Devo 6 & 2s Lipo pack

For those interested, I have tested to put a lipo 2s (7.4v / 8.2v full charge) in my Devo 6, and it works well... even better, it gives you a better brightness of the screen, and the beeps are louder. I have tested on 2 transmitters with non problem (so far).

the battery that I've found and fit's in (a little tight, but fit in) are Kipom KT850/35-2s

Is there a difference to the Devo8? We have discussed this more than once - the problems may occur later due to a higher degrading of components wirking outside their specifications. So be careful.

Do you have the Devo 6S or the original Devo 6? The non-S Devo 6's have a battery drain issue that will destroy your lipos over a period of 1 week.

This battery is fantastic:

www.hobbyking.com/hobbyking/store/uh_vie....asp?idproduct=15087

if fits perfectly and has a huge amperage.

You have only to replace the connector with a normal jst and put TWO 1N4007 in series or equivalent to drop the voltage to a safety value.

I have a Devo 7e and I've been using 500mah 2S LiPo for a while (have 2 Zippy and 2 no-namers, just clear tape...), they all fit fine, I actually keep a charged spare at the bottom of the battery hole. Same deal as the OP, straight up 7.4/8.2V fully charged. So far no problems. No shut off bug (where the TX reboots and starts up after a shutdown) and no battery drainage issues.

I am however very uneasy about the running the electronics way above spec-ed voltage part. I had a few Hitec servos designed to work at 4.8V (I didn't know, as the sales material specified 6V clearly) that I ran at 6V. They performed beautifully for a while, until they started burning and failing...

I looked all over and can't find a clear spec that says the Devo TX is designed to take blah-to-bleh Volts. Everyone points to the directions which state 4xAA=6V, but then again Walkera themselves sell ordinary 2S LiPo packs for their transmitters.

dado099,

You say "put TWO 1N4007 in series or equivalent to drop the voltage to a safety value". I get that, but what is safe? Will the diodes bring a fully charged LiPo to 8.2V - 2 * 0.7V = 6.8V (under full load, that is)? Is that safe, and if yes, what do you base that on (other than the fact that it's just a tad more than the AA pack)?

Thanks.

modemman wrote: I have a Devo 7e and I've been using 500mah 2S LiPo for a while (have 2 Zippy and 2 no-namers, just clear tape...), they all fit fine, I actually keep a charged spare at the bottom of the battery hole. Same deal as the OP, straight up 7.4/8.2V fully charged. So far no problems. No shut off bug (where the TX reboots and starts up after a shutdown) and no battery drainage issues.

I am however very uneasy about the running the electronics way above spec-ed voltage part. I had a few Hitec servos designed to work at 4.8V (I didn't know, as the sales material specified 6V clearly) that I ran at 6V. They performed beautifully for a while, until they started burning and failing...

I looked all over and can't find a clear spec that says the Devo TX is designed to take blah-to-bleh Volts. Everyone points to the directions which state 4xAA=6V, but then again Walkera themselves sell ordinary 2S LiPo packs for their transmitters.

dado099,

You say "put TWO 1N4007 in series or equivalent to drop the voltage to a safety value". I get that, but what is safe? Will the diodes bring a fully charged LiPo to 8.2V - 2 * 0.7V = 6.8V (under full load, that is)? Is that safe, and if yes, what do you base that on (other than the fact that it's just a tad more than the AA pack)?

Thanks.

Fully charged 2S LiPo should be 8.4v.

Interesting post here about using a 1S LiPo in the 7e:
www.deviationtx.com/forum/7-development/...work?start=580#11348

From what I understand there is a voltage regulator in the Tx that steps the voltage down to 3.3v.

A 2S LiFePO4 battery would be a better choice than a 2S LiPo IMO. But if the diode is removed then a 1S LiPo may be the most efficient choice. Seems like you could fit 3000mAh(+/-) 1S in the battery compartment if you can find the right sized cell(s).

