Upgrade NiMH Flight Packs to LiPo’s. By Paul Geders

The Need for a Project

Being stuck at home, except for the grocery store and getting food at drive thru locations, meant there was only one thing to do…build something!  Got down to the installation of the battery and called Mark Twain Hobby to buy what I usually use. They told me they don’t carry JR NiMh 1500 mAh 4.8V packs anymore but could order one.  Asked what everyone was doing and he said they were going to 2 cell Lipo’s with a BEC (Battery Eliminating Circuitry) which knocks the voltage down to 5.1VDC to power receivers and servos.

I happened to have some 18650 cells (3.7VDC) laying around and thought that now is the time to make up a more current battery pack using a BEC.  Chris Sostman, current member of the Boeing Phantom Flyers and soon to be Spirits member, sent me photo instructions on how to wire one up.  To make is simple I took the following photo of my assembly results with nomenclatures.

I opted to use a Castle Creations BEC – Switching Regulator which you can obtain locally at Mark Twain Hobby HERE for $26.95 with free shipping! This BEC can handle an input of up to a 6S (25.2VDC) LiPo and drop that voltage to a default voltage of 5.1VDC. With the optional Castle Link you can use your PC to change the output to any voltage between the range of 4.8V-9VDC.    Not only does it provide a constant 5.1V to the receiver, but it saves weight, 3.5 ounces total.  Could probably go to smaller size batteries like a 2S, 800 mAh LiPo to save even more weight and longer flight times when compared to the old 500 mAh NiCd batteries.

Power Tip

Many modern flight systems today will handle voltages much greater than 5.1V. All of the Futaba Receivers and many Spektrum will handle voltages as high as 9VDC as will numerous servo options which would not require a BEC, only a battery. Just be sure to make sure that all of your flight components can handle it. Retracts for example are often very finicky regarding the voltage feeding them. If your flying an older system however, 5.1VDC will insure that you are always safe.


  • Ralph Grant

    Been flying R/C since 1993. Building balsa airplanes since I was a kid. I love warbirds, aerobats, and just about anything that will fly.

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