Looking at building a new pack with Samsung 50E

Great, thanks for the information Pajda!

Pajda said:

If we talk about a specific cells. 40T and 30Q definitelly belongs to the 2. category. They lose their capacity almost regardless on load. Both are designed for continuous operation at 1.3C charge and 5C discharge and so the are best suited for powertools. 30Q has shitty cycle life (only ca 400cycles no matter when discharged at 1C or 3C continuous, there is also no benefit when the 30Q is charged to 4.1V, the capacity loss is the same as for 4.2V charging) 40T is significntly better than 30Q and can do 1000cycles with 63% of initial capacity at 100% DoD.

But for the comparison 50E will do 1000cycles with 85% of its initial capacity and so it totally outperform 40T at 100% DoD in the cycle life if your average load is lower than 1C and you do not need faster charging that 0.5C. So I can only repeat that 50E is actually the best cell for traction application in 21700 size. LG cells excells in 18650 size, but in 21700 their actual production has poor cycle life and I still did not find reason why.

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Did you have the chance to test Sanyo NCR2070C 20700 3500mAh - 30A?

I have a 6p 30q pack that sees 90A currents and start to get unbalanced. I need a new set of cells and looking at sanyos or 40Ts. I am after the most light weight pack so I do not want to add a lot of cells in P. 18Ah is plenty fine for my needs.

https://m.facebook.com/batterymooch/posts/2089343858021856

For non-FBers
https://www.reddit.com/r/electronic_cigarette/comments/8jk1ww/bench_test_results_sanyo_ncr2070c/


_____

also

https://www.google.com/search?q=test+Sanyo+NCR2070C+3500mAh+site:www.e-cigarette-forum.com

Allex said:

Did you have the chance to test Sanyo NCR2070C 20700 3500mAh - 30A?

I have a 6p 30q pack that sees 90A currents and start to get unbalanced. I need a new set of cells and looking at sanyos or 40Ts. I am after the most light weight pack so I do not want to add a lot of cells in P. 18Ah is plenty fine for my needs.

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No, I have only tested NCR20700B 4200mAh some time ago aka High Energy density cell, when this new format was available on the market.But it took only few months to find, that this particular format will not have shiny future and will be replaced by 21700 and so I lost interest. I have tested 40T and it will work for you well, even with your 90A peaks at 6p, much better than 30Q in terms of cycle life.

Ok, so after going back and forth between 40T and 50E I built my battery with the 50E because of the cycle life rating of >80% after 500 cycles. The 40T had same rating as 30Q which is what my current pack used.

Here's the build details.

20s7p - due to space constraints I hot glued 16s7p on the bottom and laid 4s7p flat on top. Fish paper between 16s7p cells and 4s7p. Large copper bus bars at positive and negative battery ends. Used 8mm strip of .15 nickel and one wide strip of .125 copper utilizing the sandwich spot welding technique to connect the cells. Embedded thermistor in center of 16s7p part of pack. 90A BMS.

Charged it to 81.6V so just under 4.1V.

Did a test run and here are my observations.

Did a 20 mile run with some pretty steep hills. In 50.5 minutes used 11.4A so that averages 13.54Ah - approx .4C. Max A reached was 48.89 - approx 1.4C. Used 847.75wh - 41.1 wh/mi. Battery voltage at end of ride was 74.8V. Min voltage reached was 68.9V.

Pack temp started at 20.3°C and ended at 34.4°C. Half hour later pack temp decreased to 33.9°C so it does not cool off quickly. I imagine it is a heat sink and with no active cooling takes a lot of time to cool.

Not sure what to make of the pack temperature. Problem with my setup is I have no easy way to cool the pack and am wondering if that is going to be a problem. I don't doubt if I continued riding that the pack would have continually increased in temp.

The 50E data sheet has temperature rating of:

3.16 Operating Temperature(*2) Charge: 0 to 45°C
(Cell Surface Temperature) Discharge : -20 to 60°C

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Does this mean I can get close to 60°C and not be concerned? At what temp will the pack start to be damaged?

Note that when charging at 2.4A the pack temp reached 35°C so if I took the battery off charge and immediately started riding the temps would start at 35°C. Not sure if that is an issue or not. My last pack did not have an embedded thermistor so I'm wondering if I had heat issues with my old pack and that helped it degrade.

Thanks for any comments/feedback.

Edit: must've misread the temperature when charging. Pack doesn't get to 35°C when charging at 2.4A, appears to stay at ambient room temp which was mid 20s.

At a constant 30 ° C , the cycle life can drop up to around 20% vs a constant 20°C , but ambient temperature in a lot of places can stay at that level for long stretches of time, so I wouldn't stress over it. If it gets to say, 45°C, I'd take a break for a while if possible.

dukestar said:

Ok, so after going back and forth between 40T and 50E I built my battery with the 50E because of the cycle life rating of >80% after 500 cycles. The 40T had same rating as 30Q which is what my current pack used.

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40T has signifiantly lower DCIR than 30Q. ("LG" 10sec 0.5C load DCIR test method at 50% DoD): New 40T has ca 16 mOhms, new 30Q has ca 25 mOhm, new 50E has ca 34 mOhms at 27°C. But as I mentioned many times before, almost all modern cells with low DCIR does not have good cycle life! In fact there only few cells on the market with low DCIR and great cycle life.

dukestar said:

Did a test run and here are my observations.

Did a 20 mile run with some pretty steep hills. In 50.5 minutes used 11.4A so that averages 13.54Ah - approx .4C. Max A reached was 48.89 - approx 1.4C. Used 847.75wh - 41.1 wh/mi. Battery voltage at end of ride was 74.8V. Min voltage reached was 68.9V.

