Hi John,
Your NiMH pack would have a discharged voltage of around 12V.
According to the 702 manual the external battery low voltage
threshold is 11V, so I suspect that the external pack reaches a point
where it cannot supply sufficient current to run the 702 before the
power management circuit detects low voltage and switches to the
internal battery.
The solution would be to either get the factory to change the low
threshold point to something like 12.5 or 13V for use with the 12
cell pack, or to use a 10 cell instead.
cheers
Paul
On 30/11/2007, at 3:39 PM, John Hartog wrote:
> Hi group,
>
> I ran into a perplexing problem using an external battery pack with my
> SD 702. Tech support at Sound Devices are perplexed also, but they
> are trying to figure out what might be happening. In the meantime, I
> thought I would post this to the group as a word of caution for those
> considering external powering schemes and also by chance anyone here
> can provide some insight.
>
> Using 14.4 V external battery pack made up of twelve 1.2 V AA NiMH
> (2500mah) rechargeable batteries, the recorder does not switch over to
> the attached battery when the external battery runs low, but rather
> the recorder shuts down prematurely leaving a corrupted file.
>
> I have done a bit of troubleshooting; though I have not tested with
> another recorder yet. I do have some thoughts on this myself, but none
> that answer why the recorder does not switch over with some battery
> packs. It's almost as if the 702 gets confused when both voltage and
> power from the external pack drop too low too quickly.
>
> John Hartog
>
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