Brad Vietje wrote:... don't be lulled into thinking that a strong alkali is any better than a strong acid. In fact, some solar pro's are worried that the electrolyte could even be worse, since all you need to clean up a battery acid splash is baking soda. There are concerns that getting the alkaline solution in your eyes, for example, might be worse that hydrochloric acid.
Dave Redvalley wrote:I've been living with a bank of NiFe batteries for over a year now. I love them and won't be going back.
Fabrizia Annunziata wrote:Diego from Permaculture Voices had a podcast about those type of batteries a while back.
Dave Redvalley wrote:...I have my 24v bank set to cycle from 32v down to 18v. These things take the abuse and keep coming back for more. I replaced a 1400 amp lead acid bank with a 500 amp NiFe and we are using our genset about a quarter as much as the previous owners and our family is 3 times the size. Like I said I'll not be going back to lead batteries, this seems to be a perfect application for the NiFe technology.
Markku Salmela wrote:I got the battery bank with 50€ after it had been replaced from a locomotive diesel motor starter battery
Andrew Ray wrote:...I was able to find information on depth of discharge vs. life expectancy, and somewhere I even have notes about this, but I decided on the 27TMX because I should be able to discharge it to 50% with the fence charger and get 10 years of life out of it, and only need to charge it every two weeks (for dead-of-winter over cast days when the solar panel doesn't provide anything, never needing charging in the summer).
For lead-acid batteries, if it doesn't have in the documentation either some chart or at least table showing life expectancy at different depths of discharge then it isn't worth buying.
The 80% rule, AFAIK, is more for automotive batteries, which is why they suck for electric fence (unless you have a supply of free car batteries that no longer start cars, and then you can extend their useful life another 6 months or so...).
Andrew Ray wrote:AFAIK, vinegar should work. Suffice it to say the best protection for eyes are goggles, and worthwhile. My 7th grade science teacher, seeing that my passion for pyromania couldn't be dissuaded said, "Andrew, at least always wear eye protection." and this has stuck with me.
Dave Redvalley wrote:The biggest difference is the depth of discharge (DoD) that you can achieve with these batteries. Lead acid batteries should really only be discharged to 80% max, while the NiFe's can routinely be drawn down to 20% with no damage, thus the 3 times smaller battery bank, with better performance. I do like that math by the way, I see now problem with it at all! LOL. The only reason I have a 24v system vs. 48 or 12 is that is what it was when we bought the place. I would rather spend the money on the batteries than on replacing all of the inverters and switching gear. The 24v seems to be working good for us.
Brad Vietje wrote:As for the question about the battery bank voltage: most inverters are more efficient at 24 volts, and even better at 48 volts. Higher battery voltage affects the way the solar panels and batteries are wired, but higher voltage systems need smaller gauge wires and smaller gauge battery cables, and smaller gauge wire means a lot less copper or aluminum. If your solar panels are a long distance from the batteries and charge controller(s), you can save a LOT on wire by designing your system to operate at higher voltage. I have a few customers with solar panels about 300' away from the house, and when voltage drop and all that are factored in, they saved about $1000 on copper wire by using a 48-volt inverter.
Brad Vietje wrote:Hey Cam,
The Iron Edison batteries do look like great performers, but don't be lulled into thinking that a strong alkali is any better than a strong acid. In fact, some solar pro's are worried that the electrolyte could even be worse, since all you need to clean up a battery acid splash is baking soda. There are concerns that getting the alkaline solution in your eyes, for example, might be worse that hydrochloric acid.
The incredible long life is absolutely spot-on, though, and I agree that if there was greater demand, and more manufacturers, the price would be a lot more reasonable.
I own NiFe batteries, I have since 1994. I know them well. The BIG reason to NOT buy them, they are incredibly expensive, they are charging you 9x the price of a lead acid and guarantying you only 5x the life. NiFe batteries are VERY inefficient, which means a significant fraction of the energy you put in, does not get stored, something like around 25%. They are VERY VERY gassy, that is why there is such a huge head space on them to hold SO MUCH extra water, which MUST be distilled water ONLY. They have a high rate of self discharge, so if you just leave them there, they can loose 10% or more of their charge PER DAY.
so yeah...they have a very long life, but everything else they have is a huge disadvantage.
Richard Hauser wrote:In all the comments I haven't seen the one problem I've heard about NiFe and that is self discharge. i.e. If you just store them, they will go dead. Wikipedia lists self-discharge at 20-30% per month. That seems like a lot to me. I think the better storage system is micro-hydro or pneumatic. Either avoid an awful lot of nasty chemicals and are proven and popular technologies.
Steve Harris wrote:They have a high rate of self discharge, so if you just leave them there, they can loose 10% or more of their charge PER DAY
Richard Hauser wrote:
The first usable tech is microhydro, which is the pumping of water up to the top of a hill to store in a pond. On my property I have a 300' hill and if I could build a windmill to pump water from the stream at the bottom up to a pond at the top, I could then set up a microhydro generator which could then power the property as needed. On flatter ground, I agree that a tower could be used, but the stored energy would likely be too low to be of much use. Even with my situation the pond has to be very large to provide much storage, though I don't have good hold on what .001 MJ/kg is, (http://en.wikipedia.org/wiki/Energy_density) but you have to be at least a little impressed that once set up, it rains electricity. Also even if you don't setup microhydro, you can still use it for irrigation, so no effort is wasted. The disadvantages are that it is immobile, you need to have key situations in place to make it even possible and there will be pumping losses due to pipe friction and pumping inefficiencies. The advantage is that there is little or no self discharge and the tech is proven and used by the power companies.
