Hi Allan, I like the classic/wiz bang jr. This allows really good end amp control as all loads are accounted for.
Higher C rates equal higher internal temps which definitely will shorten the life. On Thu, May 21, 2015 at 10:56 AM, Allan Sindelar <[email protected]> wrote: > Wrenches, > In the last few years I have changed my approach to off grid system > sizing, primarily due to higher battery costs and lower module costs. > Rather than shooting for a traditional 80-90% of winter load profile > target, I will size a larger array and smaller battery bank, figuring > (especially here in the sunny Southwest) that batteries will recharge more > quickly, will spend more of their time full (and thus last longer), and > will be at least partially charged during cloudy weather. This even allows > for smaller battery banks that are cycled more deeply (as long as there's a > backup gennie in the mix); the lower cost of a smaller size may allow for a > set of higher-quality industrial cells. > > I first began to rethink my design approach after reading Christopher > Freitas' Solar Pro article on large battery banks a few years ago. Being > able to refill in a day was part of his strategic approach to battery bank > design. I used and wrote about this approach in my tiny house article in > the current Home Power. However, I'm just beginning to get owner feedback > about greater water consumption and the need for more frequent watering. > This is especially the case when I add array to an existing system, and the > old watering schedule is suddenly not enough. > > When I design new systems I now encourage larger arrays and smaller > battery banks, as the batteries spend more of their time happily full and > recover more quickly after a discharge period. But I am thinking that I > will have to begin changing charging setpoints in response. Flooded > batteries have a range of recommended bulk setpoints, from 28.8 to 29.6 > volts on a 24V system. When arrays were smaller we set to the higher end of > the range to take advantage of topping off when available, and a two hour > or longer absorption was considered beneficial, as long as the CC could > transition to float at 2% of capacity or so. With a larger array a better > approach may be to lower the bulk/absorption setting, as well as reduce > absorption time and raise the float transition current ("done amps"). > > I'm writing to encourage a discussion among off grid Wrenches. Are you > changing the relative relationship between array and battery capacities? If > so, how are you adjusting charge controller setpoint programming? For > example, how would you program a Midnite Classic, Outback FM or Schneider > XW if you could achieve a C/10 or C/15 charge rate? > > Thanks, Allan > > *Allan Sindelar* > [email protected] > NABCEP Certified PV Installation Professional > NABCEP Certified Technical Sales Professional > New Mexico EE98J Journeyman Electrician > Founder (Retired), Positive Energy, Inc. > *505 780-2738 <505%20780-2738> cell* > > > -- Jay Peltz Peltz Power [email protected]
_______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
