Thanks Dan. You mentioned some excellent pointers. One advantage to using a 24 or 48 V system is that you don't have as bad of compatibility issues. Depending on the brand (and therefore the maximum charging voltage and maximum voltage tolerance specifications) you can flex the number of cells per string. You can't really do it with a 12 V battery because 10 cells in series is too high for a lot of equipment, and 9 cells is too low, but 9.5 cells would be just right for many brands. With a 24V system, you can use 19 cells, and with a 48V system then you can choose between 38, 39, and 40 cells depending on the equipment you're using.
I am using an Outback Radian inverter, and the charge voltage for a 40 cell battery would actually void my warranty if I were to fully charge it with the inverter still connected, so because of my equipment, I use 38 cell strings. Because of this string length, I can fully charge my batteries from a generator through the inverter if I wanted, but because I have finally added enough PV, I never waste the fuel to do it. I have heard that the XW inverters can actually handle the full 40 cell voltage so if you're doing your design around Ni-Fe batteries then that might be a better choice. Jay, As far as water use... my battery powers a micro-grid and my parent's commercial building so my water usage does not accurately reflect what a house may use but we could do some math and estimate it.... * My battery is 2000 Ah @ 48V (nominal) and my PV is 18 kW, I have a 7.2 kW Bergey windmill on a 160' tower, and I have to run my 22 kW generator for a few hours perhaps 10 to 15 days per year. 1. I have heard that with water consumption is more closely related to PV size than battery size (I am not sure about that). I use roughly somewhere around 20 gallons per month. If you were to combine all my power sources, perhaps it would be fair to say that it's the equivalent of having 20 kW of PV so I would estimate that you will use 1 gallon of water every month per kW of PV. 2. If we go by battery size, I use a gallon per 100 Ah @ 48V. So if you have a 500 Ah, 48V battery then maybe it would use 5 gallons per month. If you have a 400 Ah, 24V battery then perhaps it might use 2 gallons per month. * I think that #1 above would be more accurate. Perhaps if I were to calculate out my Wh/month of charging then that would be even more accurate.... but I don't think I'll do that today. These gas differently than Lead Acid batteries... Lead acid batteries only gas when you charge them above a certain voltage (the latter part of the charge) but Ni-Fe batteries gas during all phases of the charge cycle. That's probably a large factor of why they use more water than Lead Acid batteries. * I would be really interested to hear what other's water usage might be. Dan, have you monitored your water usage at all? * Dan, do you have the auto watering system? Iron Edison did a recall a couple years ago on their auto watering system because it could concentrate hydrogen so I ended up waiting a long time for mine. Now that I finally have it, I can just hook up the pump and watch it go. It is so much easier. Thanks, Kienan Maxfield Solar maxfieldso...@hotmail.com<mailto:maxfieldso...@hotmail.com> (801) 477-0-SUN (477-0786) (801) 631-5584 (Cell) ________________________________ From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> on behalf of Jay <jay.pe...@gmail.com> Sent: Thursday, November 22, 2018 8:42 AM To: RE-wrenches Subject: Re: [RE-wrenches] Ni-Fe update? Hi Dan and Kienan I’m curious how much water you are adding monthly? Jay Peltz Power. On Nov 22, 2018, at 7:08 AM, Dan Fink <danbo...@gmail.com<mailto:danbo...@gmail.com>> wrote: Wrenches; I have run my house on 12 volt NiFe batteries for 3 years now. I was going to write a long essay, but Kienen beat me to it. It's an excellent analysis, I agree with each of his bullet points. All I'll add is that the batteries charge with decent efficiency up to 80% SOC. To get that last 20%, they do require 1.65 volts per cell, which most standalone inverter / chargers won't do off a generator - they freak out at a bit above 15v and shut down. I've used 2 tactics to get that last 20% when using a generator, and I have experienced the same issue that Kienen mentioned -- they need to get a nice strong, charge cycle every so often or else they will behave like a heavily sulfated FLA, but of course the NiFes don't sulfate. 1) after charging to 80% SOC with the generator, both of my charge controllers (outback and midnite) have no problem being programmed to a 16.5v absorb cycle, I set absorb at 6 hours, on a sunny day that does the trick here. 2) If no long, sunny day available and you are forced to use a generator and charger that won't let you get to 16.5v, remove one cell from the series string, and charge the other 9 cells. Then put the one you removed back in the string, and remove one of the ones you discharged, and generator charge again. Then re-assemble back into a 10-cell string. I've only had to do this a couple times. In general, I'm happy with these batteries, and happy to never have to deal with sulfation again, and remember I have the worst case scenario here with a 12v bank, undersized because of the greater DOD capability of NiFes, a refrigerator that surges very hard, and a magnum inverter that goes wonky with big surges at low voltages. I would sell Iron Edison NiFes to a client...but unless they are a special sort of off-grid 12v person, I'd only do 48v because of the surge issue. Dan Fink Professor of Solar Energy Technology, Ecotech Institute IREC Certified Instructor™ for: ~ PV Installation Professional ~ Small Wind Installer Executive Director, Buckville Energy NABCEP Registered Continuing Education Providers™ NABCEP PV Associate 970.672.4342 On Wed, Nov 21, 2018 at 11:35 AM <d...@foxfire-energy.com<mailto:d...@foxfire-energy.com>> wrote: Hi Guys, I have a potential customer inquiring about installing a pre packaged Iron Edison system.. I recall hearing strange stories about Ni-Fe batteries but don't recall the specifics. I have done a few searches with mixed results.. And have friends advising I run like a Rabbit.. Thought I'd run it by you folks for an update.. Thanks, and Happy Turkey Day. db Dan Brown Foxfire Energy Corp. Renewable Energy Systems (802)-483-2564 www.Foxfire-Energy.com<http://www.Foxfire-Energy.com> _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org> _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org<mailto: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<http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org>
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