Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Batteries, Chargers, and Battery Management Systems.
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zacksc   100 mW

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Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by zacksc » Mar 08 2020 11:05am

I have been reading a number of great posts here on batteries, including “Li-ion cells ageing”, and I would like to ask a question pertaining to some specific cells and configurations. This involves some small, 200 Wh batteries, but you can easily scale it up to larger sizes by imagining doubling or tripling the number of parallel channels (and the projected current draw). Of the following choices, which would you prefer?

1) a 14sx1p battery made with 21700 40T cells (50.4 V)
2) a 10sx2p battery made with 18650 30Q cells (36 V)
3) a 10sx2p battery made with 18650 MJ1 cells (36 V)
4) a 10sx2p battery made with 18650 MG1 cells (36 V)

These all contain roughly the same power (200 Wh). I am thinking of a continuous current draw of about 5 amps for the first choice, which is a nominal 50.4 volt battery, and a current draw of 7 amps for the other three choices (which are each 36 volts). Happy to explain why I picked these 4 at some point, but I didn’t want to initially prejudice the discussion that I hope may follow. I would be really interested and appreciative of thoughts, comments, feedback, expanding the question, etc.

john61ct   100 GW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by john61ct » Mar 08 2020 11:52am

Just in general

voltage of the pack is usually a given for this type of question

determined by the motor/controller limitations and top speed desired.

Once you have the desired pack voltage, then use Ah for range and for reducing the C-rate required to get to the desired battery current capacity.

Watt-hours really are rarely relevant, needed only when comparing systems at different voltages.

john61ct   100 GW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by john61ct » Mar 08 2020 11:55am

to give specific cell reco's, need more info about your use case

especially C-rate peak vs continuous, which involves, what sort of riding, terrain etc

eMark   100 W

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by eMark » Mar 08 2020 12:38pm

There are too many unknown variables ... not enough specifics (application) to offer another/different opinion at this time. That said, assuming you can adequately justify your reasoning for these 4 choices should we disagree? It's your money, your DIY build, your specific application, your preference, your opinion :)

All 4 of these brand name cells are [reasonable] choices depending on the specific application. Money is always a factor if possibly deciding to go with another cell should you find a good deal on a comparable cell :D
Happy to explain why I picked these 4 at some point.
Sooner than later would be helpful ... :thumb:

leffex   100 W

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by leffex » Mar 08 2020 1:14pm

zacksc wrote:
Mar 08 2020 11:05am
1) a 14sx1p battery made with 21700 40T cells (50.4 V)
2) a 10sx2p battery made with 18650 30Q cells (36 V)
3) a 10sx2p battery made with 18650 MJ1 cells (36 V)
4) a 10sx2p battery made with 18650 MG1 cells (36 V)

These all contain roughly the same power (200 Wh). I am thinking of a continuous current draw of about 5 amps for the first choice, which is a nominal 50.4 volt battery, and a current draw of 7 amps for the other three choices (which are each 36 volts). Happy to explain why I picked these 4 at some point, but I didn’t want to initially prejudice the discussion that I hope may follow. I would be really interested and appreciative of thoughts, comments, feedback, expanding the question, etc.
I take from memory packs 36v 7.8ah (288wh) 10s3p using 5a cells their absolut max draw is 500w or 13a shared they are 4,33 a per cell or 350w / 3,1a for the most majority of these 10s3p packs.

Your 5a draw for the 40t pack and 7a draw shared between the 2 cells packs should be sufficient for ebike use.

What I would go for: Cost, time to build depending on which pack to choose. For the 2-4 pack I would go with MJ1 cells if I had the choice all other things being equal.
Salestech in an ebike store

zacksc   100 mW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by zacksc » Mar 08 2020 1:41pm

Here is some additional specification. This is for riding on flat terrain exclusively, so the current draw would be essentially constant at 5 amps for the 36 volt option, and 3.5 volts for the 50.4 volt option. So that is pretty close to "C" in each case, but I did not want to define it as "C", since that would imply a variability that I don't intend. I am not expecting to use a higher current at any point. The controller would be a Baserunner or a Grinfineon type like C4820, and driving a small motor such as a Bafang G310. I am thinking those can handle either 36 or 51 volts so I didn't see anything obvious that would preference one or the other voltage.

