Asian batteries. 122Ah at 12V runs $840.
122AH Lead Acid deep cycle batteries in the UK are over £100 so NiFe with a life of 20 to 50 years seems financialy viable.
Brian [ Parent ]
Golf cart battery is 225 at 6v or near equal to the 122ah 12v. Current report of golf cart battery cost is $67 (@sam's? Or Costco?
NiFe $840 / $67 = 12.5 sets of golf cart batteries.
Assuming golf cart battery last 7 years, for the same money have Life of 12.5 * 7 = 87.5 years for the same money. Anything past 50 years is no concern to me, don't expect to be here! Golf cart battery life I hear is 3 to 7 and more years, depends on battery care. Mine is 3 years old still going.
Charging efficiency for NiFe is low at 70%. Lead acid is 91% when SOC blow 80% dropping down as SOC goes up. Charging system must be 120% to place same charge in battery. Solar this is very expensive, wind maybe no big deal?
Summery NiFe is interesting, currently price and needs it's too expensive in several ways.
Have fun, Scott. [ Parent ]
Part of being off-grid for many people on this board is independence and self-reliance. Lead-acid batteries are basically a consumable, so the permanence of ni-fe batteries are quite attractive and worth some premium.
I think batteries are going to get much better in the next ten years, so it might be worth burning through a set of lead-acids before a big purchase of ni-fe's. It is a big investment.[ Parent ]
Good point about 20% SOC, had to look up Quintupled: Five times as much in size, strength, number, or amount. 20% is hardly Quintupled!
NiFe Pricing 10x takes it off my list. With the 120% needed by solar panels would take it off my list just for that even if the price were the same. If the price were the same may consider a mixed system, charge NiFe with spare amps and keep for the dark days, get the benefits for both batteries types.
Yet, this year hear about newer solar panels claims of $1/watt etc, times are changing. When I see them I will believe them. Been hearing these claims since the 70's.
Can the 0% DOD voltage be included if the inverter kicks off at 10.5V?
Will DC items such as CFL, stereo, TV, LED bulb... function at below 10.5V?
To me it sounds like comparing the total WH in a giant cap to a small battery. I only give a hoot about power available between 11.0 and 14.8V. A 12V system with 10KW of 10V available doesn't mean anything to me.
Scott, Gas was $1/G then? PVs are $5/W now. A basic marketing twist gives us <$1/W PVs! :-) And a 1 terrabite HDD was how much in the 70'S? So now PVs are almost free!
I admit I didn't look at any charts. I am stressed at the moment. G- [ Parent ]
A 200 amp-hour (labeled) lead acid run down from 100% to 80% and then recharged has one fifth the effective capacity of 200 amp-hour ni-fe battery that can be run from 100% down to 0%. The fair comparison would be a 200 amp-hour lead acid and a 40 amp-hour ni-fe. The lower you go on lead-acids before recharging, the shorter their life. It may still make sense for you to buy lead-acids but don't expect them to last long if you are running them all the way down.[ Parent ]
Looking for applications abusing lead acid battery's. Do we really need to work at the top 20% to get decent life from a battery? Fork lift or golf carts are good examples.
Pick Golfing since often recommend golf cart batteries for RE applications.
Ask around at local golf courses with electric carts:-). Some golf courses replace the batteries every couple year. Others let them go until near dead. What I hear a set of batteries may last 3 to 8 years. http://golfcartsalesllc.com/tech.shtml "Batteries last from 3 to 8 years under normal circumstances". (bottom of page)
Most RE systems are designed for a number of days power. Worst case for MI is around 11 days, to size a battery for this is way over Kill, worst case does not happen Every year! Just may seem like it.
Battery charging efficiency, to operate above 80% SOC is deliberately working at the lowest charging efficiency of the battery. Makes NiFe look good.
If a golf course can get 3 (and more) years with deep cycling their lead acid batteries, why can't RE? With better care extending it out to the 7-8 is very reasonable expectations. Mine have 3 years and still going.
I ran into a guy off grid using solar panels, he had a HUGE battery 11 days only discarged to 50%, designed for worst case. His battery was about 5 years old and not holding a charge past 5-6 days forced to run the generator. Equalizing charge was done Quarterly using a generator. Expensive battery. Solar panels were sized about 20% larger than his normal (average) loads. Realized due to the battery charging efficiency above 80%, the batteries were fully charged only once each quarter. Batteries were sulfating due to all the time below fully charged. Considering the charger efficiency and battery charging efficiency the battery on the average was never above 80% SOC! To be honest I did not figure this out until years later. I had him deep cycle the battery which brought back some life. Told him to deep cycle the battery to 50% before each equalizing charge. I took care of a 1Mwhr battery in the Navy. We discharged the battery 25% or more before each equalizing charge. Battery was replaced every 7 years, still had most of its capacity. Very expensive battery. The battery was pampered, frequent SP readings, watered weekly, cell voltage measured every hour etc. any changes the battery was immediately gone over to see what was going on.
What are the dangers of following this advice? Why saving 75% on the cost of a battery. Deep cycle lead acid batteries are designed to be deep cycled. To baby them is a huge waste of money. Yes the life may be longer than the 25% sized battery, yet the life will NOT be 4x. Charging system must be much larger to keep battery nearly fully charged more frequently than once each quarter. Doing an equalizing charge more than quarterly actually abuses the battery. :-) don't you love it? Understand industrial batteries life are around 20 years, if you get 5 or so years from your battery, by 20 years you will have spend less than an industrial battery.
In summery I would size NiFe to handle what I needed and make the Lead acid 20% bigger to match the capacity.
Be careful of optimizing one efficiency, each system has many possible efficiency's, to over optimize on one and ignore the rest will not get the results your looking for.
Have fun, Scott.[ Parent ]
I don't want to pamper a battery. I don't want to think about equalization charges or whether I'm burning through battery life by going too low in SoC. I'd rather have a smaller bullet-proof battery for 48 hours and a generator. But that's me.[ Parent ]
