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Aug 24, 2012, 02:11 AM
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Stumblebee's Avatar

A product idea

I am wondering how hard it would be to build this circuit. Many of us know how to get extended flight times using lipos hooked in parallel. A variation of this would be a simple circuit that does lipo switching. Lipo A would be used to get the quad up to altitude. This is where a lot of current is used. When Lipo A drops to 3.8 volts per cell, the circuit would switch in Lipo B which is fully charged. Lipo B would only have to maintain altitude and perform manuevers. I figure this configuration would produce longer flight times than having the two lipos in parallel. I figure this should not be a difficult circuit to build and as such, should be something that folks handy with a soldering iron should be able to put together cheaply. There are enough pricey little gizmos out there.

Any suggestions or feedback on this one? Could this be an "open source" product?
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Aug 24, 2012, 02:33 AM
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You would need a relay or switch with enough capacitance to switch over without interrupting, or something that can bridge both batteries and disconnect primary one after. Anyway, at the currents you're talking about (sounds like a heavy copter with possibly 50A+ going through) all this is going to be very heavy and very unlikely to be done cheaply (or reliably)
Aug 24, 2012, 02:45 AM
What's a servo?
Short answer, yes.
You can get what they call "make before break" switching contactors. Go right ahead and design your switch.

Long answer, why?
Having two batteries in parallel and switching them over when one drops below a threshold voltage will product no difference whatsoever to the flight times than if you just run both batteries in parallel without the switch.
I am sorry to say, the idea would serve no purpose.
Aug 24, 2012, 04:03 AM
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the flighttime should be lower due the additional weight.
theres no sense of switching when u could use them in parallel.
the flighttime could only be a bit longer when you drop the empty lipo after switching to the other one.
Aug 24, 2012, 07:11 AM
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SSM's Avatar
Dropping a battery is a neat idea ... but haven't you seen the "in flight" refuelling quadcopter video on the v939 thread?
Aug 24, 2012, 08:30 AM
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as warthox says, jettisoning used LiPo would be one idea, but there could be issues about the power switchover and the disconnection of the power wires.

Alternative idea: attach a firework rocket to each arm and then *hope* they all fire at the same time
Aug 24, 2012, 12:07 PM
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Stumblebee's Avatar
This certainly produced an international response. I was thinking of this idea for a quad, not a heli. I have a bunch of helis and hate to admit it but my F450 quad is lot more fun to fly. A lot less moving parts and things to go wrong. Anything to increase flight time is always a good thing.
Aug 24, 2012, 12:15 PM
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You can start by junking that huge + heavy plastic frame.
Aug 27, 2012, 09:20 AM
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Zen09's Avatar
Originally Posted by Stumblebee
I figure this configuration would produce longer flight times than having the two lipos in parallel.
How did you figure this out?

Having an RC controlled mechanism to disconnect one of the batteries (which would have a folded parachute) and connect the other through a relay would be an interesting task though.

Only if you're lazy to land and simply replace the battery.
Aug 27, 2012, 08:21 PM
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Stumblebee's Avatar
You guys are just no fun at all.

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