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 On Mon, Jan 25, 2016 at 1:28 PM, <ma...@berkeleysolar.com> wrote: > Dan, > > Can you give us a quick over view of the ins and outs of the NiFe > batteries? > > Thanks, > > Mark Frye > > > > > > Marco; > > Winter storms, hurricanes, earthquakes, tornados, floods, etc. - backup > > power. Maybe load shaving as the utilities get more persnickety on time > of > > use upcharges. > > > > Of course for most folks, an infernal combustion generator is far more > > cost > > effective than batteries. But for an extended grid outage and with a > > critical loads subpanel installed, PV charges on sunny days, generators > > still need fuel which may be in short supply or inaccessible. > > So, preppers. Most are surprised at how little autonomy time they get > from > > a really expensive battery bank, but if it's TEOTWAWKI at least their > > solar > > "fuel" is free, minus the amortized cost of the battery bank. I get lots > > of > > phone calls from preppers who really need lithium prescribed by their > > psychologist far more than they need it in a backup battery bank...... > > > > Lithium batteries seem impressive on how long they can sit unused / > float > > with no degradation, but I'd rather let all y'all be the guinea pigs on > > them for awhile. I'm doing my part by guinea pigging NiFe batteries off > > the > > grid. So far, so good, and darned glad I now know their ins and outs > > compared to lead acid. I would have been horribly embarrassed if I'd done > > my first NiFe battery bank for a customer instead of for myself....I > chose > > NiFe here simply because of decades of historical data, I don't trust > > Lithium yet for longevity, but thanks Larry C and others on this list who > > have been doing lithium batteries for years and reporting their results > > here. > > > > This Wrenches List is the gold standard of good information! > > > > > > Dan Fink > > Adjunct Professor, Ecotech Institute > > IREC Certified Instructorâ„¢ for: > > ~ PV Installation Professional > > ~ Small Wind Installer > > Executive Director, Buckville Energy > > NABCEP Accredited Continuing Education Providersâ„¢ > > 970.672.4342 > > > > > > > > On Sat, Jan 23, 2016 at 1:28 PM, Marco Mangelsdorf <ma...@pvthawaii.com> > > wrote: > > > >> Aloha Larry, > >> > >> > >> > >> To take a step back…what’s the compelling value proposition from the > >> homeowner’s perspective to incur this non-trivial additional expense? > >> To > >> be blunt, what’s in it for them? Back-up power? First adopter mojo? > >> > >> > >> > >> Thanks, > >> > >> marco > >> > >> > >> > >> > >> > > _______________________________________________ > > List sponsored by Redwood Alliance > > > > List Address: RE-wrenches@lists.re-wrenches.org > > > > Change listserver email address & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > List-Archive: > > > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > > > List rules & etiquette: > > www.re-wrenches.org/etiquette.htm > > > > Check out or update participant bios: > > www.members.re-wrenches.org > > > > > > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > >
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