Devo 8 battery

sbstnp, if that works & probably would then great. I always think down the line of more mah=more time in the air. Although you will get efficiency your route, surely physical size of the battery with the extra cells would reduce the possible mah you could squeeze in the tx, but I hear you, with the increased efficiency maybe this will be outweighed, be interesting to know. My original hopes were a 1s to fill the battery bay would give me the most time and probably will but would need to be careful on the low voltage cut off, unfortunately though Devo hardware isn't accurate enough for me personally to risk that.

Ooh it just occurred to me why I never tried to do what you are trying, I was going to try a bec. It will be difficult to tell how much voltage/mah is left in your battery using the regulator, unless of course you run a separate monitoring solution ...

You can get efficiency both ways, by using higher voltage and very efficient stepd-down converters or bringing the voltage down close to the actual running level (there are losses so they can't be equal).

I think the second option is harder and implies risks (like transmitter shutting down on you), at least on my Devo 10 which likes 12V stock. Can't go too low.

So, I chose to go the second route because a 3S LiPO stores 3 times the energy found in the same mah 1S pack. No real math here, but at 12V efficiency of the normal reg is around 41% (probably lower) and goes to around 55% at 9V. Compare this with 95% stated efficiency at 12V for the switching reg and you get worlds aparts.

Ooh it just occurred to me why I never tried to do what you are trying, I was going to try a bec. It will be difficult to tell how much voltage/mah is left in your battery using the regulator, unless of course you run a separate monitoring solution ...

Using a BEC yes would be very difficult to monitor the charge. That's why I opted for replacing the on board regulator. The one I linked is a drop-in replacement for the 7805 on my Devo 10. No idea what you have on board on the 8S.


Anyway, apologies for the offtopic, just wanted to point out different solutions to the same problem.
Good luck!

sbstnp wrote: You can get efficiency...... 95% stated efficiency at 12V for the switching reg and you get worlds aparts. The one I linked is a drop-in replacement for the 7805 on my Devo 10. No idea what you have on board on the 8S.

Hi sbstnp

Your solution for the Devo10 should work great, please keep us posted.

The Devo8 has no regulator to replace, the battery voltage goes directly to the LDO regulators, so we need a accurate low voltage alarm to use Steve's 1s proposal. I'll see if I can trace more of the analogue circuit, perhaps there is a mod we can do.

RandMental, I managed to find a solution?

No, Have not yet studied the code but I did get a copy of the STM32F103 datasheet to understand how the A/D works - no news yet.

I did this for Devo8S Tx battery connected in parallel with two pieces. www.ebay.com/itm/271200646607?ssPageName...p3984.m1497.l2649How How many volts can renew? How long is safe?
First time Tx 4.08 V.
After 80 minutes of show 4:02 V.

Best would be to follow the instructions on the battery.

Normally Li-ion cells gives 3.6V, not 3.7V as these say, so I have no idea what they really are and whether it is save to connect them in parallel.

I've been using using a 1700mah 2s LiFe battery for almost a year now, for a couple of reasons.

1. Fast charge.
2. The lcd screen is significantly brighter on 6.6v (almost readable in sunlight)

The LiFe when fully charged is above 7v, but as soon as you take it off the charger it drops to ~6.8v. And when you power on the tx, within 30 seconds the voltage is down to 6.6v; it just pretty much sits at 6.5 to 6.3 for most of the pack. I have my alarm at 6.2v because it starts dropping fast after that. I found if it's around 6.1-6.2v, ~1700mah goes back in when I charge it.

Hi flint723 - looks like a good choice, definitely something to consider.

Hi dobosatti - Here is a primer on RC batteries, perhaps a bit dated but still relevant:

www.rcmodelreviews.com/baffledbybatteries.shtml

I was wrong question.
3.6-3.7V Tx safe?

1S Battery (3.7V) will not damage Devo8s.

BUT

V3.7/V3.6 is very low, as I tested the Transmitter stops working at +/-3.5 Volt.
With Walkera Software you cannot be set the Alarm level below 3.6V, which indicates that Walkera agrees you should not use it at 3.6V or below.)

would not be better to use a 1s lipo? I at 12s is a lipo 1s 3000mha, since I have an 8 3.3v regulator idela would work with a few 1s and 3,7 2000mha? or even two 1200mha in parallel we think it will be much more efficient (only one will have to be used on tablets because the discharge rate is much lower than those used in airplanes.

I'll buy a tablet that might leave the reservation for my 12s so I'm giving the hint.

As discussed above and confirmed through actual tests on a Devo8, a Devo8s was not designed to run of a 1S Lipo. As I said before it won't damage your Devo8, but at 3.6V and below the TX's RF output starts to decay and looks intermittent on a Spectrum analyzer.

Of course using higher capacity 1S battery means it will take longer to get to 3.6V, however personally I am not prepared to take the risk flying with a battery near 3.6V - one a bad connection somewhere in the chain or the LCD back-light comes on when you accidentally touch the screen, down drops the voltage and down your model goes.....

I am convinced you will eventually crash your model flying at TX battery voltages at or below 3.6 volt on a Devo8s.

These conditions/warnings do not apply to a Devo10 or Devo12 which have different battery and PSU designs, but should apply to the Devo7e.

EDIT: I have said what I think can and should be said about the Devo8s Battery options - from my side I am closing this thread.

Not sure why you all have so many discussion on this thread. I am using 2S LiPo battery to power up the Devo8S without any problem. Walkera officially has a 2S battery pack for Devo 8S for sale. I feel quote strange when I read this thread.

WOW has one also.
www.wowhobbies.com/battery800amh2s15cjstdevo8devo6.aspx
I have one of these I haven't used. I'm using another Lipo battery instead.
If anyone wants it let me know.

I am running a 3 s lipo in devo-10. Is this bad? It's run with it for many hours like 25 at least.

flint723 wrote: I've been using using a 1700mah 2s LiFe battery for almost a year now, for a couple of reasons.

1. Fast charge.
2. The lcd screen is significantly brighter on 6.6v (almost readable in sunlight)

The LiFe when fully charged is above 7v, but as soon as you take it off the charger it drops to ~6.8v. And when you power on the tx, within 30 seconds the voltage is down to 6.6v; it just pretty much sits at 6.5 to 6.3 for most of the pack. I have my alarm at 6.2v because it starts dropping fast after that. I found if it's around 6.1-6.2v, ~1700mah goes back in when I charge it.

Can you give some more details about this mod? Brand and type of LiFePo4? Maybe some photo's also?

I have orderded this LiFePo4 battery:

6.6V 1600mAh LiFePO4 (Lithium-Ferrite) compact receiver battery. UK seller

This should fit in the battery compartment of the 8S.