What batterie should work min. 48V

[monette999]

Hi Forum my E-Kart is going into the finish line. I have made some test runs with my lab power supply. I do see high amount on current when I am changing load on my motor.

What are the batteries that could be affordable 18650 or 32700 or Lifepo4 cell.

I do need a low ESR since my Motor is a 70A alternator driven by a 1300W BLDC Controller.

Any proposal.?

Greetings
Bob

Gesendet von meinem CPH1911 mit Tapatalk

 

[john61ct]

Trying to save money up front will just cost you more, maybe not even get good enough.

First narrow down chemistry

LFP lasts 10x longer at least compared to the higher voltage LIs

but - do you need lowest possible weight per kWh?

If not maybe get started with cheap local lead in the meantime, maybe 1/5 the cost

then when you get your LFP pack built it will be about half the weight and volume, and of course more power too for zoomzoom

 

[Hillhater]

A 1300 W drive system, is not going to demand a powerful pack ..48v x 30 A ..could be 4 lead batteries.
but the size and weight will not help performance at that motor power.
PS your gearing looks very “optimistic” for a 1300W motor ?

 

[amberwolf]

What are the batteries that could be affordable 18650 or 32700 or Lifepo4 cell.

What does "affordable" mean to you? Meaning, what is your exact budget?

How much space do you have for the battery, and it's actual dimensions?

How much weight can you allow for the battery?

What are the exact specifications you need your battery to be capable of? You need to know what the battery has to do before you can make a battery to do it. Meaning:

--what is the average voltage your battery must maintain during the entire runtime?
(is it a "48v" controller? Or a 72v? Or a 5v? or a 1v? etc)

--what is the maximum voltage your controller and the rest of the system is capable of?
(will it explode if you connect it to a 6v battery, or does it take 124v to destroy it, or does it run fine as long as it's less than 84v, etc?)

--what is the kV of your motor, meaning how many RPM does it spin for each volt you give it? And how fast do you need it to spin, to do what you want?

--what is the average current it must output during the entire runtime?
(when running the kart around a track, does it typically take 40A, or 2647A, or half an amp, or etc?)

--what is the maximum current it will ever have to output during the entire runtime?
(when starting the kart from a stop at full throttle, or climbing a steep hill, does it take 80A, or 9275A, or a quarter of an amp, etc?)

--what is the maximum runtime you need, at what power level?
(do you need the kart to drive for 4 minutes at 1743watts, or 75 hours at 10 watts, etc?)

 

[monette999]

All good points,
But do you see my motor. It is a converted 70A alternator. Running on a 3phase 1300W controller cheapo style from PRC.
The controller can take max. 72V on 32A. That's what the lable saying.
I have no dyno at home to establish the load characters of my motor.

I know that it was delivering 70A at 14.4V when it was an alternator.
But as you know a rectifier was in between.

Now I am pushing 48 to 72V though the Stator Coils with an phase shift on 120°.
The motor has no hall sensors.
The controller works on the EMF Mode. This is why I have chosen this controller. I have not seen many other high power controllers which will work on EMF Mode.

So for the commercial side. I don't think that I want to spend a fortune into this project. So I will find my floor. The motor was free. The controller was 35€.
The cart was 150€. So I think 250€ is my budget for the batterie pack.

I would also go with used cells.
This is more an upcycle project.
The kart is vintage. Nobody will use this for racing anymore. The motor could be from the junkyard.
The controller is a cheapo. Maybe it needs an extra cooling fan plus an cooling body to make it robust.

I know my bottleneck is 1300W. So let's design the cells as well for 1300W Voltage 72V.

I know with no load at full speed one phase is taking 6A at 72V.

So far so good. I guess I will start with 18650 and will learn my lessons.

Greetings Bob

Gesendet von meinem CPH1911 mit Tapatalk

 

[Hillhater]

Good batterys are not cheap.
But For cheap, quality cells, from a reliable supplier in Europe,..i would suggest considering Timich here..
https://endless-sphere.com/forums/viewtopic.php?f=31&t=61608
To save the difficulty, time, hassle and risk of building your own pack, he has 48v 21Ah packs for $199.
But enquire he often has other packs..36v etc.