Voltage increase & Gear Ratio decrease effects on Torque

[wizardket]

Which PQ motor did you go with?

[Gale Hawkins]

Originally Posted by athomas03

Odyssey has some specs on the cycles, it depends on depth of discharge and some other factors. Definitely a specialty battery, not for long distances.

I guess a deep discharge cycle makes no sense in racing because speed not range is the same?

Do you have to take more than one bank or there charging breaks between different heats?

[72volt_ezgo]

Originally Posted by athomas03

Amp draw is around 310 at 50mph with the PQ, it is setup for racing so the amp draw is high. The EMP was around 170 amps at full speed. 50 amps is low, I know 72volts is more efficient with its amp usage to achieve speeds. What is your setup like?

Dang I did not expect 310 amps even at 48 volts but power has to come from somewhere to push against the aero drag at 50 mph!
So if your pack voltage did not sag below 48 volts during the run then:
310(amps) X 48 (volts) = 14880 Watts. At 72 volts that would translate to:
14880(W) / 72 (V) = 206.6 Amps theoretically at 50 mph.

So compared to the 50 amps I'm drawing at 30mph at 72 volts (don't know what my pack voltage saggs to but I do have a couple tired batteries in there!)
3600W that indicates the wind resistance really kicks off above 30 mph.

My setup is nothing fancy.Everything is stock on the cart EXCEPT:
The alltrax 7245, my 72 volt pack that is made out of 12 car batteries
in a 2 parallel 6(of those) in series configuration, and I installed my mazda protege's 13" wheels on the back to give me a little gearing for speed and to lower the motor rpm at the same time. (my cart has the 12:1 gearing)

[athomas03]

Originally Posted by wizardket

Which PQ motor did you go with?

The Assassin, tweaked for speed.

[athomas03]

Originally Posted by Gale Hawkins

I guess a deep discharge cycle makes no sense in racing because speed not range is the same?

Do you have to take more than one bank or there charging breaks between different heats?

I've only got one bank. Race and quick recharge, go again. This will be my first year racing, new to me.

[athomas03]

Originally Posted by 72volt_ezgo

Dang I did not expect 310 amps even at 48 volts but power has to come from somewhere to push against the aero drag at 50 mph!
So if your pack voltage did not sag below 48 volts during the run then:
310(amps) X 48 (volts) = 14880 Watts. At 72 volts that would translate to:
14880(W) / 72 (V) = 206.6 Amps theoretically at 50 mph.

So compared to the 50 amps I'm drawing at 30mph at 72 volts (don't know what my pack voltage saggs to but I do have a couple tired batteries in there!)
3600W that indicates the wind resistance really kicks off above 30 mph.

My setup is nothing fancy.Everything is stock on the cart EXCEPT:
The alltrax 7245, my 72 volt pack that is made out of 12 car batteries
in a 2 parallel 6(of those) in series configuration, and I installed my mazda protege's 13" wheels on the back to give me a little gearing for speed and to lower the motor rpm at the same time. (my cart has the 12:1 gearing)

That sounds like a cool setup. What are the batteries? How about your overall tire height? My voltage did sag pretty low, it was more like 41.5v at top speed. I think once I drop some weight and change batteries it won't be so low. I still had 8 trojan t-105's in with those numbers.

[Gale Hawkins]

Originally Posted by athomas03

I've only got one bank. Race and quick recharge, go again. This will be my first year racing, new to me.

Going with starting batteries will move you fast and let you double/triple your recharge rate I expect? Are you going to use 4 heavy duty 12v chargers to recharge fast? Are chargers in the pits limited by rules?

Sounds exciting.

[athomas03]

Originally Posted by Gale Hawkins

Going with starting batteries will move you fast and let you double/triple your recharge rate I expect? Are you going to use 4 heavy duty 12v chargers to recharge fast? Are chargers in the pits limited by rules?

Sounds exciting.

Trying to decide on the charging. I have a 48v charger that works pretty good but, tops out at 56volts during charge then settles back. May go with two odyssey ultimizer 3bank 50amps for quick recharge back to 14.7v per then they will settle back. Schumacher has a SE 1072 that is slower charging but, a cheaper route to go to charge up to 72v at once. Not sure, yet.

[72volt_ezgo]

Originally Posted by athomas03

That sounds like a cool setup. What are the batteries? How about your overall tire height? My voltage did sag pretty low, it was more like 41.5v at top speed. I think once I drop some weight and change batteries it won't be so low. I still had 8 trojan t-105's in with those numbers.

Batteries are (car)dealership rejects from the bad pile. All been murdered a couple times in their life but a quick test,charge,retest some seem to come back to life,then I use it. All mismatched age,size,some top post some side post lol. This is not a performance cart just a cheap as possible around the house kind of cart.

Overall tire diameter on the rear is 22" vs the stock 16-ish.
So if I did my math right motor rpm at 30 mph on stock tires= 7856 rpm!
13" Mazda tires (22" od) = 5711 motor rpm at 30mph. Lot better!
That's why I don't want to push my luck with the stock motor on 12.44:1 gears. I want 8:1 or 6:1 eventually

I'm not sure about your weight savings helping much once you're at speed.
Sure during acceleration is good to be light but I can't imagine the weight adding that much more rolling resistance once going. I have not tested this though,I'm just guessing!

[athomas03]

Originally Posted by 72volt_ezgo

Batteries are (car)dealership rejects from the bad pile. All been murdered a couple times in their life but a quick test,charge,retest some seem to come back to life,then I use it. All mismatched age,size,some top post some side post lol. This is not a performance cart just a cheap as possible around the house kind of cart.

Overall tire diameter on the rear is 22" vs the stock 16-ish.
So if I did my math right motor rpm at 30 mph on stock tires= 7856 rpm!
13" Mazda tires (22" od) = 5711 motor rpm at 30mph. Lot better!
That's why I don't want to push my luck with the stock motor on 12.44:1 gears. I want 8:1 or 6:1 eventually

I'm not sure about your weight savings helping much once you're at speed.
Sure during acceleration is good to be light but I can't imagine the weight adding that much more rolling resistance once going. I have not tested this though,I'm just guessing!

I will try to test some this weekend, I have some different batteries (Odyssey 925's). I'll see if the topend picks up or if it is just my takeoff.