Building a large capacity battery for bicycle trailer

[flippy]

So you suggest I change the batteries because I don't think these batteries can support 80A and perhaps none out there can. One EV battery that I have can only support 1C max (20A) and the other one is china 18650 which came with a 4A charger and I am sure might blow if you charge it that fast.

if you use the samsung 35e you can charge at 40A in 2 hours and still stay within spec.

the big problem is not the battery, its the plug. you will be more limited on how much you can pull from the wall then what the battery can take.

even at the "offical" limit of 35E cells you are already at a solid 3kW from the wall.

 

[azad]

So you suggest I change the batteries because I don't think these batteries can support 80A and perhaps none out there can. One EV battery that I have can only support 1C max (20A) and the other one is china 18650 which came with a 4A charger and I am sure might blow if you charge it that fast.

if you use the samsung 35e you can charge at 40A in 2 hours and still stay within spec.

the big problem is not the battery, its the plug. you will be more limited on how much you can pull from the wall then what the battery can take.

even at the "offical" limit of 35E cells you are already at a solid 3kW from the wall.

Are you sure about the rating of 35e? It seems it only has 8A continuous discharge current and is rated at 0.57C (~2A) for max charging current.

https://voltaplex.com/samsung-35e-18650-battery-inr18650-35e

 

[flippy]

yes. i am sure. a 20S20P pack can absorb 40A.

40A*72V=2880W
at 84V peak charging you will see 3360W

 

[uPET]

Just a thought, how about a 120Ah BMW i3 module? Stick some wheels on it and use that? It's 44V nominal, maybe a bit low, but long cycle life and got to be better than welding a load of 18650 cells together and more power density than LiFePO4.

 

[flippy]

Just a thought, how about a 120Ah BMW i3 module? Stick some wheels on it and use that? It's 44V nominal, maybe a bit low, but long cycle life and got to be better than welding a load of 18650 cells together and more power density than LiFePO4.

cycle life does not really matter here. the rest of the bike will fall apart before you kill a 18650 pack of that size. and its 10kg lighter and can be made in a more practical shape...

 

[Chalo]

cycle life does not really matter here. the rest of the bike will fall apart before you kill a 18650 pack of that size. and its 10kg lighter and can be made in a more practical shape...

Calendar life kills 18650s way sooner than some other more commercial/industrial formats. Agreed that charge-discharge cycles won't be the end of the pack in question.

Also this:

got to be better than welding a load of 18650 cells together

 

[flippy]

cycle life does not really matter here. the rest of the bike will fall apart before you kill a 18650 pack of that size. and its 10kg lighter and can be made in a more practical shape...

Calendar life kills 18650s way sooner than some other more commercial/industrial formats. Agreed that charge-discharge cycles won't be the end of the pack in question.

Also this:

got to be better than welding a load of 18650 cells together

calender life has nothing to do with it. general usage kills a battery long before it goes over its "best by" date.

and spending some time welding to shave off a lot of pounds and size of a pack and save money at the same time is not wasted time.

go to the residential battery storage forum in praise lifepo cells there where its actually useful. in this forum you need to be more neutral.

 

[sleepy_tired]

I think that for this situation lifepo4 is the way to go.

Using this as a example:
https://www.aliexpress.com/item/33054219276.html

3.2v 100ah Lifepo4 prismatic = 1.98 kg per cell.

16s1p = 16 cells = 31.68kg

versus:
https://ru.nkon.nl/rechargeable/li-ion/21700-20700-size/samsung-inr21700-30t-3000mah-35a.html

3.6v 3ah Samsung INR21700-30T = 68.2 grams

13s34s = 442 cells = 30.11kg


I would be more then happy to give up 1.5kg of trailer capacity in order to avoid piecing together 442 21700 cells.

Normal lifepo4 loses hard because of it's low max continuous current draw. But I don't think that it applies in this case since the goal is range, not performance.

