[RE-wrenches] FLA battery setpoints with larger arrays

Dan Fink danbob88 at gmail.com
Fri May 22 10:17:16 PDT 2015


Bill; The Whizbang can mount on the main shunt, and has an included
mounting option that lets you piggyback the wires from another amp-hourt
meter on it. I have mine with a magnum ME-BMK piggybacked on it.

Dan Fink
Buckville Energy
IREC Certified Instructor™ for:
~ PV Installation Professional
~ Small Wind Installer
NABCEP / IREC / ISPQ Accredited Continuing Education Providers™
970.672.4342



On Fri, May 22, 2015 at 8:28 AM, frenergy <frenergy at psln.com> wrote:

>  Hey Jay,
>
>         From what I've heard form battery manus, the C rates likely
> even in a well PV-ed system still will not produce C-rates high enough to
> approach a high or "longevity reducing" internal battery temp, assuming a
> typical bulk, absorb, float cycle.  Of course, battery environmental
> location (typical temps) would set a baseline from which batt temp would
> rise from.  Here in the Sierra, ambients are not very high 95% of the time.
>
>         Just curious, how does the wiz bang account for all loads...2
> shunts?
>
> Thanks,
>
> Bill
> Feather River Solar Electric
>
> ----- Original Message -----
> *From:* jay peltz <jay.peltz at gmail.com>
> *To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
> *Sent:* Thursday, May 21, 2015 8:07 PM
> *Subject:* Re: [RE-wrenches] FLA battery setpoints with larger arrays
>
> 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 <allan at sindelarsolar.com>
> 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*
>> allan at sindelarsolar.com
>> 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
> jay.peltz at gmail.com
>
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