To All,
Great insight on the lithium movement. I do am looking for anyone
dealing with the new Aquion batteries. I’ve got a couple of potential clients
that have inquired about them. Saw them at a NABCEP training session last
spring and while the idea is moving I wasn’t impressed. Perhaps it’s time to
start a new thread, “Aquion batteries”.
Thanks,
Christopher
From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf
Of d...@energysolarnow.com
Sent: Friday, 29 January, 2016 00:49
To: Dan Fink
Cc: re-wrenches@lists.re-wrenches.org
Subject: Re: [RE-wrenches] LiFePO4; WAS Availability of Powerwall Batteries
Thanks for sharing your experience with these batteries, Dan.
I have similar SOC issues with an off-grid customer who has the Aquion Hybrid
Ion batteries.
It has difficulty reaching full charge from solar, requiring the genny to kick
on each morning even in the summer.
This is even worse in cold winter weather.
Your explanation of the change in Peukert's exponent above 80% SOC with NiFe
batteries sounds like what is happening here as well.
Do you have any experience with Aquion batteries that you can share?
Thanks
Don Barch
Energy Solar
d...@energysolarnow.com
Message: 2
Date: Mon, 25 Jan 2016 15:51:26 -0700
From: Dan Fink <danbo...@gmail.com>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Subject: Re: [RE-wrenches] LiFePO4; WAS Availability of Powerwall
Batteries
Message-ID:
<CAF+3LndeD2av3Ji9CPRZi1mrw04ohFCk2UgMtu=rowlpr3r...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hello Mark;
My NiFes went in last March, I'm almost at a year living with them off the
grid.
To avoid writing a novel here I'll group my comments into Oddities,
Advantages and Disadvantages.
Advantages:
~ at least 25 year lifespan
~ 10 year warranty
~ Can add more parallel strings at any time/age, just drain and replace
electrolyte of old batteries
~ 80% depth of discharge no problem, so can size smaller amp-hour capacity
Oddities:
~ alkaline electrolyte, neutralize spills and clean tops with white vinegar
~ Specific gravity of electrolyte does not change with state of charge so a
hydrometer is useless
~ Charge / discharge efficiency changes greatly with state of charge.
Sometimes my Magnum ME-BMK amp hour meter matches the Midnite Whizbang Jr
exactly, sometimes they are way off from each other. For ground truth, the
state of charge vs. voltage curve from the battery manufacturer seems right
on, not counting false readings when the batteries are not at rest for a
couple hours.
~ Fooling PV MPPT charge controllers into dealing with NiFes involves
setting a very long and high Absorb voltage
~ Charge efficiency is great up to 80% state of charge, but after that
drops way off. Above 80% SOC these batteries want to see 1.65v per cell to
really fill up. No problem for modern MPPT PV controllers, but-
~ Some inverter / chargers (Magnum here) freak out and shut down at 1.6v
per cell, so the solution from the battery manufacturer is-
~ Run fewer cells during times of year when charging is frequent from the
generator, put the extra cells back in the string during times of year when
the charging is mostly PV. Sitting uncharged does not damage these "extra"
cells.
~ So I am running a 10.8v battery bank right now, will bring it back to 12v
this spring. No big deal, but does affect inverter surge capacity. Would
not be as much of a problem at 24v or 48v.
~
Disadvantages:
~ The high Absorb voltage to get that last 20% SOC efficiently bubbles
through a lot of distilled water. My schedule is 1-2 gallons every 40 days,
and the company sends a reminder email at that interval.
~ The bubbling gets the tops dirty fast. A cleaning every 40 days is about
right.
~ High cost
~ Twiddling with string voltages semi-annually. This would not be an issue
if most charging is from PV.
My thoughts:
My overall impression of being married to NiFes way off the grid has so far
been favorable.In a grid standby situation, I think string voltage
twiddling would be a non-issue, who cares about the last 20% of SOC charge
efficiency in that situation? Off the grid with daily cycling, generator
use, etc, I would not consider these to be batteries for off-grid
beginners. But anyone who has been off grid for a few years with lead acid
batteries will immediately appreciate the advantages and only occasionally
curse the quirks of Nife.
Plans here: Increase my PV by about 30%. Cheap and easy, no more taking
cells in and out of the string, and less winter generator run time. Get 'em
to 80% on genny during tough snowbound times and let PV do the rest. Figure
out some Arduino solution for monitoring when Peukert's exponent changes
depending on SOC. Complain to inverter/charger manufacturers to make them
work better with NiFe.
Best regards;
Dan Fink
Adjunct Professor, Ecotech Institute
IREC Certified Instructor? for:
~ PV Installation Professional
~ Small Wind Installer
Executive Director, Buckville Energy
NABCEP Accredited Continuing Education Providers?
970.672.4342
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