[DECtalk] Fw: Looking for a home for a couple of serial synths

[Don]

On 9/9/2021 3:08 AM, Tom Kopec wrote:
> A DECTalk Express should power-up OK on external power with a dead/missing
> battery.

I'd have to check that.  It might rely on the battery as a voltage clamp.

> The battery uses 600mAh prismatic ni-cad cells, which are very difficult to
> find.. I don't think they are in current production.
> I have seen some Chinese NiMH cells that might sort-of work, but the charger
> circuitry is not compatible with NiMH cells.

And, the different chemistry will yield a different, overall, "battery"
voltage (9V -- 7.5 if you opt for just 5 cells -- instead of 7.2V)

> There isn't a lot of room in there to hack in another solution. With
> significant hacking it is might be possible to convert to a lithium battery,
> but that's not plug-and-play.

Again, different chemistry means yet another incompatible battery
voltage (likely 8.4V instead of 7.2).  Though you can likely
find some flat "bag cells" and *possibly* trick them into
fitting in the available space.

[I can't recall if the DX reports battery status as this would be
another aspect of operation that would be altered.  "Low battery"
may not be!]

The smarter approach is to design a pack that sits outside the
device (or, at least interfaces to the power inlet).  This gives
you a bit more leeway on characteristics and capabilities.
E.g., a pair of 18650's would likely power the device for
a whole (solar) day!

But, at the end of the day, it's still a pretty big box for what
it does.  Compare to the synthetic speech you get from a cell phone
(that easily fits in your pocket and runs all day).