best value cell size and more

[Sparfuchs]

Hello EV friends,
i'm planing to build a strong 20s (maybe little more) battery with lots of amps for a qs 205 4T, and at the moment a unlocked sabvoton 72150 but one day a nuclear or asi bac controller, so i want to know what options i've got.
i think i'd prefer round cells because i want to use it for a MTB/DHB and want to build it in a space saving design but i'd make compromises if there are other good solutions. And i want to find the best possible price-performance ratio.

So of course there are the 18650 with high CDR (25A,30A ect.) but low mah, so i'd have to buy a lot of them and spot weld a lot if i want acceptable capacity. Then i've heard of the 26650 with much better CDR what makes it sound quite interesting for me. Some guys on youtube use the liitokala 26650 with 5000mah and they are quiet satisfied with them. they are really cheap, so i'm a litle skeptical. What do you guys think of these cells ?

Are there other common or affordable and good round cell sizes or models ?

Is lifepo4 or lipo in my case a better option than for example the liitokala 26650 li ion ?
Lipo is too dangerous right ?

thanks a lot for your help

 

[goatman]

the 26650 weighs twice as much as a 18650. 2-25r would give more than 1-lk26650 for less $$$ i think.

id run a 40T/21700

 

[Hillhater]

Lipo is too dangerous right ?

Any high power pack can be dangerous..
...actually even small, low power packs,. Remember the hover board fires ?
Ignoring what the RC guys do to their packs, i suspect that Ebike users of RC packs have no more fires than those with cylindrical cells.
RC lipo (hobby king etc) pouches can be more compact than equivalent cylindrical cells, and have the advantage of being easy to assemble... prewired, plug and play,..which eliminates the human error risk when connecting multiple small cells, which is a common cause of pack melt down.

 

[999zip999]

I'm trying Samsung 40t 30amp cell
Soon.

 

[jonescg]

In my experience LiPo is never the best option for cost effective. It serves a purpose - crazy high power - but it's pretty poor on most other measures, particularly cycle life, energy density and cost.

I think the LG MJ1 cell is a standout for $/Wh with the Panasonic NCR18650BD pretty good too, but these are low power cells.

21700, 26650, 18650 - doesn't really matter they're all limited by the cost of the black stuff inside the cell.

 

[john61ct]

In my experience LiPo is never the best option for cost effective.

Could you link to a build thread for your racing packs?

Those were basically better-quality LiPo right, sold as single cells? Are they still on the market?

Looking for creating custom shapes for odd spaces, max power density damn the cost.

 

[jonescg]

Could you link to a build thread for your racing packs?

Those were basically better-quality LiPo right, sold as single cells? Are they still on the market?

Looking for creating custom shapes for odd spaces, max power density damn the cost.

You mean these links in my sig?

VVVVV

 

[Sparfuchs]

the 26650 weighs twice as much as a 18650. 2-25r would give more than 1-lk26650 for less $$$ i think.

id run a 40T/21700

Thanks for your reply goatman,
so if i want a cheap, powerful, space saving solution you would recommend to build it with 18650 25r cells ? Or is the 40T a better solution ?

 

[Sparfuchs]

Lipo is too dangerous right ?

Any high power pack can be dangerous..
...actually even small, low power packs,. Remember the hover board fires ?
Ignoring what the RC guys do to their packs, i suspect that Ebike users of RC packs have no more fires than those with cylindrical cells.
RC lipo (hobby king etc) pouches can be more compact than equivalent cylindrical cells, and have the advantage of being easy to assemble... prewired, plug and play,..which eliminates the human error risk when connecting multiple small cells, which is a common cause of pack melt down.

Thanks for your reply hillhater (awesome name btw. ).
so even if i'm very carefully and build a metal sheet case to protect them from physical damage..they are quite expensive aren't they ?

 

[Sparfuchs]

I'm trying Samsung 40t 30amp cell
Soon.

Thanks for your reply 999zip999,
would you please tell me what are the reasons or benefits that you see in the 40T cells ? Thanks
The datasheet looks quite good to me.

 

[Sparfuchs]

In my experience LiPo is never the best option for cost effective. It serves a purpose - crazy high power - but it's pretty poor on most other measures, particularly cycle life, energy density and cost.

I think the LG MJ1 cell is a standout for $/Wh with the Panasonic NCR18650BD pretty good too, but these are low power cells.

21700, 26650, 18650 - doesn't really matter they're all limited by the cost of the black stuff inside the cell.

Thanks for your reply jonescg,
you are right with the $/Wh but i'd really need a lot of cells to get more than 200 amps

 

[999zip999]

Ask me after 5 years . I take in info and science then I pick up the dice and I roll them I've get a dart and I throw it at the four pictures on the wall and then I make my educated choice.
Samsung 40t 4,000 mAh 35amp ceell 5.99
Samsung 25r 2,500 mAh 25amp cell 3.99

 

[goatman]

the 26650 weighs twice as much as a 18650. 2-25r would give more than 1-lk26650 for less $$$ i think.

id run a 40T/21700

Thanks for your reply goatman,
so if i want a cheap, powerful, space saving solution you would recommend to build it with 18650 25r cells ? Or is the 40T a better solution ?

youre in Austria, are you going to to be running the bike in the winter?

