Help with choosing the right battery for powerful motor

General Discussion about electric bicycles.
Post Reply
Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 02 2021 12:22pm

Hi everyone,

I want to make sure I am choosing the right battery for my electric motorcycle/e-bike.
I modified a 125cc old cafe racer into electric motorcycle, I've already collected all parts that I need for my build.. except the battery :(

My motor is the 3.5T 3000-5000W QS Motor, the input Voltage Range for it is 48V/60V/72V, MAX DC current: 100A Max Phase current: 250A

My controller is the Sabvoton 100A, suitable for 48V/60V/72V
MAX DC current: 100A Max Phase current: 250A

My bike weight is gonna be around 50-55kg (without battery)
I weight about 90kg so the whole bike with rider is gonna weight about 140kg.

I'm looking for a battery that's gonna let ride for about 60-100+ km on one charge.

Should I go for 72V battery or 48V is gonna have satisfactory top speed with 140kg weight as well?
How many Ah should I go for to get good range?
And the most important question for me is - should I look for a battery with 100A current or lower current is gonna be fine? Is it gonna be bad for the motor to - for example - put 80A battery?

Thank you so much for all your help!

User avatar
E-HP   10 MW

10 MW
Posts: 2286
Joined: Nov 01 2018 9:20pm

Re: Help with choosing the right battery for powerful motor

Post by E-HP » May 02 2021 1:08pm

Janjarmosz wrote:
May 02 2021 12:22pm
My motor is the 3.5T 3000-5000W QS Motor, the input Voltage Range for it is 48V/60V/72V, MAX DC current: 100A Max Phase current: 250A
That's interesting. I haven't seen BLDC motor specs that included a spec for MAX DC current. Most of the time that I see that used, it's relates to the maximum battery current to the controller. Can you provide a link to the spec sheet; curious. Thanks. :thumb:

Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Re: Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 02 2021 1:35pm

E-HP wrote:
May 02 2021 1:08pm
Janjarmosz wrote:
May 02 2021 12:22pm
My motor is the 3.5T 3000-5000W QS Motor, the input Voltage Range for it is 48V/60V/72V, MAX DC current: 100A Max Phase current: 250A
That's interesting. I haven't seen BLDC motor specs that included a spec for MAX DC current. Most of the time that I see that used, it's relates to the maximum battery current to the controller. Can you provide a link to the spec sheet; curious. Thanks. :thumb:
Sure, here you go, I took it from the description of the motor I bought

https://www.ebay.co.uk/itm/333680044405 ... 1438.l2649

User avatar
E-HP   10 MW

10 MW
Posts: 2286
Joined: Nov 01 2018 9:20pm

Re: Help with choosing the right battery for powerful motor

Post by E-HP » May 02 2021 1:40pm

E-HP wrote:
May 02 2021 1:08pm
Janjarmosz wrote:
May 02 2021 12:22pm
My motor is the 3.5T 3000-5000W QS Motor, the input Voltage Range for it is 48V/60V/72V, MAX DC current: 100A Max Phase current: 250A
That's interesting. I haven't seen BLDC motor specs that included a spec for MAX DC current. Most of the time that I see that used, it's relates to the maximum battery current to the controller. Can you provide a link to the spec sheet; curious. Thanks. :thumb:
Everything past the section titled "Advantage" appears to be a description about a controller, but the auction is only for a motor. Looks almost like they copied the description for a motor & controller kit.

Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Re: Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 02 2021 3:41pm

E-HP wrote:
May 02 2021 1:40pm
E-HP wrote:
May 02 2021 1:08pm
Janjarmosz wrote:
May 02 2021 12:22pm
My motor is the 3.5T 3000-5000W QS Motor, the input Voltage Range for it is 48V/60V/72V, MAX DC current: 100A Max Phase current: 250A
That's interesting. I haven't seen BLDC motor specs that included a spec for MAX DC current. Most of the time that I see that used, it's relates to the maximum battery current to the controller. Can you provide a link to the spec sheet; curious. Thanks. :thumb:
Everything past the section titled "Advantage" appears to be a description about a controller, but the auction is only for a motor. Looks almost like they copied the description for a motor & controller kit.
Yup, that's very possible, my controller was the one that was "recommended" for this motor.
still need help with finding the right battery :( can I go for one that provides 80A output or it's gonna damage my motor?

gobi   10 W

10 W
Posts: 79
Joined: Jan 09 2021 5:30pm

Re: Help with choosing the right battery for powerful motor

Post by gobi » May 02 2021 4:52pm

Higher Voltage = lower current
I would aim for a balance,
20sXp

X= how much space you have to add capacity.

I am thinking of splitting my battery in 2x36volt batts and then plug them in series to get my desired voltage. then it won't be 1 massive batt,

10s4p each batt with it's own BMS.

Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Re: Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 02 2021 7:15pm

gobi wrote:
May 02 2021 4:52pm
Higher Voltage = lower current
I would aim for a balance,
20sXp

X= how much space you have to add capacity.

I am thinking of splitting my battery in 2x36volt batts and then plug them in series to get my desired voltage. then it won't be 1 massive batt,

10s4p each batt with it's own BMS.
is 2x12Ah enough for weight of my bike? I feel like the range is gonna be really small, also, with 2 small batteries isn't current much smaller as well? Surely 2x30A battery does not equal 60A current?

User avatar
serious_sam   10 kW

10 kW
Posts: 591
Joined: Mar 05 2017 8:07am
Location: Australia

Re: Help with choosing the right battery for powerful motor

Post by serious_sam » May 02 2021 7:49pm

Janjarmosz wrote:
May 02 2021 12:22pm
Should I go for 72V battery or 48V is gonna have satisfactory top speed with 140kg weight as well?
How many Ah should I go for to get good range?
And the most important question for me is - should I look for a battery with 100A current or lower current is gonna be fine? Is it gonna be bad for the motor to - for example - put 80A battery?

Thank you so much for all your help!
This will answer all of your questions.

https://ebikes.ca/tools/trip-simulator.html

999zip999   100 GW

100 GW
Posts: 10055
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Help with choosing the right battery for powerful motor

Post by 999zip999 » May 02 2021 11:39pm

The only thing that can melt your motor is the throttle or the controller. build the battery bigger and stronger and more powerful than you need and then you won't use it to its limits and it won't wear out prematurely. Remember your controllers are programmable and it's called the controller for the reason you are thinking. 72v is good and what space do you have ? You need 20ah or more 35ah. Good high quality cells. Remember if they say Tesla like cells it's probably a scam. You have to know what cells like Samsung 40t or Samsung 25r there are a lot of other good quality cells but batteries cost a lot of money. Where are you located ? As there are tons of junk batteries for sale with false promises. How much battery experience do you have ? Please answer all questions. Thanks
Oh you can have the mods move this to the battery section.

User avatar
E-HP   10 MW

10 MW
Posts: 2286
Joined: Nov 01 2018 9:20pm

Re: Help with choosing the right battery for powerful motor

Post by E-HP » May 03 2021 12:51am

Janjarmosz wrote:
May 02 2021 3:41pm
still need help with finding the right battery :( can I go for one that provides 80A output or it's gonna damage my motor?
Yes, YOU can damage the motor, but it's up to your throttle hand. I would say it would be difficult to damage it, since I regularly put 60A at 72V into my 1000W 9C clone and over 80A off the line, and it seems to take it fine as long as I check how hot it is (hand test) once in a while if I feel like I've thrashing it. I you're using a temp sensor, and the controller scales back the power when the motor heat up, then you wouldn't need to worry about it at all. Add some Statorade in order to help dissipate the heat.

Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Re: Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 03 2021 2:19pm

999zip999 wrote:
May 02 2021 11:39pm
72v is good and what space do you have ? You need 20ah or more 35ah. Good high quality cells. Remember if they say Tesla like cells it's probably a scam. You have to know what cells like Samsung 40t or Samsung 25r there are a lot of other good quality cells but batteries cost a lot of money. Where are you located ? As there are tons of junk batteries for sale with false promises. How much battery experience do you have ? Please answer all questions. Thanks
Oh you can have the mods move this to the battery section.
Hi there, thanks so much for taking the time to help me out with my build!
I want to build a custom box for my battery, the maximum that will fit into my bike frame is 35cm x 30cm, to be honest, I was thinking about buying a ready battery instead of building my own.
I'm located in Wales, UK. I have no battery experience, this is my first build.

Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Re: Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 03 2021 2:21pm

E-HP wrote:
May 03 2021 12:51am
Janjarmosz wrote:
May 02 2021 3:41pm
still need help with finding the right battery :( can I go for one that provides 80A output or it's gonna damage my motor?
Yes, YOU can damage the motor, but it's up to your throttle hand. I would say it would be difficult to damage it, since I regularly put 60A at 72V into my 1000W 9C clone and over 80A off the line, and it seems to take it fine as long as I check how hot it is (hand test) once in a while if I feel like I've thrashing it. I you're using a temp sensor, and the controller scales back the power when the motor heat up, then you wouldn't need to worry about it at all. Add some Statorade in order to help dissipate the heat.
Thank you for letting me know, I will definitely do the Statorade thing. What do you mean by the throttle hand damaging the motor? Wrong throttle voltage for the controller? Any tips on choosing the right twist-n-go throttle?

User avatar
MadRhino   100 GW

100 GW
Posts: 7350
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Help with choosing the right battery for powerful motor

Post by MadRhino » May 03 2021 4:10pm

Motors are damaged by heat. Yet, it is pretty uncommon to overheat a big DD hub. You need to be unconscious to do that. Now most big hubs are equipped with a temp probe, and many controllers have a temp cut-off setting. Even without any temp protection or monitoring, big hubs need to be abused badly to overheat: Riding very slow a bike that is built very fast, for an example; or, repeated stops and hard accelerations up a steep hill... A 30 lbs DD hub is capable of very hard acceleration, and faster speed than most would want to ride more than a few seconds.

It is common practice to build powerful ebikes with more batteries than required: more capacity and higher C rate than we need. A 72v 12 a/h battery is small for the motor size and winding that you have.
Make it fool-proof, and I will make a better fool.

User avatar
E-HP   10 MW

10 MW
Posts: 2286
Joined: Nov 01 2018 9:20pm

Re: Help with choosing the right battery for powerful motor

Post by E-HP » May 03 2021 9:23pm

Janjarmosz wrote:
May 03 2021 2:21pm
E-HP wrote:
May 03 2021 12:51am
Janjarmosz wrote:
May 02 2021 3:41pm
still need help with finding the right battery :( can I go for one that provides 80A output or it's gonna damage my motor?
Yes, YOU can damage the motor, but it's up to your throttle hand. I would say it would be difficult to damage it, since I regularly put 60A at 72V into my 1000W 9C clone and over 80A off the line, and it seems to take it fine as long as I check how hot it is (hand test) once in a while if I feel like I've thrashing it. I you're using a temp sensor, and the controller scales back the power when the motor heat up, then you wouldn't need to worry about it at all. Add some Statorade in order to help dissipate the heat.
Thank you for letting me know, I will definitely do the Statorade thing. What do you mean by the throttle hand damaging the motor? Wrong throttle voltage for the controller? Any tips on choosing the right twist-n-go throttle?
I mean that it's up to how you ride the bike, you are in control of how long you run the motor over the continuous rating. It would be difficult to melt the motor, but, absent something that automatically rolls back the power, you still could overheat it. The Statorade would help, but by using the controller in conjunction with a temp sensor to scale back power when the motor heats up, you wouldn't need to worry about an over zealous throttle hand.

