How to determine a battery capacity?

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nprawira
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When a battery pack is 60V/45 Ah, what does that actually mean? Can I determine the maximum speed, range and electric consumption from that figure alone?

Thanks y'all

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Spaceangel
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Joined: 07/15/2009
Points: 491
Re: How to determine a battery capacity?

Well you can get it very close using that figure. The real key is KW hours in the battery pack. BCI rates lead batteries on a 20 hour discharge and if you pull it out in one quick sitting you just don't get it all back out. Maybe your 45 AH battery will give you 2 Amperes for 20 hours but only 30 Amps for a 60 minute period. I have a Amp meter on my XM-3000 and I try to keep amps below 60 and maybe I can get back home. I average it out to 20 amp hours but I need to get one of those power meters like cruising equipment made and other make for scooters to measure power drawn per time used. If I keep it full speed and exceed 60 amps my range is Zilch. To determine actual top speed you need to know other parameters like controller design specs and gearing. I can get 18 to 24 Miles range on Silicone Greensavers for a 3000 Watt controller and 12 miles wide open. Some get top speeds of 30 to 45 MPH and possibly more. Brushless motors tend to be a more efficient motor.
The best bet for testing a 45 AH battery pack is draw 1/20 current for 20 hours till 1.8 or 1,9 v/c

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nprawira
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Points: 10
Re: How to determine a battery capacity?

Is there a way to set the amount of ampere drawn as we like it? What about the voltage, what does that imply? Thanks again

antiscab
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Joined: 07/07/2007
Points: 1678
Re: How to determine a battery capacity?

space angel is correct, though i would add it also depends greatly upon the specific battery you are refering to...

in general, the pack voltage determines how fast how can go,

how fast you actually go determines discharge rate.

the only way reduce discharge rate is to go slower.

how fast is fast depends rather a lot on your setup.

case in point, I have been playing around with a xm-5000li

with the 72v 400A controller and 24 cell 60Ah battery (~72v) it makes peak power at 70kmh (of around 22kw) and top speed is ~90kmh (give or take 10kmh depending on road conditions).

the same battery and controller in a new (or even old) Emax gives peak power at 40kmh and max speed of 65kmh.

are you looking at a specific bike?

Matt

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Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
conversion
Spent so far: $5800 + $7000 + $2040 + $1200 + $425 + $800 + $140 + $3000
Cost to do it again: $1000 + $3800 + $2040 + $1200 + $425 + $800 + $140 + $1500 (lasts longer)
Cost for a Petrol bike:$6000 + + $1440 + $7560 + $1000 + $1600 + $4000 servicing
Total spent: $20405
Total to do again: $10905
Total to have used a petrol bike: $21600
Total distance travelled so far: 102'120km

Other vehicles:
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nprawira
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Joined: 07/20/2010
Points: 10
Re: How to determine a battery capacity?

So if I can sum up, the higher V is, the faster your motor can spin, hence your speed. But, the faster I go will relatively deplete my battery capacity faster than if I go at a slower speed. And the Ah determines the amount of energy juice stored in the battery.

Now is there a draw back from having higher voltage battery? And for example there's a 12V20Ah battery. If I want to have 4 cells in series does that mean I now have a total of 48V80Ah battery pack??

I'm currently looking for new models from China and would like to learn more about batteries. I'm from Indonesia by the way.

Spaceangel
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Joined: 07/15/2009
Points: 491
Re: How to determine a battery capacity?

Whoa! Hold there, that would be nice

Now is there a draw back from having higher voltage battery? And for example there's a 12V20Ah battery. If I want to have 4 cells in series does that mean I now have a total of 48V80Ah battery pack??

I'm currently looking for new models from China and would like to learn more about batteries. I'm from Indonesia by the way.

Power as in Watts equals volt times ampere and BCI rates batteries in volts and AH for our play toys like 12v/20AH so we can't multiply both up front. In series voltage adds up and parallel the amperes go up so you will have 12 volt 20 AH x4 = 12 v/80 for parallel. And series is the other number~er bigger.

If you look at a bike with 48 volt 20 AH it is not going to do what a C-130 can do or a VX-1 as for speed or range. But if you look at a XM-5000 it might start to compare with the two bikes.

I guess after a while you can guess if a bike is going to go faster than some other bikes. I go to the drags here in Lowell and try and guesstimate what bike is going to do the 1/4 mile first~tis and usually correct. It is fun seeing an FLH racing against a Suzi or Kaw, An H-D is a torgue~ing machine not a quarter miler. So you can get an idea of voltage and Watts in an electric bike.
I did put in lighter batteries in XM-3000 but having to move my 225 pound bod I gained back some acceleration but not all. weight of bike and person affects range and acceleration too. So check weight.

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