[RE-wrenches] 24V charging with 60 cell modules

Tue Jun 4 11:34:31 PDT 2013

I know this isn't Facebook, but if there were a 'like' button, I would
click it.

This is probably a more common question than we realize, and I agree with
the answer by Allan/Bob-O. I wonder if we could convince Solar Converters,
Inc. to make a cost effective and flexible DC converter to boost the PV
voltage and make this possible.

*Jason Szumlanski*

*Fafco Solar
*

On Tue, Jun 4, 2013 at 1:34 PM, Allan Sindelar <
allan at positiveenergysolar.com> wrote:

>  Eric,
> Please explain further, as what you wrote makes no sense to me. Mac didn't
> indicate whether he wanted to charge a flooded battery (~29.2V) or sealed
> (~28.4V). The C-series of PWM controllers has a fixed two-hour absorption,
> which it only counts down once the bulk voltage is reached. If the bulk
> voltage setpoint is above the MPP of the module, as it is in this case, how
> can it ever reach float, as you suggest?
>
> And further, this is spec-sheet calculation. In all but the coldest winter
> weather, the Vmp of the module will be lower still as the module
> temperature rises above 25ºC, and is likely to be even below the float
> voltage in hot weather. And in the winter, if the battery is also cold, it
> will need a higher voltage still to get fully charged.
>
> So I'm with Bob-O on this one. You can't charge a 24V battery with a 20V
> module. Please tell us how I'm wrong.
> Thanks, Allan
>
> P.S. - And while I'm on a virtual roll, please tell your engineering folks
> to build a charge controller with a higher voltage input window. I don't
> mean 600 volts at $1,500 or whatever it is; just higher than 150V. On a 48V
> system, we're stuck with series strings of three modules if we use the
> lowest-cost-per-watt 60-cell modules. That means that systems have to be
> designed with arrays in ~750-watt increments. Give us another 50-100V or so
> of headroom, so we can design with strings in multiples of 3, 4, or 5.
> Outback, are you listening too? The Midnite Classic does this for us...
> Thanks.
>
>  *Allan Sindelar*
> *Allan at positiveenergysolar.com* <Allan at positiveenergysolar.com>
> NABCEP Certified Photovoltaic Installer
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder and Chief Technology Officer
> *Positive Energy, Inc.*
> 3209 Richards Lane (note new address)
> Santa Fe, New Mexico 87507
> *505 424-1112*
> *www.positiveenergysolar.com* <http://www.positiveenergysolar.com/>****
>
> *****************
> *
>
>  On 6/4/2013 10:43 AM, Eric.Bentsen at schneider-electric.com wrote:
>
>
> Hi Mac,
>
> A PWM charge controller, such as the C35, will work in this application,
> because it will
> act like a switch that connects the panel to the battery. While the bulk
> voltage will likely be slightly
> higher than Vmp, once the controller transitions to float, which is approx
> 27V for most battery types,
> it should allow the module to operate very close to Vmp.
> Typically, MPPT controllers require a higher Vmp than the target charge
> voltage.
>
> Eric Bentsen
>
> _____________________________________________________________________________________
> *
> Eric Bentsen*  |  * Schneider Electric **  |  Solar Business*  |   *UNITED
> STATES*  |   *Technical Support Representative* *
> Phone:* +(650) 351-8237 ext. 001#  |   *
> Email:* *eric.bentsen at schneider-electric.com*<eric.bentsen at schneider-electric.com> |
> *Site:** www.schneider-electric.com/solar*<http://www.schneider-electric.com/solar> |
> *Address:* 250 South Vasco Rd., Livermore, CA 94551
> *
> * <http://www.schneider-electric.com/solar>
> *** Please consider the environment before printing this e-mail
>
>
>
>   From: Mac Lewis <maclewis1 at gmail.com> <maclewis1 at gmail.com>  To: RE-wrenches
> <re-wrenches at lists.re-wrenches.org> <re-wrenches at lists.re-wrenches.org>
> Date: 06/04/2013 08:05 AM  Subject: [RE-wrenches] 24V charging with 60
> cell modules  Sent by: re-wrenches-bounces at lists.re-wrenches.org
> ------------------------------
>
>
>
> Hello wrenches,
>
> Is there a good method to charge 24V battery bank with single 60 cell
> modules?  Ideally, I'd like to charge a 24 V bank with a Kyocera 245GX-LFB.
>  However, at NOTC the Vmp is 26.8V.  Any good way to do this?
>
> Thanks in advance.
> --
>
>
>
> Mac Lewis
>
> "Yo solo sé que no sé nada." -Sócrates
>
>
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