In terms of watt-hours...

https://ebikes.ca/tools/simulator.html?motor=M2706&batt=B4816_GA&cont=C40&axis=mph&cont_b=C40&motor_b=M2706&batt_b=cust_48_0.2_116.5&bopen=true&autothrot=true&autothrot_b=true&throt=58&throt_b=62.6&mass_b=135&frame_b=fat

I choose to add 55 kg to the bike + rider weight and choose "fat tire" to try to make up for the extra drag of the trailer.

By adding the 100ah to the existing battery the range at 20mph goes from 55 miles to 290 miles.

That's 14.5 hours of riding... More then I would want to spend on a bicycle in a single day. Even if you add the pain of hills and stopping and acceleration I expect you would still have no problem clearing 250 miles. And if you go faster it's not going to change much in the comparison because rolling resistance doesn't really matter a whole lot in the face of aerodynamic losses.

Unless you are planning on touring with it out in the wilderness I don't see much point to all that additional capacity, though.

https://batteryhookup.com/products/new-3-2v-25ah-lifepo4-topband-navitas-prismatic

You could spend 720 dollars there and get 16s3p 75ah 3.84kWh. Should weigh around then 33kg after it's been assembled, I think.

Seems like a win to me.

 

[azad]

yes. i am sure. a 20S20P pack can absorb 40A.

40A*72V=2880W
at 84V peak charging you will see 3360W

Ah! you meant to change the voltage as well which in turn would mean replacing the battery and motor altogether leaving the old bike frame only. A new build from scratch I guess in this case!

 

[flippy]

I think that for this situation lifepo4 is the way to go.

Using this as a example:
https://www.aliexpress.com/item/33054219276.html

3.2v 100ah Lifepo4 prismatic = 1.98 kg per cell.

16s1p = 16 cells = 31.68kg

versus:
https://ru.nkon.nl/rechargeable/li-ion/21700-20700-size/samsung-inr21700-30t-3000mah-35a.html

3.6v 3ah Samsung INR21700-30T = 68.2 grams

13s34s = 442 cells = 30.11kg


I would be more then happy to give up 1.5kg of trailer capacity in order to avoid piecing together 442 21700 cells.

Normal lifepo4 loses hard because of it's low max continuous current draw. But I don't think that it applies in this case since the goal is range, not performance.

In terms of watt-hours...

https://ebikes.ca/tools/simulator.html?motor=M2706&batt=B4816_GA&cont=C40&axis=mph&cont_b=C40&motor_b=M2706&batt_b=cust_48_0.2_116.5&bopen=true&autothrot=true&autothrot_b=true&throt=58&throt_b=62.6&mass_b=135&frame_b=fat

I choose to add 55 kg to the bike + rider weight and choose "fat tire" to try to make up for the extra drag of the trailer.

By adding the 100ah to the existing battery the range at 20mph goes from 55 miles to 290 miles.

That's 14.5 hours of riding... More then I would want to spend on a bicycle in a single day. Even if you add the pain of hills and stopping and acceleration I expect you would still have no problem clearing 250 miles. And if you go faster it's not going to change much in the comparison because rolling resistance doesn't really matter a whole lot in the face of aerodynamic losses.

Unless you are planning on touring with it out in the wilderness I don't see much point to all that additional capacity, though.

https://batteryhookup.com/products/new-3-2v-25ah-lifepo4-topband-navitas-prismatic

You could spend 720 dollars there and get 16s3p 75ah 3.84kWh. Should weigh around then 33kg after it's been assembled, I think.

Seems like a win to me.

your math is completly broken. you are comparing crappy chinese used cells thst will NEVER reach their rating or lifespan with brand new cyclindricals wich are way too expensive.

are you lying on purpose to make prsmatic look better then they are?

