Bit of a noob power wise. What is diff between an Mppt and an ordinary buck convertor?

Bit of a noob power wise. What is diff between an Mppt and an ordinary buck convertor?

Well a mppt is a buck converter, just a more complicated one. Complicated in that it is always testing the input and adjusting its output for maximum power.
If at all possible I try to stay with good quality pwm controllers as you will get decades of trouble free service from them.

Another change to my system do to these new type of batteries. I had been using a heavy duty automotive battery charger (and sometimes my converted welder) in the winter for my lead acid batteries. Not the most efficient power wise but solid and reliable.
With these new type of batteries and because they charge so much faster and efficiently than my old lead acid, I am changing to a different charger (s),
Four of them to be exact. (You wouldnt really use these type with lead acid)

Each rated for 30 amps, hooked up in sets of two, then each was adjusted to output 15 amps each for a max total of 60 amps. I am using them well below the rated capacity. I actually tested this last winter with a 12 volt switching power supply so I know it will work, I just wanted more charging capacity this winter so ordered in 4 units. They were 28 dollars each, less a couple bucks because of a promotion and shipping was free, so for 100 bucks I have a very efficient 60 amp charger.

(Devil in the details)... Actually if the battery terminal voltage is really low, like 12.6 the chargers put out close to 20 amps each this brings the voltage up fast, as the battery voltage rises (around 13 volts) the amps taper off to 15 amps each, as the voltage rises further (13.4) the charging current tapers off to about 10 amps each, pretty much ideal.

So my neighbours kid bought a adjoining 20 acre property that is off grid. She got possession this weekend and I went over to have a look at the place and get the power system up and running. Never have I seen such a poor system in my life and the sad thing is the guy paid a fortune to have it put in. It has a huge (was)good quality lead acid battery system that I am certain was murdered within months of being put in. For reasons not understood this battery bank was charged with only about 300 watts of solar. This could never have driven his bank through a absorption cycle let alone aequalization cycle. I have never seen anything like it. I was told the system was put in maybe 15 years ago (so its been through lots of batteries). I am thinking that the price of panels was really high back then and maybe thats why so few, but the guy never discovered that the price fell in around 2012/2013. So never added any more.

So it looks like I will be helping her add a few thousand watts of panels and ripping out the old lead acid. Well I wont be moving the lead acid batteries, I will supervise, she can find some strong backs to move that stuff.

This leads me to my posts purpose.....I was sourcing availability and pricing of components for her and to my surprise I have found Lifep04 batteries now available for as little as 338 dollars per kwhr ( prismatic cells stocked in Alberta). Thats roughly 1/3rd the price from when I started changing over. Its absolutely dirt cheap by comparison to what it was. If only I could have waited. Oh well.

The picture below is of the murdered lead acid bank that is going to be replaced with lithium. Batteries ordered today but the supplier didnt have enough stock so another couple batteries will come in the fall. A killowatt of panels and one charge controller on the way, more will follow.
I found the date codes on the solar system components and they were all manufactured in the year 2000, So its nearly certain the system was put in in 2001 and that would make the system 20 years old. The inverter is a old 12 volt Trace sw2512, with all the bells and whistles. I bet it cost 4000 Canadian back then, a really well built inverter. She will keep using it since it is still working fine.

With all the new panels and new battery technology that she is up grading the system with it would have been a good time to think of moving to a 24 volt system (some would say 48 volts) but if everything works fine, why bother? People would be very surprised at the number of older 12 volt systems , what would now be called legacy systems, running homes trouble free year after year.

One of those batteries weighs something like 125 pounds. That bank would have cost somewhere around 4500.00 to 5000.00 Dollars. It will be replaced by 4800.00 worth of lithium, giving a bank 1120 amp hrs in size or 14.3 kwhrs in size (fully useable). Likely the panels will add up to 5000 watts or there abouts by the time its all done. Maybe only get a couple thousand up this year. Every thing takes time.

14.3kw of lithium batteries would be roughly = to a lead acid bank of greater than 25 kwhrs. Well thats some what incorrect, maybe roughly = if thinking of useful useable power but in life cycles the lithium far surpasses the lead acid.

Edit..Thats a thousand pounds of lead batteries that will be replaced by roughly 250 pounds of lithium batteries.

So with the first thousand watts of panels incoming, I am faced with the question of how to mount them, while meeting the criteria of fast, strong and cheap. I will have to sleep on the problem. A kilowatt of panels will take up a area of roughly 5 feet by 12 feet. A trip to the scrap metal yard may be required.

Edit; 5 feet by 14ish feet.

This is the type of battery going into my neighbours place. I bought one for myself to add into my bank. 280 amphr for 1245.00 including shipping. I am thinking of ordering more of these for myself and kicking the first four batteries I bought out of my bank and use those 4 as a mobile power supply for around the property. I may make my ridding mower electric, rotortiller electric, things like that. (already have the electric motors to do so)

EDIT, I just did a price check, using on line prices for the Lead acid T105s and when comparing the useable amp hr between the two types (lead acid vs lithium ) the cost is equal now.

With great reluctance, I ordered in a large mppt controler to replace the smaller mppt unit that I was testing last winter. This will get me more power for my hydroponic use in winter. (more power because it can handle greater power from what were panels used for water heating )

Just for fun I looked back at what I paid when I started switching over to lithium in 2019 and my first battery would give me a per amp hr cost of 12.00 dollars.
Now with this last one I bought the price is 4.28 per amp hr. Huge drop in price. This begs the question, will it fall even lower? I have enough batteries now but its so tempting to buy more just to bring the average price I paid per amphr down. I will wait until September, then buy another 280 amp hr one, hopefully the pricing will be better.

Its decided now, I will be pulling the first four 100 amphr batteries out of my system and buying more of the 280 amp hr batteries. I really like the form factor of these, fewer inter battery conections, infact I am thinking of hooking these up with solid copper buss bars. Another battery this fall, two next year, and a couple the year after that will give me a battery size of 6x 280= 1680 amphrs + the one 240 amp hr bought last year, So a total of 1920 amp hrs or 24.6 kwhrs. Hugely more storage than I need.

My daily consumption has been creeping up, now at 6 kwhrs a day. A number of reasons. Security is one. I leave a light on 24/7 in the garage with a radio playing. Outside lights on the house run 24/7. Inside the house every light is 100 watt equivalent LEDs. I am running two chest freezers when a single larger one would be smarter. Computers never shut off. I am not running as tight of a ship energy wise as when I started but I am not concerned now that I am using these type of batteries.

Bought some solid copper buss bar material for use in a couple years when my system is in its final form. Not just for the battery buss barrs but I plan to use it in place of wiring from the charge controllers , in place of wiring to the inverter even. Complete over kill. Standard length is 12 feet, so if your are not cutting it down you better bring a 2x4 to tape it to otherwise the length sticking out your tailgate will bend with the first bump you hit. Something very primal about handling pure copper.

Thought I better get it now.

After much reading I am beginning to think and its looking like the price of these batteries may continue to fall. The patents for the chemistry and lifepo4 cathode manufacturing begin expiring in 2022. China produces 95% of the world supply and from most accounts I could find had roughly been following export limitations agreed to by the patent holders. That all can start to change in 2022, in fact more production plants are being built right now in anticipation of the loss of patent protection. Maybe even the falling prices I am seeing this year is from China jumping the gun a bit and exporting more than they are permitted under licensing agreements with the aim of nailing down greater future market share that will preclude manufacturing start-ups elsewhere.