MMM availibility date dropped!

[SpEEdyBL]

Originally Posted by Sower

The only thing I can say here is that the intention for most people to go with the 6s vs 4s isn't the "more power" argument as much as efficiency. By reducing the amp draw with higher voltage things just run better. I have no problem with the 2200 motor except on 6s. Some people may be fine with it, but I feel it's outside the motor's ideal efficiency. Especially if you're looking to race. Otherwise I'm sure you could have a lot of fun with it. I mean heck, who wouldn't think it's cool to see a 1/8 truggy blasting by you at 70mph?

Like I said, the neu motors are efficient enough that you dont need to worry about running it in their "efficiency range." That was only true for feigao motors. At most power levels you don't need 6s to still have a very efficient setup. The mmm will still handle the amp draw of a powerful 4s setup (btw if the mmm can handle its own motor on 6s, it definately can handle same motor on 4s). That said, I don't see why people would have any problems running the 2200 on 4s for racing. As motors and escs advance, the benefit of running 6s vs 4s at a given power level becomes less and less, especially when the amp rates are well within the escs range. Although power loss is rI^2, the resistance of the motor increases by the square as kv increases. So a 1515 1.5y on 6s is theoretically going to create the same amount of heat as a 1515 1y on 4s at the same power level, because the 1.5y has 2.25 times the resistance.

Benefits of running 4s vs 6s are:

1. Bigger lipo cells holder ther voltage better C wise. So a 6000 mah 4s pack made up of 6000 mah cells is going to hold a higher voltage per cell at 60 amps than a 4000 mah 6s pack at 40 amps.

2. There is less of a possibility for one cell to go below the safe voltage in a 4s pack than in a 6s pack, unless you moniter each cell individually (most cutoffs dont).

In the end, you really do only need 6s for power. Is it better to have two motors or two packs? You can charge one while running the other if you do have two packs. I can only see the 1515 1.5 being absolutely necessary if the 1y is already too much on 4s.

[Just go Play]

Up front I admit to being somewhat clueless about the detailed workings of electric motors so please excuse me if I'm missing something.

Originally Posted by SpEEdyBL

Although power loss is rI^2, the resistance of the motor increases by the square as kv increases. So a 1515 1.5y on 6s is theoretically going to create the same amount of heat as a 1515 1y on 4s at the same power level, because the 1.5y has 2.25 times the resistance.

The spec sheet that I have for Neu 1515 motors shows the 1Y rated at 110 max amps with an internal resistance of .006 while the 1.5Y is rated 70 max amps and .011 internal resistance. This equates to the 1.5Y having 1.83 times the resistance of the 1Y.

Based on the spec sheet the 1.5Y would have a power loss of 53.9 and the 1Y 72.6. While they are close the 1.5Y appears to be noticeably more efficient. Like I mentioned it is entirely possible that there are other considerations that make this not as simple as I think it is.

Originally Posted by SpEEdyBL

Benefits of running 4s vs 6s are:

1. Bigger lipo cells holder ther voltage better C wise. So a 6000 mah 4s pack made up of 6000 mah cells is going to hold a higher voltage per cell at 60 amps than a 4000 mah 6s pack at 40 amps.

Based on user experience this sounds right but I cannot find any reliable documentation that proves it. (for that matter who has 6000mAh cells available today?) The discharge graphs proved by many pack builders seem rather questionable if there are any available at all. Whats worse is that there does not seem to be any standards when it comes to testing or rating lipo cells from one brand to another. Could you point me to any reliable data on cell discharge rates that confirms this claim?

Originally Posted by SpEEdyBL

In the end, you really do only need 6s for power. Is it better to have two motors or two packs? You can charge one while running the other if you do have two packs. I can only see the 1515 1.5 being absolutely necessary if the 1y is already too much on 4s.

I really don't think that this is a valid argument. Both motors are capable of creating almost the same amount of power at simular RPM's. I also don't think that anyone can reasonably argue that low voltage high current is more efficient than high voltage low current setups. If this was the case then everyone would be building rc's with ultra high kv motors to run on 7.4v packs right?

[SpEEdyBL]

Originally Posted by Just go Play

The spec sheet that I have for Neu 1515 motors shows the 1Y rated at 110 max amps with an internal resistance of .006 while the 1.5Y is rated 70 max amps and .011 internal resistance. This equates to the 1.5Y having 1.83 times the resistance of the 1Y.

Based on the spec sheet the 1.5Y would have a power loss of 53.9 and the 1Y 72.6. While they are close the 1.5Y appears to be noticeably more efficient. Like I mentioned it is entirely possible that there are other considerations that make this not as simple as I think it is.[/COLOR]



Based on user experience this sounds right but I cannot find any reliable documentation that proves it. (for that matter who has 6000mAh cells available today?) The discharge graphs proved by many pack builders seem rather questionable if there are any available at all. Whats worse is that there does not seem to be any standards when it comes to testing or rating lipo cells from one brand to another. Could you point me to any reliable data on cell discharge rates that confirms this claim?



I really don't think that this is a valid argument. Both motors are capable of creating almost the same amount of power at simular RPM's. I also don't think that anyone can reasonably argue that low voltage high current is more efficient than high voltage low current setups. If this was the case then everyone would be building rc's with ultra high kv motors to run on 7.4v packs right?

To answer your questions:

1. From those specs it looks like the the 1.5y isn't ideally 1.5 turns in comparison to the 1y. An ideal 1.5 turn would have wire that is 1.5 times the length has a 1 turn and 2/3 the cross sectional area (to fit in the same space), making it have 1.5 x 1.5 = 2.25 times the resistance and 2/3 the kv. That said, the motors cannot be considered "equivalent" with the 1y on 4s and the 1.5y on 6s.

2. http://www.enerland.com/product/p1.php?num1=1&num2=4 These are considered to be some of the best cells in the industry. It's quite obvious that bigger cells hold their voltage better under a load than smaller cells when you look at the discharge curves. True that there seem to be no 6000 cells available, but that has nothing to do with my point. I was comparing 4000 mah cells to 6000 mah cells for the sake of simplicity.

3. I never said that lower voltage was more efficient than high voltage. In fact i never even said they were equal in reality. I said that a neu 1y on 4s is efficient enough for it not be necessary to use a slower motor on 6s. So how can a 4s setup that a.) that still runs cool and b.) has all the power you need, be inadaquate?

[starscream]

Originally Posted by SpEEdyBL

To answer your questions:

1. From those specs it looks like the the 1.5y isn't ideally 1.5 turns in comparison to the 1y. An ideal 1.5 turn would have wire that is 1.5 times the length has a 1 turn and 2/3 the cross sectional area (to fit in the same space), making it have 1.5 x 1.5 = 2.25 times the resistance and 2/3 the kv. That said, the motors cannot be considered "equivalent" with the 1y on 4s and the 1.5y on 6s.

2. http://www.enerland.com/product/p1.php?num1=1&num2=4 These are considered to be some of the best cells in the industry. It's quite obvious that bigger cells hold their voltage better under a load than smaller cells when you look at the discharge curves. True that there seem to be no 6000 cells available, but that has nothing to do with my point. I was comparing 4000 mah cells to 6000 mah cells for the sake of simplicity.

3. I never said that lower voltage was more efficient than high voltage. In fact i never even said they were equal in reality. I said that a neu 1y on 4s is efficient enough for it not be necessary to use a slower motor on 6s. So how can a 4s setup that a.) that still runs cool and b.) has all the power you need, be inadaquate?

1. I don't have an opinion on the motor choice as I certainly won't be buying a 1515 2200kv motor.

2. I'm not sure which discharge curves you're looking at but if you take a look at the charts for a 2S 4500mAh and compare to a 4S 2000mAh you'll see that the 4S pack holds its voltage just as well or better than the 2S pack. With this kind of performance you'll get more efficiency from the higher voltage system.

3. This question is relative to the end user. Cool to you may be hot for me. My ESC's typically don't run much over 100F. I equate efficiency just as high as power. In other words, just because a system can put out 4hp doesn't justify its usage especially when there is a more efficient system available that can produce the same power using less resources.