Quote:
Originally Posted by xanlexian
Since it is just a two-wire battery (no 'smart' leads/contacts) could you not just swap it with something of equal voltage (possibly higher mA for longevity) so long as it fit in the restricted space? Li-Ion, of course. Also -- leads being attached and whatnot.
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In theory, yes, though
I take no responsibility for any damage or personal injury which may result from my advice.
FYI:
The biggest issue is to make sure any replacement cell has a "protection circuit" on it -- that it's not just a raw cell. I haven't looked at the PRS-505 battery in particular, but I've never seen a consumer device that hasn't had the protection circuit attached directly to the battery. It's a strip of a PCB usually spanning the width of the cell attached to one end and covered with the heat-shrink outer packaging. There are usually metal tabs that come off the cell, terminate on the PCB, go through the circuitry on the board, and terminate at the wire leads that go to the main appliance PCB.
The protection circuit PCB has a protection IC that comprises comparators and switching logic to switch [usually] off-chip MOSFET transistors. It monitors overvoltage, undervoltage, and overcurrent conditions on charging or discharging and cuts the cell off of the rest of the circuit if the settings are exceeded. Since LiIon (and to a much lesser extent, LiPo) cells are subject to thermal runaway on overcurrent conditions, the protection circuit protects you against burns and/or fire, as well as consequential damage to the appliance. It also protects the cell against over-charging or over-discharging.
Aside from the protection-circuit issues, the only other concern is that the charging circuitry on the PRS-505 PCB has enough power dissipation/current-handling ability for a potentially higher mAH cell you may install. Given the size constraints, you PROBABLY don't have anything to worry about, because the existing charging circuit is probably already overrated for the cell they have in there. I know a lot of LiIon charging ICs from all the major manufacturers, and in my experience it's hard to find one that handles less than 500-800mA, and the cell in the PRS-505 has got to be in the 300mAh range (charging max current is usually set to <= 1C).
But as I said before, please understand that the risk is and must be all yours. I'm making estimations based on what I've seen in the marketplace of products and ICs, and I don't know for sure. Therefore, I take no responsibility for any damage that may occur as a result or in the course of having listened to my advice!