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j14152
j14152
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This is a question that no one seems to answer directly and clearly. It has to do with watt-hours, which is never mentioned in these answers. Is the voltage differential between the LiPO cells and the power output at a lower voltage just wasted, or is it useful energy that translates into useful power?

Example - I can use a 2S 7.4V 1600mAh1600 mAh LiPO cell with a UBEC to power my radio and servos. Let's say I can fly safely for 40 minutes with this setup. The battery (in theory) contains 11.4 watt-hours of energy, which lasts for about 40 minutes.

Now, what if I use a 3S 11.1v 1600mAh1600 mAh battery with the same UBEC and radio setup? Does my flying time increase by maybe 50% because I have gone from 2S to 3S, which has 17.76 watt-hours, or 50% more power than the 2S LiPO battery?

If the answer is that energy is not simply wasted (as would be the case if a resistor was used to lower voltage), an increase the number of cells with the same mAh rating will translate into increased flight timepower output at the same amperage and voltage. One can then state that if you increase the number of LiPO cells of the same capacity, your power output will increase accordingly. If you double the number of cells, you will (closely) double the length of time that the reduced voltageUBEC output is available (at the same loadamperage and voltage).

Likewise, if you replace a 5v5V 2000 mAh Nicad battery powering a receiver and servos with a 7.4V 2000 mAh LiPO battery and a UBEC, you will increase your flight time significantly, maybe by 40% or a little more.

This is a question that no one seems to answer directly and clearly. It has to do with watt-hours, which is never mentioned in these answers. Is the voltage differential between the LiPO cells and the power output at a lower voltage just wasted, or is it useful energy that translates into useful power?

Example - I can use a 2S 7.4V 1600mAh LiPO cell with a UBEC to power my radio and servos. Let's say I can fly safely for 40 minutes with this setup. The battery (in theory) contains 11.4 watt-hours of energy, which lasts for about 40 minutes.

Now, what if I use a 3S 11.1v 1600mAh battery with the same UBEC and radio setup? Does my flying time increase by maybe 50% because I have gone from 2S to 3S, which has 17.76 watt-hours, or 50% more power than the 2S LiPO battery?

If the answer is that energy is not simply wasted (as would be the case if a resistor was used to lower voltage), an increase the number of cells with the same mAh rating will translate into increased flight time. One can then state that if you increase the number of LiPO cells of the same capacity, your power output will increase accordingly. If you double the number of cells, you will (closely) double the length of time that the reduced voltage is available (at the same load).

Likewise, if you replace a 5v 2000 mAh Nicad battery with a 7.4V LiPO battery and a UBEC, you will increase your flight time significantly, maybe by 40%.

This is a question that no one seems to answer directly and clearly. It has to do with watt-hours, which is never mentioned in these answers. Is the voltage differential between the LiPO cells and the power output at a lower voltage just wasted, or is it useful energy that translates into useful power?

Example - I can use a 2S 7.4V 1600 mAh LiPO cell with a UBEC to power my radio and servos. Let's say I can fly safely for 40 minutes with this setup. The battery (in theory) contains 11.4 watt-hours of energy, which lasts for about 40 minutes.

Now, what if I use a 3S 11.1v 1600 mAh battery with the same UBEC and radio setup? Does my flying time increase by maybe 50% because I have gone from 2S to 3S, which has 17.76 watt-hours, or 50% more power than the 2S LiPO battery?

If the answer is that energy is not simply wasted (as would be the case if a resistor was used to lower voltage), an increase the number of cells with the same mAh rating will translate into increased power output at the same amperage and voltage. One can then state that if you increase the number of LiPO cells of the same capacity, your power output will increase accordingly. If you double the number of cells, you will (closely) double the length of time that the UBEC output is available (at the same amperage and voltage).

Likewise, if you replace a 5V 2000 mAh Nicad battery powering a receiver and servos with a 7.4V 2000 mAh LiPO battery and a UBEC, you will increase your flight time significantly, maybe by 40% or a little more.

Source Link
j14152
j14152
  • 1
  • 2

This is a question that no one seems to answer directly and clearly. It has to do with watt-hours, which is never mentioned in these answers. Is the voltage differential between the LiPO cells and the power output at a lower voltage just wasted, or is it useful energy that translates into useful power?

Example - I can use a 2S 7.4V 1600mAh LiPO cell with a UBEC to power my radio and servos. Let's say I can fly safely for 40 minutes with this setup. The battery (in theory) contains 11.4 watt-hours of energy, which lasts for about 40 minutes.

Now, what if I use a 3S 11.1v 1600mAh battery with the same UBEC and radio setup? Does my flying time increase by maybe 50% because I have gone from 2S to 3S, which has 17.76 watt-hours, or 50% more power than the 2S LiPO battery?

If the answer is that energy is not simply wasted (as would be the case if a resistor was used to lower voltage), an increase the number of cells with the same mAh rating will translate into increased flight time. One can then state that if you increase the number of LiPO cells of the same capacity, your power output will increase accordingly. If you double the number of cells, you will (closely) double the length of time that the reduced voltage is available (at the same load).

Likewise, if you replace a 5v 2000 mAh Nicad battery with a 7.4V LiPO battery and a UBEC, you will increase your flight time significantly, maybe by 40%.