ThinkJet 2225B battery pack question

[Jeff_Birt]

(01-26-2024 01:03 AM)Dave Frederickson Wrote:  What we know about the battery pack:
1. A good battery pack fully charged outputs 8.5V
2. Typical output is 7.2 to 7.6V
3. The Power LED will indicate a low battery and flash if the voltage drops to 6.2 to 6.5V
4. The fuse is rated at 5A.

If the fuse was derated by 25% then the output would be 3.75A.
So a power adapter with an output of 7-8V at 4A should work fine.

Be very careful about trying to run a battery-operated device from the charging connector. Most often there is a current limiting resistor in series. This is part of the charging circuit but if you try to pump the full operational current through it the voltage drop and power dissipated will both be too high.