Fix for poor battery life on PRS-500?

[HarryT]

Originally Posted by InspectorGadget

So regardless of the mAh capacity of the cell you put in, it'll charge at 500mA max under A/C power. No surprise there -- it's the max they can draw on a high-charging USB port.

I'm not sure that's the case. The Sony charges a LOT faster using an external PSP-type mains charger than it does via USB, so that would seem to indicate that it will accept a higher current. The PSP charger is, I believe, rated for 2A @5.2V.

[InspectorGadget]

Originally Posted by HarryT

I'm not sure that's the case. The Sony charges a LOT faster using an external PSP-type mains charger than it does via USB, so that would seem to indicate that it will accept a higher current. The PSP charger is, I believe, rated for 2A @5.2V.

Well, I may have incorrectly implied that it WOULD charge at 500mA from the USB. It could do this, given the settings that it has (100mA/500mA). But it could only do this if their USB implementation negotiates a high-current device mode with the USB host controller. Otherwise, they would just charge at 100mA on the USB.

Now obviously just because the PSP charger can put out a maximum of 2A doesn't mean that the PRS-505 draws this much. In fact, given the part values that they have on the charging chip, it apparently can only draw a maximum of 500mA, regardless of the source.

So if your observation is that it charges a LOT faster on the mains charger than on USB, my guess would be that it's charging at 100mA (max) on the USB, and 500mA (max) on the mains.

I'll take another look at the schematic this weekend if I get the chance and see if it suggests anything else with the charger control inputs.