Yeah - I know that the wall wart is nothing more than a (hopefully=20 decent) little 5V power supply rated at some amount of current. What=20 I found interesting was the algorithm that the tablet uses to charge=20 that fairly large (10AH) battery. Most charge circuits follow a=20 fairly standard and simple curve. This one was unusual in that the=20 current is modulated according to some scheme. I guess that I mentioned it to see if anyone else has noticed devices=20 that do similar things - and to ask *why* it might be doing that. BTW - you *can* purchase wall-warts that *do* have the Li-Ion or LiPo=20 charger built right in. Those don't come with USB connectors,=20 obviously. They are convenient. My bike light came with such a=20 unit: the battery pack is 4 cells in series-parallel (2+2) and the=20 wall-wart charger has a connector that mates to that on the battery=20 pack. I haven't bothered to see what that unit's charge current=20 profile looks like. dwayne At 10:39 PM 1/9/2015, Robert Dvoracek wrote: >>Interestingly enough, the current reading oscillates between=20 >>several values every few >>seconds. I have *no* idea why it does that. The voltage out of=20 >>the wall wart seems to remain constant as the current varies. > >That is just whatever charging scheme they decided to use in=20 >operation. The wall wart is never anything more than a "stupid" CV=20 >SMPS, sometimes with a current trip for safety, but it isn't really=20 >designed to charge the battery directly. All of the "smart" battery=20 >manglement stuff is inside the s/phone/tablet/g. If you want to=20 >"roll your own", I highly recommend the MCP73832, but it's actually=20 >cheaper to just buy one of the LiIon chargers on eBay. The charging=20 >current can be set by changing a resistor. --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .