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Old Jan 14, 2013, 02:38 PM
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I was worried about a lipo being too much voltage so I shoved in the 2100mah life battery. Was a lot of work though.
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Old Jan 14, 2013, 08:55 PM
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Originally Posted by itsmillertime View Post
I was worried about a lipo being too much voltage so I shoved in the 2100mah life battery. Was a lot of work though.
What do you use to charge it?

I had the same concerns as you about using a lipo battery. Fully charged a 2s pack is 8.4 volts.
WOW, and other vendors sell Lipo's for Devo TX's, so maybe it's OK.
As an experiment I tried a 3S 800mah lipo in my 2801 Pro, and ran it for 2.5 hrs. down to 11.1v. No smoke, and it ran fine. Using a 2200mah lipo it would run forever.
I have'nt tried a lipo in my Devo 8 yet.
It would be nice to know what the max. power supply voltage ratings are for the Devo's.
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Old Jan 14, 2013, 08:59 PM
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There were reports of the Devo 8 not turning off when using a 2s lipo. They had to disconnect the battery to turn them off. I also use a 2s LiFe pack. 1700mah though, and it almost fits in, just a half a mm too thick. So I have to tape my battery door shut.

Pretty much all lipo chargers support LiFePo4 aka A123 packs.
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Old Jan 14, 2013, 09:18 PM
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Yeap, multi-chemistry charger and I take it out to charge. Anything more than 6V will just be wasted in heat by the voltage regulators so that's why I didn't go with a lipo. Fully charge life is still 7.2 though.
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Old Jan 14, 2013, 11:39 PM
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Originally Posted by lasakro View Post
The V120 manual has the procedure to clear a fixed ID so we are missing something.
There are 2 versions of RXes in V120d02s : 2801 and devo. The latter supports fixed ID while the former doesn't
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Old Jan 14, 2013, 11:48 PM
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Originally Posted by suvsuv View Post
There are 2 versions of RXes in V120d02s : 2801 and devo. The latter supports fixed ID while the former doesn't
Actually there are four. 3 axis and 6 axis each having a 2801 and Devo version. Looks like Walkera again had their act together on this one. This topic was brought up on the 120 thread and they also were unable to make it work with the 2801. I just needed to know that the problem wasn't between the receiver and transmitter (Me). Thanks guys.
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Old Jan 15, 2013, 03:27 PM
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Originally Posted by flint723 View Post
There were reports of the Devo 8 not turning off when using a 2s lipo. They had to disconnect the battery to turn them off. I also use a 2s LiFe pack. 1700mah though, and it almost fits in, just a half a mm too thick. So I have to tape my battery door shut.

Pretty much all lipo chargers support LiFePo4 aka A123 packs.
I don't understand how the TX would know where the amps are coming from. If you can find the link to those claims please send them to me.
Thanks.
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Old Jan 15, 2013, 03:42 PM
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I don't understand how the TX would know where the amps are coming from. If you can find the link to those claims please send them to me.
Thanks.
http://www.rcgroups.com/forums/showp...&postcount=739
http://www.rcgroups.com/forums/showthread.php?t=1585028
But in that thread there is at least one person running a lipo with no problems, so apparently there may be some variation in tx's.

Here's what PB said about how the unit powers down since the switch doesn't physically cut the power.

"The way the switch works is that when the switch is 'on' the Tx power control is bypassed and the Tx will be powered on.
When the switch is 'off' a pin on the MCU is pulled up indicating the off state. During this mode, the MCU is responsible for maintaining power. The mcu does the necessary saving and then pulls the output low, shutting down the MCU."

