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[Bl4kkat]

This might sound a little sillY but I was wondering if the motor was AC because it's voltage input is only 24-48v and has regen capabilities.

But I think I rember reading somewhere that it is a DC motor so I'm a bit confused

thanks

[frodus]

Well, in all actuality, all motors are AC. DC motors create the AC signal via commutation. AC motors do this electrically via the controllers.

But, with respect to "is it AC powered or DC powered", the answer is, DC.

There are field windings on the outer part of the motor that create north and south poles. This field winding is seperately powered from the armature with a DC signal. The field windings are usually much lower in current and voltage, but there is a higher amount of turns in the copper to create a strong field for the armature to push/pull against. The armature is also DC powered, but commutates and swaps poles as the armature rotates. Sepex requires 4 connections, one set for armature, one set for Field, both getting a seperate DC signal.

[Richard230]

One interesting feature that I have noticed when operating the D&D sepex motor on my GPR-S is the way the motor produces electrical power as I brake (which of course it is supposed to do). The power produced starts around 50 amps at high speeds and decreases to just a few amps as you approach a stop. Right before the bike comes to a stop, the power reverses and my Cycle Analyst shows something like 16 amps draw. Then when I stop, the power draw starts to fluctuate between 4 and 6 amps, with my hands off the brake. However, when I place my hands on the brake (and the brake light is lit), the power draw drops to between 2 and 4 amps. I find that somewhat odd, but it must have something to do with the motor's electromagnets generating of a magnetic field when the brake is off and the bike is ready to move when the throttle is turned. But when the brake is on, the motor must be powered down and the electromagnets are not receiving any current. At least that is my guess. Frodus would know for sure.

[Bl4kkat]

So basically the sepex motor is like a step up transformer?

But between the Sepex and Etek motors, sepex has a higher efficiency. With that said how much harder is it to configure compared to the Etek... or is the extra pair of wires from the Sepex the only difference (1 pair ea. for field and armature).

I kno the AC motors are three phase (3 wires) so setup for those are a little more complex than DC motors. I'm just trying to picture exactly how easy/difficult this project will be and how long I should plan it out

[frodus]

So basically the sepex motor is like a step up transformer?

Not at all. It's got 2 sets of coils that are each powered..... but its nothing like a step up transformer. They're purely DC, and they're not magnetically coupled and mechanically fixed to eachother.

But between the Sepex and Etek motors, sepex has a higher efficiency. With that said how much harder is it to configure compared to the Etek... or is the extra pair of wires from the Sepex the only difference (1 pair ea. for field and armature).

Not neccessarily. Both have brushes. It depends on the motor specs, air gap and turn count. I think Permanent magnet motors are generally more efficient because they do not have to generate the Field flux via Coils, it's already generated by the magnets. Sepex are a little harder to configure, and they need to be set up for the correct coil voltage and current limit, as well as armature current limit. Regenerative braking and field weakening need to be configured as well. Richard would know more about that.

I kno the AC motors are three phase (3 wires) so setup for those are a little more complex than DC motors. I'm just trying to picture exactly how easy/difficult this project will be and how long I should plan it out

In level of complexity of low to high:
Series motors and permanent magnet motors
Seperately Excited motors
AC Induction motors
Brushless DC motors

They're really not THAT hard, just make sure you get a matched motor/controller if you go sepex, ACIM or BLDC.

[Richard230]

I had an Etek GPR-S before my current sepex GPR-S. The D&D motor is about 35 or 40 pounds heavier than the Etek (according to the EMS website). Then you add on another 4 Hi Power battery cells on my 72-volt bike and the motor has to push around at least another 50 pounds. The D&D motor does not perform as well as the Etek did in my 60 V GPR-S, due to reduced power draw caused by the Hi Power batteries sagging from 76 volts to 51 volts under a load. It goes up hills at a much slower speed. My 2008 bike would climb a 6% grade at 55 mph, while the 2009 sepex D&D powered bike will climb the same hill at 35 mph. The regenerative braking adds between 2.5% and 3.5% to my range on a typical ride, which includes going up and down 8 large hills during a round trip to the neighboring city. If I knew then what I know now, I would have opted for a 2009 Etek-powered GPR-S and demanded a different brand of batteries - such as Thundersky, which are the standard batteries currently being installed in the 2009/2010 Native GPR-S.

[Bl4kkat]

Wow that sucks sorry to hear that Richard... I thought the Sepex was overall better motor compared to the Etek. But now seems like the Sepex is a little bit more efficient + regen capabilities at the cost of power. Correct me if I'm wrong but I guess there's a reason why slot of people go with the Etek motors, more bang for ur buck I guess.

But Richard if ur current batteries are sagging under load couldn't u just upgrade to a LiFePo4 battery chemistry? I kno they're more expensive but IMO they are worth it.  I've already made up my mind that the system I'm planing is going to be lithium and not SLA

[Richard230]

My Hi Power batteries are LiFePo4 prismatic-type. They apparently just don't like a high current draw.

The D&D motor is rated at a peak 29 HP by EMS, as against 15 or 19 HP for the Etek types. Unfortunately, I don't know where that 29 HP came from. According to the power/torque graph that I have for the motor, it puts out 15 Hp and 55 pound-feet of torque - but you have to feed it around 500 amps to get that kind of performance, not around the 150 amps that my batteries can provide. However, the lower power draw does offer a longer range - at a slower speed, of course. Keeping up with around-town and expressway traffic will net me around 30 to 40 miles before the 50 Ah batteries go flat (after using 40 Ah).

My plan is to solve all of my power and range problems by upgrading to a Brammo Enertia when they come out next year. I already have my order in.

[frodus]

Richard, don't blame the performance on the motor, its 100% those batteries. The controller has to limit power because of voltage sag.... so its not really the motor not performing well, its the batteries. Its a higher HP motor, requiring more juice. Also, I bet the gearing is a little different as well. The HP required is the same for both vehicles going up the same hill, so something else has to be different. If you had higher quality batteries batteries, same bike, but tested different motor setups, the Sepex would perform better, but be a little heavier.... but not 35-40lbs. The D&D is only 28lbs heavier.

I've seen MANY builds that use a sepex and have far better performance than an Etek. Its a great motor package, but you need to make sure you're batteries are not the weak point.

The D&D Is a higher HP motor, it'l do higher peak HP, but you may never see that out of it if the batteries are the weak point. kw is kw. If you don't have the power to give the motor, it won't perform.

Hi-power are 1-2C batteries, not nearly enough for ANY EV IMHO. I think bare minimum is 3-4C, and that's pushing it. I chose 5-10C batteries, so hopefully they won't be the weak point.



With all systems, you need to match all components. These hipower batteries just weren't matched well, thats all.

[Richard230]

I am sure you are correct, Frodus. I have no doubt that the batteries are the weak link in the bike's performance. I must have not expressed my thoughts clearly. Regarding the additional weight, I was adding in the additional 4 batteries that my 72 volt GPR-S has, compared with the 20-cell, 60 V 2008 bike.

Unfortunately, I can only comment on my personal experience as I have never seen another D&D motor in action, other than the one that I have.

The motor certainly looks sturdy and well built and I like that it is built in the US. I have a feeling that it will be the last thing on the GPR-S that will wear out. Some day I would like to try Thundersky, or another brand of batteries that have a higher quality - I am waiting for prices to drop a bit and for the HP batteries to sufficiently irritate me enough to be worth the cost of replacement.

[frodus]

Oh, so it was also at a lower voltage? Yeah, 60V and hipower with the D&D is going to perform like poo compared to an etek at higher voltage. The higher voltage means you use less current for the same amount of power than you do at 60V.