25r and 40T arent the best for cold temperatures. my 25r sag pretty bad at cooler than 10 celsius and capacity/range drops alot

 

[john61ct]

You mean these links in my sig?

VVVVV

Thanks, my system does not render any sigs, but will login from elsewhere to check yours out.

 

[Sparfuchs]

Ask me after 5 years . I take in info and science then I pick up the dice and I roll them I've get a dart and I throw it at the four pictures on the wall and then I make my educated choice.
Samsung 40t 4,000 mAh 35amp ceell 5.99
Samsung 25r 2,500 mAh 25amp cell 3.99

haha, i don't really know how to interpret your "information" ?

 

[jonescg]

You mean these links in my sig?

VVVVV

Thanks, my system does not render any sigs, but will login from elsewhere to check yours out.

Ahh I see. I didn't realise you can do that...
Anyway, here's a link to the main LiPo pack builds I do:
https://endless-sphere.com/forums/viewtopic.php?f=31&t=38252&p=1408828#p1398812
The big liquid cooled battery for the Prelude conversion leaked and ruined the battery. I heard GM and Tesla had a few batteries do this too, so I don't feel so bad.

 

[electric_nz]

Could look at vtc6a 21700

 

[serious_sam]

If you're going for outright performance then go LiPo.

But, if you want some cycle life, and better Wh/kg, then I suggest the Sony VTC6. 20S7P will give you 21Ah @ 210A+ peak, 105A+ continuous. Good compromise for performance and longevity. They've got the lowest DCIR for 18650, and I'm really impressed with the relatively low rate of degradation. https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=400#p1547164

 

[goatman]

some batteries dont like to be charged right away, like the vtc6, mj1, cant remember about the P42a. dont know what that means for regen.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=108661#p1591576

40t and 30Q seem to like it,

https://endless-sphere.com/forums/viewtopic.php?f=14&t=108547#p1592108

but they dont like the cold temperatures whereas the p42a does

in my tests with the 10/7.5/5/2.5 amp discharge the 40T does better than a p42a for cycle life but if you go to Mooch bench tests at higher amp discharge

https://www.e-cigarette-forum.com/threads/bench-retest-results-molicel-p42a-4000mah-21700-beats-40t-one-of-the-best-batteries-available.901847/

lots of variables

 

[Sparfuchs]

the 26650 weighs twice as much as a 18650. 2-25r would give more than 1-lk26650 for less $$$ i think.

id run a 40T/21700

Thanks for your reply goatman,
so if i want a cheap, powerful, space saving solution you would recommend to build it with 18650 25r cells ? Or is the 40T a better solution ?

youre in Austria, are you going to to be running the bike in the winter?

25r and 40T arent the best for cold temperatures. my 25r sag pretty bad at cooler than 10 celsius and capacity/range drops alot

Thanks for thinking of the temperature, but in my case its not a problem because i guess i won't use it in winter and in case that i would i wouldn't be long outside and would store the battery inside. As a student my bigger problem is the money I've to spend on high quality :lol: But i would spend it if its invaluable needed

 

[Sparfuchs]

Could look at vtc6a 21700

Thanks for your reply electric_nz,
the datasheet looks nice but they seem quite expensive to me. But i'll calculate that first

 

[Sparfuchs]

...And i want to find the best possible price-performance ratio.

So of course there are the 18650 with high CDR (25A,30A ect.) but low mah, so i'd have to buy a lot of them and spot weld a lot if i want acceptable capacity. Then i've heard of the 26650 with much better CDR what makes it sound quite interesting for me. Some guys on youtube use the liitokala 26650 with 5000mah and they are quiet satisfied with them. they are really cheap, so i'm a litle skeptical. What do you guys think of these cells ?

does anybody here know anything about the liitokala cells ??
Or another cheap alternative ?
cheap cheap cheap...i'm a student :lol:

 

[999zip999]

Oh about my rant
I mean with all their information and everything you can accumulate you still have to take an educated guess about what to get because we will not know how well the battery is or works to after 5 years and eight hundred cycles
Time will tell
Last battery was A123 heavy and long lasting.
Now going for the Fandango Samsung 40t. As I like to have over powered battery or samsang 40t at 6 p for 180amps to be use at 90 amp so lots of headroom. And in my mine long life. Good luck.

 

[goatman]

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?

 

[Sparfuchs]

Oh about my rant
I mean with all their information and everything you can accumulate you still have to take an educated guess about what to get because we will not know how well the battery is or works to after 5 years and eight hundred cycles
Time will tell
Last battery was A123 heavy and long lasting.
Now going for the Fandango Samsung 40t. As I like to have over powered battery or samsang 40t at 6 p for 180amps to be use at 90 amp so lots of headroom. And in my mine long life. Good luck.

The 40 T seems to be one of the affordable and most used in high discharge right ?
i think this will be one of the cells on my shortlist