Building a 20s 150A continuous discharge battery back pack style.

KryceS

1 mW
Joined
Dec 7, 2020
Messages
12
Hello everyone,

My name is Kryce, I recently build an Ebike Enduro frame with a Sabvoton 72150, Qs 205 5000W motor and 20s20p batterie pack with MJ1 cells (smart BMS).

I actually upgrading my old but great Ebike (BBSHD/Phaserunner/CA with 2 batteries from EM3eV mounted in parallel 52v40Ah total) with a CYC X2 Pro Gen 2 and ASI BAC 2000 with the same batteries.

I would like to build a new backpack battery that can be use on both of my Ebikes. I would like to be able to get 150A continuous out of this batterie pack but with a good capacity (around 70Ah will be great).
I’m not afraid of the weight and size of it.

I don’t really witch cells 21650, 18650… I saw the Liitokala 50ii or VTC6 or… I don’t know.
But I also don’t really know where I can find good copper sheets that I can solder on top of thick nickels strips spot welded on the cells ?
How can I build such a powerful pack ? If anyone can answer me that will be great.
 
building a pack out of 5000mah 21700s vs 3500mah 18650s comes down to this

1kg lighter on 21700 pack
280 cells needed to build it vs 400 for 18650
this will result in another decrease in weight due to less welds needed
and overall size of the pack would be smaller

21700s come in nice brands such as
molicel m50
samsung 50E/G
 
Thank you for your answer, what do you think about Liitokala cells ?
For a 150A how many layers of 0.2 nickel strips do I need ?
 
KryceS said:
Hello everyone,

My name is Kryce, I recently build an Ebike Enduro frame with a Sabvoton 72150, Qs 205 5000W motor and 20s20p batterie pack with MJ1 cells (smart BMS).

I actually upgrading my old but great Ebike (BBSHD/Phaserunner/CA with 2 batteries from EM3eV mounted in parallel 52v40Ah total) with a CYC X2 Pro Gen 2 and ASI BAC 2000 with the same batteries.

I would like to build a new backpack battery that can be use on both of my Ebikes. I would like to be able to get 150A continuous out of this batterie pack but with a good capacity (around 70Ah will be great).
I’m not afraid of the weight and size of it.

I don’t really witch cells 21650, 18650… I saw the Liitokala 50ii or VTC6 or… I don’t know.
But I also don’t really know where I can find good copper sheets that I can solder on top of thick nickels strips spot welded on the cells ?
How can I build such a powerful pack ? If anyone can answer me that will be great.
 
KryceS said:
KryceS said:
Hello everyone,

My name is Kryce, I recently build an Ebike Enduro frame with a Sabvoton 72150, Qs 205 5000W motor and 20s20p batterie pack with MJ1 cells (smart BMS).

I actually upgrading my old but great Ebike (BBSHD/Phaserunner/CA with 2 batteries from EM3eV mounted in parallel 52v40Ah total) with a CYC X2 Pro Gen 2 and ASI BAC 2000 with the same batteries.

I would like to build a new backpack battery that can be use on both of my Ebikes. I would like to be able to get 150A continuous out of this batterie pack but with a good capacity (around 70Ah will be great).
I’m not afraid of the weight and size of it.

I don’t really witch cells 21650, 18650… I saw the Liitokala 50ii or VTC6 or… I don’t know.
But I also don’t really know where I can find good copper sheets that I can solder on top of thick nickels strips spot welded on the cells ?
How can I build such a powerful pack ? If anyone can answer me that will be great.

Hello Kryce,

we building high power battery packs from cells. We develop our method, to omit the nikkel strip due to its high internal resistance instead copper plates are used. The copper is very hard to weld with electric spot welder and usually an electric spot welder generates so mutch localized heat, which shortens the battery life. Therefore, we use tig spot welding with a TIG spot welding torch developed by us.

Check out in this thread: https://endless-sphere.com/forums/viewtopic.php?f=31&t=112693
We also offer cnc machined copper plates in different patterns.

If you have some questions, feel free to ask.
 
Depending on your level of risk tolerance there is always RC Lipo. That will do 150 amps all day long.
 
spinningmagnets said:
If drawing more than 30A per cell, nickel is more of a resistor than a conductor.

Consider the option of flat pouch cells from a hybrid car.

Thank you, I indeed saw some people use this type of flat pouch, but my idea is to put them in a back pack and still have a good range out of my batterie. And I don’t really know where I can buy theses cells. If you have a link or something.
 
HK12K said:
Depending on your level of risk tolerance there is always RC Lipo. That will do 150 amps all day long.

I was thinking of Lipo batteries indeed but I don’t feel really safe with it… if you have an experience with it can we talk about it ?
 
kartoon said:
KryceS said:
KryceS said:
Hello everyone,

My name is Kryce, I recently build an Ebike Enduro frame with a Sabvoton 72150, Qs 205 5000W motor and 20s20p batterie pack with MJ1 cells (smart BMS).

I actually upgrading my old but great Ebike (BBSHD/Phaserunner/CA with 2 batteries from EM3eV mounted in parallel 52v40Ah total) with a CYC X2 Pro Gen 2 and ASI BAC 2000 with the same batteries.

I would like to build a new backpack battery that can be use on both of my Ebikes. I would like to be able to get 150A continuous out of this batterie pack but with a good capacity (around 70Ah will be great).
I’m not afraid of the weight and size of it.

I don’t really witch cells 21650, 18650… I saw the Liitokala 50ii or VTC6 or… I don’t know.
But I also don’t really know where I can find good copper sheets that I can solder on top of thick nickels strips spot welded on the cells ?
How can I build such a powerful pack ? If anyone can answer me that will be great.

Hello Kryce,

we building high power battery packs from cells. We develop our method, to omit the nikkel strip due to its high internal resistance instead copper plates are used. The copper is very hard to weld with electric spot welder and usually an electric spot welder generates so mutch localized heat, which shortens the battery life. Therefore, we use tig spot welding with a TIG spot welding torch developed by us.

Check out in this thread: https://endless-sphere.com/forums/viewtopic.php?f=31&t=112693
We also offer cnc machined copper plates in different patterns.

If you have some questions, feel free to ask.

Thank you I will have a look on it
 
KryceS said:
HK12K said:
Depending on your level of risk tolerance there is always RC Lipo. That will do 150 amps all day long.

I was thinking of Lipo batteries indeed but I don’t feel really safe with it… if you have an experience with it can we talk about it ?
I run lipos in all of my bikes. 20s 72v 20ah in my Raptor, 18s 66.6v 20ah on my Revive. Both set to over 150 battery anps on the controller and the cells don't break a sweat. Pound for pound they'll put out more amperage than just about anything else commonly available. They're incredibly easy to use to configure a pack of any voltage or capacity. Prices aren't bad. They can be charged very quickly. You can't run them lower than around 3.5v per cell or they'll quickly start to go out of balance, and you need to watch them like a hawk to ensure no cell ever goes above or below allowable limits. They really should be stored and charged outside, or in a location away from anything that can burn. HIstory has taught us that they can and do go up in flames from time to time. That said I have been using them for years and years in both bikes and rc vehicles without ever having one burn (knocks on wood). They require a hard sided enclosure, continuous monitoring, an eye on balancing, and you can never be complacent. They're not for everyone and many here would strongly advise against them, but nothing short of a repurposed EV pack can really compare when the amp requirements are high. At least not without using hundreds of cells and associated interconnects.

That said if you have hesitation or don't think you can stay on top of them, they're probably not for you.
 
KryceS said:
I was thinking of Lipo batteries indeed but I don’t feel really safe with it… if you have an experience with it can we talk about it ?

It's healthy not to feel safe with lipos. If you feel safe, you might let your guard down. Once you know their characteristics, you can control the risk, but can't eliminate it.
If you decide to go that direction, you might want to get a RC car/truck/etc. and start with small lipos rather than a 20Ah bomb. That way you can get a feel for how they discharge, especially how the voltage drops off of a cliff once they get around 3.6V-3.5V/cell.
 
I'm pretty much in the same boat. Have a stealth Alpha (genuine) so battery room is slightly smaller

Options were
18650- 200 cells at 20s10p, for 72v 30-35AH depending on cells
21700- 160 cells at 20s8p for 72v 30ah- Molicel P42

Packs with a smart BMS were around $2000AUD built so i would advise doing it right the first time
 
millzy555 said:
I'm pretty much in the same boat. Have a stealth Alpha (genuine) so battery room is slightly smaller

Options were
18650- 200 cells at 20s10p, for 72v 30-35AH depending on cells
21700- 160 cells at 20s8p for 72v 30ah- Molicel P42

Packs with a smart BMS were around $2000AUD built so i would advise doing it right the first time

I already build a battery for an Ebike, a 20s20p with lg MJ1 cells with smart BMS, i program it at 80A continuous discharge and 120A peak. But when I run the bike, my amperage is stuck a 55A and don’t why (I have a Sabvoton 72150 that I try to program with a computer)… but I have some issues with saving the parameters into the controller and voltages differences between my measurements, what the Sabvoton software read, BMS readings and screen display…

For this new battery I would like something câble of 150A continuous (just for the accelerations, when you are cruising the amp drop to a more « normal » level).

I saw Andy Kirby and Vortech use liitokala ii50 cells but I don’t know their reliability and cycles life. People told me about molicel or Samsung (for 21700 cells), LiPo (but I don’t feel really safe with it) or prismatic cells (but the shape and size of it will make a back pack style difficult I think).

The other thing that I doubt is the welding part (for my previous battery I solder two 0.2 mm nickel strips with a spot welder (6 welds on each cells) and solder copper on top of that. Someone advice me that), I don’t know which material to use and how to solder it on to the cells of high discharge currents. I saw in YT video (Bruno Power) the making of a high power battery for a suron, that they use only nickel strips for the connection and copper bus bar at the end + and -…
 
HK12K said:
KryceS said:
HK12K said:
Depending on your level of risk tolerance there is always RC Lipo. That will do 150 amps all day long.

I was thinking of Lipo batteries indeed but I don’t feel really safe with it… if you have an experience with it can we talk about it ?
I run lipos in all of my bikes. 20s 72v 20ah in my Raptor, 18s 66.6v 20ah on my Revive. Both set to over 150 battery anps on the controller and the cells don't break a sweat. Pound for pound they'll put out more amperage than just about anything else commonly available. They're incredibly easy to use to configure a pack of any voltage or capacity. Prices aren't bad. They can be charged very quickly. You can't run them lower than around 3.5v per cell or they'll quickly start to go out of balance, and you need to watch them like a hawk to ensure no cell ever goes above or below allowable limits. They really should be stored and charged outside, or in a location away from anything that can burn. HIstory has taught us that they can and do go up in flames from time to time. That said I have been using them for years and years in both bikes and rc vehicles without ever having one burn (knocks on wood). They require a hard sided enclosure, continuous monitoring, an eye on balancing, and you can never be complacent. They're not for everyone and many here would strongly advise against them, but nothing short of a repurposed EV pack can really compare when the amp requirements are high. At least not without using hundreds of cells and associated interconnects.

That said if you have hesitation or don't think you can stay on top of them, they're probably not for you.

Thank you, I indeed don’t feel confident enough to go with LiPo RC cells, I already use them with my sport welder and don’t feel safe. It may be stupid but this Ebike world and battery stuffs are new to me.

People told me about (Everything Ebike Channel) lipo cells (apparently safer) that require no soldering….
 
E-HP said:
KryceS said:
I was thinking of Lipo batteries indeed but I don’t feel really safe with it… if you have an experience with it can we talk about it ?

It's healthy not to feel safe with lipos. If you feel safe, you might let your guard down. Once you know their characteristics, you can control the risk, but can't eliminate it.
If you decide to go that direction, you might want to get a RC car/truck/etc. and start with small lipos rather than a 20Ah bomb. That way you can get a feel for how they discharge, especially how the voltage drops off of a cliff once they get around 3.6V-3.5V/cell.

It is indeed when you let your guard down that something bad can happen.
 
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