Justin Kenny's suggestion earlier reminded me of something, so I went looking through my spare parts and found some regulators boards that have variable MP2307 regulators. I originally got them to use with 3.3V microcontrollers, but never used them because they have flaky outputs. I'm pretty sure the problem with them is the cheap variable resistors, I think if I replace those with a fixed voltage divider they might be ok. However, I think the problem with them is the cheap variable resistors they use June 2, 2020 6:30 PM, [email protected] (mailto:[email protected]) wrote: Peter, Can i suggest a lm723 voltage regulator configured as a shunt regulator. I have used the datasheet design with solar panels. Lee may be able to recommend a better design than the barebones design in the datasheet. As the solar panel is a current source of limited output you could probably forgo the load resistor and simply dump all the excess energy into a large enough power transistor. The standby current of the device is typically 1.7ma with 30v source according to the datasheet so id expect it to be lower in your application. The addition of an output diode would disconnect the reg once the solar input was removed. Regards, Justin On Jun 3, 2020 10:58, Peter VanDerWal via EV <[email protected] (mailto:[email protected])> wrote: Yes, Lee has already pointed this out, so I am looking into putting the zener in parallel to the PV panel and then a schottky, etc. in series to the battery.
The problem I have with the cheap CV/CC circuits from china is that in my experience they have a high failure rate and, just like buttered toast, the failures tend to happen in the worst possible mode. June 2, 2020 3:17 PM, "Justin Kenny" <[email protected] (mailto:[email protected]) (mailto:[email protected] (mailto:[email protected])?to=%22Justin%20Kenny%22%20<[email protected] (mailto:[email protected])>)> wrote: Not sure if you understood the previous 2 messages, the Zener diode will drain your battery, and a diode will not stop it from overcharging. I really suggest to use the right tool for the job, $3.25 for a constant-current constant-voltage converter isn't much cost to save your battery pack from being killed prematurely, or at worst preventing a fire/destruction by overcharging: https://www.amazon.com/dp/B00LPK0IKQ (https://www.amazon.com/dp/B00LPK0IKQ) (https://www.amazon.com/dp/B00LPK0IKQ (https://www.amazon.com/dp/B00LPK0IKQ)) - Justin On Tue, Jun 2, 2020 at 2:57 PM <[email protected] (mailto:[email protected]) (mailto:[email protected] (mailto:[email protected]))> wrote: I'm thinking of using two panels, one tilted 45 degs to the east, and the other tilted 45 deg to the west. That should provide a fairly flat power output through the day with something like .375 ma max. If I put a 4.3V zener across the panel, then that should bypass some of the current, so I should only see a swing from perhaps 0.2V to 0.3V and the 0.2V will likely occur when the panel voltage is lower. At any rate a 0.1V variation is close enough for my purposes. I've got a selection of diodes on order, so I'll see what happens when I test it on the bench. Pete. June 2, 2020 1:51 PM, "jkenny23 via EV" <[email protected] (mailto:[email protected]) (mailto:[email protected] (mailto:[email protected]))> wrote: > Another very important note; diodes don't drop voltage the same at all > current levels. Meaning; they will NOT stop your 4.5V panel from > overcharging your battery to 4.5V if you don't have a dedicated charging IC. > > If you want to charge your battery to an unusual voltage, I highly recommend > using an adjustable CC/CV (constant-current/constant-voltage) buck > converter. They're widely available from China on eBay and Aliexpress, and > probably available from the US through Amazon. This way you can set a safe > current limit (say 400mA), and a voltage limit that is lower than 4.2V (say > 3.9 or 4.0V). Then you could even use multiple panels in series and not > worry about charging, the input limit for the common LM2596 modules is 35V. > > Here's some data for a common 1N5819 Schottky diode illustrating the issue > of voltage drop as current tapers down at the end of charging: > 1.0A - 0.41V > 0.5A - 0.35V > 0.1A - 0.28V > 20mA - 0.23V > > -- > Sent from: http://electric-vehicle-discussion-list.413529.n4.nabble.com > (http://electric-vehicle-discussion-list.413529.n4.nabble.com) > (http://electric-vehicle-discussion-list.413529.n4.nabble.com > (http://electric-vehicle-discussion-list.413529.n4.nabble.com)) > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > (http://www.evdl.org/help/index.html#usub) > (http://www.evdl.org/help/index.html#usub > (http://www.evdl.org/help/index.html#usub)) > ARCHIVE: http://www.evdl.org/archive/index.html > (http://www.evdl.org/archive/index.html) > (http://www.evdl.org/archive/index.html > (http://www.evdl.org/archive/index.html)) > INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > (http://lists.evdl.org/listinfo.cgi/ev-evdl.org) > (http://lists.evdl.org/listinfo.cgi/ev-evdl.org > (http://lists.evdl.org/listinfo.cgi/ev-evdl.org)) > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA > (http://groups.yahoo.com/group/NEDRA) (http://groups.yahoo.com/group/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/20200602/9714388d/attachment.html (http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20200602/9714388d/attachment.html)> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub (http://www.evdl.org/help/index.html#usub) ARCHIVE: http://www.evdl.org/archive/index.html (http://www.evdl.org/archive/index.html) INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org (http://lists.evdl.org/listinfo.cgi/ev-evdl.org) Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/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/20200603/721c570f/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)
