On Wed, Apr 20, 2016 at 11:38 PM, Dwayne Reid wrote: > What is the current consumption pattern? Is this for a > night-lighting application or is the circuit expected to supply power > during sunlight hours? > Will supply a pump a few times per day at about 250mA. > > This is relevant because the easiest charge circuit would simply turn > OFF when full charge is reached, then not turn back on until sunlight > the next day. That won't work if you need to supply current from the > battery during the daylight hours. > > You will need, at the very minimum, a diode in series with the solar > panel so that the panel doesn't discharge the battery when there > isn't sufficient light. > Yes, I think this is the simplest way because the solar panel will self limit the charging current on it's internal resistance, it's a small panel.... > > I'm thinking of a circuit that charges the cells at the maximum > available current until the end-of-charge terminal voltage is > reached. Monitoring cell temperature is dicey given your ambient > temperature. > > Dumb question: could you change to a single Li-Ion or LiPo cell > instead? Much easier to charge than NiMh. > Good question indeed. Microchip Li-Ion charging ICs are quite inexpensive. I wasn't able to supply with low cost Li-Ion here and stuck on AA size Japanese accumulators. Now looking back perhaps it wasn't such a good idea, however Li-Ion at acceptable prices are still coming here via China and had with them bad experiences. Did you heard that the same Chinese product varies for different countries where are exported? I guess it's just a different way of quality testing... thx, Vasile > > dwayne > > > At 12:27 PM 4/19/2016, embedded systems wrote: > >Hi all, > > > >I need to build very quickly a bunch of solar chargers for 3xNiMH 2500mA= h. > >The max charging current would be max 200mA from a solar panel with 5.5V > >output. > > > >I've seen a lot of possible choices. However I will love a low cost > version > >using a battery management IC. Something like MAX639 or DS2715 but less > >expensive. > > > >There is also an option of using a venerable LM555 or just a simple > >parallel stabilizer with two transistors (and/or TL43x) which cut the > >voltage at the solar panel output when the NIMH is fully charged... > > > >I do not want to use a microcontroller for this job since charging NIMH > >lower than full capacity is not an issue for my application. > > > >Since the system will work in full sun at perhaps +40C, which will be yo= ur > >favorite option? > > > -- > Dwayne Reid > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > 780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free > www.trinity-electronics.com > Custom Electronics Design and Manufacturing > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=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 .