Thanks for the replies Bill and Russell! On Thu, Oct 6, 2011 at 2:14 AM, RussellMc wrote: > As others say LiPo is essentially just LiIon charge wise. Ok, that's encouraging. > Max charge current allowed is C/1 =A0=3D 1 mA per mAh. I'm always going to be below that - the charge current comes from a USB port, and the battery will be >500mAh. > Note that modern NimH cells are now about as energy volume-dense as LiIon= .. > Not that NimH are marvellous - they are hard to charge well in limited > energy situations. I'm enjoying the Li-ion cells as I can run my 3.3V circuit using an LDO off a single cell. > LiIon are very easy to charge reasonably well (even though the Max1811 > doesn't manage to do so). > _______________ > > Max 1811 data sheet > > =A0 =A0 =A0 =A0 =A0http://datasheets.maxim-ic.com/en/ds/MAX1811.pdf > > It would work OK. > Assuming I understand the data sheet properly, iIt's a=A0rather limited c= harger*. > Bbut is hard strappable which may explain how something so limited can ex= ist. > 100 or 500 mA charge only > 4.1 or 4.2V Vend settable - USE 4.1V! > > The implications of the "stop at Vmax" system, is that the cell will > only be at about 70% - 80% of capacity when it trips into hyper-low > charge mode BUT the cell will last a lot longer. > If you want maximum capacity from your cell the Max1811 is not the > charger for you. > > * Doesn't seem to have a sensible end of charge termination - ie > battery current shutdown at 4.2V is 0.1 to 2 uA. > Graph at top left on page 4 is incorrectly labelled** =A0BUT suggests > there is NO current taper. > I have never before seen a LiIon cell charger with no taper. > What it does mean is that you can plug it in and out as often as you > wish or charge it for random periods and it does not overcharge. > > ** Should read "Charge current versus battery voltage". Ah, interesting information about the MAX1811. I chose that chip when I did the original board (about a year ago) based on my total inexperience with this technology, the fact that it's made for USB charging, and that I managed to have a great chat with an FAE about what I was doing. Also, it was physically in a small package. The downside is that it's a bit pricey, plus as you mentioned it doesn't do a stellar job. So far, battery life hasn't been a problem, thankfully. I'm completely open to new suggestions though. I'm looking at something in the neighbourhood of a 800-1200mAh cell, usb charging. I might also need to be looking at integrating discharge/overcharge protection onto my board as many of the LiPo cells don't seem to have it. Ideas for both would be appreciated. Small size is nice too, though maybe, maybe I might be able to squeeze more room on the board. Thanks! Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. =A0 =A0 =A0 =A0 -Douglas Adams --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .