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Old Apr 28, 2012, 10:01 AM
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Spektrum NIMH battery upgrade voltage difference

Installed 4 Eneloops yesterday and charged them to 5.8v. Verified with screamer and Fluke meter but DX7S info screen shows 5.5. Anybody know why the difference? Thanks
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Old Apr 28, 2012, 10:05 AM
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Originally Posted by bimmerland View Post
Installed 4 Eneloops yesterday and charged them to 5.8v. Verified with screamer and Fluke meter but DX7S info screen shows 5.5. Anybody know why the difference? Thanks
Just the "normal" offset error in voltage readings on the Spektrum radios.
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Old Apr 28, 2012, 10:15 AM
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Originally Posted by bimmerland View Post
Installed 4 Eneloops yesterday and charged them to 5.8v. Verified with screamer and Fluke meter but DX7S info screen shows 5.5. Anybody know why the difference? Thanks
Because there is a factory acceptance tolerance of +/-0.3V. Yours meets that tolerance. Some radios are dead-on.

Andy
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Old Apr 28, 2012, 10:47 AM
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Did the meters have a similar load (200-300mahish) on the batteries as the DX7S ? I doubt they would hold peak voltage 1.45v a battery while powering anything, heck they wont even be at 1.45v/batt after a few days.
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Old Apr 28, 2012, 12:07 PM
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Originally Posted by AndyKunz View Post
Because there is a factory acceptance tolerance of +/-0.3V. Yours meets that tolerance. Some radios are dead-on.
I can vouch for that, the one I have here is spot on.

I still find 0.3V a surprisingly large acceptable variation, but I certainly can't complain about mine.

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Originally Posted by pach View Post
Did the meters have a similar load (200-300mahish) on the batteries as the DX7S ? .
Probably not, but if a 200mAh load drops your voltage by that much then you have bigger problems.

I'm sure Andy has the right answer, it is just the allowed tolerance.
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Old Apr 28, 2012, 03:15 PM
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Originally Posted by Telrin View Post
Probably not, but if a 200mAh load drops your voltage by that much then you have bigger problems.
A drop from 1.45 a cell to 1.375 a cell under a normal load is perfectly fine. They are called 1.2volt batteries for a reason.

The best way to be sure is to check the packs voltage with a multimeter while the radio is on.
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Old Apr 28, 2012, 03:26 PM
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Originally Posted by pach View Post
A drop from 1.45 a cell to 1.375 a cell under a normal load is perfectly fine. They are clled 1.2volt batteries for a reason.

The best way to be sure is to check the packs voltage with a multimeter while the radio is on.
Obviously they will drop over time, but I wouldn't expect to see that much drop immediately on a freshly charged pack with such a light load.

Personally I wouldn't encourage people to try and check the pack voltage while the radio is on unless they have a pack with an alternate point to take readings from.

Either way, it is academic as we already have the right answer, the radio is not designed to provide accuracy beyond 0.3V so a different reading is generally going to be expected.
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Old Apr 28, 2012, 04:35 PM
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I just thought that if mine is off by .3 then when my alarm goes off I still have spare capacity. Kinda a good thing.
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Old Apr 28, 2012, 04:50 PM
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I just thought that if mine is off by .3 then when my alarm goes off I still have spare capacity. Kinda a good thing.
You can adjust the cut-off voltage as well so many feel it would be better to have an accurate voltage reading then decide how conservative you want to be on the cut-off.

Not exactly the end of the world though.
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Old Apr 28, 2012, 05:04 PM
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Keep in mind that Eneloops will eventually settle to around 1.3+ volts per cell when fully charged, but fresh off the charger they should be 1.4+ volts per cell.
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