|
|
Post by mrmugen on Jun 14, 2009 14:17:23 GMT 1
In my cubs I like to run 1200mah 3s Poly Quest lipo's. They offer lots of power and are very light. Just for the record.....I run a 35A motor in one of my strykers.....pulling 92A constant. Flown it about 40 times without an issue.....but it is a MEGA motor.
Kevin
|
|
|
|
Post by flydiver on Jun 14, 2009 16:04:47 GMT 1
Just out of curiosity I put 1 of the fully charged 1800's on the amp meter and Full Power draw was 32 amps (only kept it there for a second) the full power draw on the 1100 was 42 amps (just about snapped off the throttle pulling it back so fast!!). I'm not sure what this means but, eBay lipo specs were 20-25C. Did you read that note from Todd's Models? Realistically that needs to be degraded to about 15C. No one with experience believes the burst C-rating. The cheaper the lipo, the less you can believe it most times. 15 x1.8A = 27A draw capability. You admit they 'sound puny' and don't work as well. Bet you push those harder to get performance out of them. Sorry-you were likely killing them. Next: SkyArtech-15-20C (lets give them the benefit of the doubt and use 15C). 15 x 1.1A = 16.5A. These are holding up amazingly well because anywhere near full throttle you are REALLY over drawing these. At half throttle you were probably at max draw. Expect a short life span, less than 50 cycles, maybe way less. This is why lipos quality get such varied opinions. People don't know what they are doing. They kill them and blame the lipo. Manufacturers unrealistic claims certainly don't help. You either need to do some work with that wattmeter and prop down to the battery capability (opps, there goes your performance) or make sure you next set of lipos is up to some serious amp draw. You put a 35A motor in there your lipo should be good for at least 40A to not suffer unduly. (ie 2200mA @ 20-30C) Don't want to go that big and expensive? Then expect earlier lipo failure. |
|
airdale
Flight lieutenant
Posts: 42
|
Post by airdale on Jun 14, 2009 21:20:22 GMT 1
Well, I certainly can't argue with logic like that! Numbers don't lie but, all I know is that I started flying about 2 months ago with 4 new battery packs. All 4 have been flown in the same style for the same amount of time. The 1800mah's do not perform any were near as well as the 1100mah. What size prop would you recommend for this set-up 9X7.5 or a 10X7? I'm not looking to burn up the sky with it, I have a camera that I like to take up and shoot some video AND I would like to use the ailerons I added to train for future, faster planes.
I really appreciate you taking the time to answer stupid "newbie" questions. It's nice to find people that can remember when they were beginners!
|
|
|
|
Post by patmatgal on Jun 15, 2009 0:07:23 GMT 1
The 1300 will give a good 10 to 15 min flight, 10 min @ WOT will bring the battery back OK but 15 min @ WOT and it'll be over discharged. The 1750 will be a good 15 & 20 minutes with the same limitations (flying at WOT, some throttle management goes a long way) It's so easy to get caught up in the fun and fly longer than planned and whoops, over discharge...
|
|
airdale
Flight lieutenant
Posts: 42
|
Post by airdale on Jun 15, 2009 2:59:47 GMT 1
It's so easy to get caught up in the fun and fly longer than planned and whoops, over discharge...I can imagine it does!! I have the timer on my DX6I set for 8 min (when I remember to hit the trainer switch) and I still get caught up in it. I just got back from some dusk flying, and I was telling a more "seasoned" pilot about my batteries. As I was doing an overhead pass he asked me to "punch it" and after I did he said that I should probably get lined up to land cause I was running low on juice- I had been in the air for 1 MINUTE!!  When I pulled the pack out and hooked up the VM, it read 12V!! What the heck is going on? Is my ESC acting up or something? And why does it only do it with the 1800's and NOT the 1100?
|
|
|
|
Post by flydiver on Jun 15, 2009 3:37:53 GMT 1
Cuz your 1880 is sagging due to it's inability to keep up with the workload.
It gets hot cuz it can't keep up with the work load. You are asking too much of it.
Your 1800 lipo specs are garbage, don't believe them. Proof is in the results. You are seeing and hearing the results every time you fly. What exactly do you need to accept that?
