LG M36 vs Samsung 36G capacity test - 3600mAh or just marketing?

Batteries, Chargers, and Battery Management Systems.
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Matador   10 kW

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Re: LG M36 vs Samsung 36G capacity test - 3600mAh or just marketing?

Post by Matador » Feb 23 2019 11:36am

thunderheart wrote:
Sep 14 2018 9:33am
DC IR test results done with EBC-A20 (5 iterations with 15-30s pause @3600mA)

M36:
28.6, 29.7, 31.1, 30.0, 28.9mOhm

36G:
31.4, 31.9, 30.8, 33.3, 30.8mOhm
:warn: That must be AC internal impedance you're measuring not DCIR... You can see from the discharge curves that the DCIR values are way more than in the 30's. Compare voltages at different loads. DCIR = (V1 - V2) / (I2 - I1) :warn:


This is what I mean in more details : https://endless-sphere.com/forums/viewt ... 5#p1447463

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Re: LG M36 vs Samsung 36G capacity test - 3600mAh or just marketing?

Post by docware » Feb 25 2019 7:37am

Pajda wrote:
Feb 23 2019 6:41am
No problem :) , I now how the results will look like. It will be a good example for community that designing battery pack for more than 1C continuous discharge rate is problematic even with HD/HP cells in 18650 format like 30Q or HG2.

Well, we are in agreement. Designing battery pack for more than let´s say 2 - 2,5 A average continuous discharge per cell is shortly nonsense even for cells like 30Q or HG2. It is obvious that best thermal management for ebike is proper (over) design battery pack to keep low current per cell. See few graphs for illustration 2A versus 5A and one more 2A graph with another cells - PF, 29E, HG2, VTC5A and one new curve 18650B.
All cells were discharged in the expanded polystyrene isolation.

M36 polystyren 2.jpg
M36 polystyren 2.jpg (61.54 KiB) Viewed 492 times
M36 polystyren 4.jpg
M36 polystyren 4.jpg (64.33 KiB) Viewed 492 times
LG HG2 2A v 5A.jpg
LG HG2 2A v 5A.jpg (49.59 KiB) Viewed 492 times
Samsung 30Q 2A v 5A.jpg
Samsung 30Q 2A v 5A.jpg (51.64 KiB) Viewed 492 times
LG M36 2A v 5A.jpg
LG M36 2A v 5A.jpg (54.09 KiB) Viewed 492 times
Warm up B 29E PF HG2 VTC5A at 2A.jpg

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Re: LG M36 vs Samsung 36G capacity test - 3600mAh or just marketing?

Post by Hillhater » Feb 25 2019 4:58pm

docware wrote:
Feb 25 2019 7:37am
.... Designing battery pack for more than let´s say 2 - 2,5 A average continuous discharge per cell is shortly nonsense even for cells like 30Q or HG2. It is obvious that best thermal management for ebike is proper (over) design battery pack to keep low current per cell. ."
This data is excellent.
But... I see a real dilema....
In order to ensure a low current per cell, you would have to increase the battery capacity, size ,weight, and cost.
All of those factors are oposite to the fundamental ideal of an Ebike battery,...lightweight, compact, and low cost
Also, thermal dissipation on an ebike is very different to your test conditions, and with a little thought in pack design and configuration, the cell temperatures will be dramatically different in reality.
What you have highlited is the fundamental limitations of the 18650 cell format...a relatively high DCIR compared to some other cells.
This forum owes its existence to Justin of ebikes.ca

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Re: LG M36 vs Samsung 36G capacity test - 3600mAh or just marketing?

Post by docware » Feb 26 2019 5:33am

Hillhater wrote:
Feb 25 2019 4:58pm

This data is excellent.
But... I see a real dilema....
In order to ensure a low current per cell, you would have to increase the battery capacity, size ,weight, and cost.
All of those factors are oposite to the fundamental ideal of an Ebike battery,...lightweight, compact, and low cost
Also, thermal dissipation on an ebike is very different to your test conditions, and with a little thought in pack design and configuration, the cell temperatures will be dramatically different in reality.
What you have highlited is the fundamental limitations of the 18650 cell format...a relatively high DCIR compared to some other cells.

You are absolutely right, thermal dissipation on the real battery is very different. And is also different with different battery packs. Even in one battery pack you can measure different temperature through the battery and through the cell itself, depending on the design and configuration. Inner cells can have much higher temperature than cells having contact with the battery shell, even higher than my simulation indicates. And that means temperature inhomogenity through the battery pack and even through the cell. Something undesirable for cells and battery lifetime. Low current per cell has potential to diminish temperature and inhomogenity independent of pack design.

By the way, adversely oriented cells in the triangle design has good probability to have homogenous temperature through the pack.

Battery capacity, weight, size and price is always going to be dilema.
But if new incomer hesitates about such dilema, the message is that bigger capacity always means better. Better lifetime thanks to lower depth of discharge (DOD), lower temperature and better homogenity of the temperature, lower parasitic reactions thanks to lower current per cell. Lower unwanted irreversible chemical reactions that are causing lose capacity and age prematurely. Better range thanks to bigger battery capacity generally and also thanks to higher capacity per cell at lower current.

Samsung 35E 1A 2A b.jpg

So investment to as big as possible battery pay-off in the long term. Usually it means not so high increment of total weight, size and money, but can be significant improvement of the range and battery lifetime.

Very important is having properly balanced motor consumption and battery.
Example of unfit combination is 1 kW middle motor BBSHD and 13s4p battery. Such motor can draw from battery 1,5 kW or more. And very often this motor is working with efficiency 50% or lower. You can be sure battery is dead after one or two years for some riders.
For most of ebikers is standard 250 – 350 W motor with peak 500 – 600 W sufficient.

Do you mean that 5p or 6p battery is not lightweight or compact ? And such battery can be suitable for lot of of the standard motors. Often 9p battery can be still acceptable.

Each day milions of e-bikes are in service and majority of them have lightweight and compact battery. And thanks to properly balanced battery capacity to motor consumption the battery lifetime can be sufficient.

I don´t think that relatively high DCIR of 18650 is limitation for ebike. The loss power is calculated as DCIR times second power of the current. So the current is the key.
The problem is often unsuitable chosen and operated, unnecessarily highly kW motor. Style of the ride can also significantly affect battery.

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