M820 Bafang - LIGHTCARBON LCE930 Frame (lightweight)

temon10 said:
where will u get 43v BMS? Or U wanna try with 48v BMS?
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I’ve just clicked on the first I saw, bit you can relatively easily find it on Aliexpress

€ 15,76 | BeMuchSafer-Batterie BMS pour E-Bike E-Scooter E-Motorcycle, 10S, 12S, 13S, 30A, 36V, 43.2V, 48V, 43V, 10S30A, 12S30A, 13S30A, DIY
a.aliexpress.com

BeMuchSafer 10S 12S 13S 30A Batterie BMS 36V 43,2 V 48V 43V 10S30A 12S30A 13S30A BMS für DIY E-Bike E-Roller E-Motorrad Batterie - AliExpress 44

Smarter Shopping, Better Living! Aliexpress.com
a.aliexpress.com a.aliexpress.com
 
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brbr said:
I’ve just clicked on the first I saw, bit you can relatively easily find it on Aliexpress

€ 15,76 | BeMuchSafer-Batterie BMS pour E-Bike E-Scooter E-Motorcycle, 10S, 12S, 13S, 30A, 36V, 43.2V, 48V, 43V, 10S30A, 12S30A, 13S30A, DIY
a.aliexpress.com

BeMuchSafer 10S 12S 13S 30A Batterie BMS 36V 43,2 V 48V 43V 10S30A 12S30A 13S30A BMS für DIY E-Bike E-Roller E-Motorrad Batterie - AliExpress 44

Smarter Shopping, Better Living! Aliexpress.com
a.aliexpress.com a.aliexpress.com
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I have been thinking about this same thing. A custom battery would be lighter and the size you choose yourself(that can fit in the frame).
Still the original battery has can bus, does a custom battery without that work? If it will, will there be information missing?
 
brbr said:
Hey there, if bafang is late at providing the btf014, I might want to go for diy. Do you think a 12s1p micro battery would work? Just enough to do few kilometers in eco mode!
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I‘m not the expert in this, but my understanding is that its beneficial (depending on the cell type) to have some parallel batteries to ensure You can draw enough amps from the pack. For example the Samsung 21700 50E is rated continuous discharge rate 10A. If You create a parallel pack 2P, You can draw 20A. I doubt a 12S1P pack is any good for ebike application. Hope that makes sense @Waynemarlow?
 
Have anyone done some testing?

What ranges can we expect from the m820 and how small is the tube?
Would it be possible to DIY a larger "soft" battery or are we restricted by the size and form?
 
thaeber said:
I‘m not the expert in this, but my understanding is that its beneficial (depending on the cell type) to have some parallel batteries to ensure You can draw enough amps from the pack. For example the Samsung 21700 50E is rated continuous discharge rate 10A. If You create a parallel pack 2P, You can draw 20A. I doubt a 12S1P pack is any good for ebike application. Hope that makes sense @Waynemarlow?
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Yeah you’re totally right. I remember now, I used to build drones :D
So, am I wrong to say that, if we need 430W, at 43V, we need 10A, and 18650 are rated at 20A discharge current, so 1P is in theory enough? But better to go with 12S2P
 
kyphosis said:
Have anyone done some testing?

What ranges can we expect from the m820 and how small is the tube?
Would it be possible to DIY a larger "soft" battery or are we restricted by the size and form?
Click to expand...
I think the CEF50 is better for big DIY batteries, the frame is bulkier than the lce930, which is why I prefer the LC :)
 
You also have to remember the "C" rating, if you remember from drones.
 
So you can have a 20ah battery but only able to discharge at 1 amp because the connections inside the battery from one cell to the next can only handle 1 amp as an example
 
mike_kelly said:
So you can have a 20ah battery but only able to discharge at 1 amp because the connections inside the battery from one cell to the next can only handle 1 amp as an example
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Not quite, good battery build will ensure that interconnections will handle any load between cells.

You can get some cells that will handle the 20A load as a 1P design but and it’s a very big but, you will trade capacity Wh’s for instant Amps. The best and most suited cells for EBikes are those with most Wh’s with least instant Amps, meaning you will need 2P at a minimum. Add in that most cells voltage ”sags” appreciably as you get into the last 1/3 of the charge and as we need high amps, you can get into the possibility of triggering the BMS low cell voltage early. We ran into this problem on the TSDZ2 engines using similar Watts to the M820 with 2P and very high capacity cells.

As an aside the lower the engine voltage, the higher current needed to create Watts. 36 volt engines will limit your cell choice compared to 48 volts.
 
Sorry that is not true at all. If you don't need a high "C" rating it is perfectly proper to design a battery with smaller capacity connections because they are lighter. The M820 only has an XT30 connector so the max current a XT30 can handle safely is 30 amps. So that requirement is very different than a full power motor that might require 60amps.
36v does not limit your cell choice. They all use the same cells. The only difference is the ampacity of connections and their weight.
 
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mike_kelly said:
Sorry that is not true at all. If you don't need a high "C" rating it is perfectly proper to design a battery with smaller capacity connections because they are lighter. The M820 only has an XT30 connector so the max current a XT30 can handle safely is 30 amps. So that requirement is very different than a full power motor that might require 60amps.
36v does not limit your cell choice. They all use the same cells. The only difference is the ampacity of connections and their weight.
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I would largely agree however in the world of practicality and production cost you are not going to produce a new design of cell with 0.001gm lighter materials just for the Bafang M820. Instead the cell manufacturers are going to stick with their production line where they make millions of cells, all of the same form and shape. What material that goes inside is just a chemical recipe designed whether the manufacturer wants capacity or C factor ( yes there is a lot more involved than that, but that’s best discussed on another forum where proper battery whizz kids hang out )

I would suggest that the XT30 are safe 30 Amps and can handle much larger momentary loads, so why use them rather than the XT60 as per the other M series which you already have tooling and wiring for, perhaps the size and form has a factor in what is a very small motor with limited external surface area.

By all means build a few batteries with various C factors and test em out, our use in EBike motors creates quite a different discharge curve than a lab test at a set rate. As we discovered not all specs actually matched our field requirements and some cells work, others don’t. From our experience 2C is a minimum discharge rate.

As an aside again VxA=W. We as EBikers only are interested in Watts ( Power ) and Wh’s ( range ). To an EBike battery designer then they will need first to consider max Watts and then work backwards as to which cells are suitable. Eg a 36 volt 1C battery of 10A will give 360W’s x 2 giving max 720W’s in 2P format. Ticks the M820 box.
Another example cell would be 36V x 8A = 288 x 2P = max 576W’s which is probably marginal.

If however we had a 48volt motor then we would have 48 x 8 = 384 x 2P = max 768w’s. In theory the 48V motor would be fine on either cell. But requiring 3S more cells to reach the initial 48 Volts, which happens to be more weight. But more cells means more Wh’s ( range ).

Everything is a balance in design I’m afraid.
 
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I am not sure you understand Lipo batteries. If we take the 21700 cell it is available in 3ahr to 5 ahr capacities at 3.7v. There is no way to have a 10ahr battery with a single bank of cells. So you can't have a 36v or any other voltage 10a battery. Since the cell is nominally 3.7 you need 10 in series to get the 36v and the capacity would be whatever the cell capacity is i.e. 3a to 5a.. Then you would need 2p just to get the 10a if you were using 5a cells. So your 36v 10a battery would be 10s2p.
More cells in the 48v battery is just to make 48v in series cells. It does not imply anything about whrs and no increased range. The ONLY benefit is smaller wires connecting the cells. If you make a 13 cell 48v battery out of 5a cells you still have only 5a at 48v. Now 5ax48v is 240w vs 36x5 being 180w. But that is because you have more cells and more weight in the 48v battery. If you build a battery with the same number of cells it will have the same power in 36v or 48v configuration.
So I am not following your examples.
But as you said it probably is not germane to this thread.
 
Ummm where do I start, we don’t use Lipo batteries, we use Li-ion. I think you are maybe confusing the advertised nominal charge capacity and max continuous current.

If we take the Samsung 21700 50E battery you have a 0.5C charge rate (2500mAH ), a nominal capacity of 4900 mAh ( 1C ) and the important bit 9800mA max continuous discharge. Note the use of mAh and mA, they are quite different.

I would suggest perhaps doing some background reading to fully understand batteries. There’s also some excellent YouTube vids you can watch which detail this all nicely.

042343C2-21D0-4809-98A7-C803B96F0057.jpeg
 
The charge rate is not part of this conversation. The max discharge rate doesn't matter. Bottom line the limiting factor in discharge rate is the metal connecting the batteries. A 21700 is a 21700.
Ok I have insulted you and you have insulted me so now let's drop it. Nobody else cares.
 