FYI: actual proper 100Ah lifepo cells weigh 3.3kg a piece and cost 120usd per cell. 52.8kg WITHOUT copper tabs, bolts and frame to keep them compressed....


i have already done the math 2 pages ago if you cared to read the entire topic:


a 35E cell weighs in at 47 grams and stores 12.5Wh.
a winston 100Ah cell clocks in at 3.3Kg (7.3lbs) and stores 300Wh

4900Wh/12.5Wh=392 cells*47grams=18.4kg=40lbs
4800Wh/300Wh=16 cells*3.3Kg=52.8Kg=116lbs

116-40=76lbs difference and completly ignoring the steel frame you need to keep those prismatics compressed.

winston $130 per cell * 16 = $2016
samsung 35E ~$4ish a piece in bulk * 392 = $1568

making a 48V 4.9kWh 18650 pack would make you a 14S28P pack (392 cells) that will weigh well under 20kg WITH a case.

and dont forget the volume, lifepo4 is stupid big:

the volume of a lifepo pack that size is 37 Liters (aka: ~10 freedoms) versus the 9.5 Liter (aka: 2.5 freedoms) you need with 18650 cells. its litteraly 4x smaller and 75 freedoms lighter as previously mentioned.

 

[sleepy_tired]

are you lying on purpose to make prsmatic look better then they are?

Nope.

your math is completly broken. you are comparing crappy chinese used cells thst will NEVER reach their rating or lifespan with brand new cyclindricals wich are way too expensive.

No, I wasn't comparing "crappy chinese used cells".

I was comparing crappy chinese new cells. And it's just a example of where to see the specs.

I don't know if Winston is better then Calb for performance, but I don't care since this isn't a high performance application. Both are Chinese manufacturers and Calb is bigger then Winston nowadays.

If you want:
https://diysolarforum.com/ewr-carta/lifepo4_prismatic_manufacturers/

a winston 100Ah cell clocks in at 3.3Kg (7.3lbs) and stores 300Wh

And CALB CAM 100ah do actually weigh 1.9kg. The new aluminum cased cells are smaller and weigh less then the old plastic ones.

So 70 pounds, not 116.

the volume of a lifepo pack that size is 37 Liters

14 liters plus whatever case you build for them. Shouldn't be a big deal for this application. We are not trying to stuff it into a bicycle triangle or under a scooter seat.

I've built 18650 batteries before. It's a pain in the ass. Why make this a pain in the ass when it doesn't have to be? This is one of those situations were you don't have to worry about it.

 

[john61ct]

Genuine CALB is excellent, certainly in the same league as Winston, GBS, Sinopoly, CATL

but more likely to be counterfeit because more well known.

A123 / LithiumWerks is a maker of LFP in the tiny cylindricals as well as larger pouch format

and they also make NMC pouches, all top quality stuff.

LFP has 10x the cycling lifespan of the li-ion 3.7-3.7Vnom chemistries, much better overall pricing value, can last well over a decade even at abusive C-rates.

The difference in energy density is not nearly as great as some are exaggerating here

 

[flippy]

are you lying on purpose to make prsmatic look better then they are?

Nope.

your math is completly broken. you are comparing crappy chinese used cells thst will NEVER reach their rating or lifespan with brand new cyclindricals wich are way too expensive.

No, I wasn't comparing "crappy chinese used cells".
I was comparing crappy chinese new cells. And it's just a example of where to see the specs.
I don't know if Winston is better then Calb for performance, but I don't care since this isn't a high performance application. Both are Chinese manufacturers and Calb is bigger then Winston nowadays.
If you want:
https://diysolarforum.com/ewr-carta/lifepo4_prismatic_manufacturers/

a winston 100Ah cell clocks in at 3.3Kg (7.3lbs) and stores 300Wh

And CALB CAM 100ah do actually weigh 1.9kg. The new aluminum cased cells are smaller and weigh less then the old plastic ones.
So 70 pounds, not 116.