I am thinking the first two options, 1) the 40T, 2) the 30Q, are somewhat intermediate or highish current capacity cell choices. I didn't really have any idea how one might choose between these two seemingly disparate choices, which each get to 200 Wh at a similar weight, but in a very different manner (one at 51 V, the other 36 V). I am not aware of any aspect of my controller or motor that preferences one voltage over the other, and I wondered how other people feel about.

The third choice is the MJ1 and I wondered how that would perform vs the 30Q in the 10s2p configuration at the specific constant current draw of 2.5 amps per channel (5 amps total). Is that a high enough current to justify the choice of 30Q over the in many ways superior MJ1?? Suppose I charge to 80% everyday and draw down to 15% riding at a constant draw of 5 amps. Which choice would seem better after 10 rides, 50 rides, (or 100 rides)?

The last choice, the MG1, I am thinking is just straight up inferior to the MJ1, but I am not really sure and wondered what other people think about that. It is my preference to ignore $ cost for this discussion, since that could complicate things in a non-physics way that could make this discussion messy and vague.

goatman   100 kW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by goatman » Mar 08 2020 1:55pm

30q and 40t are optimal at 7 amps as far as im concerned and will be doing some testing. I have a concern of the 40t though and that's temperature. at 10 amp discharge it hit 50 Celsius, not good but if youre not pulling 10 amp continuous? then why not. Docware did the test look for the post, 40t cells and others like it I believe. here

viewtopic.php?f=14&t=102682&hilit=40t+t ... 5#p1503088

the mg1 I have a 13s5p and I wont run it at 36amps, it was lifecycled at 2.6amps? look for the datasheet. it was also tested at 10 amps and was damaged right away and was recommended not to go over 7amps so that pack is on my sons 20amp bike. mg1 is rare on info Ill do a quick look to see if I can find a link.

basically I would run a 30q or 40t and my choice would be for ah and pack dimension/what fits amps desired
3p 30q is 18mm x 3= 54mm and 9ah, 21amps
2p 40t is 21mmx2= 42mm and 8ah 14amps

4p 30q is 72mm/12ah and 28amps at 7amp/cell
3p 40t is 63mm/12ah but only 21amps at 7amp/cell

and then price difference, 40t costs more but by weight they deliver the same ah

heres mj1 at 10 amps 73 Celsius

https://www.e-cigarette-forum.com/threa ... ry.774181/

goatman   100 kW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by goatman » Mar 08 2020 2:09pm

sorry it was the mh1 that was damaged

https://www.e-cigarette-forum.com/threa ... ge.686757/

Pajda   1 kW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by Pajda » Mar 08 2020 2:42pm

zacksc wrote:
Mar 08 2020 1:41pm
The last choice, the MG1, I am thinking is just straight up inferior to the MJ1, but I am not really sure and wondered what other people think about that.
If you are considering "2900mAh" category, avoid the MG1 (very bad cycle life) and think about M29 or 29E7.

zacksc   100 mW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by zacksc » Mar 08 2020 4:07pm

eMark wrote:
Mar 08 2020 12:38pm
There are too many unknown variables ... not enough specifics (application) to offer another/different opinion at this time.

All 4 of these brand name cells are [reasonable] choices depending on the specific application. Money is always a factor if possibly deciding to go with another cell should you find a good deal on a comparable cell :D
Happy to explain why I picked these 4 at some point.
Sooner than later would be helpful ... :thumb:
Thanks eMark. I responded to your requests above, with info about the specific application and what my thinking was considering these 4 choices.

zacksc   100 mW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by zacksc » Mar 08 2020 4:11pm

john61ct wrote:
Mar 08 2020 11:55am
to give specific cell reco's, need more info about your use case

especially C-rate peak vs continuous, which involves, what sort of riding, terrain etc
Hi John. Thanks a lot for commenting. I responding above to your questions about C-rate peak vs continuous, what sort of riding, and all that in my post just a few above this. Please let me know if I left out anything important. Hoping to hear from your again!

eMark   100 W

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by eMark » Mar 08 2020 4:32pm

zacksc wrote:
Mar 08 2020 1:41pm
It is my preference to ignore $ cost for this discussion, since that could complicate things in a non-physics way that could make this discussion messy and vague.
Being your preference is to ignore $ cost what is the reason you are set on 1p (21700) or 2p (18650) instead of 3p 18650? Is your application (e-scooter, e-bike) such that the size of your pack can't be any larger than 2p (18650 cell size)?

