Finding a battery - Alibaba?

General Discussion about large electric scooters and motorcycles and other things with no pedals.
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weegee32   1 µW

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Finding a battery - Alibaba?

Post by weegee32 » Apr 06 2021 6:11pm

Hi all,

I am fairly new to this forum (and type of project) but see that it is quite helpful when it comes to these e-builds. I'll touch on a little bit about my project and then ask some questions that I hope some of you can help me with or guide me towards the proper solution.

Background: So I am working on converting an old Yamaha DT100 dirt bike/street bike into an electric one made for the road. I am an undergraduate electrical engineering student so I figured this would be a lot of good experience and would be a ton of fun. I have already purchased my motor and controller. I went with the 72v, 5kW (air cooled) golden motor. I went with the controller they were offering for the motor as well. The controller is the Vector 300 (for 5kW systems) and has a max phase current output of 300A and a continuous current of 100A. My questions now are focused on the proper battery for this system that can get me around 30-40 miles at around an average of 50mph. The battery of course should output 72v and have a continuous discharge at??? This is where I am stuck.

I believe that the battery should, at a bare minimum, discharge roughly 100A continuously. Is this correct? Should it be able to discharge more given that the controller can pull 300A in some scenarios? I am of course on a budget for the battery as well (no more than a grand). I have looked at creating my own pack from some chinese LifePo4 batteries. I know this CAN save me some money and will also allow me to mold it's shape for the frame. I am going to gander and say I need a minimum of 30Ah for the type of range I am looking for in this terrain? If I go with my own pack, I am slightly unsure of how a BMS will tie in as well. Also, batteries in parallel can discharge at twice the rate that one of the cells is rated for?

I am probably missing some things to note but this is all I can think of for now. I am sure I will have more questions for you guys soon enough. Any thoughts or opinions would be greatly appreciated. Thanks!

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e-beach   1.21 GW

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Re: Finding a battery - Alibaba?

Post by e-beach » Apr 06 2021 8:46pm

weegee32 wrote:
Apr 06 2021 6:11pm
Hi all,
.....My questions now are focused on the proper battery for this system that can get me around 30-40 miles at around an average of 50mph. The battery of course should output 72v and have a continuous discharge at??? This is where I am stuck.
Hi weegee32. Welcome to ES!

So you want speed and distance? Then you need a big battery, "and therein lies the rub."
From the most basic stand point, Volts = speed (rpms), Amps = torque, and Watt hours = distance (Battery Amp Hours).

This is all conjecture dependent on the efficiency of your bike compounded by riding style and environment. Is your bike aerodynamic? Is your weather cold? Do you have a lot of head winds? Hills? All things effect an EV, nothing new about it. So take a good look at how you are going to ride and your riding conditions to understand how big a battery you will need.
I believe that the battery should, at a bare minimum, discharge roughly 100A continuously. Is this correct?

From your controller manual it looks like your battery should be able to discharge 100A continuously, although the instructions are not super clear so having a battery that can go more then 100A continuous wouldn't hurt.
vec300-72.JPG
vec300-72.JPG (28.47 KiB) Viewed 185 times
I am of course on a budget for the battery as well (no more than a grand). I have looked at creating my own pack from some chinese LifePo4 batteries.
Ah, yes. The champagne performance on a beer budget scenario.....To be honest, it is why I drink beer :wink:

I should stop you here. It sounds like you haven't taken the time to understand different battery chemistry's and how the apply to your needs. RC Lipo is energy dense, relatively inexpensive but is volatile. High amperage 18650's are small enough to configure but you need to learn battery construction to make a shape that fits your frame. LiFePO4 is not as energy dense, but is a safer chemistry due to it's low C performance. But the battery has to be bigger to make up for the low energy density. Start researching performance of lithium battery chemistry's.

I know this CAN save me some money and will also allow me to mold it's shape for the frame. I am going to gander and say I need a minimum of 30Ah for the type of range I am looking for in this terrain?


