MambaMAX high voltage motor comparison

[Key]

I know that using 3s 11.1v on a 5700kv motor is the best overall performer when it comes to speed without voiding castle's warranty.

Here's the pitch >> Warranty aside and if we were to use a123's 4s 13.1v configuration on a 4600kv motor what kind of speed comparisons/efficiency we could expect between the two castle motors (5700 and 4600)?

11.1 x 5700 = 63270 RPM
13.1 x 4600 = 60260 RPM

Your thoughts are appreciated.

-key

[ElectricThunder]

I'd say the 4600 may win out simply because it'll be able to take a numerically lower FDR (more speed) while possibly still running cooler, and end up producing the same or possibly even a little more torque due to the higher voltage, lower Kv setup. At the very least, it'll (hopefully) run cooler than the 5700, which is always a good thing!

If they're identically setup (including gearing) in the same exact car, I have no idea then.

[TheSteve]

I think the biggest difference will be which batteries drop more voltage under load.

[ElectricThunder]

I think the biggest difference will be which batteries drop more voltage under load.
Ah...good point. From what I remember, the A123s are pretty stable and have a relatively "flat" discharge curve I guess around 6.6v for the pack or something around there; at what amperage, I don't remember:( (then they dump like a mutha). I have no idea how those lipos' curve would look. :confused:

[pinolelst]

How do these a123 cells compare energy density wise with lipos?? .they look to be longer than a full "C" sized cell and just as large in diameter.
I know one well know tester showed voltage depression to just above 2 volts per cell at 50 amp pulse disharges ...something lipos don't suffer nearly as badly from.

pinolelst.

[leomax001]

I think the biggest difference will be which batteries drop more voltage under load.


..........perfectly agree.......... :) :)
we're continuosly talking about "which motor" forgetting that the better battery quality, the better motor performances.... :) :)

AND

over the 40K-45K rpm range, the efficiency starts to drop......hence, a powerful battery and the right gearing are the keys.... ;) ;)

[jocktheglide165]

I dont know what you just said, but I just picked up what was in your sentence which was:
volts
a123 racing cell

so here is mine with voltage upgrade yeah stupid ridiculous it is, but hey it hauls if I needed to haul some merchandise from florida to california I could do it in 1 day with my power LOL...

http://img.photobucket.com/albums/v516/rapunzel_1/IMG_1553.jpg
http://img.photobucket.com/albums/v516/rapunzel_1/IMG_1552.jpg

[ElectricThunder]

You're gonna fry your voltage module jock! :eek: (A123 frowns upon the voltage doohickey being used with brushless.. :roll2: )

Cool setup though!

[jocktheglide165]

You're gonna fry your voltage module jock! :eek: (A123 frowns upon the voltage doohickey being used with brushless.. :roll2: )

Cool setup though!
thats cool I just buy another one or send it for service :D if you cant enjoy your money why have it... :)

[ElectricThunder]

thats cool I just buy another one or send it for service :D if you cant enjoy your money why have it... :)
Ah...wise words. So true. (Which is why I blew a wad o' cash on a micro-T...and it's FUN!) :eek:

[Key]

over the 40K-45K rpm range, the efficiency starts to drop......hence, a powerful battery and the right gearing are the keys.... ;) ;)

Agree. Since so much voltage is being put through the motor, it is going to draw more amps than it would if it were spinning closer to 40,000RPMs.

The motor's amp draw, however, would depend on gearing, total vehicle weight, how free the drivetrain is, and how the car is driven.

Based on the +ve feedback from all I just have a gut feeling that a 4s a123 Li-n pack together with a CM4600 would have a far more noticeable PUNCH than a 3s 20 Li-Po on a CM5700.

[TheSteve]

If you have some really good LiPo's I think they would win, if they are just average then the A123 cells would probably do better. In tests I've seen they are also very impressive in delivering excellent capacity even after 100+ cycles of hard usage. Just don't over discharge them, that seems to be the biggest killer. When they dump its so fast you should just go pick the vehicle up instead of driving it back. You can also charge them insanely fast.

[mugenX5]

If anyones familiar with RCE in Fitchburg, MA, I ran the indoor offroad track and within a half of a lap I noticed the power going down then all of a sudden,...nothing. You have to go pick up your vehicle. :(

But only having to run 2 li-ion cells and a 15 minute charge time is well worth it.

[Key]

I guess the a123's behave somewhat like fuel on a nitro. When you run out you just have to go out and get it. Telemetry would be a good idea to have when running those Li-n cells. This would pretty much give the driver a heads up before it starts dumping drastically.

It wouldn't be fair to compare a 3s Li-Po versus a 3s a123 since voltage per cell varies considerably between the two.

There's only one way to find out if those cells can perform well under a 4s setup. For the sake of testing even further maybe a kontronik twist42 (4200kv) which is sitting around somewhere in one of my boxes may be a good fit for a 4s a123 / MambaMAX combination. Not sure how a 400-450can size motor will react with the mamba but I'll have to wait and see.

[SpEEdyBL]

There are three things preventing me from buying A123s

1. Cell size. They are too large to fit in many battery trays.
2. Bad energy/weight ratio compared to lipo. A 4 cell A123 pack has 2.66 watt hours per ounce compared to my 3 cell 3200 mah kokam pack (3.52 Whr/oz) or a max amps 3s 4000 mah pack (4.58 Whr/oz)
3. A123 cells require a special charger for maximum cell life.

[Marv829]

There are three things preventing me from buying A123s

1. Cell size. They are too large to fit in many battery trays.
2. Bad energy/weight ratio compared to lipo. A 4 cell A123 pack has 2.66 watt hours per ounce compared to my 3 cell 3200 mah kokam pack (3.52 Whr/oz) or a max amps 3s 4000 mah pack (4.58 Whr/oz)
3. A123 cells require a special charger for maximum cell life.

1. Yes it would be sweet if they were sub C size.
2. Lipo bags are lighter than an aluminum can, I use lipo in my parkflyer airplanes for weight/size issues, I use A123 in my trucks for 15min charges, higher burst rates, higher life cycles and for the safety factor.
3. A123 cells require a special charger, Lipo cells require a special charger, Some lion cells require a special charger, Nimh cells require a special charger, Nicd cells require a special charger, Pb cells require a special charger. The same was said when lipo came out to compete with Nimh.

I use and like the A123 batteries and would recommend them to anyone who can accommodate their size in their trucks.

[SpEEdyBL]

Actually if 1 the 3 things I mentioned weren't true I would buy A123. I would hate to give up the capabilities of my ice for another charger, but it would be worth it if the cells fit nicely into my car or had higher capicity for the same weight.

[tcolesen]

You could use the Dapter with your ICE in NiMh mode to charge A123 cells. Or, just manually terminate the charge on your ICE to charge the cells.

I agree that the energy density is sub-par, but you gotta compromise sometimes!

As for the size of the, many of my cars/trucks are coversions, so I choose the battery mounting anyways. In the cars I have where these cells won't fit, Lipo is a better all-around choice.