best value cell size and more

[Sparfuchs]

if you follow vortecks on youtube, then you know he used the lk 26650 on his v3 build and considers them a 20 amp cell and one of the cells in the pack he built is weak/bad. his v4 build is going with 25r from fogstar in the uk for about $2/cell. heres a link to the video. im not sure if its the exact video but its in the same time area of his channel

https://www.youtube.com/watch?v=jZnN73UtzGU

the mnke 26650 5000mah test in my signature would probably have the same cycle life as the lk26650 but gives actual 5000mah capacity from 4.2v to 3.0v , is rated as a 20 amp cell. if you dont want to ship from Canada, denmark might have them. i heard mnke is a denmark company?

yes vortec and andy kirby were the two guys i saw using them on youtube. but didn't watch it long enough i guess.. i didn't know he had a problem. but is this so baad if one cell of hundreds fails if they are cheap ?? of course you have to change the cell but thats not the end o.t.w. right ?

 

[goatman]

if your getting lk 26650 for $4 or $2, id be scooping them up. the reason i tested the mnke 26650 was i couldnt find lk 26650 for less than $10/cell

i bought about 230- 25r's from salvaged packs for $2 and theyve been great

 

[999zip999]

If it hasn't hit my front door yet but after five years and 400 cycles I can give you a better idea how it's working. I'm clueless.

 

[Yermommy]

Samsung 30Q could do what you need. 20s15p would be suitable for 200a.

 

[john61ct]

30Q is no good, inconsistent build quality for in a big pack, too many failures.

VTC6

LG HG2

50E and

40T much better, last especially for high C-rates

 

[markz]

25R is good if thats what you need.

 

[Sparfuchs]

if your getting lk 26650 for $4 or $2, id be scooping them up. the reason i tested the mnke 26650 was i couldnt find lk 26650 for less than $10/cell

i bought about 230- 25r's from salvaged packs for $2 and theyve been great

i'd definitely get them as cheap. 10 cells of lk26650 for 31,77 EUR/38,48 USD free shipping. So 3,18 EUR/3,85 USD on aliexpress

 

[Sparfuchs]

Ok my friends,
thanks for all your opinions. Now i will calculate all the specs and compare the LK26650, 25R, HG2, VTC6A, 50E, and of course the 40T many of you recommended.

 

[999zip999]

Best value in cell size .
A123 20ah pouch cell 200amp 1,500 charge cycles big and heavy last loong time good value over the long run. If it fits. Plus you need more as 14s to 16s or 20s to 24s.

 

[Sparfuchs]

Best value in cell size .
A123 20ah pouch cell 200amp 1,500 charge cycles big and heavy last loong time good value over the long run. If it fits. Plus you need more as 14s to 16s or 20s to 24s.

but these are lifepo 4 and not li ion cells right ? I mean that won't be a problem to me if they are better for my use
is there a brand you' recommend of these cells ?
do you thing they are better for me than for example the 40T or just better value ?

 

[Sparfuchs]

another question :
at the datasheets of some cells there is the max. continuous discharge with and without temp. cut. and at some its not. For example the 40T has 35A(Without temperature cut) and 45A(With 80℃ temperature cut). VTC6 has 20/30 A. Of the 25r i just found the information "max continuous discharge 20A(at 25℃)". So i'm not sure how to compare them. Is the with and without temp. cut of something like "continuous" and "peak" of a battery like it is on controllers ? and how can i compare for example the amps of the 40T and the 25R ?
And is it important to note and compare all the cut off voltage or is it all in same relation ?

 

[john61ct]

but these are lifepo 4 and not li ion cells right ? I mean that won't be a problem to me if they are better for my use
is there a brand you' recommend of these cells ?
do you thing they are better for me than for example the 40T or just better value ?

I dunno if A123 makes LFP in pouch format, but they definitely make good NMC like that, 3.6-3.7Vnom

Higher energy density, but much lower lifespan than LFP at 3.2Vnom

 

[goatman]

the 40T, 30Q and 25r like the pack temperature around 25celsius to 40 celsius range

when the battery is discharging once you hit 3.2v the battery temperature will really start to climb if your pulling amps

25r and 40t will really start to sag if theyre cold like 15 celsius or lower

 

[Hillhater]

You need to prioritise your requirements..
Discharge current ..continuous and / or max
Capacity
Working voltage range ( is sag/ voltdrop important
Pack size weight
Costs
Etc
.......you will not find any one cell best at every parameter, so a compromise will have to be found to optomise your priorities.

 

[john61ct]

Datasheets wrt C-rates are not comparable between even the top-notch "honest" vendors.

Look for the standardized comparison tests published here and other forums by very respected savvy members for that, e.g. @pajda

LVC cutoff spec is arbitrary, way lower than you ever want to approach IRL for longevity stay above 3.2V at rest

One issue is, designing for high power C-rate discharge means sacrificing energy density

so focus more on the latter (M36/MJ1, VC7, 50E) for longevity unless you really **need** the former (40T), lower resistance initially, can withstand 2C discharge for short bursts better.

