Hi All, I have been trying to get to the bottom of the NiFe for RE controversy. To compare apples to apples on performance, longevity, durability, and cost. I've been studying all of the posts and flame wars back and forth. It's all very confusing. But in sifting through all of the "detritus", I did manage to find a few kernels of corn. I gotta ask ..... anybody ...... Uhmmm ...... so tell us already .....A lot of people would really like to know the details of this. So ...... Can we have the supplier details? Publicly or privately? This is a close duplicate of a post I just made on another RE forum. I'm not trying to spam or piss anybody off. Admins .... please be nice. I just want to get a little wider dissemination of my two main questions listed above. Below is my research and thinking process to date. -----------------------------------------------LONG READ----------------------------- So here are the givens. 16 degrees latitude. Tropical. Annual average temperature is +85 degrees. Tremendous solar resource. 4200W of panels. Adjusted manually once a month. 2X Outback FM60 Charge controllers. 12, 24, 36, 48 or 60VDC @ 60amps continuous. 1X Outback VFX3648 inverter. Operates on 44 – 64VDC Battery space/ventilation is not a concern. Battery warranty is not a concern. Located way out in the jungle. Its not like I am going to ship any of these batteries back to the world. 500ah Target battery bank. Please correct me if my Storage System comparison is incorrect. Deep Cycle Flooded Lead Acid. ------------------- 1.) List price at wholesalesolar (Rolls 5000 series 6v X 8 in series. 6CS-17PS) is $811.00. Times 8 = $6411 2.) Currently most widely used chemistry for RE systems. Large knowledge base. Lots of manufacturer support. 3.) Least expensive of storage chemistry used in RE system. 4.) Lifespan is a function of a combination of materials used, operating environment, and depth of discharge. Typically 3 -> 15 years. 5.) Usable energy stored is in the top 20% of bank capacity. So a 500ah flooded lead acid battery really only has 100ah usable. Repeated DOD greater than 30% shortens the lifespan of the battery. Repeated discharges beyond 50% DOD can be life threatening. Rolls surrette series 5000 gives a value of 4500 cycles @ 30% DOD. 12.32 years. 6.) High energy density. Reduced footprint. 7.) Must be stored charged and be charge topped off or trickled periodically. 8.) Storing or repeated undercharging below 80% of battery capacity causes sulphation which can be partially mitigated by equalization charging. See #16 9.) Overcharging causes electrolyte to gas out and plates to shed material. Lowering the capacity of the battery or shortening its lifespan. See #16 10.) Electrolyte cannot be added to a cell once it has been activated. If your electrolyte boils out or spills the cell WILL have a shortened lifespan. See #16 11.) Heavy charging or discharging causes plates to malform potentially causing cell shorts or opens. Once again See # 16 12.) Requires regular watering with good quality distilled water. 13.) Electrolyte is well understood, commonly available, and relatively inexpensive. 14.) Charging batteries in parallel causes unequal charging. Either overcharging or undercharging one of the parallel legs. Causes loss in capacity and lowered battery lifespan. See #16 15.) Cells in series are only as strong as the weakest cell. 16.) If a cell in a multi battery string goes bad you cannot just plug in a replacement battery. If you connect in new cells with different capacities in series either the older, (weaker) ones swing between overcharged and deep discharged until finally defective and/or the stronger ones stay undercharged and sulfates. So if a single cell goes bad in your bank you are looking at a cascading loss of bank lifespan and replacement of the entire bank. 17.) If the battery plates are exposed due to electrolyte loss the exposed area of plate no longer functions. And cell capacity is diminished. See # 16. 18.) Battery capacity increases as temperature goes up. But battery life is reduced - for every 15 degrees F over 77, battery life is cut in half. So for me my bank lifespan is reduced by 26% just because of my locale. From 12.32 to 9.12 years. Nickle Iron Batteries --------------------- 1.) BeUtilityFree (Changhong) = $20,160. IronEdison (Changhong) = $17,000, Zappworks (Cleaned Edison cells) = $29,000 40 1.2v cells. 2.) Not well known in RE circles. Highly controversial. Virtually no manufacturer support. 3.) Lifespan is a function of the materials used, operating environment, and depth of discharge. Typically 3 -> 70+ years. The difference in battery chemistry introduces the concept of "electrolyte lifespan". As Battery elements themselves are robust to abuse, the electrolyte becomes the entropic agent. 4.) 100% of energy stored is usable .... If you can find the equipment to extract it. Current manufacture of NiFe cells are rated at 6000 cycles for 30% DOD or 16.4 years. So to create a similar comparison, 4500 cycles for 40% DOD or 9.12 years. I can pull 200 usable ah out of a 500 ah NiFe battery bank. This suggests that I can accomplish the same useful energy storage with a 300ah NiFe battery bank. 5.) Low energy density. Large foot print. 6.) Can be stored discharged. 7.) Repeated undercharging does not damage the battery. 8.) Repeated overcharging can cause carbonization, lower capacity, and lower electrolyte lifespan. Cells can be cleaned and refilled with electrolyte and capacity regained. 9.) Batteries suffer from iron poisoning of positive plates. This can be lessened but not solved by the addition of Lithium Hydroxide to the electrolyte. 11.) Electrolyte can be added to a cell once it has been activated. 12.) Requires regular watering with good quality distilled water. More water than Lead Acid cells do. 13.) Electrolyte is not well understood, not commonly available, and relatively expensive. Lithium Hydroxide additive is VERY expensive. 14.) Charging batteries in parallel causes unequal charging. It can cause loss in capacity and lowered electrolyte lifespan. 15.) Cells in series are only as strong as the weakest cell. 16.) If a cell in a multi battery string goes bad you can just plug in a replacement battery. 17.) If the battery plates are exposed due to electrolyte loss the exposed area of plate no longer functions. And cell capacity is diminished. Plates are not damaged. Electrolyte will carbonize and must be replaced. To ensure a hermetic seal a "float oil" of special manufacture or food grade mineral oil topping the electrolyte is often recommended. 18.) As temperature goes up, electrolyte lifespan is reduced - for every 9 degrees F over 77, electrolyte life is cut by 20%. For my locale I can shorten my electrolyte lifespan from 16.4 to 13.2 years. ----------------------- Traditional cost analysis would state this as a time/cost problem. An apples to apples comparison would be between a ..... 500ah 8 batteries at 6vdc - 3 cells each Rolls Surrette bank at 30% DOD, and a 300ah 40 cell 1.2vdc Nife bank@ 40% DOD. 6411/9.12 = $702.96 per year for power storage. At the end of lifespan dispose of existing bank and repurchase a replacement bank. 10,650/9.12 = $1167.76 per year for power storage. At the end of lifespan drain and clean cells, replace electrolyte. $465 per year price difference. $4240 total for the lifespan of the bank. Add to that the cost of replacement electrolyte of $500 (overseas prices). Equals $4740. If longevity reports are to be believed, you will save approximately $1600 at the end of the 9.12 year time frame. And yes for purposes of this comparison it is a perfect world and the vendors never "mis-state" their facts. --------------------END LONG READ------------------------------------- Please correct and offer any sincere info here. I'll edit the breakdown to correct/add/update as needed. Thank you for your time.
Bill replied in a PM. Any Rolls dealership should be able to provide truly dry Surettes for a surcharge. The system Bill had imagined was a copy of the submarine systems used by the navy. Thank you Bill