Just use good enough cells and 1p is possible. In 21700 world the highest capacity you can easily get right now is 5ah, the samsung 50e is one of them so only 10a max for a p1 pack but if you just get a higher current cell like the 50s you can do 25a and still retain 5ah of capacity. The series connections will also need to withstand that amperage, so either need to do a few nickel strips or go copper.
 
I’m making my own battery, 36V, 30 cells, 378WH and should weigh around 1850kg.

I might go for a larger battery later but want to keep the weight down to start with
 
Goff said:
I’m making my own battery, 36V, 30 cells, 378WH and should weigh around 1850kg.

I might go for a larger battery later but want to keep the weight down to start with
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What bms are you using and how do you connect it to the can bus of the motor?
 
Bengy22 said:
but if you just get a higher current cell like the 50s you can do 25a and still retain 5ah of capacity
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Be aware that the higher current cells voltage can sag badly in the later stages of discharge. This as we have found from actual use will trigger either the battery BMS, the bikes low voltage threshold detect or simply will mean the motor will go into reduced Watts output, much earlier than an actual fully discharged battery.

Theory is one thing, in the field testing is another. Please do build a 1P setup, as there are now some pretty good on paper cells which we haven’t tried ( the Molicel P45B for example ) that has a max discharge around my 2x your max motor requirement Amps suggested minimum, maybe in this setup they will work. Do report back.
 
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@JimLee-Lightcarbon
I bougth the RS super deluxe ultimate coil for this frame (frame is quite progresive, 25% progression, and this shock has hydraulic bottom out, so it should be good for it), but I am now worried, that it migth not fit, that the ring, that is holding the spring in place migth be to wide? Do you have any information about this? I can provide some measurements, if needed.
tnx
 
Goff said:
The BMS is a Daly I have used them on my battery builds, the power cable connects to the XT30 plug on the motor.

See the link on how to build a battery

How To Build A DIY Electric Bicycle Lithium Battery From 18650 Cells

www.ebikeschool.com www.ebikeschool.com
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Looks very nice, I was planning something similar. Only the can bus confuses me. What is it for, if you don’t need it?

A DIY battery is perfect for this frame, you get long range without the bulky frame of regular e-bikes and of course a small weight saving.

Thanks for the link, been studying batteries lately, just made a Lifepo4 battery for an electric boat!
 
Goff said:
I’m making my own battery, 36V, 30 cells, 378WH and should weigh around 1850kg.

I might go for a larger battery later but want to keep the weight down to start with
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I was planning a 36V, 40 cells(21700), 720Wh. Weight per cell around 70g, so with bms and tape/packing material it should be around +3kg. I think this is maximum that can fit inside the frame, calculating from the size of the bafang 410Wh battery.
 
CanBus is a networking protocol for devices. So with a canbus Bafang battery the display can query the battery for data like voltage, current etc
 
Freda said:
I was planning a 36V, 40 cells(21700), 720Wh. Weight per cell around 70g, so with bms and tape/packing material it should be around +3kg. I think this is maximum that can fit inside the frame, calculating from the size of the bafang 410Wh battery.
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Yep sounds like a plan, it would be a tight fit
I find the 18650 are more compact, but it depends on space available 3 x 21 diameter cells would be around 70mm wide, it would pay to get your frame first before building the battery or start with a smaller one first, it’s great having multiple battery’s, I have a 900wh for my big rides, but prefer a smaller battery for weekend riding
 
Goff said:
Yep sounds like a plan, it would be a tight fit
I find the 18650 are more compact, but it depends on space available 3 x 21 diameter cells would be around 70mm wide, it would pay to get your frame first before building the battery or start with a smaller one first, it’s great having multiple battery’s, I have a 900wh for my big rides, but prefer a smaller battery for weekend riding
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I would like the 36V motor for better compability with standard bottle-batteries, but a 43V battery would be an exact fit.

43V, 12S3P, 645Wh, using 5Ah 21700 cells. 6x6 cells, so around 450mm long(plus the bms needs to go somewhere)
battery.png

The bafang battery is 470x63x52mm. So will be a tight fit yes..
 
KaroKönig said:
Hallo @JimLee-Lightcarbon , does the frame already have the new UDH standard for the new Sram Eagle Transmission circuit? I've seen Karbon bike use this circuit on your frame.
How far are the L-frames, can you already give a delivery date ?
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yes, the frame can fit for the newest dram eagle transmission, just like you find in other web,
size L now in early of June
 
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