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

[Chris Mason]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20120720/906b281b/attachment-0003.html>