Correction, My panels have 2x12 cells. ~5.5V at VMP, ~7V VOC Now that I think about it, I don't think just using diodes will work. The VMP and VOC are two far about to make it practical.
June 2, 2020 10:20 AM, "Peter VanDerWal via EV" <[email protected]> wrote: > Now why didn't I think of that? > The chargers I've been looking at have MPTT(or at least they claim to), > however I could just use > two panels. > > I have a couple dozen panels left over from an abandoned project: 5V @ 240ma, > they have conformal > coating so reducing them to 5 cells instead of 6 would be difficult. > However, I could run a couple diodes in series... > > June 2, 2020 10:02 AM, "Matt via EV" <[email protected]> wrote: > >> What about no charge control, a solar panel whose Voc is 4.5v (so only 5 >> series cells) and a >> schotkey diode to prevent back flow >> >> That would have the effect of limiting max voltage to ~4.2v, but at 4v only >> around 20% of Imp would >> flow (ie charge rate slows right down past 3.6v) >> >> How much power are you thinking? >> >> Sent from Mail for Windows 10 >> >> From: Peter VanDerWal via EV >> Sent: Wednesday, 3 June 2020 12:55 AM >> To: Electric Vehicle Discussion List >> Cc: [email protected] >> Subject: [EVDL] Question about charging small LiIon batteries >> >> Somewhat off topic, but I'm hoping someone can help. >> >> I'm building a solar powered weather station and plan to use 1 or 2 18650 >> cells. There are tons of >> small solar chargers available for these, however they all charge the cells >> to ~4.2V. >> To maximize life from the LiIon batteries I'd like to keep them between >> 40-80% charged. >> >> So what I'm looking for is either a solar module that I can set to only >> charge the cells to ~3.9V >> or a way to make a 4.2V charger work. >> Since I'm not having any luck finding 3.9V chargers what I've been thinking >> about is perhaps using >> a schottky diode to drop the 4.2V to around 3.9V. however that would prevent >> the charger from >> seeing voltage from the battery and it might not start charging. >> So I'm thinking maybe putting a 100 ohm resistor in parrel with the diode, >> that would allow the >> charger to see the battery voltage. >> I still have to figure out how much current the microcontrollers, etc. will >> draw, but it's going to >> be at least 10 mA when idle, with bursts up to several hundred ma when >> transmitting. >> >> Does this sound like a reasonable plan? Any better suggestions? >> >> Thanks, Pete. >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: >> <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20200602/3cd29a40/attachment.html> >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> ARCHIVE: http://www.evdl.org/archive/index.html >> INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) >> >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: >> <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20200603/9de4e27d/attachment.html> >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> ARCHIVE: http://www.evdl.org/archive/index.html >> INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/index.html > INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