But then shorter lifespan, to get great value increase Parallel grouping size, total Ah capacity in order to lower your C-rate required, and avg DoD% when done, maybe double the life cycles you get.

 

[Hillhater]

I dunno if A123 makes LFP in pouch format,

They certainly used to make a 20Ah pouch and a 14 Ah 3.2v, “NanoPhosphate pouch...i assume they still do
https://www.altertek.com/products/lithium-ion-pouch-cylindrical-cells/a123-li-ion-cells/a123-20ah-lithium-ion-ultraphosphate-pouch-cell/
Some of the best around if you can get the genuine cells . (lots of used/defective cells have been advertised.)

Remember there are independent test sites with huge amounts of data that can be helpful when choosing cells
EG:-
https://lygte-info.dk/info/batteryIndex.html

 

[Sparfuchs]

I don't know my needs yet but i tried my best in my thread.. but lets try more detailed:
battery used for qs 205 4T/ 18" and unlocked sabvoton 72150, maybe one day nuclear or asi bac 4000/8000 ?
acceleration more important than top speed (but 20s might be good) or lots of range.
average top speed 35 kph daily and legal use but great acceleration to that speed, out of traffic up to 80 kph might be nice.
will be fitted on a DHB in frame or under the frame (not having the dirtbike yet) so customizable form/size needed.
Budget: I'm a student so i willing to pay what it needs but want really good value and good price-performance ratio.
Weight and size as small as possible because no stealth bomber but DHB. So maximum wide is 70mm or 65mm slim :wink: ..but
well distributed up to 140 or max maybee160 cells 7s/8s (if its a 18650).
it would be great if i could drive for a few hour.
What would you guys buy if you were me ??

 

[goatman]

have you seen the video, e-hp linked to in this thread, i run 17s these guys run 16s

https://endless-sphere.com/forums/viewtopic.php?f=3&t=109551&p=1604135#p1604135

i know a battery builder that really likes the 40T

if you go to the last post in my 40T battery test, youll see me comparing the 30q capacity discharge curves and "desulfating" 30q and 40T batteries.

if youre planning to be using strong regen current, it doesnt hurt 30q, actually likes it and most likely the 40 T but that will be the next test.

vtc6 degrades twice as fast if there is no wait time between discharge/charge, thats what regen is

i havent tested an hg2 yet, i havent heard any bad things about them but lg batteries recommend waiting between discharge/charge

 

[john61ct]

I don't know my needs yet but i tried my best in my thread.. but lets try more detailed

None of that info is relevant.

You need to know your required C-rate per cell, both continuous and peak (for say 20-30sec bursts).

C-rate is easily reduced if you can afford to build a higher Ah capacity

If you think you will need to go over say 3C regularly then maybe better off with 40T, accept lower energy density and shorter lifespan.

Otherwise 50E is very solid.

Also if need for C-rate is lower, MJI/M36 VC7 and 35E have trememdous energy density and stellar longevity.

Maybe spending just a few hundred on a cheap-chinese disposable pack will let you figure things out IRL, get you started, then build your ling-lasting pack from the most suitable cells

 

[Thorin]

Someone asked about Liitokala.
I found this: https://electrotinker.com/en/analysis/degradation-ncr18650b-liitokala/

390 cycles with Loss of 12.91% (4.19v - 2.9v)

 

[Hillhater]

https://lygte-info.dk/review/batteries2012/LiitoKala%20INR26650-50A%205000mAh%20(Black)%20UK.html

 

[Sparfuchs]

I don't know my needs yet but i tried my best in my thread.. but lets try more detailed

None of that info is relevant.

You need to know your required C-rate per cell, both continuous and peak (for say 20-30sec bursts).

Maybe spending just a few hundred on a cheap-chinese disposable pack will let you figure things out IRL, get you started, then build your ling-lasting pack from the most suitable cells

i guess you are right, but its really not easy to know those things in technical details when you are a newbie and don't have the knowledge yet. i know what i want..but not what i need

i also guess i should not build the pack with a cheap-chinese cells because i could use 40T cells and copy the connections of my 20s6p pack to make sure its correctly..but idk.

 

[Sparfuchs]

At the moment i have a triangle 20s6p pack made of 120, 35E cells. In case that i buy 120, 40T cells.. could i just copy the triangle connections of my pack with the bigger cells ? That would make sure that i don't plan a wrong connecting And could i spotweld first all connections on one side, then turn around and weld all connections on the other side or do i have to follow a step order ?

 

[999zip999]

Title said best value and that's the only why I said A123 longevity..
I have move on to Samsung 40t 20s6p. I thought it would fit in it em3ev bag and template fit the bag but bag is 18650 wide not 27100 40t cell.

 

[Sparfuchs]

Title said best value and that's the only why I said A123 longevity..
I have move on to Samsung 40t 20s6p. I thought it would fit in it em3ev bag and template fit the bag but bag is 18650 wide not 27100 40t cell.

So you did exactly what i'm thinking of doing ?? You built a 20s6p triangle with the 40T ?? Did it work like expected ?