the volume of a lifepo pack that size is 37 Liters

14 liters plus whatever case you build for them. Shouldn't be a big deal for this application. We are not trying to stuff it into a bicycle triangle or under a scooter seat.
I've built 18650 batteries before. It's a pain in the ass. Why make this a pain in the ass when it doesn't have to be? This is one of those situations were you don't have to worry about it.

you are comparing (as john already hinted at) fake chinese cells from a shady used cell reseller with REALLY expensive name brand 21700 cells from a offical european importer. that is litterly the oppsites of each segment. i have quite a bit of difficulty believing that you did not make such a insane comparison on purpose to make cyclinders look bad.

and FYI: CALB does not sell 100Ah cells in metal housings. even cursory look into the weight of lifepo4 cells would give you a clear red flag that those cells are fake, even ignoring that CALB does not even sell that model. the closest they sell is 72Ah at 1.9kg and that is still 30% less capacity ar ~100 bucks a cell. so that would give you still a $1600 price tag (for real cells) for 30% less capacity, more weight and more volume and you still need a strong compression frame to keep those cells from puffing up.

and that YOU dont like building 18650 cells is NOT a valid reason to tell someone else not to do it. i hate needlepoint, i am not going around telling other people not to do needlepoint it because i dont like to do it.

 

[TrotterBob]

Battery hookup is shady? From what I've heard they have a decent reputation. And I've placed 3 orders with them with no issues. The cells I got seem to be A grade and unused.

 

[flippy]

Battery hookup is shady? From what I've heard they have a decent reputation. And I've placed 3 orders with them with no issues. The cells I got seem to be A grade and unused.

you get what you pay for. fake cells are still fake cells. same goes with the used ones they sell. even if they sell "original" cells at a considerable lower price what i can get them for by my wholesaler that buys them by the container from the factory you cannot expect to get original cells. they will probably work, but you simply dont know what you are actually getting.

 

[john61ct]

Trustworthy vendor compared to others buying and selling in the secondhand, scrap, liquidation market

is one thing.

Actual Grade A genuine brand new and matched sets from the factory

is a completely different thing.

And that dimension of difference is completely orthogonal from

prismatic vs pouch vs cylindrical vs LiPo

also chemistry is a separate discussion again

LFP vs LTO vs li-ion

as is larger Ah / fewer cell count, vs lots of little ones

and welding / soldering vs other assembly tech

Each of these factors really deserve their own discussion

there is no one "best" for all use cases.

 

[TrotterBob]

Say what you want and trash talk them if you choose. But from what I've heard they do test their batteries and the description of what they're selling is accurate. The cells I bought were described as new and both looked new and others have tested them and found them to be at or above their rated capacity.

I paid slightly over $2 per cell for a new product and these normally sell for $5 to $7 each.

If the idea of buying used puts you off then dont buy used.

 

[flippy]

Say what you want and trash talk them if you choose. But from what I've heard they do test their batteries and the description of what they're selling is accurate. The cells I bought were described as new and both looked new and others have tested them and found them to be at or above their rated capacity.

I paid slightly over $2 per cell for a new product and these normally sell for $5 to $7 each.

If the idea of buying used puts you off then dont buy used.

then dont compare a reseller of used and/or fake cells with a actual offical vendor that sells certified original cells at MSRP.

 

[TrotterBob]

I will absolutely compare a reseller with a solid reputation to other vendors that charge the full MSRP. And I will continue to patronize battery hookup and any other reseller I choose.

Not going to argue with you. I disagree with the way you've chosen to characterize a reputable vendor. So far they've been very upfront as to what they're selling. If you can manage to find someone who claims otherwise I'd be glad to listen to what they have to say.

 

[john61ct]

Yes BH is very well thought of here, so far no bad reports.

And of course you can compare personal opinion about value across vendors of different categories of batteries.

Posts showing terrible social skills whether as a result of a member's neurodiversity or just them purposefully being obnoxious, are IMO best just ignored.

 

[sharinginfos]

HI can someone copy paste the link to the multiple pages lifep04 pouches assembly without soldering nor welding? thanks