the >30mΩ range. Max discharge capability of a cell is not necessarily the deciding factor in identifying a "high" or "low" drain cell.

Here is an example from my database of all the cells that have a 10A max discharge which included ICR, INR, NCR, and CGR chemistries.
Wolf

View attachment 27451
Hi Wolf happy to see your explanation
So the C-rate is not only item to determine 'high' or 'low'. We also need to take a look the AC IR of the battery.
Well noted and thank you.

Now I need your reccomendation related battery tester tools.I want to buy one of SkyRc product, imax b6ac. I think it is all in one tools. What do you think Wolf...?
Or I still need YR1035...?
 

italianuser

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Ah - so obvious! But ICR in the chart above is marked *low drain....

These ICR18650 MF1(s) were from 20cell ebike packs from BatteryHookup and eBay a few years ago. As ebike packs the 10a might have provided some amount of surge capability.
That's true... it's not a 100% strict rule, some cells are half way between what we call low-drain (for our low-amp-hour per cell applications) and high-drain which we have in our power tools.

I found some interesting literature about Li-Ion cells chemistries but I refuse to go too much in-depth! 😁 There's so much to learn, I can't make it!

power-vs-energy.jpg
(https://www.batterydesign.net/power-versus-energy-cells/)

This was an interesting graph, I'm quite sure that LG ICR MF1 cells do have some characteristics that make them similar in some way to high-drain cells. LG's datasheet reports a low IR, too, <=35mOhm, not a typical ICR IR.

@vicriz "Or I still need YR1035...?" -> Oh yes, if you want to work with cells you must have an IR tester to learn more about your cells. @Wolf 's n.1 lesson I learnt is "know your cells" :cool:
 
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