So how I understand that is, the mcu is trying to regulate the power down to whatever voltage it takes to shut it down, but is unable to due to the much higher voltage of a 2s lipo.
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Old Jan 15, 2013, 03:49 PM
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actually, no my description has nothing to do with why a 2s would prevent power-down. I would need to go through the entire power circuit, but my guess is that too high of a voltage results in residual voltage on either the voltage-detect pin or the power-up FET, preventing the circuit from properly functioning. In any case, the switch is not used as a simple -on-off switch, there is a bunch of circuitry involved. I've posted the power-control circuit in this thread in the past if someone is interested. I didn't go through the voltage-regulator stuff, but it covers the power up/down and sense logic.
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Old Jan 15, 2013, 04:27 PM
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Polite reminder of the name of this tread: "Walkera DEVO Tx Hacking", Thank you.
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Old Jan 15, 2013, 04:35 PM
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Originally Posted by PhracturedBlue View Post
actually, no my description has nothing to do with why a 2s would prevent power-down. I would need to go through the entire power circuit, but my guess is that too high of a voltage results in residual voltage on either the voltage-detect pin or the power-up FET, preventing the circuit from properly functioning. In any case, the switch is not used as a simple -on-off switch, there is a bunch of circuitry involved. I've posted the power-control circuit in this thread in the past if someone is interested. I didn't go through the voltage-regulator stuff, but it covers the power up/down and sense logic.
Thanks for straitening that out.
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Old Jan 15, 2013, 04:50 PM
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Originally Posted by flint723 View Post
http://www.rcgroups.com/forums/showp...&postcount=739
http://www.rcgroups.com/forums/showthread.php?t=1585028
But in that thread there is at least one person running a lipo with no problems, so apparently there may be some variation in tx's.

.
Thanks Flint. I'm convinced. I'll stay away from lipo's for the TX.
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Old Jan 15, 2013, 08:47 PM
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Walkera are supplying this with the recommendation to use or actually even with a LiPo...

http://www.walkera.com/en/showgoods.php?id=1650

I guess the Devo series just has a reg with a wide input voltage. Expect it to get hot with a 3S LiPo in place of 4 alkalines though. I just use 4x NiMh 2500mAh AA cells for mine though and keep them showing at least 2 bars on the battery meter.

So no need to hack any hardware it would seem, though if we have the code of the actual VReg we can check the datasheet to be sure. Anyone here got that?
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Old Jan 16, 2013, 12:49 AM
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I run both a 1800mah NiMH and a 2500mah LiPo pack in my Devo 10 without any problems. I just alternate my packs when it's time for charging. Both give me aprox. same usage time. Devo 10 is rated 12V, so full charge on a LiPO isn't problem, probably would work on 14V too, I'm sure there's a regulator with a big tolerance inside.

If you have NiMH there's no reason to go to a LiPO. If you have both, do as I do, cycle them.

NiMH use looks like this: full charge, rapid drop to around 10.5V-11V, then steady drop to around 9V when it's time for charging.

LiPO goes the same way, drops fast from 12.6V to around 12.V then steady to 11.1V when it goes in the charger.

(voltage display it's done courtesy of Deviation, stock firmware doesn't show it).
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Old Jan 17, 2013, 04:02 AM
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Originally Posted by thwaitm View Post
Walkera are supplying this with the recommendation to use or actually even with a LiPo...

http://www.walkera.com/en/showgoods.php?id=1650

I guess the Devo series just has a reg with a wide input voltage. Expect it to get hot with a 3S LiPo in place of 4 alkalines though. I just use 4x NiMh 2500mAh AA cells for mine though and keep them showing at least 2 bars on the battery meter.

So no need to hack any hardware it would seem, though if we have the code of the actual VReg we can check the datasheet to be sure. Anyone here got that?
Although the regulator of Devo10 does support input voltage over 12v, using 4x NiMh is much safer than using 3S Lipo. I already heard several cases that Devo10 got burned during switching on or off when using 3S Lipo.

Here is a detail post, however in Chinese , describing why 3S Lipo could cause issues in Devo10: http://bbs.5imx.com/bbs/forum.php?mo...ead&tid=703868.

Marked with a red circle in the attached image, the capacitor , to the left , and the MOSFET , to the right, will get damaged when your devo10 is burned. It is because the VGS of the MOSFET(IRLML6402) is only 12v.

If your devo10 got burned ,you can replace the MOSFET with AO3409 , whose VGS is 20V. Then your devo10 should be safer when using 3S Lipo
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