What terrain is that you speak of? 30A doesn't sound like a 50mph at 40 mile motorcycle to me. It is really based on watt hours used per mile. (watts per mile.) On my main e-bike I use 27 watts per mile average. So, 36v x 15Ah = 540 watts / 27 = 20 miles of distance, which is what I get at my normal riding style. If I go really slow, I can double the distance.

If I go with my own pack, I am slightly unsure of how a BMS will tie in as well.

A good BMS should keep your cells / cell groups from over charging, over discharging and should balance them at the end of your charge.
Also, batteries in parallel can discharge at twice the rate that one of the cells is rated for?
Each will discharge at 1/2 of it's C rating. 4 in parallel will discharge at 1/4 of it's rating. So if a cell is rated for 30 amp discharge continuous, and your controller pulls 30 amps, then two of those cells in parallel only needs to discharge at 15 amps each to make the 30 amps needed.
I am probably missing some things to note but this is all I can think of for now. I am sure I will have more questions for you guys soon enough. Any thoughts or opinions would be greatly appreciated. Thanks!
We always miss something in diy ev's :lol:

If I were you, I would study battery chemistry and construction and decide if you need to build a battery or not.

Trusted battery vendors around here are:

ebikes.ca
PingBattey
EM3EV

:D :bolt:
Favorite Quotes:
"This is L.A., sugar. There is no 'over the top." Chris Erskine
"At a certain point the entropy wins." Maria Helena Braga

Current Build: ProFlex 757 Expert full suspension. Yescomusa 36v 800w Rear DD, upgraded 10AWG solid core through axle phase wires. 15ah Headway, 1000+ cycles, 80% DOD 30A Tronsung controller.

Past: Trek 4500 Yescomusa 36v 800w front DD.
Liahona, Yescomusa 36v 800w generic front DD.
1992 Trek 800, Yescomusa 800w 36v front DD.

markz   100 GW

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Re: Finding a battery - Alibaba?

Post by markz » Apr 06 2021 9:05pm

The rub is also in buying from random sellers online, and not reputable sellers. But lets add to your list, Unit Pack Power is also an option. Though all the options given, ebikes.ca, em3ev and perhaps even ping would net you 36V, 48V, 52V or 72V in ranges up to 25Ah and perhaps 30Ah but only 40A sometimes 50A.
So you want speed and distance? Then you need a big battery, "and therein lies the rub."

weegee32   1 µW

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Re: Finding a battery - Alibaba?

Post by weegee32 » Apr 06 2021 10:04pm

I should stop you here. It sounds like you haven't taken the time to understand different battery chemistry's and how the apply to your needs. RC Lipo is energy dense, relatively inexpensive but is volatile. High amperage 18650's are small enough to configure but you need to learn battery construction to make a shape that fits your frame. LiFePO4 is not as energy dense, but is a safer chemistry due to it's low C performance. But the battery has to be bigger to make up for the low energy density. Start researching performance of lithium battery chemistry's.
I mention LifePo4s because that seems to be the go to battery for ev's. No? I understand they have a moderate discharge rate compared to other lithium batteries. However, I am aware that they have a large cycle life and that is why I am primarily interested. If, however, my controller requires 'a lot' of current by LifePo4's standards then should I look to a different lithium battery?

