Amount of cells? many or few

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Ianhill   100 MW

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Re: Amount of cells? many or few

Post by Ianhill » Apr 29 2021 5:13pm

Id be looking to load test them cells sag under load so how much voltage deflect you get per amp applied etc amd also check its heat output by doing a IR measurment you should have an idea of the losses to expect.

Ive done a bit of digging on the bms front and found active balancing and resistive balancing.

Active balancing acts quicker its equalizing the voltages the battery degrades a fraction less so they say, there's far less heat created moving energy to one cell rather than a resistor and heatsink so i found by having a read about.

I'm happy my resistive bms will suit its purpose its in a basic brushed ride and the most i want from the display is basic shunt functions and been just 1 cell in the pack balancing wont be to heavy anyway.

I found a jikong 24s 2amp active balance bms 200amp so ill be having a play around with that ive got a chargery so i can run upto 88.8v nominal for some real serious shit.

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Re: Amount of cells? many or few

Post by MK2R » May 04 2021 1:08pm

ah i see ianhill.

yeah i guess i'll need to test a few of them.


but for a more serious build i am looking at buying brand new cells. but wow it's a jungle out there when it comes to prices of what u get.
18650
20700
21700

so many to choose from, and i don't know what to get really. I want to be able to convert my project into something that can safely provide the QS 90h motor and votol 150 controller at least, even if i am not going to start with it, i want to be able to use this pack for that later on.

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Re: Amount of cells? many or few

Post by Ianhill » May 04 2021 6:05pm

MK2R wrote:
May 04 2021 1:08pm
ah i see ianhill.

yeah i guess i'll need to test a few of them.


but for a more serious build i am looking at buying brand new cells. but wow it's a jungle out there when it comes to prices of what u get.
18650
20700
21700

so many to choose from, and i don't know what to get really. I want to be able to convert my project into something that can safely provide the QS 90h motor and votol 150 controller at least, even if i am not going to start with it, i want to be able to use this pack for that later on.
Same issue im faced with mk2r all us sparks are.

What ive found is my next viable option is to repurpose car packs or possibly order the same cell new.

Lg chem 60ah prisamatic cells have a 1c charge and 3c discharge so in the car they do about 180amp a cell but can be pushed to 200 if need be for short durations and i can not imagine holding 15-20kw wide open for too long so i think thats my next path much easier constuction no special tools other than wisdom.

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Re: Amount of cells? many or few

Post by MK2R » May 04 2021 6:47pm

Ianhill wrote:
May 04 2021 6:05pm

Same issue im faced with mk2r all us sparks are.

What ive found is my next viable option is to repurpose car packs or possibly order the same cell new.

Lg chem 60ah prisamatic cells have a 1c charge and 3c discharge so in the car they do about 180amp a cell but can be pushed to 200 if need be for short durations and i can not imagine holding 15-20kw wide open for too long so i think thats my next path much easier constuction no special tools other than wisdom.
Yeah there are options out there. i am just having trouble believeing what i am reading.
I found this site thanks to this forum, battery prices are not too bad, i bet you can find better thou.

https://eu.nkon.nl/rechargeable/li-ion/ ... h-18a.html

I could do with this cell, but from what i read there are many versions of the Sanyo cells out there. i am having a hard time to believe that this cells actually do work up to 18A. at 3,6V that is 65w per cell, and that is alot, 15C if u look at capacity. i don't know what nominal voltage of them are, i have a feeling that 18A is some kind of short use max discharge

And maybe this could do
https://eu.nkon.nl/rechargeable/li-ion/ ... fepo4.html
it at least claims constant discharge at 33A and max 40A. but i need to buy quiet a lot to make it price-worth. like if you get 600 cells, and they are only rated at 1.1Ah you just get about 2.1kwh in total. a lot discharge current capacity but low.

And then we get into the quiet interesting section of 20700 / 21700 types.
https://eu.nkon.nl/rechargeable/li-ion/ ... h-30a.html
https://eu.nkon.nl/rechargeable/li-ion/ ... h-35a.html
https://eu.nkon.nl/rechargeable/li-ion/ ... -3-2a.html
https://eu.nkon.nl/rechargeable/li-ion/ ... clear.html
https://eu.nkon.nl/rechargeable/li-ion/ ... clear.html

a lot interesting stuffs. it get's more pricy thou in that segment, but maybe it is worth it?

and then some bigger cells in the lifepo4 category
https://eu.nkon.nl/rechargeable/li-ion/ ... fepo4.html

oh well, so many options...