Pack temp started at 20.3°C and ended at 34.4°C. Half hour later pack temp decreased to 33.9°C so it does not cool off quickly. I imagine it is a heat sink and with no active cooling takes a lot of time to cool.

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This is exactly example what I am talking about. If you are able to design a battery, where the average load is lower than ca 1C, you will not have problem with heating even when used HE cells with higher DCIR. 40°C is absolutelly ok as operating temperature in traction app. It is also because you are not able to hold this temperature during use for longer period of time (days) instead of stationary app.

dukestar said:

Not sure what to make of the pack temperature. Problem with my setup is I have no easy way to cool the pack and am wondering if that is going to be a problem. I don't doubt if I continued riding that the pack would have continually increased in temp.

The 50E data sheet has temperature rating of:

3.16 Operating Temperature(*2) Charge: 0 to 45°C
(Cell Surface Temperature) Discharge : -20 to 60°C

Click to expand...

Does this mean I can get close to 60°C and not be concerned? At what temp will the pack start to be damaged?

Note that when charging at 2.4A the pack temp reached 35°C so if I took the battery off charge and immediately started riding the temps would start at 35°C. Not sure if that is an issue or not. My last pack did not have an embedded thermistor so I'm wondering if I had heat issues with my old pack and that helped it degrade.

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The effect of temperature on the cell wear is much related to the length of exposure. Exponential dependence can be expected.
Even 60°C continuous discharge temperature should be completely safe for operation, but it will of course affect cycle life. The temperature where you can expect instant internal cell damage is above ca 90°C, but this differs from cell to cell. It should be noted that to pass UL tests cells must withstand hot oven test of 130-140°C with no explosion, no fire, only leak is allowed.

Pajda, thanks so much for doing this work.

Pajda said:

40T has signifiantly lower DCIR than 30Q. ("LG" 10sec 0.5C load DCIR test method at 50% DoD): New 40T has ca 16 mOhms, new 30Q has ca 25 mOhm, new 50E has ca 34 mOhms at 27°C. But as I mentioned many times before, almost all modern cells with low DCIR does not have good cycle life! In fact there only few cells on the market with low DCIR and great cycle life.

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Could please you specify them?

My use case is low C-rate, no temp concerns, lower density either way is no problem, don't care about DCIR.

So really the only "quality" factors left are Ah capacity and cycle count longevity

Pajda, thanks for your input much appreciated. Your comments about pack temps is reassuring. Do you think if I max the pack temp at around 40°C - 45°C that I will be ok with regards to preventing pack cycle life degradation due to excessive heat? I think I can manage that without active cooling. If not, I'll look at adding a fan to my battery case to get some airflow over it.

Thanks again...

john61ct said:

So really the only "quality" factors left are Ah capacity and cycle count longevity

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john61ct, based on your quote the 50E may be a good option for you but note the datasheet has a recommended charge current of 2.45A for pack longevity, max 4.9A (not for cycle life). If you need a fast charge it may not be the cell for you.

HTH

dukestar said:

john61ct said:

So really the only "quality" factors left are Ah capacity and cycle count longevity

Click to expand...

john61ct, based on your quote the 50E may be a good option for you but note the datasheet has a recommended charge current of 2.45A for pack longevity, max 4.9A (not for cycle life). If you need a fast charge it may not be the cell for you.

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Thanks, discharge and fast charge might approach 0.6C occasionally, but usually both kept under 0.3C

As stated not a propulsion use case.

Hi there, I know this was a couple years ago, but I'm facing the same dilemma deciding between the 40t and 50e. How has your pack held up a couple years later? Thanks!

Sent from my SM-S901E using Tapatalk

My 50E 14S3P pack which is now about 18 months old and circa 100 charges has not shown any real change from new. In some ways it took about 10 charges before it settled down at better than manufacturer specs. Max is 20A but I do fully charge it and run it down to below 2.9V at times, everything you shouldn't do.

For the cost, if I get 500 charges or even less I don't care as by then there will be superior cells available probably lighter and with more capacity, everything an EBiker would want..

Waynemarlow said:

My 50E 14S3P pack which is now about 18 months old and circa 100 charges has not shown any real change from new. In some ways it took about 10 charges before it settled down at better than manufacturer specs. Max is 20A but I do fully charge it and run it down to below 2.9V at times, everything you shouldn't do.

For the cost, if I get 500 charges or even less I don't care as by then there will be superior cells available probably lighter and with more capacity, everything an EBiker would want..

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Ok sweet that's good to know, thanks for the response!

So your controller draws 20amp max? Do you notice if the battery ever gets hot, especially over summer?

Also do you know if your cells are in a plastic holder, spacing them apart? Or are they stuck directly on to each other?

Thanks again

Sorry the battery is located in a compartment so there’s no real way of looking at the temp. I thought of fitting a BT BMS and should have in some ways, but the cheapo simple types with a temp sensor on seem to be OK as a backup in case of a high core temp.

Our batteries are shrouded in thick heatshrink and sealed with silicon at any cable exit points to stop water ingress, what’s the point of plastic spacers when there’s no airflow. Double sided sail tape locks the cells together whilst building them, works well.

We are looking for light weight, max energy in minimum space with reliability, that rules out longevity in my view.

Waynemarlow said:

Sorry the battery is located in a compartment so there’s no real way of looking at the temp. I thought of fitting a BT BMS and should have in some ways, but the cheapo simple types with a temp sensor on seem to be OK as a backup in case of a high core temp.

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As long as they actually respond to the sensor, yes. See Methods' failure analysis thread on a Daly BMS about what happens when they don't.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=118344