Hi Bill;
If the battery is in an insulated box indoors, it definitely can over
heat. Also if ambient temps get into the 90s, the additional heat from
charging can push the battery into the danger zone. In hot desert or
tropical climates, it may actually be difficult to keep the battery
below 105F.
I'm very glad to hear Midnite added the high temp disconnect to their
system. They may have saved a life.
Bob, is battery temp logged, so we could see how often a system quits
charging for high temp, and just what the battery temps are running?
Many of our systems may need additional cooling. A recent HUP install
in Haiti comes to mind.....
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 5/22/2015 8:28 AM, frenergy 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 <mailto:jay.pe...@gmail.com>
*To:* RE-wrenches <mailto:re-wrenches@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
<al...@sindelarsolar.com <mailto:al...@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*
al...@sindelarsolar.com <mailto:al...@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 <tel:505%20780-2738> cell*
--
Jay Peltz
Peltz Power
jay.pe...@gmail.com <mailto:jay.pe...@gmail.com>
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