Is 72V 5Ah the same as 36V 10Ah?

I'm currently using a 36V LiPol battery pack with 10Ah capacity. It is coupled with 20A controller and a 9c high speed motor.
I'm planning on changing to 72v 5Ah battery. If I ride on the same speed (around 30km/h) will the range stay the same? I'd like to have a possibility to draw more power out of the bike but I don't want to loose range in every day commute.

In theory it's the same amount of cells and Watt-hours. however, I suspect you'll generally use more watts running on 72V than you would on 36V. - But that may depend of the motor, as well...

Not much English but try to explain.
my case.
48v-15ah (48x15=720) changes to 72v 10ah (72x10=720) so I stay the same autonomy but with more torque and speed.
your case
36v10ah (36x10=360) changes to 72v5ah (72x5=360) some autonomy more power and Speed.

(Google Tranlator) Sorry edit because I'm wrong now fixed

what is lipol?

how will you cut the 10Ah rows of the battery down to 5Ah?

JeromeBaldino said:

I'm currently using a 36V LiPol battery pack with 10Ah capacity. It is coupled with 20A controller and a 9c high speed motor.
I'm planning on changing to 72v 5Ah battery. If I ride on the same speed (around 30km/h) will the range stay the same? I'd like to have a possibility to draw more power out of the bike but I don't want to loose range in every day commute.

Click to expand...

In general, with the same bike, motor and controller and just changing battery, speed is the major determining factor in how much energy you will use.

So, the easy answer will be yes. Your range will stay the same at the same speed.

Your 36V 10Ah battery has a Wh capacity of 360Wh (36*10)

The 72V 5Ah battery has a Wh capacity of 360Wh (72*5)

But you will have to take in the fact that humans will go faster if possible, especially at your power level. If you don't somehow electronically limit your throttle (CA or 3 speed switch), you may find yourself going faster and thus using more Wh/mi than you normally would.

If I understand your battery, it's modular, convertible, wonder experimenting toy. But what do you want 72v for? If you can make that speed you want at 36v, there's noting to be gained at 72v. The strain in doubling the amperage from the batteries will wear them out sooner. You have to explain what is supposed to happen when you replug them and double the voltage for someone to answer your question.

Lipol said:

LiPol Battery has developed, and introduces a liPo battery that achieves an ultra-thin under 1mm with high performance through its own original technology and high reliability employing a complete gel-type electrolyte.

Main Features of LiPo Battery

* High Performance and High Reliability with Newly Developed Complete Gel Type Electrolyte
The newly developed polymer electrolyte obtains superb long life reliability, featuring more than 500 recharging cycles while also achieving high performance (LiPo battery gravimetric energy density of 166Wh/kg & volumetric energy density of 348Wh/l).

* Excellent Discharge Characteristics that Allow for Discharge at -20°C
Typical points of weakness for liPo battery were its load and temperature characteristics. This newly developed polymer electrolyte possesses high ion conductivity even at low temperatures, thus making possible discharges at -20°C.

* Achieves an Ultra-Thin Type Thickness of Under 2mm
It was possible to achieve both an ultra-thin type thickness of under 2mm and obtain high leakage-resistance even when utilizing thin and light aluminum laminated film as the exterior packaging material for LiPo battery because the electrolyte is completely gel-type.

Click to expand...

Thanks for all the replies. I am looking for increased speed. I can now go around 35km/h (22mph) and I want to occasionally go 50km/h (32mph) when traveling on street (to keep up with traffic and avoid constant passing by cars on narrow road). But since I very rarely travel outside of bike lanes such speed is impossible (right now I rarely use full 35km/h speed). From what I've read on this forum this is the easiest way to go.

Since I want to double to voltage I imagine that at the same speed I will draw half the current so it should be better for my batteries?

No. 72v 5 ah will mean the same wattage will be the same c rate. 72v will be double the voltage but half the amps. So the discharge rate on the battery of a given wattage will be the same. But with the 72v 5 ah, you can easily double the wattage, and double the discharge rate, hammering your battery into dogshit.

To go farther, you must either slow down, or get more battery. 72v 10 ah in other words. Then you can have your speed when you need or want it, but still double your range when riding slower.

I think I'm beginning to understand but just to be clear: 1C is 1A per 1second right?

So right now while riding at 35 km/h I use 20A on 36V = 720W of power (example). So in once second of riding my batteries give off 20C (C=20A*1s).
In desired solution i will be riding at 35km/h using same amount of power - 720W. Since the voltage is 72V than the amperage will be 10A. Thus in one second the battery bank will be giving out 10C.

Where is the error in my understanding ?

with a fixed resistance double the voltage and it quadruples the watts!
not exactly what is going on here, but imo you need to use a 10ah pack or even MORE to be real happy at 72v.

JeromeBaldino said:

I think I'm beginning to understand but just to be clear: 1C is 1A per 1second right?

So right now while riding at 35 km/h I use 20A on 36V = 720W of power (example). So in once second of riding my batteries give off 20C (C=20A*1s).
In desired solution i will be riding at 35km/h using same amount of power - 720W. Since the voltage is 72V than the amperage will be 10A. Thus in one second the battery bank will be giving out 10C.

Where is the error in my understanding ?

Click to expand...

Not quite correct.

1 "C" just means 1 Amp of discharge current per Amp-hour capacity of the battery. - So if you have a 1C-rated, 10 Amp-hour battery, you can realistically discharge at a rate of 10 Amps. - a 2C-rated battery with the same capacity of 10 Ah can discharge up to 20 Amps continuous. - For Low C-rated batteries, you need to have a HUGE capacity to supply a lot of amps to your controller. This is the case with LiFePO4 batteries. in contrast, HK LiPo batteries are typically rated as 20C or higher - so a 20C-rated 5Ah battery can discharge 100A of current. It will just burn through that current very quickly - in a matter of 3 minutes.

Maybe this will help you figure out something.

Your top speed will be watts dependent, assuming you aren't limited by something like a motor winding will not rotate fast enough at a particular voltage.

So if your motor will rotate at 35 kph on 36v, using 750w, then it will rotate 35 kph on 750w using 72v. Nothing much changes. Sure, there may be some small differences in efficiency of a controller, or a motor. But in the main, traveling the same speed on the same bike will use close to the same wattage no matter what motor you choose or what voltage you run it at. 72v doesn't make it use more watts to go 35 kph. It uses the same watts, but since voltage changed you need less amps to get 750 w.

20mph takes 400w, 25 mph takes 700-, 30 mph takes about 1200w, and so on. Unless you change the aerodynamics of the bike, the watts each speed will take varies very little. You can find various rpms where this motor or that motor on this or that voltage is outside the generally efficient rpm, but when you compare motors or voltages that are still in the happy efficient rpm under load, you find x watts gets you y kph no matter what you are using.

This is why you can take a monster motor capable of 5000w, and still run it very efficiently at 100w if you want to, on flat ground.

The best example I can think of for making calculating c rate easy is, 10 ah at 1c is 10 amps. 10 ah at 2c is 20 amps. From there, if you can do ratios in your head, you can derive other c rates fairly easy, like 5 ah at 1 c is 5 amps.

need an ammeter or wattmeter at least for practice on starts and hills.
36v 20a=720w
72v 20a=1440w
every hill and start will fast drain pack if u dont learn to use part throttle.
wind too!
i just converted a scooter to 36v from 24 and it blew a fuse on a steep hill at part throttle, so i'm learning too!
good luck!

right, I'm new and can't get some things too... in that case (48x15=720) (72x10=720) the power is the same, how does it affect the motor performance?

If we use more amps does it mean it will be more powerful when climbs hill and slower on flat?

Using more volts does it means it will go faster on a flat and have problems climbing?