4 of these in parallel might fit (3400mAh):
www.hobbyking.com/hobbyking/store/uh_vie...m.asp?idproduct=7649

2 of these in parallel might fit as well (2400mAh):
www.hobbyking.com/hobbyking/store/uh_vie....asp?idproduct=23320

More info on battery for 7E here:
www.deviationtx.com/forum/how-to/1455-ba...imitstart=0&start=40

modemman wrote: dado099,

You say "put TWO 1N4007 in series or equivalent to drop the voltage to a safety value". I get that, but what is safe? Will the diodes bring a fully charged LiPo to 8.2V - 2 * 0.7V = 6.8V (under full load, that is)? Is that safe, and if yes, what do you base that on (other than the fact that it's just a tad more than the AA pack)?

Thanks.

Devo tx'es have a LINEAR voltage regulator taking down voltage to 3.3 V.
The surplus voltage goes into heating, so If you try to feed 8.2 V to the regulator you risk "barbeq", while 6.8 V is a decent one (very similar to
an alkaline battery set)

dado099 wrote:

modemman wrote: dado099,

You say "put TWO 1N4007 in series or equivalent to drop the voltage to a safety value". I get that, but what is safe? Will the diodes bring a fully charged LiPo to 8.2V - 2 * 0.7V = 6.8V (under full load, that is)? Is that safe, and if yes, what do you base that on (other than the fact that it's just a tad more than the AA pack)?

Thanks.

Devo tx'es have a LINEAR voltage regulator taking down voltage to 3.3 V.
The surplus voltage goes into heating, so If you try to feed 8.2 V to the regulator you risk "barbeq", while 6.8 V is a decent one (very similar to
an alkaline battery set)

Just read a datasheet of a typical 3.3 V linear regulator:
Input Voltage: 3.3 - 8 Volts

So better to follow manifacturer indications.

Guys

We have done extensive battery tests on the Devo8s, this might help...

www.deviationtx.com/forum/3-feedback-que.../1966-devo-8-battery

and rather use these 6.6V type of lipo

www.hobbyking.com/hobbyking/store/__2381...k_Futaba_T14SG_.html

You guys made it very clear and now I get it. I read all the linked threads with interest and learned some stuff in the process.

RandMental (and others) - you guys did an impressive amount of research on these transmitters.

LiFePO4 packs seem to be a great choice (and a bit safer) as far as what I was looking for. If I'm not mistaken they charge up to ~7V then "rest" down to ~6.8V, which should be more than OK for the 3.3V regulator.

Thanks dado099 for all the answers.

Sorry for adding fire to a never-ending debate - lol.

Sorry to beat a dead horse, but why not a 2S lipo with a 6V BEC? A 6V/3A BEC will fit easily inside the case, roughly constant 6V voltage until the lipo drops to point where buck regulator drops output voltage below 6V, which for most buck regulators ought to be around 7V battery voltage, or 3.5V/cell, and can set alarm when voltage drops 0.2V below the "constant voltage" provided when battery above regulator dropout voltage.

Just curious if others have tried this route and succeeded or failed.

Thx.

BEC is a linear regulator, it converts everything above 6v into heat. Then in the Devo itself another linear regulator converts 6v-3.3v into heat as well. You use less than half of you battery power. If you use 2S 500mAh Lipo with all these regulators it would be as is you used 1S with less than 500mAh battery if the regulator is switch mode.

I frankly don't understand why these people try to save so little on good power supply circuitry.

No, I meant an SBEC/UBEC (such as www.ebay.com/itm/HOBBYWING-RC-UBEC-5V-6V...se-BEC-/221664131656 ), which is switching buck regulator, not linear. I would just like the higher power density of Lipo than 4 NiMH batteries.

This is more reasonable, although there is one substantial problem. Unlike integrated solution where measures are taken to prevent consuming power when off, your buck regulator will always consume some amount, and unfortunately there is no information in this ebay listing of how large this consumption is.

If you could feed Devo 6/7E just with 1S LiPo that would be ideal. I'm not sure it is possible though.

BTW, I just checked - Devo 7E works from 1S battery!

You're right about power drain while off and I had not considered that. I would also have to add external switch to disconnect battery from UBEC. Guess I'll just save my pennies for a 12s instead.

Thanks for the replies.

What about using a step up regulator as used for usb charging terminals?