Building a large capacity battery for bicycle trailer

azad

10 W
Joined
Sep 20, 2019
Messages
96
Hi,

I want to build a large capacity battery (>100Ah) for the mid drive (48V). What is the best and inexpensive alternative? Should I build one with 18650 cells or with Lifepo4 cells? What are best cells and where to buy them?
 
If you use 18650 cells, you're looking at a pack of 400 to 600 cells. It doesn't make any sense; there are too many opportunities to have a faulty connection.

If you really want a 5 kWh pack (which will be big, heavy, and expensive), then you should probably be looking at prismatic cells in the Ah range you want.
 
EV Battery (Spinning Magnets)

Prismatics (Chalo)
https://www.evwest.com/catalog/index.php?cPath=4
https://www.osnpower.com/48v-lithium-batteries_c16
https://osn.en.alibaba.com/productgrouplist-805986014/48v_battery.html?spm=a2700.shop_index.88.28
 
that would be 400 cells clocking in at a solid 45lbs just for the cells alone.

even doing high speed at 25mph without pedaling yourself that would give you 160+ miles of range.

yousure you got your numbers right?

and forget lifepo4, the bike would break in half just from the weight and size.
 
azad,

I bought littokala

100ah, LIFEPO4 PRIZ cells, 4 of them shipped to USA was $170

so I have a 100ah battery for my trolling motor for $170 plus a $15 bms.

If you are going with a 48v battery you will 16 of these,

16x$43 = $$$$
They not heavy as 280ah cells, I like it.
if you guying that many, maybe you can look at a group buy,

Avoid 18650 or cell cylindrical cells, the best value is not in LIFEPO4 100 ah cells,
Most of them are capable of 1C = 100A discharge for my Littokala cells.
My littos are probably Grade B cells, but for the price I am good.
 
sorry but that is utter dumb advice. a 100Ah lifepo4 battery weighs in at 100+lbs. no to mention that for that price the quality cannot be anything else then shit.

recommending lifepo on a bike is just flat out bad advice. especailly with a $15 bms.
 
flippy said:
sorry but that is utter dumb advice. a 100Ah lifepo4 battery weighs in at 100+lbs. no to mention that for that price the quality cannot be anything else then shit.

recommending lifepo on a bike is just flat out bad advice. especailly with a $15 bms.

Flippy, good point, weight is important.

Littokala 100ah 3.2v nominal cells each weight 4 lb ish,
16 will 65 lbs, :shock:

Energy density?? maybe someone post a comparison.

Here are the cells I bought,

https://www.aliexpress.com/item/1005001651207341.html

I did a capacity test and it pulled FULL capacity at 20A,

As Flippy pointed out, please consider price/quality/weight etc.

Pouch lipo cells are the lightest
 
100ah 3.7v Lipo pouch cell looks very attractive being 1/10th weight of the LIFEPO4 cells.

10000mah 25C:10564155,Dimensions is Thickness x Width x Length =10.5x64x155mm,weight:196g
 
an actual 100Ah lifepo cell from winston for example tips the scale at 7.2lbs. 16*7.2=115lbs.

if its lighter it probably is not 100Ah....

and i verified the weight. i have a couplr dozen sitting on my bench and floor.
 
flippy said:
recommending lifepo on a bike is just flat out bad advice. especailly with a $15 bms.

The OP's question isn't about a bike; it's a trailer.

I used a briefcase-sized LiFePO4 pack on my cargo bike for a while (made of old low performing cells), and it was fine. It gave me more range than my NMC prismatic pack and didn't take up that much more space (though it was heavier). That LiFePO4 pack had a cheap generic BMS that worked great, and I inspected cell voltages often to be certain (because of the old cells).

The same pack is still doing work for Austin Bike Zoo now, and it's still fine. I don't know what rationale you base your assertions on. Maybe you assume the use of a bike that isn't competent to carry weight?
 
gobi said:
100ah 3.7v Lipo pouch cell looks very attractive being 1/10th weight of the LIFEPO4 cells.

10000mah 25C:10564155,Dimensions is Thickness x Width x Length =10.5x64x155mm,weight:196g

That's 10 Ah, not 100. So the weight sort of makes sense. 37 Wh / 0.196 kg = 189 Wh/kg

As opposed to A123 AMP20 LiFePO4 pouch cells:
64 Wh / 0.496 kg = 129 Wh/kg
 
Chalo said:
flippy said:
recommending lifepo on a bike is just flat out bad advice. especailly with a $15 bms.

The OP's question isn't about a bike; it's a trailer.

I used a briefcase-sized LiFePO4 pack on my cargo bike for a while (made of old low performing cells), and it was fine. It gave me more range than my NMC prismatic pack and didn't take up that much more space (though it was heavier). That LiFePO4 pack had a cheap generic BMS that worked great, and I inspected cell voltages often to be certain (because of the old cells).

The same pack is still doing work for Austin Bike Zoo now, and it's still fine. I don't know what rationale you base your assertions on. Maybe you assume the use of a bike that isn't competent to carry weight?

120lbs on lifepo versus 40-ish lbs on 18650's is QUITE the difference, especially on a bike, trailer or not. its a LOT of dead weight to be dragging along. even ignoring the difference in volume wich is also very much at a premium.

lifepo4 has its place. just not on bikes.
 
flippy said:
Chalo said:
I don't know what rationale you base your assertions on. Maybe you assume the use of a bike that isn't competent to carry weight?

120lbs on lifepo versus 40-ish lbs on 18650's is QUITE the difference, especially on a bike, trailer or not. its a LOT of dead weight to be dragging along. even ignoring the difference in volume wich is also very much at a premium.

lifepo4 has its place. just not on bikes.

I just went to Battery Hookup to have a look at their offerings. The highest capacity 18650 loose cells they have for sale contain 173 Wh/kg. Their 6Ah LiFePO4 cells contain 136 Wh/kg. (That's pretty much in line with the 129 Wh/kg I just calculated for A123 pouches.)

In case you were wondering, that's not a 3:1 ratio like 120 lbs. vs. 40-ish lbs.

I'll ride a pedal bike that's 25-30% heavier than necessary, to get better strength, reliability, longevity, safety, and usability. Why wouldn't I do the same with a battery?

Anyway, making a multi-kWh pack out of vape pen cells is silly.
 
Chalo said:
Anyway, making a multi-kWh pack out of vape pen cells is silly.

tell that to tesla.

you are being dumb. they are not even vape cells.

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

5000Wh/12.5Wh=400 cells*47grams=18.8kg=41.44lbs
4800Wh/300Wh=16 cells*3.3Kg=52.8Kg=116lbs

116-41=75lbs difference.

winston $130 per cell * 16 = $2016
samsung 35E ~$4ish a piece in bulk = $1600

ps: energy density for a 35E is (21*47gram=)987g (21*12.5Wh=)262,5Wh

mathz.

GbTmjKt.gif


might want to get your money back from that US educational system.... :lol: :mrgreen:
 
flippy said:
Chalo said:
Anyway, making a multi-kWh pack out of vape pen cells is silly.

tell that to tesla.

you are being dumb. they are not even vape cells.

Okay, flashlight cells. Whatever. Something you need 400 to 600 of to make the OP's desired pack.

And sure, you can compare a limited power, limited life portable device cell to something that was intended for stationary applications, but I already did the math for you using cells that compare more relevantly to each other.

4.8 kWh of those Battery Hookup LiFePo4 cells cost $938 and weigh about 78 lbs, by the way. And they won't be gasping for breath in their second year.
 
Chalo said:
Okay, flashlight cells. Whatever. Something you need 400 to 600 of to make the OP's desired pack.

