7.4V Lipo to replace 6V NiMH - RC Groups
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Sep 16, 2009, 07:45 PM
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7.4V Lipo to replace 6V NiMH

Hi, I'm just after some advice on batteries. I have a truck, and use 4xAA's as the power for the receiver. I want to know if I can replace the 4xAA's with a 7.4V 800mAh 2-cell Lipo (Battery that came with a E-flite heli) and use that as power for my receiver. Thanks
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Sep 16, 2009, 08:22 PM
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freechip's Avatar
Generally RX or receiver and servo can only take up to 6v in power input. they normaly have a input range of 4.8v-6.0v and the reason for this is this, 4.8v from 4 rechargeable 1.2v AA cells and 6.0v from 4 alkaline 1.5v AA cell.

If you want to use a 2s lipo 7.4, well 7.4 volt is average and a fully charge 2S will be 8.4v way to much for you're electronics designed to be power at the most with 6.0v

If you must then you are going to need a voltage regulator to drop it down.
Sep 16, 2009, 08:52 PM
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marc1's Avatar
4 cell nimh is considered 4.8V nominal, 5.8V fully charged
5 cell nimh is considered 6V nominal, 7.3V fully charged

A servo spec'ed for 4.8V is designed for 4 cell nimh (5.8V max), a servo designed for 6 V is compatible with 5 cell nimh (7.3V max). But hey, don't take my word for it, call Hitec / Futaba / JR yourself.

A fully charged 2 cell lipo is 8.4V, probably too high for most 6V rated servos, however, a 2 cell A123 is 7.2V, same as a 5 cell nimh, so that would be a good alternative.

As for your 4 x AA, are they alkaline or rechargeable? If alkaline, you have 6V max, can you find the specs for the servo and receiver in the truck?

Most modern receivers can operate up to 7 - 9.5V, again check the specs on your equipment.

Another thing to keep in mind is that the higher the voltage, the higher the current that will be drawn by the servos.

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