You're correct that I do need to research these chemistries more. I have worked with LiPos before and am aware they have a high C discharge rate and subsequently can be dangerous. In fact, I made an electric skateboard to run off LiPos. But as I said, if my controller requires a larger discharge rate, would it make sense to go LiPo route or another type? My only concern really is buying another battery in 5 years when I could have a LifePo4 that lasts me 10 years. Let me know if this is a valid concern and if I should consider a different chemistry like LiPo. I will continue to read about my different options in the meantime.
What terrain is that you speak of? 30A doesn't sound like a 50mph at 40 mile motorcycle to me. It is really based on watt hours used per mile. (watts per mile.) On my main e-bike I use 27 watts per mile average. So, 36v x 15Ah = 540 watts / 27 = 20 miles of distance, which is what I get at my normal riding style. If I go really slow, I can double the distance.
I live in Florida, parts where it's pretty flat but average roads around me are 45mph. Don't get me wrong, I don't plan to use this as my sole purpose for transportation, just a little thing to ride around on really. Also, are you suggesting the battery be more than 30Ah? These are just estimates as of right now but if you believe it'll end up being a larger capacity (based on my speed x range) then I'll take your word over mine haha.

Thanks for your feedback! It is very very helpful :)

john61ct   100 GW

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Re: Finding a battery - Alibaba?

Post by john61ct » Apr 07 2021 6:52pm

LFP is only rarely used for EVs.

Much longer lifespan, thus better value by far

much safer, thermal runaway (boom, fire) less likely

but also lower energy density, thus slower performance and/or lower range.

Tesla using it in the China-produced models only.

Otherwise the 3.6 - 3.7Vnominal chemistries are used much more widely in commercially produced EVs sold into the developed world.

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e-beach   1.21 GW

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Re: Finding a battery - Alibaba?

Post by e-beach » Apr 07 2021 6:54pm

weegee32 wrote:
Apr 06 2021 10:04pm
........I mention LifePo4s because that seems to be the go to battery for ev's. No?
The answer is "Not necessarily." Depends on your application and needs.

I run LiFePO4 due to it's safe reputation. I feel comfortable leaving it charging in my garage all night. If I went to a modern 18650 cell, I could get the same distance with a much smaller battery at faster speeds off the line due to higher C ratings. However they sometimes, and not to often, but sometimes short internally, caused by all sorts of reasons, and catch fire.

viewtopic.php?t=87975

However if you have a safe place to charge your battery why not go for the most energy dense stuff?

It really depends on your EV and your desired outcome vs your budget.
I understand they have a moderate discharge rate compared to other lithium batteries. However, I am aware that they have a large cycle life and that is why I am primarily interested.


My main e-bike battery is 8 years old, has over 1100 cycles on it, is at about 80% of it's original capacity and and sags really badly. It needs to be changed out. I have a new set waiting for my to actually do it.
If, however, my controller requires 'a lot' of current by LifePo4's standards then should I look to a different lithium battery?
Again, depends on what you want. If you want a crouch-rocket LifePo4 probably won't do it unless you have a lot of room for a big heavy battery. LiFePO4 has low C ratings, which is also why it is a safer chemistry.

I am familiar with your DT, I used to have a Yamaha DT1F years ago, but it got stolen. :oops: I don't recall the actual size of the triangle, but it had a good amount of room. You might be able to get a LifePo4 pack in there, but you can get a comparable battery of smaller dimension and a higher C rate with different chemistry.
If my controller requires a larger discharge rate, would it make sense to go LiPo route or another type? My only concern really is buying another battery in 5 years when I could have a LifePo4 that lasts me 10 years.

If your controller has a maximum amp draw of 100A, then you need to build a battery that can handle 100A at least. Overkill is always better. Any battery chemistry will do, it is the other factors that you are facing, like the size and weight of the battery.


No battery is going to last you 10 years and perform as new in 10 years and have acceptable performance. Manufactures test their cells at very low C rates to maximize the lifespan of their sales pitch. If you want your cells to last a long time, baby them. Don't push them until they heat up, don't fully charge them and don't fully discharge them. By saving on cycles, they will last longer. You will also have to calculate in the shorter distance you will go before recharge, but, in the grand scheme of things that distance missed is really not that much.
I live in Florida, parts where it's pretty flat but average roads around me are 45mph. Don't get me wrong, I don't plan to use this as my sole purpose for transportation, just a little thing to ride around on really. Also, are you suggesting the battery be more than 30Ah? These are just estimates as of right now but if you believe it'll end up being a larger capacity (based on my speed x range) then I'll take your word over mine haha.
Well lets have something to compare to. My main e-bike weighs 80lbs. I weigh 220 lbs. 300lbs total. After 8 years of riding it, I know I use an average of 27 watts per mile in stop and go traffic. My new 36v 15Ah battery gets me 20 miles before LVC.