And sure, you can compare a limited power, limited life portable device cell to something that was intended for stationary applications, but I already did the math for you using cells that compare more relevantly to each other.
no, you picked and choose the cells that to fit your narrative and you failed.

and there are 50+ cells in a regular ebike battery. they seem to work just fine on a bike. even ignoring the 8000+ in a tesla....
 
flippy said:
Chalo said:
I already did the math for you using cells that compare more relevantly to each other.
no, you picked and choose the cells that to fit your narrative and you failed.

and there are 50+ cells in a regular ebike battery. they seem to work just fine on a bike. even ignoring the 8000+ in a tesla....

I told you what I did-- I went to Battery Hookup, which is where I got the last five packs I bought, and I compared their best loose LiCo 18650s (2200 mAh, like in most commercial devices) to their best loose LiFePO4 cells.

There's a manufacturing and engineering infrastructure that goes along with Tesla's 18650s that you and I don't have. Anyone here who builds a pack from 8000 vibrator cells is going to have a troublesome money pit at best.

My last 18650 based pack (from Luna Cycle, with 52 cells) had trouble, and I had to dismantle and repair it. My friend had one like it that stopped working, and I had to take it apart and replace some cells. That was a nuisance of a job.

Both my current battery packs have much higher capacity. One has 13 prismatic cells, and the other has 24 pouch cells. They haven't given me any reason to take them apart, despite being in service for longer than I had my Luna vape cell pack.
 
so, you go to some dodgy AF website to buy crappy cells and then complain about the end result? :lol:

that is also why your math dont work.

weird that litteraly billions of devices all around the world have zero issues with 18650 cells but you always seem to have bad luck with them....

i must have sold more then 100.000 cells in the past decade or so. all of them 18650 from a certified importer and brand new cells from pansonic, samsung, lg and whatnot. guess how many failed....
 
My only vape cell packs were commercial ones from Luna, but they became troublesome. All my larger format packs have been homemade by me, and have been reliable. Make of that what you will.

I think 18650s for high energy packs are silly not only because of the huge numbers required, but because you heat damage each cell when you attach it (if you aren't Tesla). Put a steel sheet the thickness of an 18650 can in the palm of your hand, then weld a nickel strip to it and see how much you like it.
 
wow, that is one exeptionally dumb way of reasoning you got yourself there.

you could just say you have no clue what you are talking bout.

what is next? the earth is flat? the rona vaccine has 5g tracking? :lol:
 
As a new guy, I value the input and the discourse,
One rule I try to follow is if you oppose you gots to propose.

As an over weight dad who has little time to focus on hobbies, I tend to go for "simple is beautiful".

One thing we share here is our first hand experience, and time and time again we have seen that failure happens, it is not IF but WHEN stuff will fail. Some designs are more likely to fail.

Sometimes our skills or lack of it steer our decision.

Take my chunky azz for example, I have no tools to make a pouch cell battery.
My value conscious brain performs a ROI of buying more tools and goes suboptimal and I end up buying both the tool and a finished product.

Welds make me very very nervous, as I have aged I like not to worry and focus on time for my haircare instead of debugging failures.

My go to cells for small (25ah) solution is a Priz LIFEPO4 cell, heavy but I can slap one together in little time, I even make bus bars with ring terminal.

How about we share feasible solutions and list PROS and CONS.
 
gobi said:
100ah 3.7v Lipo pouch cell looks very attractive being 1/10th weight of the LIFEPO4 cells.

10000mah 25C:10564155,Dimensions is Thickness x Width x Length =10.5x64x155mm,weight:196g


Lipo cells are also not very light. 1.4kg approximately and cost around 70$ each. Wouldn't be buying multiple 18650 48V packs be inexpensive and/or better alternative?
 
The OP's question isn't about a bike; it's a trailer.

Yes but it is more like cargo trailer than a camper!
I am intending to carry additional weight on the trailer. Recommended max weight for the trailer is 25kg.
 
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