The second tech is pneumatic storage which is also used by power companies. As stated pneumatic storage suffers from thermic losses due to compression and there will also be thermic losses at expansion. There will also be temporary thermic losses due to cold weather or possible over pressure losses due to hot weather. As for the the danger of energy storage, well that problem is universal. The more energy you store, the more danger you have. Even that pond on a hill can kill you. I think many of the issues can be mitigated by doing larger lower pressure storage. If you took a 500 gallon propane tank and then wrapped it with fiberglass for reinforcement and installed a pair of burst valves, you would end up with a storage system as safe as any battery and with minimal maintenance and care, one that could last nearly forever. As for the durability of an air pump, I would point you to an automotive AC compressor which can last decades, even in cars in Florida. The issues with reliability are related to use of home air compressors where they limit oil injection because many uses need "dry air". We want our air wet, which will go a long way in saving all the moving bits. On the flip side pneumatic storage can make use of stored thermal energy, so if you pipe the output of your pressure tank through a pipe that is heated by your RMH, but keep it under the smoke point for the oil, you turn that heat into usable energy. You could make this system mobile by storing the thermal energy in molten salts. Pneumatics are a proven technology is use all over the place. The Amish call it "Amish electricity" to power their kitchen appliances. You can buy a pneumatic chainsaw. Why not make a pneumatic tractor? They are making pneumatic cars and motorcycles. I understand that those are using extremely high pressure systems, but that is not a requirement, it just increases energy density.
The second tech points to the third tech, thermal storage. Nothing too crazy, but the phase change of melting Potassium Nitrate can store a lot of energy. This can then be converted using pneumatics, steam engines, Stirling Engines or Peltier chips.
The last energy storage is the one we are most accustomed to, wood. Wood has 1/3 the energy by weight as gasoline and that statistic still blows me away. To convert wood into usable energy we need to burn it and then use that thermal energy to run a motor: again pneumatics, steam engines, Stirling Engines or Peltier chips. Of the group the most efficient is the Stirling engine. These are generally dismissed as unworkable (the head of the Stirling Society has a diesel engine converted to a steam engine as a backup power source) but there is one thing that makes me think it is possible and accessible by this audience, rolling sock seals. You see most people build seals by creating close tolerances between machined parts, but as anyone who has seen an air piston on a truck brake will tell you, there is another way, use a flexible fabric to seal the two pieces together in such a way that the fabric unrolls to allow the piston to move. This system is used in both the Philips MP1002CA and in a new motor created by a company called Sunvention http://www.solarheatengines.com/2012/01/10/tamera-video-of-sunvention-sunpulse-engine/. The later uses the sun to heat oil to run the motor, but could also use a RMH to heat the oil to run the motor.
Richard Hauser wrote:
The first usable tech is microhydro,
The second tech is pneumatic storage
The second tech points to the third tech, thermal storage.
The last energy storage is the one we are most accustomed to, wood.
Richard Hauser wrote:
The last energy storage is the one we are most accustomed to, wood. Wood has 1/3 the energy by weight as gasoline and that statistic still blows me away. To convert wood into usable energy we need to burn it and then use that thermal energy to run a motor: again pneumatics, steam engines, Stirling Engines or Peltier chips. Of the group the most efficient is the Stirling engine. These are generally dismissed as unworkable (the head of the Stirling Society has a diesel engine converted to a steam engine as a backup power source) ...
Marcos Buenijo wrote:
The most cost effective alternative that I have seen so far is a new forklift battery. I priced a unit recently (see www.giantbattery.com). A 24 volt, 800 amp hour (at 20 hour rate), 1100 pound unit was quoted at $2453 with price including delivery in the continential U.S. There is a 7 year warranty on defects, and the battery is rated for 1500 full cycles. My research shows that 10 years is a conservative estimate for the operational life of these batteries in the off grid renewable energy setting. I've seen several accounts at 15-20+ years. The same company also picks up discarded batteries without charge, so you know they are recycling batteries for compensation. I did not verify, but it seems a significant discount on a new battery could be demanded when presenting a discarded battery in trade, and this should lower costs further.
A lot of lead acid batteries seem to die inside of 5 years in the RE setting. Long term battery costs get very high in that case. If the forklift battery will deliver 10+ years of service, and do so reliably (and all evidence I've seen shows that it will deliver), then it seems hard to beat. If anyone knows of a more cost effective alternative, then please let us all know.
NOTE: On the massive size and weight of a forklift battery, a practical solution for this seems to be placing the unit onto a platform on heavy casters. A battery could be delivered and placed onto the platform, then maneuvered to the desired location. I have moved large safes on several occasions using this approach, and I've found it to be a practical solution.
John Master wrote:Just found out about these batteries yesterday, cool old technology. Wondering how they do in the freezing cold, I see lots of conflicting information? What would performance be like at 0 deg c of one of the modern manufactured units? any problem with them working upside down, leakage?