i'd like to get a rechargeable battery pack for my ad-20 and rolls pb-223, the ad-20 just takes a 9v and the rolls has been modded to take 2 9vs, any ideas on what to get?
The Rolls pb-223 has an internal 12 Volt linear regulator (the schematic is available on the net I found).
It accepts 14 to 18 volts as it is. I take this to mean that the 12V regulator is mounted without
a heatsink and simply gets too hot if you go above 18 volts.
The AD-20 (Vin 7(?) to 24 VDC) has an internal 5 V linear regulator. No heatsink. At a draw of
50mA you get worst case (24 Volts in=> 19 volts across regulator: 0.050 x 19 V drop =
1 Watt). I would guess the small regulator is HOT trying to get rid of all that heat.
What options do you have then?
The minimum common voltage is 12 volts:
Both units could be run on a 12V SLA (11. - 14. volts). This voltage is too low for the regulator in the pb-223 to work and a mod could be necessary. Max phantom voltage available ((not counting losses) is 4x the voltage on regulator output.
Mid range voltage:
Add together rechargeable cells (9.6 + broken pack) to get 13.5-18 Volts and run both units unmodded.
High range voltage (from 2 x 9.6 NiCd/NIMH (or 2 x 12 volts SLA))
Now you face a thermal issue. The regulators get *hot*. That means you have to add heatsinks to the regulators and/or insert a carefully sized power resistor (and a diode or two is a good protective measure
against polarity reversal) in each feed to drop the voltage seen by each unit when in operation.
And a fuse close to the battery is always prudent.
Best
Jon