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#### Killzilla

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In order to understand better my motor's performance I asked Golden Motor for their 72V and 96V graphs to compare with the 48V motor's graph and performance. If anyone can help in making sense of it I'd greatly appreciate it. The graph is really convoluted and doesn't make complete sense to me. My question being that provided I go to a higher voltage system (72 or 96) would a GM motor do the needful or I'd still look into getting a forklift motor for my needs?

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#### kennybobby

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Those curves have nearly the same shape for the different voltages, and not a lot of power difference due to being packaged in a similar sized frame. There is only so much power that can be created and dissipated in a certain volume.

They can wind the motor with smaller gauge wire to allow operation with higher voltage, but the current goes lower due to higher resistance. The no-load speed is nearly the same, the peak torque is 29 vs 32 N-m, and the peak output power used to rate each motor is 13 vs 15 kW, not really meaningful differences.

As Major said you really need to get an accurate vehicle load curve (speed vs torque at drive wheel). You can do this with the present motor and battery up to the limits that it will do. Without knowing your requirements you have no idea if you need to double the power of your motor, or increase it 5-fold or even 10x.

Nobody can tell you what size motor you need without seeing some data. The biggest load factors are related to vehicle weight, tire friction and aerodynamics. At the least you need to measure the total vehicle weight, the gear ratio used, the wheel size, and you need to measure the voltage and current while running on a flat level road at several different speeds, like every 5 or 10 mph up to your max speed. You can do some coast-down tests also to get data on rolling friction. Then some math is required--but first you need to get the data...

#### major

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In order to understand better my motor's performance I asked Golden Motor for their 72V and 96V graphs to compare with the 48V motor's graph and performance. If anyone can help in making sense of it I'd greatly appreciate it. The graph is really convoluted and doesn't make complete sense to me. My question being that provided I go to a higher voltage system (72 or 96) would a GM motor do the needful or I'd still look into getting a forklift motor for my needs?
Hi Kill,

It appears the graphs represent 3 different motors (or windings). Each designed to yield similar speed torque characteristics at respective voltages of 48, 72 & 96, nominal. I believe the motor package remains the same therefore the rated power likely is the same for all 3 models. Changing between the 3 models is unlikely to solve your problem.

major

#### Killzilla

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Thanks for your prompt reply. I feared that even changing the voltages won't make a massive difference. I will try getting the speed vs torque curve at the drive wheel and graph it out. That should give me a clearer idea.

#### Killzilla

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Question regarding a new build.
Previously I used Lead Acid batteries (48V 200Ah) and got up to 30-35 mph. My motor was a 10 KW BLDC motor. I tried every possible gearing but was not able to reach my optimal speed of 50 mph. My assumption is that the battery pack simply cannot provide enough juice.

Therefore I am about to invest in a completely new drive train. I am looking at the AC-9 Motor (http://www.electricmotorsport.com/ac-9-kit.html) along with a Lithium ion battery pack, 48V 100 Ah (MnNiCo Composite Material + LiMn2O4 chemistry). This is my max budget that I can put into the vehicle.
Vehicle weight is 650 kgs with 2 passengers.

#### dain254

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A lot of the talk has been about the motor performance, which really isn't the issue IMO. The motor kicks out what you feed it! There are quite a few ways to increase the performance of your specific vehicle... some are cheap, some expensive, none are wrong, here are a few:

1. Cut weight - switch to a lithium pack, keep your 10kw motor & current controller

2. Increase controller amperage by buying more powerful controller, amps=torque. A 400 amp capable controller will help you get to 50mph

3. if you have 8 batteries, tie them all in series and increase to 96V (new controller too?), gear 10:1, more volts at same amperage = more power!

Your last assumption is innaccurate about lead acid batteries being able to actually deliver power... but the more amps you draw from lead acid the higher the Peukert gain (example: 100ah battery only lasts 20ah when you draw high amps).

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