Would be helpful if you tell us a little about the e-scooter or e-bike you envision will be powered by your 10s2p or 14s1p DIY build.

zacksc   100 mW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by zacksc » Mar 08 2020 4:47pm

eMark wrote:
Mar 08 2020 4:32pm
Being your preference is to ignore $ cost what is the reason you are set on 1p (21700) or 2p (18650) instead of 3p 18650? Is your application (e-scooter, e-bike) such that the size of your pack can't be any larger than 2p (18650 cell size)?
The reasons are: weight and smallness. I want to keep it as small and light as possible. I plan to take it with me when I park the bike. 200 Wh is about all I need, and even with just that I expect to stay in the 80 to 20% SoC range.

john61ct   100 GW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by john61ct » Mar 08 2020 4:50pm

Avoid 30Q, lots of reports wrt inconsistent QA.

Again, not sure why you'd go to a higher voltage with the 21700 40T unless you wanted to increase top speed, and that would reduce range, of course less efficient.

Better to talk Ah instead in comparing, calculate weight and volume for a given Ah "size".

MG1 is out, but M29 is worth looking at in that 2900 category, 29E7 also maybe a great value, Pajda is "da man" to pay attention to here, way more than me or some others responding so far..

Pricing is important, especially when coupled with decent **energy** density and excellent cycle longevity.

Obviously you do not need to spend extra money on **power** density, high C-rate discharging.

MJ1 / M36 has even higher energy density at 3500, different category really, so compare to Samsung 35E and SONY VC7, depending on price


leffex   100 W

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by leffex » Mar 08 2020 6:53pm

zacksc wrote:
Mar 08 2020 4:47pm
The reasons are: weight and smallness. I want to keep it as small and light as possible. I plan to take it with me when I park the bike. 200 Wh is about all I need, and even with just that I expect to stay in the 80 to 20% SoC range.
I would add that if you want your bike to be lighter then you could even go 10sx1p 21700 40t. Weight will be 668 g plus extras vs about 1kg for 10s2p. 142wh vs 200wh that is quiet only your spec that you haven't changed

142wh will take you 20km easy with alot of assistance and 40km with minimum assistance. (150w battery power is needed to keep 25km/h)

Price.
55 euro 40t 21700 cell
vs
75 euro for the 30q 18650 cell
Salestech in an ebike store

goatman   100 kW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by goatman » Mar 08 2020 7:20pm

I agree with what most are saying, I wouldn't use a 30q at 3amps or the 40t but I would be looking at the Samsung 50e/21700 if I was thinking 21700. according to the datasheet after 500 cycles at 4.9 amp discharge it still has 3802mah, pretty much what a 40t starts with.

https://www.imrbatteries.com/content/samsung_50E.pdf

heres a link to a pajda comment

viewtopic.php?f=14&t=103092&start=100#p1512060

I know nothing about 50e batteries

zacksc   100 mW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by zacksc » Mar 08 2020 8:29pm

Pajda wrote:
Mar 08 2020 2:42pm
zacksc wrote:
Mar 08 2020 1:41pm
The last choice, the MG1, I am thinking is just straight up inferior to the MJ1, but I am not really sure and wondered what other people think about that.
If you are considering "2900mAh" category, avoid the MG1 (very bad cycle life) and think about M29 or 29E7.
Thanks Pajda. Will do.
do you feel okay about the 30Q? I think Grin uses those in LiGo+.

zacksc   100 mW

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Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

Post by zacksc » Mar 08 2020 11:36pm

leffex wrote:
Mar 08 2020 6:53pm
zacksc wrote:
Mar 08 2020 4:47pm
The reasons are: weight and smallness. I want to keep it as small and light as possible. I plan to take it with me when I park the bike. 200 Wh is about all I need, and even with just that I expect to stay in the 80 to 20% SoC range.
I would add that if you want your bike to be lighter then you could even go 10sx1p 21700 40t. Weight will be 668 g plus extras vs about 1kg for 10s2p. 142wh vs 200wh that is quiet only your spec that you haven't changed

142wh will take you 20km easy with alot of assistance and 40km with minimum assistance. (150w battery power is needed to keep 25km/h)

Price.
55 euro 40t 21700 cell
vs
75 euro for the 30q 18650 cell
Thanks! That is a really good idea. Much appreciated!

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