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Re: Amount of cells? many or few

Post by Ianhill » May 05 2021 1:41am

Lifepo4 tend to come with a lower amount of apacity and or discharge vs its lithuim cousin but also tends to be safer so if i was building a ride that was riding in sensitive areas id use lifep04 or an indoor powerwall lifepo4 but for a high power ride lithuim cells is what id pick.

Theres a molicell available from fogstar warehouse uk im sure they get stocked over norway thats a decent budget cell.

Problem i see with diy packs is lack of care to build a absorbing pack that insulate correctly most fires can be contributed to a vibration fault from pack terminals thats overridged busbar setup and internal faults occur that tends to be prismatic cells or wearing down a single barrier of insulation 18650 favourite mistakes.

Ive seen a clever trick from the automotive industry to terminate prismatics while keeping the bus system slightly flexible to absorb vibration, rather that use a thick piece of copper they use thin sheets that accumulate into the current carrying of the solid bar take up little extra room if any but doesnt pass vibration across the pack.

Theres so much to consider outside the cell type to choose.

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Re: Amount of cells? many or few

Post by MK2R » May 05 2021 6:56am

yeah LiFePO4 is rumored to be safer.

do you think that it's reasonable that the cells i linked:
https://eu.nkon.nl/rechargeable/li-ion/ ... fepo4.html

LiFePO4: 1100mah 33A discharge rate and "pulse load" 40A /10 seconds.
Is it reasonable? or is it scam values :?

or
https://eu.nkon.nl/rechargeable/li-ion/ ... fepo4.html
3000mah 30A discharge and 45A pulse.

I mean if it is true values then i would concider paying the price. even if it is just 15A that is safe it's still good enough for my project. why i tend to look at those cells is general cell life time. right now i have about 200 "good" 18650 samsung/panasonic cells. and those 700 chinease cells (FST). so i will use what i got, but when i feel like i know what i am doing and have experimented some i will buy brand new cells together with a QS motor, hopefully around this summer. and then i want to buy something that lasts years (hopefully). and in working outside temperatures between 5-35deg Celcius (taking 5 as lowest, might be rainy during the spring or atumn etc)

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Re: Amount of cells? many or few

Post by Ianhill » May 05 2021 7:50am

Whats your planned ride ?

Thise 26650 will soon stack into a very large pack.

I seen a few scooters but theres nothing under a 12inch wheel that tickles my fancy.
The artisan evo is a small bike that looks decent and comes with a qs138 3000w stock but its belt drive so its not going to be as efficient as a hub drive.

Qs motor do a 212 racing hub thats their v4 design so its powerful and 91% efficent in a 10 inch wheel 7000w, 14kw max theres 4 different wind configs but finding a frame with a 230mm wide dropout is no easy task a custom swingarm is needed.

Easiest fastest ride i can see is to get a artisan evo £2g secind hand and fit a foc controller so it can top out closer to 60 mph with better pulling power maybe wheelie capable if lucky, theres a controller i have in mind £350 and fitting would unlock that ride wide open for modern traffic it be up with 250cc till 50mph or so.

Id love to do something with that little hub though been small it wouldnt half pull well and 14kw rated on its 16mm phases would just begining to tickle it into life if 2 could be fitted to some ride and 44 60ah pouch cells a 40kw ride would rise up and smash 100mph mark beat most cars under 6 figures to 60mph.

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Re: Amount of cells? many or few

Post by MK2R » May 05 2021 4:06pm

I am planning to convert this
street-2t-approved-exhaust-arrow-kit-derbi-gpr-50-nude-2004-2007-arrow-51510su.jpg
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I have one with a broken engine with very low milage on it, just 2600km on it so practically brand new in that sense

but i am still debating with myself on how much i should spend on it, first of all i will try the things i got at home to make it run, and then i will make an upgrade, there is a lot of space for batteries inside of those fairings and that big tank (for a controller or other things, who knows what to hide in there)

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Re: Amount of cells? many or few

Post by MK2R » May 10 2021 4:38pm

Okay, will continue on this thread. i did read some on nickle strip carrying Amps. i found this thred on here where someone called Matador posted a nice chart of Matador's Conductor Strips Ampacity Charts (conservative values, which is good, more safety margin).

So this nickle strip i got is 0.15mm thick, 8mm between cells in the paralel string and 6mm connection between each cell row
185251108_871863323724335_6455284462125706781_n.jpg
185251108_871863323724335_6455284462125706781_n.jpg (260.55 KiB) Viewed 167 times
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If one look at this sample it represents a 3s10p pack. both are but they are very different in arrangement. the left one provides 3 cells to carry current to the next serie and the right one provides 10 cells to carry current.

