[RE-wrenches] Small battery bank vs too large array

Philip solarphil at gmail.com
Fri Jul 20 22:11:41 PDT 2012


Page 127 of the Mate3 manual.

Phil




On Jul 20, 2012, at 7:49 PM, Chris Mason <cometenergysystems at gmail.com> wrote:

> Is there a document available on how this world?
> 
> On Friday, July 20, 2012, Phil Undercuffler <solarphil at gmail.com> wrote:
> > Hi all, I just got a correction from Darren - global charge control is in the Mate3, and therefore works with any FM or MX controller that has the GT mode. It uses the current sense from the FN-DC and the GT mode signal to control the output of the controllers.
> >
> > Sorry for any confusion
> >
> > Phil
> >
> > On Jul 20, 2012 4:11 PM, "Chris Mason" <cometenergysystems at gmail.com> wrote:
> >
> > Phil,
> > Good explanation of the feature. When did GCC make it into the firmware, and can the older ones be updated? It sounds like a perfect solution for some of my installations.
> >
> > On Fri, Jul 20, 2012 at 12:34 AM, Phil Undercuffler <solarphil at gmail.com> wrote:
> >
> > OutBack implemented Global Charge Control in the FM charge controllers
> > a while back, based on the input of the good folk at SELF who worked
> > to power a number of hospitals and clinics in Haiti after the
> > earthquake.  In some of those systems, the PV array was based on the
> > typical running consumption of the hospital, in the 30 - 100 kW if I
> > remember right, and the battery bank was relatively modest. However,
> > on the weekends and holidays without the normal AC loads the PV input
> > was considerably more than the battery could absorb without
> > destructive heating, something like a C2 or C5 rate.
> >
> > Global Charge Control is implemented using the MATE3, a FN-DC and FM
> > charge controllers set to GT mode.  You set a high charge current
> > limit in the M3, and then it monitors the charge current going to the
> > batteries.  In normal operating mode the controllers stay in wide open
> > mode, harvesting as much power as possible.  However if the loads drop
> > and the total current from the charging sources begin exceed the
> > global charge limit, the system compensates and the controllers back
> > off to prevent sending too much current to the batteries.
> >
> > In today's world of PV modules being cheaper than diesel, we're seeing
> > a lot more systems that can use this tool.
> >
> > Hope this helps,
> >
> > Phil
> >
> >
> >
> > On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
> > <boB at midnitesolar.com> wrote:
> >>
> >>
> >> I didn't see that Brian T had the same idea until after I sent that email
> >> off to Allan...
> >> boB
> >>
> >>
> >>
> >>
> >>
> >> On 7/19/2012 7:53 PM, Allan Sindelar wrote:
> >>
> >> Wrenches,
> >> I forwarded Brian's post on to Robin at Midnite, as I thought it was an
> >> interesting idea. Below is his response, as well as boB's.
> >> Allan
> >>
> >> Allan Sindelar
> >> 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
> >>
> >> Allan, It is simpler than what is being suggested. The reason they want to
> >> limit to 20 amps is because the battery doesn’t need anymore than that. The
> >> controller will automatically limit the charge current as the battery gets
> >> full. If a large load is turned on, the controller will try to refill the
> >> battery up to its capacity. The 80 amps will quickly be reduced because the
> >> voltage will rise to the point where the charge tapers off.
> >>
> >> There is nothing else that needs to be done. If the problem is that the
> >> battery bank is too small for a big controller, the best answer is to get
> >> more batteries. A 80 amp charger into a 200 amp hour battery is going to
> >> raise the battery voltage so quick, it will not affect the battery at all.
> >> By the way, discharging a battery at 60 or 80 amps is probably going to do
> >> damage to a small battery also. We do have an input on the Classic that
> >> could probably be programmed to do as requested. That input feature has yet
> >> to be implemented. I’m sure we will have discussions about this when the
> >> time comes to write the input code. Maybe this feature will be designed in,
> >> but it doesn’t sound like it is a very good feature to spend a bunch of time
> >> on. After all, the main problem is that the battery bank is just too darned<
> 
> -- 
> Chris Mason
> President, Comet Systems Ltd
> www.cometenergysystems.com
> Cell: 264.235.5670
> Skype: netconcepts
> 
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