Clamp NimH at 1.45V (+/- X) per cell max and at low current wrt cell capacity they will be fine. At low current/capacity lower capacity cells will last "long enough" [tm]. AA >=3D 2000 mAh should not be trickle charged in "serious" applications. OK in low use applications. AA <=3D 1500 mAh trickle charge OK. Scale down for smaller cell sizes. Very very very rough rule of thumb - capacity of AA is ~~~ 2500 mAh at 30 grams. This will vary with special features. eg Sanyo Eneloop and GP ReCyko LSDs are about 2100 mAh at 30 grams. About ??? 10 grams is fixed weight (actual figure escapes me at present). Very small button NimH from even Duracell allow constant charging at 1 C rate !!!! YMMV but as long as capacity is not near leading edge they seem OK. Clamping Vmax art somewhere below 1.4V makes them fairly safe. Say 1.3V - lose some capacity but probably no worries about change with temperature or brand differences. Capacity will be slightly down but WMW. For long life do not discharge NimH below 1V at low discharge currents. Minimal capacity below there but kills cycle life. At high currents internal R drop mat allow 1.0V terminal voltage under load= .. This will soon bounce to 1.1V + to ++ when load is removed. Russell .. On 5 June 2011 11:36, V G wrote: > On Sat, Jun 4, 2011 at 6:26 PM, Al Shinn wrote: > > > Perhaps of interest and perhaps on topic > > > > I just opened up 3 different solar path lights. > > > > 1) $1.00 from dollar store has 1 amorphous solar cell on glass (in > > circuit V =3D~ 1.3V in bright light), 1 IC (pn ANA618) w 4 leads 1 lar= ge > > button cell (the tag on the lamp says NiMh 1.2V/60mAh), 1 white LED, 1 > > inductor, and a switch. At first I thought that the inductor was a > resistor > > but that did not make sense so I approached it with a magnet, not only > was > > the magnet strongly attracted (not really proof) but the light got > brighter > > - proof to me. > > This unit's tag says from L'Image Home Products made in China > > > > 2) $2.00 from orchard supply has 4 small crystal solar cells potted i= n > > plastic, 1 IC (pn 6N06) w 4 leads 1 aaa NiCd cell 1 white LED 1 > inductor > > and a CdS cell. same inductor story. This one blinks when the battery > gets > > low. > > > > 3) $2.00 from orchard supply - has 1 amorphous solar cell on glass > (1.33 > > in circuit w bright light, 1 IC (pn 5252F) w 4 leads 1 aa NiCd cell 1 > > white LED 1 inductor. same inductor story. > > Tag says made for Orchard Supply in China > > The circuit in this one is as follows: > > pin 1 of IC has Sol+ > > pin2 B+ and L > > pin3 B-, Sol-, Led- > > pin4 Led+, and L > > > > Can't find any such chips on Google. But if you could, it might be a go= od > > thing for the solar guitar tuner, I bet (at least $0.25) the chip has a > > boost current source that could be a voltage source with a bit of > tweaking - > > diode + cap + Zener?. You could go to OSH for the chips and all for $2= .. > > > > Note the NiMh button cell in #1 (a solution to some size objection to > NiCd > > s by the OP.) > > Note - none of these have visable diodes in series w the solar cell - > and > > the cell V was too low to allow one in #1 and #3 (1.3V in circuit, > perhaps a > > fet is used to block reverse current to the solar cell? > > > > But > > > > > Thanks! That sounds interesting, but it seems that you can't do a constan= t > voltage charge on Ni based batteries. Lithium ion seems really good. I'll > stick a a 2xAAA holder on there as well, but will probably not be needed. > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .