Difference between 100ah & 60ah

[Shinigaimi]

Hey all

I am curious what would be the difference in two different scenarios

Both are at 72 volts but one is 100ah and the other is at 60ah? What would change?, top speed, distance? I am curious

Thanks! And forgive my newbieness!

 

[ohzee]

40 ofc

that's a large cell.. without other specs it's hard saying how much you can pull from it amp wise , but
you would just have more distance with the larger pack.

Ah is just like gas tank size.. the bigger the number the further you can go on the same voltage.

 

[Farfle]

If your efficiency is 2 miles per ah, (very rough average for low wattage legal ebike consumption) you will get 120miles out of a 60ah pack, and 200miles from a 100ah pack. BUT a 60 or 100 ah pack is not going to fit on a bike, and will add so much to the weight that you will see much less than that 2 miles per ah unless you only travel long distances on flat ground while not stopping.

 

[SamTexas]

I don't think the OP is talking about e-bicycles. 60 and 100Ah battery is probably for a motorcycle or 3 or 4 wheel vehicle.

OP: If it's for a high power motor then in addition to a longer range you would also get better performance due to less voltage sag.

 

[wesnewell]

Range (distance) would be the difference. 100ah would go about 65% farther than the 60ah

 

[parajared]

Greater Ah= greater range

It may be worthwhile to note that double the ah never seems to equate to double the range. Same problem in remote controlled cars.

 

[Shinigaimi]

Hey all sorry This setup is for a motorcycle conversion! so far here is the setup that I have

Donor Bike:
some sort of sports bike - I want to get atleast 60mph the more the merrier but my focus is on range mostly

PARTS:
Motor Motenergy ME1003 Permanent Magnet DC
Controller Alltrax 7245
Batteries Either 100Ah | 90Ah | 60Ah
System Voltage 72v volts
Charger Zivan NG1

also if anybody sees anything wrong with the setup that I have chosen for any reason

I have also dont some rough calculations I have no idea if they are correct at all but here we go
Also my calulations are as follows on how I got the numbers

also I assume a perfect world where I have 0 wind resistance and my bike with all the electronics are weightless

Watts = Amps * Volts
Watts per mile = 125 (I read that a motorcycle uses about 100ish watts/mile)
Total Miles = Watts / Watts per mile

If any of these calculations are WRONG please let me know

First Battery pack 100AH @ 72v
Amps 100
Volts 72
Watts 7200
Watts per mile 125
Total Miles 57.6

Second Battery pack 90AH @ 72v
Amps 90
Volts 72
Watts 6480
Watts per mile 125
Total Miles 51.84

Third Battery pack 60AH @ 72v
Amps 60
Volts 72
Watts 4320
Watts per mile 125
Total Miles 34.56

 

[arkmundi]

There are the trade-offs. More AH, more weight, therefore more motor to push the load, etc., a diminishing return situation. Its why EV's are being so avidly researched, because getting it all right is not easy. One thing not mentioned is, the more cells you have in your battery, the more you need a sophisticated BMS to keep it in good shape.

There is a reason why the other end of the spectrum, of light EV, small packs, less sophistication, less range and also less costs, is, in full consideration, an option that many of us choose. I like being able to drag my LEV at 36V 20AH up the steps and inside into my apartment, for both protection from the elements and theft and overnight charging. I expect only 20 miles, but that's double my average daily commute.

Moral of the story: right sizing your LEV to your average travel needs, both speed and range. Sexy/flashy is not the point. Doing LEV for cost savings. I'm spending pennies on my travel now. Wow, in a world where gas is going to break $5 USD a gallon. Plus since my LEV qualifes as a bicycle (<750 watts), no insurance, etc.

 

[Njay]

Higher capacity cells will also allow you to do higher discharge current (-> higher motor torque, if the motor can handle it), for the same conditions (cell life, cell efficiency, ...).

 

[amberwolf]

also I assume a perfect world where I have 0 wind resistance and my bike with all the electronics are weightless

The former assumption is a very bad one to make, because at the speeds you want to go, there is an awful lot of that resistance, which will eat up your power. Below 10-15MPH it doesn't make all that much difference, but I don't think you'll be below those speeds hardly ever.

