4.5V battery

As I don't have the time or money (or knowledge) to design my own
electronics I'm taking an existing product and modifying it It runs off
three 1.5V watch batteries in series. I'd like to replace this with a single
4.5V rechargable battery and charge it from a USB port. Does a 4.5 volt
battery exist that would take up a similar amount of space? What sort of
cicuit would I need to charge the battery (if any).

Many thanks,
Michael

 

"Michael C"

* Yeah right - like all " watch batteries" are exactly the same size.

** Errr - how much space was that again ???




............ Phil

 

If you have power available all the time it's no more difficult to
design and build a voltage regulator to eliminate batteries than a
battery charger.

AFAIK you won't get any rechargeable batteries that are compatable in
size to watch batteries.

Nor are watch batteries all the same technology. The best and most
expensive are silver oxide, for which cheaper options exist if the
voltage stability isn't critical.

 

Hi John,

The device is USB but it is wireless so won't always have power. I do have a
fair bit more space than the 3 watch batteries, probably enough for a single
AA battery. I was thinking that I could have a usb plug on the device that
was used for charging only, instead of supplying the customer yet another
charger.

Michael

 

"Michael C"

** Had to DRAG simple fact that out of the PITA prick.

Go check the WES catalogue for Akai Video Backup Batteries.

Cat # BVS8 = 4.8 volt, 80 mAH.

Costs = $10 .




......... Phil

 

WES Components at Ashfield (NSW) list a 1.2V 80mAh NiMH that measures
16mm x 6mm (tagged for PCB mounting). It's code no. is RB80. They're
somewhat more expensive than watch batteries (probably close to
double).

Four in series would give you 4.8 volt.

 

When I originally posted I didn't have that much space but came up with a
better way to do it.

Thanks phil, I'll give them a call next week.

 

How would you go about charging them from a 5V source?

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

 

"Franc Zabkar"

** Boost regulator.



........... Phil

 

What's one of them then?

Michael

 

"Michael C"

** Try Google.


.......... Phil

 

LM2750 -- $5.81 from Farnell (awaiting stock).