goatman   100 MW

100 MW
Posts: 2980
Joined: Jun 23 2019 6:50pm
Location: Surrey, B.C.

Re: Help with choosing the right battery for powerful motor

Post by goatman » May 03 2021 9:55pm

if youre tight for space id go with a 17s/61 volt battery
not what other people call a 60 volt battery, 16s is 58v not 60v

the difference being how the bike feels with a dead battery

if youre using 18650's, 17s8p or 17s9p of a higher power cell rated for 3000mah or better is what id be looking for

999zip999   100 GW

100 GW
Posts: 10055
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Help with choosing the right battery for powerful motor

Post by 999zip999 » May 04 2021 2:01am

A throttle ask 4 wattage voltage from the controller the controller demands it from the battery. That's iit

The battery is very dumb that's why it needs a BMS a battery management system
. A controller controls
A throttle demands from the controller.
Never mind a throttle will only tell sometime tomorrow what to do with what the controller will let it do.
A battery will run like a horse to it dies that's why it needs a BMS but you can still kill a battery if it is not over powered for it's denands.
You don't beat a horse to a dies.
Last edited by 999zip999 on May 08 2021 12:55pm, edited 1 time in total.

ColinB   100 W

100 W
Posts: 147
Joined: Jun 29 2011 1:50pm
Location: British Columbia, Canada

Re: Help with choosing the right battery for powerful motor

Post by ColinB » May 07 2021 3:27pm

Just to highlight this again - if you ask for too much power from your battery, expect fewer recharge cycles, more heat, maybe balance issues. More voltage sag, less power.

So, you need to ensure your battery will give you the speed you want (voltage), range (capacity) and power (c rating.) For the range and power, I believe it is wise to over estimate, at least a bit, so you are not running your battery at 100%.

Colin

999zip999   100 GW

100 GW
Posts: 10055
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Help with choosing the right battery for powerful motor

Post by 999zip999 » May 08 2021 12:56pm

Give us all the dimensions of your battery box.

Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Re: Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 09 2021 3:15pm

999zip999 wrote:
May 08 2021 12:56pm
Give us all the dimensions of your battery box.
I’m gonna build a battery box, biggest one that’s gonna fit in my frame is about 300x300x150

999zip999   100 GW

100 GW
Posts: 10055
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Help with choosing the right battery for powerful motor

Post by 999zip999 » May 09 2021 9:49pm

I would look into used leaf cells or other automotive grade cells that will fit.

Janjarmosz   1 mW

1 mW
Posts: 15
Joined: Apr 12 2021 8:49am

Re: Help with choosing the right battery for powerful motor

Post by Janjarmosz » May 12 2021 11:07am

999zip999 wrote:
May 09 2021 9:49pm
I would look into used leaf cells or other automotive grade cells that will fit.
Sounds like a great idea, I did some research, do you know if the wiring has to be changed or just used leaf battery can be easily connected to sabvoton controller?

User avatar
MadRhino   100 GW

100 GW
Posts: 7350
Joined: Sep 03 2010 5:28pm
Location: Montreal QC Canada

Re: Help with choosing the right battery for powerful motor

Post by MadRhino » May 12 2021 2:46pm

Janjarmosz wrote:
May 12 2021 11:07am
999zip999 wrote:
May 09 2021 9:49pm
I would look into used leaf cells or other automotive grade cells that will fit.
Sounds like a great idea, I did some research, do you know if the wiring has to be changed or just used leaf battery can be easily connected to sabvoton controller?
You’d have to make your own battery with used Leaf cells. Then you order a BMS for the voltage and power that you need, and the connectors to match your actual wiring.
Make it fool-proof, and I will make a better fool.

999zip999   100 GW

100 GW
Posts: 10055
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Help with choosing the right battery for powerful motor

Post by 999zip999 » May 12 2021 3:19pm

: Many many articles and threads on how to use and repurpose leaf modules.

Post Reply