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Old Jan 12, 2014, 01:43 PM
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Bought 4S by mistake. Should I just return?

Ordered some more batteries from HK and got 4S rather than 3S by mistake.

Was going to send them back but before I do is there any reason why I can't use them?

I've got a HK2.1 FC, 30A Turnigy Plush ESCs, and 1100KV Turnigy motors.

What would happen if I use a 4S battery?

I've also got some LEDs attached with a 3S balance plug connector to power them. Assuming I can get an adaptor would they blow on a 4S?
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Old Jan 12, 2014, 02:06 PM
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Hmm on the HK page for my motors it says

Prop size: 7.4V/11x7 14.85V/7x3

So I guess on a 4S pack I should be using 7" props? Given I'm running 9" then using a 4S pack would be a bad idea?
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Old Jan 12, 2014, 02:09 PM
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Check if your ESCs support 4s. Running 4s might be less efficient for your particular build, but I'm guessing it'll fly. As for the LEDs, not sure. Again, check what voltage they'll support.
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Old Jan 12, 2014, 02:12 PM
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They will take 4S packs. However won't my motors draw too much current at 14V with 9" props perhaps?
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Old Jan 12, 2014, 02:16 PM
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Look for the datasheet for your motor with various prop sizes and battery voltage.
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Old Jan 12, 2014, 02:28 PM
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Hmm the datasheet that came with the motor says 7.4-11V in the Volts column for all options, but then in the Battery/Prop column says

LiPox2/2x6
LiPox4/9x6

for D2836-8

Seems pretty contradictory that it says 11.1V as max voltage but then says what props to use on a 4S pack (which oddly seems to be 9" which I have).
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Old Jan 12, 2014, 04:15 PM
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Am I right in thinking that the change in power from the motors would mean needing to re-setup all my FC settings?

If so then using the same quad on a mix of 3S and 4S packs would quickly become quite annoying...
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Old Jan 12, 2014, 05:21 PM
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The different 3s vs. 4s settings in your FC would mostly be in the gains (if you're flying Naza) or the PIDs for APM/Multiwii/KK2). It shouldn't be much different and you should be able to fly with the 3s settings just fine.
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Old Jan 12, 2014, 05:28 PM
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Hmmmm interesting thanks. Read another thread with some guy who tried a 4S and his quad immediately started oscillating etc.
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Old Jan 12, 2014, 05:33 PM
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You might have to adjust your PID's,otherwise you will be fine. I run 3S and 4S on my quad and tricopter and while my tricopter is fine,my quad has some oscillations on 4S,but much more power. You might buy some more 4S after you fly with it.
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Old Jan 12, 2014, 06:19 PM
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4S should be fine on everything but the LEDS. They will run REALLY HOT @ 16 volt which is what your 4S charge to. The 3 cell charge to just over 12 v which is what your leds are set for.

What I do is run a DC-DC Buck step down converter to my LEDS so they run cool and don't get the backing hot enough to pull off which they did a LOT before I used the buck converter.

I bought a boat load of these

http://www.ebay.com/itm/130984316514?

they come in really handy as you can adjust them to whatever output voltage you need
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Old Jan 13, 2014, 02:48 PM
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Thanks!

Thinking about it though, if the LEDs run off pins 1 & 4 of the 4pin 3S balance plug couldn't I just modify the plug so I can plug them into pins 1 & 4 of the 5pin 4S balance plug?

The pins come from either side of each cell so I'd be getting the same number of volts as I'd only be using 3 cells in effect?
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Old Jan 13, 2014, 03:04 PM
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Quote:
Originally Posted by SoulB View Post
Thanks!

Thinking about it though, if the LEDs run off pins 1 & 4 of the 4pin 3S balance plug couldn't I just modify the plug so I can plug them into pins 1 & 4 of the 5pin 4S balance plug?

The pins come from either side of each cell so I'd be getting the same number of volts as I'd only be using 3 cells in effect?
I always ALWAYS fly with voltage alarms connected to my balance plugs so I never have an open one handy But yes in affect you should be able to do that. The red lead goes to the + tab of the 1st cell then a black goes to the - of the 1st cell and + of the 2nd cell then another goes to the - of the 2nd and + of the 3rd etc.

Best way to check is just use a volt-ohm meter
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Old Jan 13, 2014, 05:09 PM
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I've got a voltage alarm from my KK FC so my balance plug is free. Will check with a multimeter
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Old Jan 13, 2014, 07:57 PM
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I don't think it's a good idea to discharge a battery from only part of the cells on a balance plug. Even if you do, you must balance charge it every time or risk a fire or worse...
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