So if i do the math correctly.
Left: 3*4,9 = 14,7A
Right: 10*3,7 = 37A

So if you need more current (material wize at least) it is better to build like the right pack with more interconnections than the left pack if i get it all right.

So i will probably build like the right pack due to the nickle strip i got.
If i want to push more current out of each row i see 2 solutions
1: add more cells (more interconnections)
2: add another piece of nickle strip (same as above), making the thickness 0.3mm.

Is there a 3rd option where i can just add another strip over the interconnections and make the interconnections stronger? or do i still have to add another piece all over? (in my mind i visaulize that the electrons will tend to travel more over the interconnections than between the cells in paralell when u draw current from the batteris, but i might be thinking wrong)

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flippy   100 MW

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Re: Amount of cells? many or few

Post by flippy » May 10 2021 5:02pm

the parralel strip only keeps the cells in balance. it does not carry any meaningful current. that is why they go on top last and generally stick out the side so you can attach your balance leads.

extreme/perfect example in this 20S18P pack:

Image

note that there is just a single P strip and the S strips are also used to connect the different levels without soldering wires.

even at full 180A load (offical rating of the cells) each strip only sees 20A.
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Re: Amount of cells? many or few

Post by MK2R » May 10 2021 5:59pm

nice pack flippy!

So in that regards the 8mm that connect the paralell is kinda "pointless", it would have been much better using 6mm to connect the paralell and 8mm to connect the series right?

and the parellel u have sticking out - is where u connect the bms leads?

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flippy   100 MW

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Re: Amount of cells? many or few

Post by flippy » May 10 2021 7:01pm

the pic is from a very old pack i made long ago and was halfway during construction.

you use 8mm because that is what you are already using. there is zero reason to use a different strip for that. prehaps thinner like .1 or .15 if you are doing the series with .2 for example.

ps: 8mm fits exactly in the aliexpress holders. going from 7 to 8mm is the simplest way to add 15% current capacity without increasing thickness and it perfectly fills the cutout for the strip.
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Re: Amount of cells? many or few

Post by MK2R » May 10 2021 8:28pm

flippy wrote:
May 10 2021 7:01pm
the pic is from a very old pack i made long ago and was halfway during construction.

you use 8mm because that is what you are already using. there is zero reason to use a different strip for that. prehaps thinner like .1 or .15 if you are doing the series with .2 for example.

ps: 8mm fits exactly in the aliexpress holders. going from 7 to 8mm is the simplest way to add 15% current capacity without increasing thickness and it perfectly fills the cutout for the strip.
I am not sure if i did give the information about how the nickle plate is looking like, if u see in the picture that's the only way i can fit the nickle strip, i just tried to put it at 60degree in the cell holder and it is to narrow to fit the 8mm part, i can only put the 8mm in a straight row with the batteries (hence the paralell part only) the 6mm part will connect to the serial connection unfortunately. but there is room for more than 6mm i can clearly tell, it's just the design that is flawed and prevent's me from putting the nickle strip in any other way.

Idea:
I get more nickle strip, 7 or 8mm wide. i diagonally connect the serial connections, then i put this nickle strip on top of it giving an additional 3,7A current capacity + interconnections in the paralell cells.
I guess if you have to choose you put the wides and thickest strip closest to the battery and if u go thinner or narrower u should put it on top of it

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flippy   100 MW

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Re: Amount of cells? many or few

Post by flippy » May 11 2021 12:20am

i dont use that double row stuff for this reason. its too restrictive for most pack designs or real high currents. and often cheap steel.

i use hex shaped holders only if there is a space restriction. otherwise i only use straight holders so the pack is stronger and there is more air between the cells.
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Re: Amount of cells? many or few

Post by MK2R » May 11 2021 4:53am

flippy wrote:
May 11 2021 12:20am
i dont use that double row stuff for this reason. its too restrictive for most pack designs or real high currents. and often cheap steel.

i use hex shaped holders only if there is a space restriction. otherwise i only use straight holders so the pack is stronger and there is more air between the cells.
Ah i see, so if i use this holder my only shoot to get more amp is to increase the thickness due to this "stupid" limitation then

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Re: Amount of cells? many or few

Post by Ianhill » May 12 2021 4:29am

MK2R wrote:
May 11 2021 4:53am
flippy wrote:
May 11 2021 12:20am
i dont use that double row stuff for this reason. its too restrictive for most pack designs or real high currents. and often cheap steel.

i use hex shaped holders only if there is a space restriction. otherwise i only use straight holders so the pack is stronger and there is more air between the cells.
Ah i see, so if i use this holder my only shoot to get more amp is to increase the thickness due to this "stupid" limitation then
My honest truth id dump 18650 on a bike and go for a prismatic less connections to worrys about and on a bike that bashes about the road vibration is gonna find any weak links over time so for road use id want a fully potted pack like tesla do it or prismatics with flexible tap connections to absorb vibration rather than pass it into the cell structure.

