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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Solar panels
Date: Fri, 31 May 2024 15:48:35 -0700
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On 5/31/2024 2:15 PM, boB wrote:
> 72 cells is a common PV module (panel) configuration.
> 
> So is 60 cells.
> 
> An MPPT charger is usually a buck converter so that's how it gets
> there.  A nominal 48V PV array will need to have a higher Vmp than the
> battery voltage to charge that battery bank.

Not intended to "charge" the battery but, rather, for the battery
to look like an ideal capacitor.

I can "charge" it from the mains, after hours (as well as supplement
any load that I feel needs to be powered in the absence of sunlight)

> Sounds like Kevin knows his stuff regarding this and you aren't far
> off, if at all.
> 
> Rapid Shutdown requires the array at the string (HV) inverter or
> charge controller input to be at or below 30V in 30 seconds after its
> clear to go signal is removed.  At least those who are being inspected
> to NEC.

If I can let the array look like a single 48V panel (a bunch of them,
each contributing some amount of current to a single/shared load),
I figure it simplifies the deployment by distributing the electronics
among multiple relatively low power (300-400W) sources.

Otherwise, you have to reengineer a solution for each deployment -- 3KW,
5KW, 6KW, etc. each requiring a bigger "power supply" (to produce the
48V from the AC generated by microinverters or a string inverter)

E.g., I can use a single panel, by itself -- as long as my solar load
is ~300W (supplementing with mains-derived power if it exceeds this
on the short term or if the sun hides)