I average 12mph over that 20 miles. Now, say I found a route that allowed me to go 24mph, then I would increase the watts burned by maybe double....(probably a little less then double due to motor efficiencies at high speed) So 36v x 15Ah = 540 watts. And 540 watts / 50 watts burned per mile at 24mph = 10.8 miles before LVC. I will get there faster but at the expense of watts burned. Now if I had a 72v 30Ah that would be 2160 watt hours to burn. But, if I go 48mph that would burn around 100 watts per mile. So, 2160 / 200 watts per mile would also go 21.6 miles before LVC. Then add the extra weight of a motorcycle vs a bicycle, and your distance will be reduced.

A stipulation, my e-bike will never go that fast so these numbers are theoretical, but they illustrate the point. You will need a bigger battery then 30ah if you want to go 30-40 miles at 50mph.

(EDIT) 72v at 60ah minimum?

If you want to check out my numbers use Ohm's Law on volts watts and amps.

:D :bolt:
Favorite Quotes:
"This is L.A., sugar. There is no 'over the top." Chris Erskine
"At a certain point the entropy wins." Maria Helena Braga

Current Build: ProFlex 757 Expert full suspension. Yescomusa 36v 800w Rear DD, upgraded 10AWG solid core through axle phase wires. 15ah Headway, 1000+ cycles, 80% DOD 30A Tronsung controller.

Past: Trek 4500 Yescomusa 36v 800w front DD.
Liahona, Yescomusa 36v 800w generic front DD.
1992 Trek 800, Yescomusa 800w 36v front DD.

weegee32   1 µW

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Re: Finding a battery - Alibaba?

Post by weegee32 » Apr 07 2021 9:30pm

However they sometimes, and not to often, but sometimes short internally, caused by all sorts of reasons, and catch fire.

viewtopic.php?t=87975


What a crazy story, I'm glad I am asking these questions..


I am familiar with your DT, I used to have a Yamaha DT1F years ago, but it got stolen.


I am afraid the 100 will make me look like a clown on a bike :lol: -- I have some ideas to stretch the riding position at least. I love the DT1 as well, I chose this enduro pretty much randomly off of craigslist but have fallen in love with the look since. I somewhat want to turn it into a cafe racer type mold. Shame yours was stolen :/


If your controller has a maximum amp draw of 100A, then you need to build a battery that can handle 100A at least ...
So, like many, I am confused whether or not I should worry about the max phase current when choosing a battery for the controller. If mine pulls 300A for a few seconds, I shouldn't worry my battery only supplies say.. 135A?


One last thing for now, if I decide to build my battery from many cells, I surely wouldn't want to cheap out on the BMS and charger. Are there any reputable sellers you could reference? I think you have swayed me off of LifePo4 for now, still need to research but all this info has been extremely helpful.

Once again, thanks

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e-beach   1.21 GW

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Re: Finding a battery - Alibaba?

Post by e-beach » Apr 08 2021 10:31am

weegee32 wrote:
Apr 07 2021 9:30pm

.....
So, like many, I am confused whether or not I should worry about the max phase current when choosing a battery for the controller. If mine pulls 300A for a few seconds, I shouldn't worry my battery only supplies say.. 135A?
Phase current is on the output side of the controller. It is the number to look at for a motor, not a battery. If your controller is rated for 100A, then you need a battery that can handle it. As an example, most LiFePO4 battery's can handle 2C continuous. So if your battery is a 50 Ah LiFePO4 battery, then it most probably handle a 100 amp controller. (50Ah x 2 = 100Ah). However if your cells are say something like a INR18650-30Q that is rated at 5C continuous discharge, then you can get away with a 20Ah battery. (INR18650-30Q = 3 amps. They have a 15 amp continuous discharge rating...15/3= 5C)

Although, you can build a 20ah battery to run your bike, the 50ah battery has more overall capacity and will get you farther between charges. So depending on the chemistry of the battery used you need to make choices. Battery size is always an issue with EV's.