RESTING voltage has very little to do with WORKING voltage. I have some lipos that show great VOLTAGE and balance fine and simply DO NOT put out. They are garbage.
You have a wattmeter. That's the tool. It TELLS you what your system is doing if you hook it up and look at the numbers. I can't tell you what prop to use. I have no experience with that motor but I can tell you that the one you have is too big since you are pulling too many amps for both the motor and the battery. The motor has specs, I just showed you how to figure the battery capability. Get smaller props. Test them. Stay inside the parameters or not, your choice.
|
|
airdale
Flight lieutenant
Posts: 42
|
Post by airdale on Jun 15, 2009 3:52:16 GMT 1
I just ordered a couple of Zippy Flightmax 2200MAH 20C from HK. They got some really good reviews from a few Customers. I'll start over with them and prop down when I figure out what I need.
Thanks again for the help.
|
|
|
|
Post by flydiver on Jun 15, 2009 4:15:28 GMT 1
Those capacity draws I did above are theoretical. That's what the lipo SHOULD do if it is REALLY up to the specs given. It seems patently obvious your eBay 1800's are not.
When you get the Flightmax you should see. In the meantime get some smaller props and start sorting out what a useful tool the wattmeter is. The numbers don't lie. The ads lie, the manufacturers lie, the shops lie, and the mess of information on the forums can be confusing, but the wattmeter you can believe.
|
|
|
|
Post by duck9191 on Jun 15, 2009 6:01:17 GMT 1
flightmax 2200's are a good battery, i have a few and havent had any problems, a few friends have them also and so far so good.
|
|
airdale
Flight lieutenant
Posts: 42
|
Post by airdale on Jun 15, 2009 12:24:02 GMT 1
flightmax 2200's are a good battery, i have a few and havent had any problems, a few friends have them also and so far so good. I sure hope so! I also ordered a little "variety pak" of props from Heads Up RC to check them out. It seems like all the 20C and up packs that HK had that would drop-in to the SC were on B.O. Oh Well, probably should cut up the B. box anyway cause it gives me more options. |
|
|
|
Post by flydiver on Jun 15, 2009 15:56:07 GMT 1
It's almost impossible to stickanything larger than a 1300 in the stock box.
You would have to get 30C to keep up with your current motor and prop:
30 x 1.3 = 29A
And even that is not up to the peak rating of the motor.
|
|
|
|
Post by mrmugen on Jun 15, 2009 16:50:17 GMT 1
You might find it easier to get the right motor for the application. There is no real reason to need more than 25a for this airframe IMO.
Kevin
|
|
airdale
Flight lieutenant
Posts: 42
|
Post by airdale on Jun 15, 2009 17:56:11 GMT 1
Am I wrong or is it alright to run a motor below Peak Rating? Just because a motor is "rated" @ 35A doesn't mean you have to power up for 35A does it? Or does the performance of these motors suffer if you are underpowered? I know on the 3.0 Merc. in my boat they say to run it AT or Very Close to MAX RPM for the longest life and most efficiency ( I don't do that either) ;D
Just a general question- I know I'm over propped in this case but, I only need to go vertical once in a while!
mrmuguen- I agree 100% as a matter of fact, I have a 2409-18T (KV100 16A Max draw) that I think I'll slap in her just to see the difference. Now I'll probably be Over-Powered with the new batteries!
|
|
|
|
Post by admiralev on Jun 15, 2009 20:23:52 GMT 1
with some wire snips and creativity you could put whatever you want in that battery box...or in the fuse at least
admiral
|
|
|
|
Post by mrmugen on Jun 15, 2009 20:38:26 GMT 1
I fit my 2100's in mine just fine using the same method I posted years back when we first started this site. CHeck it out if you haven't already. Easiest and fastest method hands down. Only need one strip of velcro and a set of side cutters or a dremel.
Oh yeah and 3 minutes of your time.
Kevin
|
|
When I pulled the pack out and hooked up the VM, it read 12V!! What the heck is going on? Is my ESC acting up or something? And why does it only do it with the 1800's and NOT the 1100?