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Old 01-16-2012, 02:39 PM
usafitz is offline
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Is it safe for the batteries?

Hey everyone, and thanks again for taking the time to answer.

I am currently buying new batteries, but I need to know if I'm still safe with the setup that I'm about to fly (maiden, Kyosho 540 EP). I bench ran it with two of my 3S's in series. The batts said 45A continuous/80A burst. When I went to full throttle, the voltage went down to as low as 9%, but that was very temporary. I went back to half throttle and it went back to about 45%. So my question is, am I good to go (safely) with about a three minute flight on these batts? Here's my setup:

PLANE: Kyosho 540 EP
MOTOR: E-flight Power 52
ESP: Pheonix ICE 75
BATTS: Series 3 cell / 20C / 2200mAh
PROP: E-Flight 12x7

Also, this is my first large electric so please pardon my lack of experience. One further question. If I get a 45C / 5000mAh, will that percentage be higher when I throw full throttle? I know I'll have more flight time, but does that bigger pipe buy me some more safety?

Thanks again!
usafitz
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Old 01-16-2012, 04:58 PM
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If you are pulling voltage below 50% you are severely over-stressing your batteries.

I do a LOT of electric flying from the PZ Vapor up to a 15 lb 5000 watt EDF powered model (working on a plane that will take twin 5000 watt EDFs) I NEVER pull the LiPo packs down below 3.0 V/cell. My big EDF units can demand more than 100 amps.

Something is set up very badly in your model.
I don't know of an E-Flite Power 52... Power series is: 15, 25, 32, 46, 60... So I can't say if you have the right prop or not. Having the 12X7 on the Power 32 shouldn't overload as badly as you are indicating.

Higher capacity battery should drop less voltage under load. But with the system pulling voltage down to 9%... all you'll be doing is making a bigger fire.
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Old 01-16-2012, 05:11 PM
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ha, that's funny about the fire. Definitely don't wanna do that! I think you may be right about the prop. When I order those batteries, I'll order a few more props and see what works.

thanks for the advice!
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Old 01-16-2012, 06:13 PM
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You need an experienced e-flyer to look at that thing and to check your readings. We don't usually list by % voltage.

The Power 32 swings a APC 12X6E just fine all day on 4S LiPo. 12X7 on 3S should be no issue.

If you are feeding a Power 32 3S X 2 in series that's not good The motor can't take 6S for anything more than a few seconds. In parallel is fine.

The Phoenix ICE is a good ESC and will try to deal with almost anything you hook up to it. But if you hook up the wrong voltage for the motor.... it will do a good job of helping you burn up the motor and/or battery.
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Old 01-16-2012, 06:53 PM
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its just running rich, you can tell by the smoke.
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Old 01-16-2012, 07:09 PM
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On line motor calculators suggest that your setup would try to pull about 90A at full throttle, and would last only a couple of minutes with your batteries (turning the prop at over 12K RPM.). Don't know why you felt the need for 6 cells. As FHHuber says it should work pretty well on 3S, so parallel them. Peak current and RPM will be lower. Current will be comfortable for your batts, shouldn't see any of that 9% nonsense.
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Old 01-16-2012, 09:04 PM
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I did mis-speak about the prop. It is a 12x8; but we're talking about a different motor. I have an E-flight Power 52. (http://www.e-fliterc.com/Products/De...odID=EFLM4052A). In a 6S, it recommends the 12x8 and should have a max draw of 75A. I wasn't sure if the '20C' on the battery would make it heat up or hurt it and I wasn't sure if that was related to the '9%' that I saw, which basically brought the voltage draw to less than 11V.

I am actually realizing now that I only had my battery meter hooked up to the cell leads on one of my batteries. Correct me if I'm wrong, but you would then multiply that by two because there are two batteries in series?!?

Incidentatlly, after flying for about three minutes, the batts were still at 3.8 volts per cell, which is what I store them at

BTW, if you wanna see the maiden, check it out here. I didn't do too much b/c this was my first electric over .30, but I do have this to say... if you get a Kyosho, make sure you re-enforce the landing gear! It was the same landing as my smaller planes (okay, almost) and there are no pot holes there... the damn gear ripped right off : ( On the bright side, I don't mind a bit because I love to work on my planes! Now I can change this one around to what ever I want. I'll post my build in the correct forum, but this one was pretty fun.

IMG_2107.MOV (1 min 6 sec)
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Old 01-16-2012, 09:26 PM
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Sounds like right prop for the motor and 6S should be good for that motor.

A meter hooked up wrong simply gives bad data.... which can make you think everything is OK when it isn't... or can make you think that you have a serious problem when you don't.

I run some 20C/40C burst 4400 mah pulling 105 amp peak (4950 watts at peak), 60 amp max sustained, 40 amp average over the flight with no issues. (Turnigy Super Brain data logging ESC) They get a bit warm, but not above 120 F when its 105 F in the shade. I don't like my LiPos to get above 120 F even though 130F is supposed to be OK.
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