L or XL motor for my 1/8th buggy...thoughts?

[sleebus.jones]

I started off doing a conversion of a Hyper 7 a while back, and after a bit of thought, bought a Fiegao 10L motor for it. I was intending on running it on a MM controller with 4S LiPo. 10L= 2458Kv, which brings it slightly over 36K rpm with that battery setup.

Well, I decided that I didn't want to work the MM that hard (yeah, I know folks do it, but I wanted something more reliable, no worries, etc...) so i took the ESC out, and it sat on the shelf. When mike dropped the prices on his remaining BK controllers, I jumped and got the 9920. I figured I could run it with 4S, or 5S if I wanted to go crazy a bit. It was pointed out to me that running a 10L with 5S would spin it a bit fast (heh, forgot about that bit) and it'd run hot. Yep, makes sense to me. So, I figured I'd just run 4S then. However, with finnster filling my head with all this good stuff about the virtues of higher voltages (which I knew, but....well....wasn't as focused on as I should have) it got me thinking again...shouldn't I go for 5S?

Now the 9920 is rated for 20 cell operation, with 1.2v/cell, so that's 24v. A fully charged 5S brings me to 20v, which still gives me some headroom. 6S would be *right* at the limit, and I don't want to gamble if it'll pop every time I plug it in, so 6S is out...not to mention the CCBEC input voltage limit is 25v too. So that all comes together to say that 5S is as high as i can go.

So, since I'm going to run 5S all the time, in the name of efficiency/etc I know I have to change to a different wind that's more suitable. Here's where my question comes in...should I get another L can or go for XL?

To me, the XL can seems like overkill for an 1/8th buggy, but I have heard of folks who've done it. I'm not sure if all that much torque would be helpful, and then there's the extra weight too. I also have the RC-M heatsink for the L motor, so there'd be the additional expense of buying a XL version. Not only that, but the XL motors are more expensive too. The one that would work for me would be the 9XL, but I was told the 10XL might be a better choice in terms of gearing flexibility, etc.

If I was to get another L can motor, I'd pick up the 13L. It's 1890Kv, which would work fine with a 5S, and my concerns listed above would go away...but is it the right choice?

Edit:

I'm also guessing if my Kv between the L motor and the XL motor is approximately the same, will the draw be the same? Seems that it might, or since the XL can is longer, will the draw be lower? I guess I should have also added that keeping my amp draw low is another goal. If I have to spend $10 more for the XL to lower my amp draw, that's worth it to me, because then that reduces the load on my batteries, and I don't have to spend as much on those for the amp handling capability.

Idealy, I'd like to run with one of the true rc 5000mAh 5S, but they are rated for 50A continuous, or 75A burst and I'm not sure if that's enough, although they seem to perform well. I want to avoid 2P configurations due to size and weight concerns....and cost! I'm scratching my head here and trying to figure how much power I might need for this, but since my high-voltage experience is limited to 3S, I'm not much good figuring what kind of power requirements I might need. Is 75A cont sound about right?


Any input appreciated,
Sleeb

[MetalMan]

For the same power output, the XL motors should run cooler than the L motors, simply because they have more surface area (in terms of copper and the longer can). That said, you should be able to get more power out of a XL when it is operating at the same temp as a L.

Pretty much all Feigao motors are going to run hot, but the XLs shouldn't run as hot as the Ls. Simply because of that, I'd choose a XL, as the small weight gain and $10 greater cost aren't important to me.

As for you already having a L motor clamp, you can simply use longer screws and have it fit the XL motors. It won't look as good, but it's an easy way to save money.

The True RC 5s 5000mah 10C could be enough, but I wouldn't trust it. I know you don't want to go 2p, but I think a True RC 5s 8000mah 10C or 5s 6400mah 15C would be a better option.

[lincpimp]

+1 for the xl can

I have a few of each and have run a xl can in a buggy. The 9 or 10xl will work well on 5s, and depending on your gearing and mph requirements, the current draw should stay below 75amp. Keeping the heat down on the system will help the draw stay lower too. The l cans are too small for a heavier 4wd vehicle IMO. I have had success with l cans in 10th scale 4wd and 2wd emaxx trucks, but the added load of 4wd and a heavier vehicle will need a xl can to run coolish. I am basing this on a desired temperature, which is lower than some people run. I have heard that a 15l feigao is a good motor to run on 5 or 6s.

[sleebus.jones]

Ok, 2 votes for the XL can. :)

MM, you are right on about just getting longer screws for the heatsink, that should work fine, and I don't anticipate it getting incredibly hot either. Even running it as is with my very ghetto 18 cell pack, it still didn't get much past 140 or so.

linc: 75A does sound reasonable. Running some quickie numbers, that comes out to around 1300w, which should be fine for goofing off. I don't think I could keep the tires hooked up long enough keep it loaded at the 75A level. I wish I hadn't nuked my BEC, because then I could get some real-world load numbers with my test setup.......ahhhhh, but I DO have a RX pack I could slap in there temporarily to test it out. Then I could see how it's loading with the 10L and make a guess from there! Yeah, that'll work....it'll at least give me a direction. Now why the heck didn't i think of that before. Derr.

MM, those true rc 5000's are rated for 50A with a 75A burst. I'm thinking this sytem may work, unless you exploded some already, haha! I really don't want to just blow (literally) money away. I dunno, I guess we'll see the tale of the tape if I get a chance to run the car this weekend and do some analysis.

Sleeb