Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Don Y Newsgroups: sci.electronics.design Subject: Re: Solar panels Date: Sun, 2 Jun 2024 11:06:32 -0700 Organization: A noiseless patient Spider Lines: 68 Message-ID: References: <7jin5j59trq97s2f5n39foi9iuq6h0rdte@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sun, 02 Jun 2024 20:06:57 +0200 (CEST) Injection-Info: dont-email.me; posting-host="e79f7ac043832d1b2aa3558b3a8c0f4f"; logging-data="3644832"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19coGby7pdFp3TUgRVnCoPc" User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Cancel-Lock: sha1:oIUPwiNCWv4nzwbAIIajbeMOf9Q= In-Reply-To: Content-Language: en-US Bytes: 4363 On 6/2/2024 10:21 AM, KevinJ93 wrote: > On 6/1/24 8:32 PM, Don Y wrote: >> On 6/1/2024 6:29 PM, boB wrote: >>>>> Not sure how to avoid excessive charge currents into the battery if it can't >>>>> take the full solar output. >>>> >>>> I think you have to be able to "talk" to the module to tell it how you would >>>> like it to behave, NOW. >>> >>> The MPPT controller simply raises the PV operating voltage above >>> Vmp...  At Voc, the current becomes zero. Whatever Vpv gives the >>> correct controller output voltage to the battery it is charging. >> >> You have to signal to the controller that the battery is charged; >> that it can't (shouldn't) continue to accept charge. > > That will happen automatically when the battery reaches the set voltage. *If* you have a charge controller for the battery, the controller limits what will flow into the *battery*. But, I use loads in much the same way that one would use a battery; if there is excess capacity available, then I will bring more loads on line. There's no other "storage" for that excess capacity -- use it or lose it. > Some of the charge controllers allow configuration for various parameters such > as 100% charge voltage so that it will work with different chemistries. > > In your case your load could be directly across the battery. > > The one thing that is not obvious to me is how to limit the charge current if > you use a small battery where the solar available could exceed the allowable > battery charging current. See above. Unlike a typical application where you would "store" the excess produced into the grid, I am avoiding that complication. I'll just "do extra work" with it, storing the results of that "work" instead of the electrons themselves. That's why I need more intimate control and knowledge of what the available power, battery reserves and loads are. Power FROM the grid is always available to supplement my needs -- but, that doesn't want to be the main source of power. E.g., I could find it advantageous to charge the battery at C/100 (!) in preparation for darkness if I can make use of all of the available solar power to "do real work" (cuz that won't be possible, later). Likewise, if the battery doesn't have sufficient reserves to bridge the dark period, rely on mains-sourced power -- but, as a temporary stopgap. I.e., you continuously are making supply and demand decisions trying to minimize the expected cost of your usage: "Is it better for me to delay this 'work' until tomorrow when I *expect* to have a surplus of solar power available? Or, have I already 'borrowed' to heavily from that future source?" It's just a resource management issue: should I wash the dishes, laundry, irrigate the yard AND take a shower now? Or, can I distribute those loads to better use the available water (and hot water) to eliminate the need to up-size my supply? > Maybe you could add a controllable dump for when solar generation significantly > exceeds your load consumption? > > kw