If you want a reasonably successful first try, that gets close to your expectations, you will need to do all of your figuring while using both an approximate weight vs actual terrain, and wind resistance vs actual speed.

 

[Shinigaimi]

Are there any fancy calculators or formulas that I can use to estimate the distance using a top speed?

 

[arkmundi]

Are there any fancy calculators or formulas that I can use to estimate the distance using a top speed?

Ya, its called a brain. :lol:

 

[Njay]

There's a spreasheet around on elmoto.net that will do some of that.

 

[docnjoj]

The ebikes.ca simulator takes air resistance and weight into account.
otherDoc

 

[Njay]

Here's my version of the original spreadsheet by Lennon Rodgers. I heavily modified it to include more realistic battery behavior and motor required characteristics (not rely only on power but consider torque/current and speed/voltage), ISO units, a table of a few well known DC-brushed motors, many other minor changes. Comments are welcome!

 

[oatnet]

Are there any fancy calculators or formulas that I can use to estimate the distance using a top speed?

Ya, its called a brain. :lol:

What a dick. Feel free to ignore him shinigaimi, arkmundi is new here, has almost no ebike experience, and none whatsoever with e-Moto's. We are all scratching our heads as to why he keeps posting "advice" here, but there you have it.

It looks like you are progressing nicely on your research, and you are correctly measuring in WH not AH, we appreciate people who do homework before asking questions. WHM will vary widely with speed, weight, overall build efficiency, and riding style. I use 150-160whm on my Vectric E-Moto, but it is a heavy (500lb) bike and I drive 40-65mph on my commute.

There are a variety of calculators, but you would really need to quantify drag coefficeint and weight to get an accurate number, and you would have to have a good sense of your riding style which is pretty hard to do. Sadly, the best way to get a feel for this is practical application of ass to saddle. My advice for a new build would be to put as much battery as you can afford and comfortably/safely carry, I don't think I have ever wished I had less range. :lol:

Watts = Amps * Volts
Watts per mile = 125 (I read that a motorcycle uses about 100ish watts/mile)
Total Miles = Watts / Watts per mile

If any of these calculations are WRONG please let me know

First Battery pack 100AH @ 72v
Amps 100
Volts 72
Watts 7200
Watts per mile 125
Total Miles 57.6

Fully discharging your battery can impact it negatively, so I would also add DOD (Depth of Discharge) to your calculation. Conventional knowledge is to use 80% of a Lithium batteries capacity (80% DOD), and use 45% of a Lead-Acid to (45% DOD), instead of the 100% DOD you are using. In the example above, usable wh on a lithium pack would be 5,760 not 7,200.

In addition... when I build an EV I spec a lithum pack to a 70% DOD, because batteries decrease in capacity as they age. In addition, be aware that the resisistance of your pack will impact the usable watts you get from it... With low-c/high resistance batteries like CALB, thundersky, and ping, a lot of energy will be converted to heat (10%? 20%), wheras a high-C/low resistance cell like a123 or Hobby King LiPo converts far less.

Anyhow, 60ah vs 100ah... For a given load, the more AH in the pack, the lower the 'c rate' of discharge. The lower the 'c rate' of the load, the less voltage drop. The less voltage drop, the less power wasted as heat, so you get a bit more WH from your pack. The lighter weight of the 60ah cell will give you slightly better WHM. If your motor is BLDC, the higher voltage will allow higher RPMs, not so for DC. That said, it is hard to envision a scenario where any of these differences will generate a significant delta. As others have said, the biggest difference is range... the 60ah will only take you 60% of the distance of the 100ah.

-JD

 

[TMaster]

72V x 20Ah = 1440 Whr
48V x 30Ah = 1440 Whr

hmmm... :?

 

[IBScootn]

If looking to do over 60mph with ease, might look to 84V pack.

 

[Shinigaimi]

thanks for all the information I will reduce my total wh by 70% to allow myself a good cushion room so i can drive to an outlet and not walk to one lol I am also still continuing research and development lol

I will also take into considerations upgrading to an 84v

Also where do you guys buy your batteries from?