Date: Thu, 19 Sep 2013 00:03:44 -0700
Reply-To: neil n <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil n <musomuso@GMAIL.COM>
Subject: Re: solar charge controller
In-Reply-To: <CABx3TkW=v=XMN-0BDcpbLG9oEBzGU4BhziyFNbPHbEtT9cWtTQ@mail.gmail.com>
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thanks Ryan
I have to wonder how various degrees of cloud cover play into this.
While testing my setuo back home in vancouver bc, really dark cliud cover
seemed to hinder panel voltage output more so than a recent cloudy morning
in La Pine OR.
@ the OP. my epsolar 10 amp controller appears to keep voltage output
at a safe level
even in full sun, panel putting out max volts. It also has a low
voltage cutout. 12.2 volts
IIRC.
not saying its the one to buy though.
On 9/18/13, Ryan Press <ryan@presslab.us> wrote:
> The improvement in voltage regulation was due to the improved accuracy of
> the more quality unit, and is not really related to MPPT technology. On
> the cheap controller I was seeing voltages well in excess of 15V on a
> normal 70 F day. This is damaging to lead-acid batteries.
>
> For small systems < 200W I think MPPT technology isn't really needed as
> long as you're using an ~17 Vmp panel. Morningstar does have the
> "Sunsaver" or "Sunsaver Duo" which are PWM. This looks like a good option
> for the more budget minded.
>
> The reason I chose the MPPT model is for the LVD and load monitoring; the
> Duo model has no load connection. With the Sunsaver MPPT the LVD will cut
> off the house circuit when the battery is too low, saving it from damage
> due to over-discharge; this voltage is also programmable and load current
> compensated. I wanted the monitoring so my small Linux computer in the van
> can create graphs of the day's load and solar production.
>
> Yes, MPPT will have an advantage on cloudy days. There is a lot of hype
> around MPPT though, I'm a bit skeptical of the claims of vastly improved
> efficiency. In my experience the Vmp of the panel doesn't change the much
> on cloudy days. I'd guess that MPPT will harvest perhaps 20% more than a
> PWM controller in adverse conditions, and not that much better in full
> sunlight. One thing that MPPT does allow is more flexibility in panel
> selection, as you're not limited to a ~17 Vmp panel.
>
> Ryan
>
>
--
Neil n
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