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4s lipo question

Old 02-05-2011, 01:15 AM
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Flysohigh
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Default 4s lipo question

Hi I am use to 3s batteries and font know how to measure 4s. What voltage is 50%. Charge on a 4s lipo pack and what is the voltage on a fully charged 4s pack?
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Old 02-05-2011, 01:36 AM
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That's easy -- math is your friend.

Just multiply your 3s lipo voltages by 4/3.
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Old 02-05-2011, 01:46 AM
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Flysohigh
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I'm not understanding sorry
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Old 02-05-2011, 02:00 AM
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flydiver
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1 cell full = 4.2v
1 cell @ 50% = 3.85v
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Old 02-05-2011, 03:32 AM
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Originally Posted by Flysohigh View Post
I'm not understanding sorry
What he means is that all you need to do to figured out 4S numbers is take the 3S numbers you already have for full charge and 50% and multiply them by 4/3

Example:

3S full charge is 12.6 (4.2 per cell times 3), multiply that by 4/3 and you get 16.8 (4.2 per cell times 4)

Do that with all the other percentage voltages you have and you will have converted them into 4S
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Old 02-05-2011, 07:38 PM
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Exactly.

Another way to put it is like this: Take what you know about your 3s LiPos, and divide those numbers by 3 -- that will give you the "single cell" voltages. Then, take the "single cell" voltages, and multiply by 4 -- that will give you the "4s voltages" you are looking for.

The physics of a 3s LiPo and a 4s LiPo are the same -- they're made of the same stuff. Just use math to figure it out.
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Old 02-05-2011, 07:47 PM
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Ok I flew today and I figure as long as I don't go lower than 15v I should be ok
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Old 02-05-2011, 11:30 PM
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Yeah, I would have told you 14.8...
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Old 02-05-2011, 11:40 PM
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14.8 should still be ok I guess I hear other people say you can go all the way down to 3.3 amps/cell but then I guess it all depends what the voltage cutt off is on the esc.
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Old 02-06-2011, 12:02 AM
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You mean 3.3 VOLTS per cell.

I set my Phoenix ESC's custom Low Voltage Cutoff setting to 3.3 volts per cell. Some people go down to 3.0 volts per cell, or even as low as 2.8 volts per cell (which is just too darned low).

Stick with 3.3 volts per cell, and you'll be good.
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Old 02-06-2011, 02:00 PM
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Here is a chart I found here on WattFlyer some time ago. Hope this helps.
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Old 02-06-2011, 09:42 PM
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Originally Posted by Flysohigh View Post
Ok I flew today and I figure as long as I don't go lower than 15v I should be ok
Or, better yet, note your flying time, then watch your charger and find out just how many milliampere hours your charger put back INTO the Lipo. If you never fly more than perhaps 60-70% of the batteries milliampere hour capacity, you'll be OK.

(Example, with a 3000 mah battery, 70% of that is 2100 mah. Why 60-70%, because you might have a bad day, fly at higher power than usual, or have someone on the field and you have to do a go-around. That remaining mah in your battery will come in handy. And, you reduce the chance of damaging your Lipo by discharging it to low in voltage.)
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