Quick battery question

[Bgt2u]

I am thinking of lowering my voltage from 60v to 48v. The reason is I am looking for more miles between charges, with the same amount of torque. My controller and motor can run
from 48v to 72v. If l changed the battery from 60v 60ah, to 48v 60ah, would l have the same acceleration as the 60v setup?

 

[fechter]

In general, the higher voltage setup will be able to pump out more phase amps for a given battery current, so will have more acceleration. It depends on the controller.

The range you get depends on how much energy the battery holds and how fast you use it. A 60v battery will have more energy than a 48v one, but will also allow you to use it faster. If you limit your speed to what you would get with 48v, the 60v battery will have more range. Speed is what really kills your range. If you want to be able to run full throttle but keep the speed down, the controller may be programmable to do this or you could limit the throttle signal with a resistor.

 

[Bgt2u]

That makes sense. The whole reason that l am considering changing voltages is that l have a 60v 60ah battery with a bad BMS, and was going to set it up differently, add some more cells, and a new BMS. My current battery has 176 cells, and l have room for a total of 400. The acceleration it provided was adequate, and it had a slightly higher top speed than l needed, but the range was too short. My Motenergy motor, and Kelly KLS controller, can both handle up to 72v. Before l build a new battery, l just want to come up with the best voltage, that will achieve the same acceleration, but with a lot longer range per charge. Any thoughts?

 

[E-HP]

That makes sense. The whole reason that l am considering changing voltages is that l have a 60v 60ah battery with a bad BMS, and was going to set it up differently, add some more cells, and a new BMS. My current battery has 176 cells, and l have room for a total of 400. The acceleration it provided was adequate, and it had a slightly higher top speed than l needed, but the range was too short. My Motenergy motor, and Kelly KLS controller, can both handle up to 72v. Before l build a new battery, l just want to come up with the best voltage, that will achieve the same acceleration, but with a lot longer range per charge. Any thoughts?

It's all in the wrist. Acceleration implies that you aren't riding at a steady speed, and acceleration uses more of your battery than anything else except climbing hills. If you're on and off the throttle a lot, you will achieve your range goal because you won't the accelerating as hard, and therefore saving that energy. You could remain at 72V and go lighter on the throttle, since riding at 83% throttle at 72V is the same as full throttle at 60V, and when you want more acceleration/speed, you just twist the throttle more.

 

[fechter]

I think there are parameters you can program in the Kelly to limit the speed. But if it's only slightly higher than you need, I don't think it will make a big difference. You can also program it for a lower current, but that will reduce the acceleration. A bigger battery sounds like what you need.

That is a crazy looking vehicle. Those are some serious tires. Fenders might be nice if you ride in mud.

How fast does it go?

 

[Bgt2u]

Thank you for the replies. I think l am just going to build the biggest 72v battery pack that l can fit, and hope that l like it.

 

[E-HP]

Thank you for the replies. I think l am just going to build the biggest 72v battery pack that l can fit, and hope that l like it.

More pics and details! Looks like the blue one has a chain drive, with the motor mounted on the opposite side, and a pretty big drive sprocket. Is that similar for the red? How is the steering setup? That's a huge controller.

 

[eee291]

Did you end up resolving that noise issue the controller/motor was making?

 

[Bgt2u]

No, l didn't. I have tried just about everything, and it still does it, unless l keep the throttle setting at 91% or below.

 

[Bgt2u]

More pics and details! Looks like the blue one has a chain drive, with the motor mounted on the opposite side, and a pretty big drive sprocket. Is that similar for the red? How is the steering setup? That's a huge controller.

The blue one has one drive motor and chain per side. The red one has a chain drive limited slip differential, and rack and pinion steering. The red one is the newest, and is currently patent pending. There are many different types of people that are In¾terested in it

 

[Bgt2u]

I think there are parameters you can program in the Kelly to limit the speed. But if it's only slightly higher than you need, I don't think it will make a big difference. You can also program it for a lower current, but that will reduce the acceleration. A bigger battery sounds like what you need.

That is a crazy looking vehicle. Those are some serious tires. Fenders might be nice if you ride in mud.

How fast does it go?

I did not want fenders, as l don't want it to be classified, or look like every other ATV. I have had it up to 62mph, l stopped there, because it was scaring the crap out of me.

 

[Bgt2u]

This is the battery that got me thinking about changing the volts that l am running. I was out riding around, and the BMS blew up. I have no idea why. The max discharge current for the battery is 120 amps, and l have the controller set to only pull 75 amps max. I took the battery upart, and saw that l can fit over double the amount of 18650 cells inside....from 176 to 400 if l want. On that note, l have decided to go with 72v. Can anyone recommend a decent BMS? The max current output will still be 120 amps.

 

[eee291]

I recommend any JBD Bluetooth bms.
I've installed like 40 pieces over the years and not a single failure, except one or two Bluetooth dongles.
I'd order the 200A version with 2 dongles just in case. Can be used for 6s up to 21s batteries.

https://a.aliexpress.com/_mNrfKGk

 

[Bgt2u]

Thank you for your suggestion, l will check it out.

 

[E-HP]

The blue one has one drive motor and chain per side. The red one has a chain drive limited slip differential, and rack and pinion steering. The red one is the newest, and is currently patent pending. There are many different types of people that are In¾terested in it

Wow! Impressive.

 

[amberwolf]

I am thinking of lowering my voltage from 60v to 48v. The reason is I am looking for more miles between charges, with the same amount of torque. My controller and motor can run
from 48v to 72v. If l changed the battery from 60v 60ah, to 48v 60ah, would l have the same acceleration as the 60v setup?

You will have less miles out of the lower voltage pack, because it is the same Ah, so it has lower Wh (capacity). If you want more range *and* more torque (which takes more power out of the pack all other hardware things the same), you need a larger capacity battery to recharge it less often.

You'll have less speed and probably have less torque at the lower voltage.

But since it is a non-hubmotor you can proportionally change the gearing ratio between motor and wheel to compensate for the large drop in voltage. If you do this the speed will drop a lot more, but you'll get more torque. Since you don't need the speed it already has, that won't hurt anything.

 

[nicobie]

Loved the quads. You don't need fenders, you need tear-offs for your helmet visor.

Amazon link

 

[Bgt2u]

As the far as battery goes, l have decided to use 420 (22 sets of 20) Tesla 2170 3.7 volt cells @20s/72v. This should give me a total of 72v/105.6ah (verusus the previos 60v/60ah) Any ideas on a BMS, that would handle this configuration?

 

[Bgt2u]

I am building a 72v lithium-ion battery using 420: 3.7v 21700 Tesla cells (same as 18650 but slightly larger, with 4800mah capacity). I will have 22 sets of 20 (20s). I do not know what the maximum discharge current for them is. The finished battery pack should have about 105.6ah capacity.l am looking into a JBD Bluetooth BMS. I am figuring that l would need a BMS with between 200a - 300a. Is having a BMS with too many amps bad, or is it a case of the bigger the better?

 

[amberwolf]

Capacity (Ah) doesn't have anything to do with current (A) capability, regarding the items in question (there is one circumstance they do, in the cell design, but that's not relevant here).

BMS current capability requirement is determined by the load you will place on it, worst case, from the controller and anything else in the system.

Once you know how much current the load will draw, worst case, you buy a BMS that can handle that current, at minimum (higher is better because the FETs / etc then are less stressed). If the BMS has a programmable current limit, you can use that to shutdown it's output when the limit the cells can handle is exceeded, in case of things like excessive loads that aren't enough to blow fuses or pop breakers but would stress the cells.

But the BMS (and the cells) has to be able to handle at minimum the worst case current the system will ever draw in normal usage. (if you don't know what this is, you should start by determining that, because if you don't, you're building things that may not be able to do what you want, and have to rebuild them later, wasting time and money and effort--experiments can be fun, but it's fairly easy to guesstimate stuff like this given known conditions and job requirements).

Then you build the battery pack with enough parallel cells to handle at least that worst case load even when nearly empty, based on the discharge curve for the cells from the manufacturer if they are new. If they are used, then derate the cells by how well samples perform in testing to compare to the manufacturer spec. If there are no specs available, then testing samples to see how they perform under various loads should be done to see what they can take safely and easily without stressing them.

ONce that is known you can determine how many you have to parallel to support the load you'll have placed on the pack as a whole.

If you don't have enough parallel cells, there will be excessive voltage sag that robs your system of power it could have used to run the motor, that is instead wasted as cell internal heating that ages the cells faster.

 

[amberwolf]

As the far as battery goes, l have decided to use 420 (22 sets of 20) Tesla 2170 3.7 volt cells @20s/72v. This should give me a total of 72v/105.6ah (verusus the previos 60v/60ah) Any ideas on a BMS, that would handle this configuration?

See your other thread for answers to that. (or I can merge it with this one)

Bms amperage vs battery capacity

I am building a 72v lithium-ion battery using 420: 3.7v 21700 Tesla cells (same as 18650 but slightly larger, with 4800mah capacity). I will have 22 sets of 20 (20s). I do not know what the maximum discharge current for them is. The finished battery pack should have about 105.6ah capacity.l am...

endless-sphere.com

 

[Bgt2u]

See your other thread for answers to that. (or I can merge it with this one)

Bms amperage vs battery capacity

I am building a 72v lithium-ion battery using 420: 3.7v 21700 Tesla cells (same as 18650 but slightly larger, with 4800mah capacity). I will have 22 sets of 20 (20s). I do not know what the maximum discharge current for them is. The finished battery pack should have about 105.6ah capacity.l am...

endless-sphere.com

Merging sounds good. Thank you.

 

[amberwolf]

Sure...done.