>Hi all,
>
>I'm trying to use a PDA for a different purpose than its original one :-)
>
>I'd like to run it from external power only. The problem is that,
>since I'll be running it from a power supply that already powers other
>equipment, and doesn't have much power to spare, I'd rather remove the
>battery to avoid it using too much current during charging (during
>normal use it shouldn't use much. It's supposed to be battery-powered,
>isn't it?)
>
>Of course just removing the battery won't work. I can get to the
>diagnostics menu with an off-contrast screen only, no normal power-on
>(blinking LEDs, presumably it knows there's no battery in there).
>Since li-ion cells are supposed to drop in charging current when done
>charging, I just stripped out the cell and left in only the battery
>circuitry. Diag shows up fine, but no power-on (no blinking). I think
>the problem is that it tries to stop charging and run from the battery
>for a moment, and, of course, it just turns off.
>
>Maybe I could add a resistor to the battery circuitry to make it
>believe it never stops charging? Although it might still try to run
>from it for a short while and still fail... Other ideas? Maybe power
>it through the battery with a suitable supply instead of through the
>charger plug? BTW, the battery is a single-cell 3.7V 950mAh.
>
>Regards,
>  
>

> Hi all,
>
> I'm trying to use a PDA for a different purpose than its original one :-)
>
> I'd like to run it from external power only. The problem is that,
> since I'll be running it from a power supply that already powers other
> equipment, and doesn't have much power to spare, I'd rather remove the
> battery to avoid it using too much current during charging (during
> normal use it shouldn't use much. It's supposed to be battery-powered,
> isn't it?)
>
> Of course just removing the battery won't work. I can get to the
> diagnostics menu with an off-contrast screen only, no normal power-on
> (blinking LEDs, presumably it knows there's no battery in there).
> Since li-ion cells are supposed to drop in charging current when done
> charging, I just stripped out the cell and left in only the battery
> circuitry. Diag shows up fine, but no power-on (no blinking). I think
> the problem is that it tries to stop charging and run from the battery
> for a moment, and, of course, it just turns off.
>
> Maybe I could add a resistor to the battery circuitry to make it
> believe it never stops charging? Although it might still try to run
> from it for a short while and still fail... Other ideas? Maybe power
> it through the battery with a suitable supply instead of through the
> charger plug? BTW, the battery is a single-cell 3.7V 950mAh.
>
> Regards,
> --
> Hector Martin (.....hectorKILLspam.....marcansoft.com)
> Public Key: http://www.marcansoft.com/hector.asc
>

>Steve Halla wrote:
>  
>
>>Which PDA is it, as control methodology is slightly different for many PDA's?
>>
>>    
>>
>
>Sharp Zaurus SL-5500.
>
>I've tested straight 3.6V through the battery connections, and through
>the battery logic into the battery connections. Same as always, diag
>OK, no normal turn-on. I think I noticed it needed the charger for a
>second with the original battery after disconnecting it to be able to
>turn on, which it has never needed before. I think the backup battery
>has something to do with this, since it's disconnected right now. I'll
>connect it and test. If it comes out to be the culprit (I thought all
>that whould happen is that the RAM would be erased if it loses total
>power, but it may also have something to do with the charging
>circuitry) now I have to emulate *two* batteries. I need to do more
>testing.
>
>I might just as well leave the batteries connected normally and  hope
>that the main power supply can cope with the charging.
>
>Regards,
>  
>

> Steve Halla wrote:
>
>>Which PDA is it, as control methodology is slightly different for many PDA's?
>>
>
>
> Sharp Zaurus SL-5500.
>
> I've tested straight 3.6V through the battery connections, and through
> the battery logic into the battery connections. Same as always, diag
> OK, no normal turn-on. I think I noticed it needed the charger for a
> second with the original battery after disconnecting it to be able to
> turn on, which it has never needed before. I think the backup battery
> has something to do with this, since it's disconnected right now. I'll
> connect it and test. If it comes out to be the culprit (I thought all
> that whould happen is that the RAM would be erased if it loses total
> power, but it may also have something to do with the charging
> circuitry) now I have to emulate *two* batteries. I need to do more
> testing.
>
> I might just as well leave the batteries connected normally and  hope
> that the main power supply can cope with the charging.
>
> Regards,

>>
> No, the problem , as I stated earlier, is that at turnon, the current
> load is heavy. The
> battery can deliver it, the regulator cannot. You have to design the
> regulator to deliver
> as much as 50X normal running current. And a low impedance output cap
> isn't a bad
> idea, either.
>
> --Bob
>

>Yup, a power issue. The supply should be able to keep up with the
>current, but the issue seemed to lie with the voltage. Incrementing it
>up to 3.8-3.9V did the trick. Thanks! Right now it is running straight
>to the battery terminals, no battery circuitry, no charger, no backup
>battery.
>
>Now that this is running with the bench supply, what do you suggest
>for lowering the original 12V from the main supply to the 3.9V that
>this requires? Wouldn't a regulator dissipate a lot as heat?
>
>Bob Axtell wrote:
>  
>
>>No, the problem , as I stated earlier, is that at turnon, the current
>>load is heavy. The
>>battery can deliver it, the regulator cannot. You have to design the
>>regulator to deliver
>>as much as 50X normal running current. And a low impedance output cap
>>isn't a bad
>>idea, either.
>>
>>--Bob
>>
>>    
>>
>
>Regards,
>  
>