Off topic:
One of the main reasons for wanting MPPT on boats and RVs is the lack of available roof space. Additional panels can be cheaper than an MPPT controller but if you don't have anywhere to put them MPPT comes to the rescue.
Grid tie panels are significantly (20%) more efficient than typical RV panels which means less roof space is required however you can only use these panels with MPPT controllers due to the higher voltage.
Horses for courses, PWM could make sense where you have unlimited space such as an off grid cabin but for those of us living mobile MPPT is king.
LiFePO4 protected with Solar BMS can last 20 to 30 years where a typical Lead Acid will only last 4 to 6 years.
He is not saying MPPT is bad it just that it wont work with this kind of on-off charger.
At the moment I manage my system (8kWh lithium with 1600W solar / 3000W alternator) with Bluesea ACRs, Bluesea RBS, Victron BMV, Victron MPPT controllers, SSRs, junsi cellog8s and some custom software. What would be interesting to me for the next release would be a "lite" version with the BMS functionality (cell voltage logging, cell LV/HV disconnect ) but using external COTS devices for power control. Multiple 100A SSRs ($50) could be used for PWM of charge sources, 500A relays could be used for load/charge circuit disconnection, and external shunts for current monitoring. This could make your box the centre of a very large (or small) system without you having to develop multiple SKUs.
Off topic:
One of the main reasons for wanting MPPT on boats and RVs is the lack of available roof space. Additional panels can be cheaper than an MPPT controller but if you don't have anywhere to put them MPPT comes to the rescue.
Grid tie panels are significantly (20%) more efficient than typical RV panels which means less roof space is required however you can only use these panels with MPPT controllers due to the higher voltage.
Horses for courses, PWM could make sense where you have unlimited space such as an off grid cabin but for those of us living mobile MPPT is king.
One thing though,this statement isn't really fair.QuoteLiFePO4 protected with Solar BMS can last 20 to 30 years where a typical Lead Acid will only last 4 to 6 years.I am pretty sure you can easily get 10 years + out of Lead Acid if you look after them.
I was referring to offgrid energy storage too.
I do know of maybe 200 installations in outback northern Australia where the batteries have never been replaced. Some of these have been around for over 10 years. Batteries are Sonneschein.
But yes they are only using 20% of installed capacity, and do have sophisticated charge controllers, although no generators.
The other thing is they get mild winters, but they do have to be careful about temperature.
Some of these have been around for over 10 years.
...systems are up to 10 years old and haven’t changed a battery bank yet
I don't know if they use Gel or Sealed or Unsealed Pb. I could find out but as you say it isn't that important. I was assuming Sealed Lead Acid.
I checked my email I have slightly misquoted the battery life.QuoteSome of these have been around for over 10 years.I Should have saidQuote...systems are up to 10 years old and haven’t changed a battery bank yet
But don't get me wrong, you have sold me on the idea of LiFePO4 and I have even suggested it to the people who installed all the Sonnensheins.
With routine maintenance and proper charging, people routinely get 10+ years from standard flooded LA T105 deep cycle batteries from a reputable brand (e.g. Trojan). Of course if you chronically undercharge your batteries or discharge them below 50% SOC, lifespan is less. Many people undersize their solar array /battery bank size. Many try to use arrays with too low string voltages (e.g. expecting a "24 volt" grid tie panel to reliably charge a 24V battery bank). These things lead to shorter lifespan. Higher temperature exposure also shortens lifespan.
For traction type flooded LA batteries (eg forklift type) 20 year lifespan is not unheard of. For example one company that markets these specifically for solar installations - the HUP Solar 1 warranties their batteries for 10 years.
Another advantage of traction batteries are ability to tolerate deeper discharge. Disadvantages include lower charge efficiency and higher maintenance needs.
Flooded LA batteries have been used for decades in solar installations so these are well established facts.
Gel batteries are a very poor choice for solar installations - so are not used very much. There are several reasons for this but a big one is that they are very easily ruined by a single mishap of overcharging - so they typically have a short lifespan in real world solar installations.
AGMs can be a good choice. They generally have a longer float life, higher charge efficiency and require little maintenance so are a good choice for battery back up systems. The do not tolerate as many deep discharges/lifespan as FLAs.
LiFeP04s have several advantages - but the biggest are high charge efficiency, the ability to discharge deeper and more cycles over lifespan. In theory they should have a longer lifespan than most FLAs IF cared for properly. But at this point they have not been proven to last more than 10 years in solar installations -they just haven't been widely available that long. We all know that real world lifespan of anything involving electricity does not always match theoretical lifespan.
For proven lifespan alone - nothing beats Nickel Iron batteries. But they have several disadvantages as well.
