Battery for Devo 8S - Screen Backlight Problem

Hi !

What kind of batteries do you folks use ?
Mine are NiMH cells, like the Devo Manual advises, four AA cells 2300mAh (soldered package).
I like NiMH's because I can charge them inside the radio (have it done all the time on my two 2801).
I'm not sure, maybe it's fancy, but I have the feeling that the voltage descents fast. Tried to measure ampere consumption, it's below 10 miiliamps. Strange, and it leads directly to the next problem, the backlight dimming.
When the voltage falls below 4 Volts, at appr. 3,8V the screen becomes unreadable.

tia
Gerhard

You're running your batteries too low.

3.8V/4 = 0.95V

You should charge them when they reach 1V. Fully charged NIMH are around 1.41V to 1.5V. That should give you plenty of runtime.

If you see voltage dropping too fast, maybe you already ruined your cells. Time to buy some new ones, I have had good experiences with Eneloops and GP Recyko low self discharge batteries.

Good luck.

EDIT:

For clarification purposes, NiMH should only be run to lower than 1V/cell when the load is greater than 1C, because voltage sags proportionally with load. 10ma is way lower than 1C, so 0.9V is pushing it.

Thanks for advice !
The cells have been new ones, and I have a second pack for spare.

I set the battery alarm now at 4,05V, hope that avoids screen going dimmed.

I had been surprised when I had found a 4 cell battery in the devo since not only my two Walkera 2801, the Nine Eagles J6 and the DX7 have had 8 cells, the Devo 10 (which I own also) has a 8 cell battery too. Unluckily the Devo 10 went broken, screen doesn't show anything but white . . .

Concerning Eneloops : Thought about them . . .
Do they demand a special charging procedure (charger) ?

Kind regards
Gerhard

I've set the alarm to 4.4V, just to be sure. And have a second set of batteries always at hand. I'm charging the batteries in an external loader.

FWIW, the DX6i also uses only 4 batteries.

Cheers,
Volker

I have an 800 mah 7m4 volt Lipo in my Devo 8. That gives me like 3 hours usage, and it recharges real fast. I actually have the balance conector sticking out in the back, so,i do leave it in there for charge. I have an alarm on 7,2 volts, and make sure its full when i go out. It would save some to have an even lower backlight setting than 1, though. I dont want to ever run the screen off, but i could go with half of even the 1 setting for backlight. Not a biggie, though. Cheers.

Hello

I've put 4 x NiMH 2500mA cells in my new Devo 8S.

Regarding the charger that could be used with the Devo8S, should we absolutely get a 200mA 8-12V charger or Amps can be higher ?

I do not understand well if Devo8S requires 200mA or this value is a minimum required ?

It is difficult to find a 8-12V @ 200mA , i found power supply within 8-12V range but current is much higher ( about 800mA - 1A )

Thanks for youre advices,

It is only a minimum requirement, any thing higher will work fine.