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flippy   100 MW

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Re: Amount of cells? many or few

Post by flippy » May 12 2021 6:02am

Ianhill wrote:
May 12 2021 4:29am
My honest truth id dump 18650 on a bike and go for a prismatic less connections to worrys about and on a bike that bashes about the road vibration is gonna find any weak links over time so for road use id want a fully potted pack like tesla do it or prismatics with flexible tap connections to absorb vibration rather than pass it into the cell structure.

o yeah, replace steel cyclinders with delicate plastic bags with some heatshrink over it. much better and safer. :bigthumb:

/s


people need to stop this flat out and outright lies about 18650 and welding, welding is litteraly the safest and strongest connection you can make that requires 0 materials.

these arguments/"advice" are utter bullshit and they need to stop before more people take a skid across the pavement with a pouch pack.
Last edited by flippy on May 12 2021 7:23am, edited 1 time in total.
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Re: Amount of cells? many or few

Post by Ianhill » May 12 2021 6:24am

flippy wrote:
May 12 2021 6:02am
Ianhill wrote:
May 12 2021 4:29am
My honest truth id dump 18650 on a bike and go for a prismatic less connections to worrys about and on a bike that bashes about the road vibration is gonna find any weak links over time so for road use id want a fully potted pack like tesla do it or prismatics with flexible tap connections to absorb vibration rather than pass it into the cell structure.

o yeah, replace steel cyclinders with delicate plastic bags with some heatshrink over it. much better and safer. :bigthumb:

/s


people need to stop this BS about 18650 and welding being bad, welding is litteraly the safest and strongest connection you can make that requires 0 materials.
Try vibrate a poor made 18650 pack its crap but if you noticed i did say a potted 18650 pack like tesla is best for 18650 i have noticed thier battery days.

The bullshit is 18650 packs been superior for entry level people when they aint if they are made by a diy have a go hero the welds aint constant and the terminations being nickle aint exactly best resistance choice and most outsource this costing best part of a grand for a silly ebike battery.

Pros and cons to each pack but way i see it is the prismatics are easier to manage and make consistently into packs, to be truthful the fire risk is only reduced when you change chemistry.

Byd blade battery says it all it dont have to be this way its stupid to have 18650s in my opinion they are the mostly fiddly Pyle of crap replacement is ridiculous.

Id get a byd car over the tesla all day much less cells not flammable and puncture proof thats where that sack of piss has lead us too a battery with 8000 cycles.

Its a no brainer for me even with nmc lg cells 60ah 20 connections for a monster pack thats as fire hungry as its 18650 cousin or many of hundreds and tons of nickel cell holders days and days of work that pointless at this level of power unless you can produce like a gigafactory.

You make your battery ill make mine but ill get mine done for £112 per kilowatt complete

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flippy   100 MW

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Re: Amount of cells? many or few

Post by flippy » May 12 2021 7:27am

stop with the outright mistreatment of facts.

your opinion is NOT facts and $/kWh is not a factor when talking about safety. if you want pouches to be at the same safety level as cyclindrical cells are you need a LOT more money and mass to compensate the fact that you MUST have compression and crash protection wich completly negates any $ profits you might get.

that cars have pouches is NOT a recommendation that you should use them too. especially using them without a huge steel compression system and crash protection around each pouch.

you are not Volvo, Crysler, tesla or any other car maker.
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Ianhill   100 MW

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Re: Amount of cells? many or few

Post by Ianhill » May 12 2021 7:42am

flippy wrote:
May 12 2021 7:27am
stop with the outright mistreatment of facts.

your opinion is NOT facts and $/kWh is not a factor when talking about safety. if you want pouches to be at the same safety level as cyclindrical cells are you need a LOT more money and mass to compensate the fact that you MUST have compression and crash protection wich completly negates any $ profits you might get.

that cars have pouches is NOT a recommendation that you should use them too. especially using them without a huge steel compression system and crash protection around each pouch.

you are not Volvo, Crysler, tesla or any other car maker.
:lol: 👋💤

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Re: Amount of cells? many or few

Post by MK2R » May 12 2021 8:47am

I mean i am taking a part a lot of cells atm and how hard they are welded to the nickel and how hard it is to remove them i am pretty confident that they will survive a lot of vibrations

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