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Dec 27, 2011, 05:27 AM
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Dodge DeBoulet's Avatar
Discussion

DX7S Battery Level Indicator


I've had my brand-new Spektrum DX7S with stock NiMH 4.8v battery charging for at least 12 hours (its been plugged in to the wall wart longer than that, with some of that time spent powered up for model programming and a firmware upgrade). The voltage reading is at 5.4v -- a number that seems even a bit high for a 4.8v battery -- but the bar indicator shows a less-than-complete charge.

My understanding is that this tx knows how to tell the difference between NiMH and LiPO batteries for charging purposes, which is borne out by the firmware actually displaying the installed battery type in the systems settings menu. Unfortunately, it doesn't appear to be smart enough to translate that information into a sensible battery gauge.

Or maybe there's simply something wrong with my tx or the way I've configured it?
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Dec 27, 2011, 09:06 AM
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pilotpete2's Avatar
A 4.8V battery is not a 4.8V battery, really
A four cell Nixx pack will read at least 5.4V when fully charged, and at about 4.4V it is considered fully discharged
Pete
Dec 27, 2011, 09:08 AM
AndyKunz's Avatar
Quote:
Originally Posted by Dodge DeBoulet
My understanding is that this tx knows how to tell the difference between NiMH and LiPO batteries for charging purposes, ...
That is done by the hardware design and charger chip, not the AirWare.

Quote:
... which is borne out by the firmware actually displaying the installed battery type in the systems settings menu.
It only displays the right type when you tell it to. When you change the battery type you have to manually adjust that screen so that the low voltage alarm works.

Andy
Dec 27, 2011, 12:54 PM
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Dodge DeBoulet's Avatar
Quote:
Originally Posted by AndyKunz
It only displays the right type when you tell it to. When you change the battery type you have to manually adjust that screen so that the low voltage alarm works.

Andy
I'm missing something, then, because the battery type field isn't editable on my DX7S. I can edit the "Batt Alarm" field, but have no way to select and edit the "Battery Type" field. Is there somewhere else I should be looking?

Regardless, even if I'm the one telling the firmware what type of battery is installed, automatically adjusting the gauge to compensate seems reasonable.
Last edited by Dodge DeBoulet; Dec 27, 2011 at 02:10 PM.
Dec 27, 2011, 01:27 PM
Registered User
The radio will not allow the chemistry type to be changed to LiPo unless a LiPo is actually installed in the radio.The number you are seeing for the NiMh pack is within the acceptable range.I think maybe your worrying about it to much.Just use it and get used to what the display is telling you.
Most important is to not leave it on the charger to long.Ive seen many who try to keep charging a pack that is mostly charged already and it will get the pack hot and degrade the cells.Too ht and it will be damaged.Dont leave it on the charger overnight for a small topping charge.Get a bit more used to how long it takes to run it down to 4.7 or below.You will be surprised.Only charge until the cells start to become warm.That means its done.You will get a feel for how long it takes to charge from various levels.That amount of time is alot less than most normally assume it would be.
As NiMh cells age the standing voltage of a charged cell will be a bit higher than when its new.This is one of the signs of a pack aging.The graph scale is likely designed to compensate for this.With a new pack dont be so worried that its not completely filling the graph.
Dec 27, 2011, 02:03 PM
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Dodge DeBoulet's Avatar
Looks like my complaint/concern has also been voiced by at least one DX6i user as well . . . There's a similar thread on its battery display elsewhere in this forum.

I wonder how many newbies have killed their batteries and/or radios by leaving it on the charger too long, expecting that bar to reach 100%?
Dec 27, 2011, 04:03 PM
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pilotpete2's Avatar
The DX6i and DX8 can both be used with "AA" Alkaline cells that will be a bit over 6V when fresh. The bar graph is probably set with that higher voltage in mind. Pop in a fresh set of Energeezers and see what the bar graph shows.
FWIW, the bar graph is on the level of "idiot lights" in your car, the voltage display is what counts.
Pete
Dec 27, 2011, 05:25 PM
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Dodge DeBoulet's Avatar
Quote:
Originally Posted by pilotpete2
The DX6i and DX8 can both be used with "AA" Alkaline cells that will be a bit over 6V when fresh. The bar graph is probably set with that higher voltage in mind. Pop in a fresh set of Energeezers and see what the bar graph shows.
FWIW, the bar graph is on the level of "idiot lights" in your car, the voltage display is what counts.
Pete
Ah, but the DX7S doesn't take anything but NiMH or LiPO packs. No way to pop in some Energeezers
Dec 27, 2011, 06:41 PM
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pilotpete2's Avatar

I forgots about that. Whatdya expect from a Futaba guy
The soldered pack is certainly better than the springy thingy battery tray any-day in my book
Pete
Dec 27, 2011, 07:58 PM
Registered User
Quote:
Originally Posted by pilotpete2
The DX6i and DX8 can both be used with "AA" Alkaline cells that will be a bit over 6V when fresh. The bar graph is probably set with that higher voltage in mind. Pop in a fresh set of Energeezers and see what the bar graph shows.
FWIW, the bar graph is on the level of "idiot lights" in your car, the voltage display is what counts.
Pete
Incorrect. While the DX6i has a spring clip battery tray the DX8 takes a 4cell pack with a plug in lead.
Dec 28, 2011, 11:40 AM
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pilotpete2's Avatar
Yo, I already had my clock cleaned for that one. Enough's, enough, already yet
Cheers,
Pete
Feb 12, 2012, 07:55 PM
Registered User
Quote:
Originally Posted by pilotpete2
A 4.8V battery is not a 4.8V battery, really
A four cell Nixx pack will read at least 5.4V when fully charged, and at about 4.4V it is considered fully discharged
Pete
Hmmmmm. My recently purchased DX7s came with the low voltage alarm set to 4.3 volts. So if it's considered fully discharged at 4.4 volts, should I actually set the low voltage alarm above 4.4 volts and not the 4.3 volts that it was set at initially?

Thanks for any info or advice.


Allen
Feb 12, 2012, 09:01 PM
AndyKunz's Avatar
We set the defaults as we did for a reason. Leave it with the defaults.

Andy
Feb 12, 2012, 10:24 PM
Registered User
Quote:
Originally Posted by AndyKunz
We set the defaults as we did for a reason. Leave it with the defaults.

Andy
Thanks for the prompt reply.


Allen
Feb 13, 2012, 07:19 AM
Registered User
richard hanson's Avatar
My experiences with the DX8 (I fly with a number of guys who have the DX8)
show that
1- the default 4.3 low point is fine -leave it alone
2- fully charged, depends on cells used -stock Spektrum NIMH or Eneloops-
Eneloops fill the scale at up to 5.8v-the stock cells about 5.5
typically- two guys use Eneloops
In use: the high reading slopes down gradually to about 5v then slowly to about 4.5
A tthat point, either pack type appears to fully recharge in say 8 hours - NEVER over 12 hours
3 the packs- either type- will warm a little
4 -NO NOT keep recharging at 5 volts!
this just leads to overheated and possibly ruined cells . One guy was doing this
Having observed five tx - the results appear to be the same
The original question about the accuracy of scale on the tx was asked by a few owners. Normal curiousity--


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