Some side notes: Lithium in general will let you use 80% of rated capacity while lead-acid batteries will only let you use about 50% of rated capacity. If you want to know more about that study Peukert's law. https://en.wikipedia.org/wiki/Peukert%27s_law

Any three phase motor will work on your motorcycle, until it over heats and burns out. The point being a small motor will not handle your controller very well. I haven't looked at the specs of your motor but I think you said it was a factory match to your controller. You will most probably will have more trouble matching your gearing with tire rpm's the worrying about the motor and controller match.

There is nothing wrong with using LiFePO4 as a battery they are just bigger then other types of battery's. If you have the room, and want a battery that lasts, you can always build an LTO battery pack. LTO is a low voltage cell, but it is high in capacity and very high C ratings. It can be charged and discharged very quickly and lasts a very long time. Or if you have an outdoor shed to charge in, you could also go with some of the inexpensive 20c RC Lipo. A 72v at 5ah Lipo battery on Hobby King is running under $200 at the moment. 5ah won't drive you very far, but at 20C it would work for your controller. (5Ah x 20C = 100A)

On pricing: Right now, lithium cells are expensive due to manufacturing cutbacks due to the Covid pandemic.
One last thing for now, if I decide to build my battery from many cells, I surely wouldn't want to cheap out on the BMS and charger. Are there any reputable sellers you could reference? I think you have swayed me off of LifePo4 for now, still need to research but all this info has been extremely helpful.
The BMS search always seems to be a problem. If you buy a battery from a reputable manufacture, the BMS comes with the battery and is generally dependable. There isn't much information on reputable aftermarket that I have read. I am sure there are some good manufactures out there, but you will have to look around for them. People are using smart BMS's with Bluetooth connectivity lately.

:D :bolt:
Favorite Quotes:
"This is L.A., sugar. There is no 'over the top." Chris Erskine
"At a certain point the entropy wins." Maria Helena Braga

Current Build: ProFlex 757 Expert full suspension. Yescomusa 36v 800w Rear DD, upgraded 10AWG solid core through axle phase wires. 15ah Headway, 1000+ cycles, 80% DOD 30A Tronsung controller.

Past: Trek 4500 Yescomusa 36v 800w front DD.
Liahona, Yescomusa 36v 800w generic front DD.
1992 Trek 800, Yescomusa 800w 36v front DD.

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e-beach   1.21 GW

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Re: Finding a battery - Alibaba?

Post by e-beach » Apr 08 2021 10:44am

Here is something I just stumbled upon. I haven't used it much and can not vouch for it's validity, but it will get you moving in a thoughtful direction.

https://www.blocklayer.com/rpm-gear-bikes.aspx

:D :bolt:
Favorite Quotes:
"This is L.A., sugar. There is no 'over the top." Chris Erskine
"At a certain point the entropy wins." Maria Helena Braga

Current Build: ProFlex 757 Expert full suspension. Yescomusa 36v 800w Rear DD, upgraded 10AWG solid core through axle phase wires. 15ah Headway, 1000+ cycles, 80% DOD 30A Tronsung controller.

Past: Trek 4500 Yescomusa 36v 800w front DD.
Liahona, Yescomusa 36v 800w generic front DD.
1992 Trek 800, Yescomusa 800w 36v front DD.

john61ct   100 GW

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Re: Finding a battery - Alibaba?

Post by john61ct » Apr 08 2021 7:59pm


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