Date: Wed, 18 Sep 2013 10:31:37 -0700
Reply-To: Ryan Press <ryan@PRESSLAB.US>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Ryan Press <ryan@PRESSLAB.US>
Subject: Re: solar charge controller
In-Reply-To: <CAB2RwfiSUPcc1qxxRRC9gNcgLPUWWGfWZgaqpLkNfjxb0Y1crQ@mail.gmail.com>
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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
On Wed, Sep 18, 2013 at 9:28 AM, neil n <musomuso@gmail.com> wrote:
> Was the improvement in regulation due design improvements (pwm vs mppt), or
> overall improvement in quality and design of your newer charge controller?
>
> My inexspensive EPsolar PWM controller works but given that cloudy days do
> happen, would a better designed PWM help harvest more power on cloudy days?
>
> As we know, MPPT controllers tend to be relatively pricey. ;)
>
> Neil.
>
>
> On Wednesday, September 18, 2013, Ryan Press <ryan@presslab.us> wrote:
> > On Tue, Sep 17, 2013 at 7:35 PM, Timmy Evens <monkey_lips@yahoo.com>
> wrote:
> >
> >> what brand/model charge controllers do folks recommend?
> >
> >
> >
> > I tried a couple cheap controllers and they all had poor voltage
> > regulation. This will decrease the life of the battery. I ended up with
> a
> > Morningstar Sunsaver MPPT, I got mine for $200. Very happy with it.
> >
> > http://www.morningstarcorp.com/en/sunsavermppt
> >
> >
>
> --
> Neil n
>
> Blog: tubaneil.blogspot.ca
>
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>
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>
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