[RE-wrenches] Charging voltages

[Kirpal Khalsa]

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
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