Lead Acid battery is normally quote as end of life at 60% of original capacity and from there degradation is steep nothing usable.
LiFePO4 is quoted as end of life at 80% of original capacity and degradation continues to be almost linear so if you want to go to 60% it will probably last 2x or more since degradation seems to slow down similar to what you see on solar PV panels.
I'm not sure where your are getting this from but it has nothing to do with real world uses IME. No one off grid would keep their batteries down to 60% unless they severely overestimated their power needs when purchasing the original pack (usually it's the opposite - people underestimate their power needs).
Solar 1's 10 yr warranty is for 80% of original capacity (prorated after 7 yrs) as is other lead acid battery warranties I have seen. Any examples of warranties on FePO4 battery packs? I'm sure there must be some - I just haven't seen any yet.
Nice graphs but not really relevant to the question of real world lifespan as I discussed in prior post.
I really hope that LiFePO4 live up to their theoretical lifespan in real world RE system use. My current 5 yr old AGM (backup) battery bank likely has 8-10 years left in it (they're rated for 15 yr float life). I'd like to be able to replace it when the time comes with a battery bank that will last 30 yrs!
Still would like to see some LiFePO4 battery warranties...
I'm mostly talking about OffGrid applications and not backup.
Sony offers 20 years warranty but only for the complete system including the BMS.
LiFePO4 is quite new about 2002 for the first commercial one if I remember correctly.
So was I. I only brought up my current system to point out that I am hoping LiFePO4s live up to the hype!
I have experience with off grid systems and that is what I was referring to previously in my posts (go back and look).
Again - off grid users who properly care for their lead acid batteries often get 10+ (or 20+ in the case of traction batteries) out of them.
Cool. Link?
I see that there are more comments about MPPT here so for those that want to see in details my argument here is a link to my recent youtube video made specifically to explain this but there are some other obsolete technologies in there related to solar PV panels price
Cool. Link?http://download.solarshop.net/english/uploads/FS-UK-Sony-Storage-system-data-sheet-10-08-2012.pdf
And I trust LiFePO4 way more since is not possible to damage by keeping it discharged because you have no sun or not doing proper maintenance in the case of flooded types.
You make a few assumptions and mistakes in this video otherwise well presented video.
Your Solar BMS chart shows 27v @ 65c panel temp however at 65c the panel Vmp will be 26v which is below the battery charging voltage so you wouldn't be getting much charge into the battery.
In warmer climates like Australia where temps regularly see 45c we get panel temps in excess of 80c so with that panel we'd be looking at a Vmp of just 24v, which would be pretty useless for charging a 24v battery.
You make a few assumptions and mistakes in this video otherwise well presented video.
Your Solar BMS chart shows 27v @ 65c panel temp however at 65c the panel Vmp will be 26v which is below the battery charging voltage so you wouldn't be getting much charge into the battery.
In warmer climates like Australia where temps regularly see 45c we get panel temps in excess of 80c so with that panel we'd be looking at a Vmp of just 24v, which would be pretty useless for charging a 24v battery.
Not true. This is something I do have first hand experience with. i have used LiFeP04 batteries in eBikes for several years and you can if fact damage cells irreversibly by failing to keep them charged. I did it once with a $500 LiFePO4 ebike pack!
You make a few assumptions and mistakes in this video otherwise well presented video.
Your Solar BMS chart shows 27v @ 65c panel temp however at 65c the panel Vmp will be 26v which is below the battery charging voltage so you wouldn't be getting much charge into the battery.
In warmer climates like Australia where temps regularly see 45c we get panel temps in excess of 80c so with that panel we'd be looking at a Vmp of just 24v, which would be pretty useless for charging a 24v battery.
Wrong about the way PV panels work.
Yes Vmp may be lower say 26V but if your battery is 27V the current will drop a bit and you will not be anymore at the max power point but still quite close.
So even if cells are at 80C and battery at 27V you will still see a charge current.
Not to mention that usually when is sunny at peak in the afternoon is when you have those cells temperature and is also when you have the most excess power anyway.
You probably had that improper BMS used on eBikes that uses that 5 pin IC designed for LiCoO2 and not LiFePO4 with 2V and 3.9V limits well outside the LiFePO4 limits of 2.8V and 3.6V
As long as you keep the battery always above 2.8V (2.5V is acceptable under high load) and below 3.6V they will last as specified.
Nope, he's not wrong.
It's not just about the power. PV panels act as current sources. But batteries have minimum voltages that they require to charge correctly.
Yep, that's the issue. If you don't have your battery connected to a charging source and voltage drops too low (due to slow spontaneous discharge) a BMS can't prevent that. So LiFePO4, just like LA can be ruined if not kept sufficiently charged - which was my point.