[RE-wrenches] Charging voltages

[Jesse Dahl]

Good info, I thought maybe the warm days the system might drag the voltage to low, that's why I asked.  

So, on to MPPT controllers.  Again limited use, so looking for some good info.  Kinda limited battery experience to be honest.  Just very small cabin/shacks.  Rewiring an array in this scenario would increase voltage to the controller, and the controller then sacrifice (for lack of a better word) voltage and increase the current?  Just looking at the ISC numbers of the array now it produces 69.2 at STC, would the re-wired array produce similar current but match programmed setpoints? 

Jesse
 

Sent from my iPhone

On May 13, 2013, at 9:51 PM, Kirpal Khalsa <solarworks at gmail.com> wrote:

> Jesse.....why wouldn't you wire at least 2 modules in series....this way you have less breakers to deal with, less cord grips if paralleling in a combiner box, less homerun cables to the combiner and you will also benefit from greater energy harvest in your MPPT conversion particularly during cold weather....
> If you go with 1 module strings and have hot weather your voltage sag in the summer you will be on the low edge of voltage window to properly charge a 24V battery bank.....
> i would check the charge voltage recommendations from the battery manufacturer for proper charging parameters....usually the voltage recommendations call for lower voltages than FLA batteries...may be helpful for being able to charge your sealed batteries from a single module.  It is still borderline...
> I have always believed that the 60 cell modules were a bit on the low side for 24V battery charging.  In the past that is what the 72 cell  modules were for....but those are fewer and farther between these days, except int he larger 300+ watt modules....
> If you had 9 modules i would even go with strings of 3....or if you want to get really efficient you could wire in strings of 4 with the Midnite Solar Classic 200 charge controller.....you would definitely be bumping into amperage limits.....but that is ok...
> good luck...
> 
> 
> Sunny Regards,
> Kirpal Khalsa
> NABCEP Certified PV Installation Professional
> Renewable Energy Systems
> www.oregonsolarworks.com
> 541-218-0201 m
> 541-592-3958 o
> 
> 
> On Mon, May 13, 2013 at 7:34 PM, Jesse Dahl <dahlsolar at gmail.com> wrote:
>> Hello,
>> 
>> I'm interested in charging voltages for AGM batteries. After my visit to the site mentioned in the battery box thread, I was thinking about the system.
>> 
>> New install, 8 solarworld 255s charging a 24V battery bank through a outback FM80 (MPPT) All 8 modules in parallel.
>> VOC - 37.8
>> VMP - 31.4
>> ISC - 8.66
>> IMP - 8.15
>> 
>> I'm interested in the setpoints people use for AGMs because it seems like this might be cutting it close to the setpoints based on the array voltage. Since the system is using a MPPT controller would it be better to increase the array voltage?
>> 
>> Battery bank is 6 12V 245ah east penn bats wired 3 strings of 2.
>> 
>> I haven't used sealed batteries outside my fish house and boat so I'm looking for some detailed info if I can get it.
>> 
>> Thanks a lot!
>> 
>> Jesse
>> 
>> 
>> Sent from my iPhone
>> _______________________________________________
>> List sponsored by Home Power magazine
>> 
>> List Address: RE-wrenches at lists.re-wrenches.org
>> 
>> Change email address & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>> 
>> List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>> 
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>> 
>> Check out participant bios:
>> www.members.re-wrenches.org
> 
> _______________________________________________
> List sponsored by Home Power magazine
> 
> List Address: RE-wrenches at lists.re-wrenches.org
> 
> Change email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
> 
> List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
> 
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
> 
> Check out participant bios:
> www.members.re-wrenches.org
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130513/90938603/attachment-0004.html>