I agree with William, SOC is just a calculation, that can change with
temperature, age of batteries, and even when the last full charge
occurred. We just had trouble with an inherited Sunny Island system that
only allows gen start settings based on SOC. The actual battery SOC
didn't correspond to the programming after a while, and the dumb thing
would shut off due to low voltage, BEFORE starting the generator. Then
being AC coupled, you also have disabled the PV charging source.
Triggering gen start off SOC and having your array AC coupled is a
RECIPE for disaster, speaking of Cooks in the Kitchen, William.
Ray Walters
Remote Solar
303 505-8760
On 1/8/21 4:24 PM, William Miller wrote:
Mick:
Here’s a thought: If the system has an FNDC, the charging may be
programmed to terminate at a specific SOC. I have been told by OB
tech support, and I believe this, that using SOC and battery voltage
over time and/or charge taper to control charging is like the old
adage, “too many cooks.”
My understanding is the best parameter for terminating an absorption
charge is charge taper, if your system has this option. Taper is the
best indication of complete charging. This is typically set at 3% of
the 20 hour AH rating. All other charge termination options should be
disabled.
Too many charge termination “cooks” may be the cause of your problem,
Mick and the problem Drake posted I believe just today.
I have been meaning to write some thoughts on the very concept of
SOC. As I understand it, SOC is a calculated value, using AH in
versus AH out and adjusted for charging efficiency. I believe this
process has a high probability for inaccuracy because the actual
efficiency value is a moving target. It changes with temperature,
battery charge state, battery age and probably other factors. This
belief is reinforced by the fact all of these SOC measuring systems
must have a built in recalibration that typically occurs when some
voltage over time condition is met. The default values for this reset
to 100% SOC are deliberately too low to ensure calibration actually
occurs, but it gives clients an inaccurate impression of when battery
charging is fully accomplished.
Way too often I have seen clients manually terminate generator
charging of a battery bank prematurely because they see the SOC is
100% and yet their generator is still consuming fuel and making noise,
something they do not want to occur unless they know it is required.
This means batteries do not get the absorption time they need for a
long life span.
I have contemplated discontinuing installation of FNDC units for this
reason. In fact, the only benefit I see to an FNDC unit is to allow
battery parameter logging. I tell my client to ignore any number
followed by a % sign. I am BCC-ing several clients on this post
because I want them to have more background on why I say this.
I am interested in what others think about the benefit, or lack
thereof, of using derived SOC values.
William
PS: I would not assume a recently purchased system has the latest
firmware.
Wm
Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com <http://www.millersolar.com/>
CA Lic. 773985
*From:*RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>] *On Behalf Of
*Mick Abraham
*Sent:* Friday, January 8, 2021 12:46 PM
*To:* RE-wrenches
*Subject:* [RE-wrenches] Radian Charges 1 hour per calendar day
Happy Friday, Mechanix~
Drake Chamberlin wrote about the Radian inverter that began running a
"too short" absorption interval after several years of normal
operations. Drake said the possible culprit is inverter firmware per
Outback; I wish to add a data point & follow up questions:
I sold an Outback SE-830BLU-300AFCI Systemedge Package--which includes
Outback batteries & all for quick deployment--to a longtime retail
client in the Autumn of 2020. Firmware seems likely to be the latest
version on all components since it shipped from OB so recently. The
client's internet service to the site was lost along with everything
else in a CA wildfire--so I can't look in remotely & I can't
physically travel to the site. He has much prior experience with
inverter/chargers, off grid living etc. but he's new to the Radian,
Mate3s, etc.
My off grid client reports his new Radian is shifting to float before
the Absorption target voltage is even reached & the shift occurs
around 56.1 volts battery voltage on the way up. The battery is cool,
not warm. He's been through the menus & couldn't find a likely suspect
for this behavior. The FM100 PV controller on the same system is able
to push the battery to the absorption target then hang there as would
be expected before it shifts to float. That's if the daylight lasts
long enough, of course. As with Drake's client, my friend needs to be
able to pump the battery to a higher state of charge with his
generator than what he's getting. His upscale (but lead acid) Outback
BLU batteries we bought in the package seem at risk of harm due to
this problem--& I'm sure Drake has similar concerns. I asked the
client to reboot the generator AC (breaker off, then back on) to see
if he could push the battery closer to the absorb voltage that way but
I am still waiting for that answer.
Thanks to the clues & cues from Drake, I'll cut & paste this into a
trouble ticket with OB. While waiting for that to percolate through
the system, here's one more question for the hive mind:
* When a Systemedge Package is purchased complete with batteries &
all, are the chargers & the FNDC battery monitor already
pre-programmed for the battery type & size? Here's hoping, and as
always, the Wrench List is the Bomb!
Mick Abraham, Proprietor
www.abrahamsolar.com <http://www.abrahamsolar.com>
Landline: 970-731-4675
Cell phone or for text messaging: 970-946-6584
ᐧ
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