Lithium 48V Battery

mnittler

I am considering replacing my Trojan T-105 48v battery banks with lithium 48V battery banks. Does anyone have any experience using lithium batteries for an inverter with a solar system.  I know Tesla, Panasonic and others sell them in the 48V range.
My research so far:
Lithium batteries are more expensive than Lead Acid.
Lithium has about twice the life span. of LA. 
Lithium can be discharged to 5-10% SOC without degradation as compared to about 50-80% SOC with lead acid which means more % of charge capacity is available per charge cycle.
Lithium has zero water maintenance.

I am assuming that my Xantrex 60-150 charge controller will charge Lithium batteries just fine using solar and the Xantrex XW6048 should work also? I noticed on the ones I have looked at that they list kw instead of a 20Ahr rating for some reason.

My logic would be to take:
Lithium Battery kw rating times 1000 times 0.9  = watts available
Watts available divided by 20 = watts available per hour for 20 hours
Watts available divided by volts = amps

Any thoughts out there on using Lithium batteries?

Estragon

A few thoughts:
There are a number of different lithium chemistries with differing safety and operational aspects.

Some (most, all?) have a better power to weight ratio than LA. Could be a factor in mobile applications.

Some are prone to fire without careful charging.

A 90% duty cycle might be pushing it a bit. My understanding is 10-90% SOC (80% duty cycle) is realistic.

Some shouldn't be charged at <0°C.

I don't know that there's enough real-world experience off-grid with these to know if longevity estimates are accurate.

I'm considering for house bank on a sailboat, or maybe a combination of AGM house/start and backup lithium start. I'll wait for lower costs and better real-world data before considering for cabin bank though.

Photowhit

If your batteries are working, I'd stick with them until they die, I think Lithium batteries are still evolving and might see enough difference in another year or 2 to make a big difference in price and quality. No reason to replace a good system.

westbranch

Suggested reading if you did not get to it yet:  Posts by  user: PNJUNCTION on this forum...  he has written extensively pros and cons...

From my readings , type specific, do not go past  the 2 knees when discharging and recharging.
Plan on ~ 60% available ~20% SoC to ~80% SoC...
Appear to tolerate partial charge states without damage. ie can  stay at 50% SoC and be partially charged for days,  time will tell...

karrak

mnittler said:

I am considering replacing my Trojan T-105 48v battery banks with lithium 48V battery banks. Does anyone have any experience using lithium batteries for an inverter with a solar system.  I know Tesla, Panasonic and others sell them in the 48V range.

The Tesla battery will not be compatible with your existing equipment, not sure about the Panasonic offering. Other commercial packaged turn key systems are available from LG, BYD, Samsung and others. As @Photowhit has said things are evolving and there will be lots happening in the next few years.

If you are going to make a DIY battery I would use LFP(LiFePO4) as it is the safest of the Lithium battery chemistries and should last longer as the individual cells are operating at a lower voltage. All lithium battery technologies only remain safe if the individual cells are kept within their safe operating voltage range. Because of this I would not make a DIY battery for offgrid use without some sort of battery monitoring/BMS.

Lithium batteries are more expensive than Lead Acid.

If you calculate the cost on the total amount of energy cycled through the battery over its lifespan lithium batteries work out comparable or cheaper than LA batteries. You can get by with a smaller lithium battery than LA battery for the same charge and discharge power requirements due to the lower internal resistance and larger daily charge cycling ability of lithium batteries.

Lithium has about twice the life span. of LA. 

Given the experience of people with offgrid systems  with LFP(LiFePO4) batteries up to seven years old I would say that a ten year lifespan is a minimum. Even though a lithium battery may loose 10%-20% of their capacity after 10 years unlike LA batteries there internal resistance remains low so they will remain usable well after they have lost 20% of their capacity.

Lithium can be discharged to 5-10% SOC without degradation as compared to about 50-80% SOC with lead acid which means more % of charge capacity is available per charge cycle.

My understanding is that lithium batteries will not last as long if you take them below 20% on a regular basis but using the 15% between 20% to 5% as a reserve which is only used now and again is OK. A few weeks ago I had my LFP battery down to ~12%. As far as I am aware charging LFP batteries above 90% is not a problem. It is a problem with other variants of lithium batteries.

Lithium has zero water maintenance.

Only maintenance for lithium batteries is to check the electrical connections and keeping the battery in balance. Balancing can either be done manually or you can get a BMS that will do it automatically. I would strongly recommend having some form of individual cell monitoring to make sure that all the cells in the battery remain in the safe operating voltage range.

I am assuming that my Xantrex 60-150 charge controller will charge Lithium batteries just fine using solar and the Xantrex XW6048 should work also?

After a quick look at the manuals for the Xantrex 60-150 and XW6048 I would say they are compatible with lithium batteries as you can manually set the bulk, absorb and float voltage and disable battery temperature compensation.

I noticed on the ones I have looked at that they list kw instead of a 20Ahr rating for some reason.

My logic would be to take:
Lithium Battery kw rating times 1000 times 0.9  = watts available
Watts available divided by 20 = watts available per hour for 20 hours
Watts available divided by volts = amps

Any thoughts out there on using Lithium batteries?

The 20Ahr rate is anachronistic to LA batteries as the amount of energy you can get out of an LA battery is dependent on the rate that you discharge it at, this is known as the Peukert effect. The Peukert effect is virtually non existent with lithium batteries. You can discharge them at the kW rating  continuously. For prismatic LFP cells from companies like Calb or Winston limiting the continuous charge and discharge rates to C/2 (battery capacity/2) and instantaneous rate to 1C will improve their lifespan.

I and others I know who have DIY LFP  offgrid systems have been very happy with the performance of the batteries. Operationally they are a huge improvement on LA batteries.

Simon

mcgivor

karrak said:

mnittler said:

I am considering replacing my Trojan T-105 48v battery banks with lithium 48V battery banks. Does anyone have any experience using lithium batteries for an inverter with a solar system.  I know Tesla, Panasonic and others sell them in the 48V range.

The Tesla battery will not be compatible with your existing equipment, not sure about the Panasonic offering. Other commercial packaged turn key systems are available from LG, BYD, Samsung and others. As @Photowhit has said things are evolving and there will be lots happening in the next few years.

If you are going to make a DIY battery I would use LFP(LiFePO4) as it is the safest of the Lithium battery chemistries and should last longer as the individual cells are operating at a lower voltage. All lithium battery technologies only remain safe if the individual cells are kept within their safe operating voltage range. Because of this I would not make a DIY battery for offgrid use without some sort of battery monitoring/BMS.

Lithium batteries are more expensive than Lead Acid.

If you calculate the cost on the total amount of energy cycled through the battery over its lifespan lithium batteries work out comparable or cheaper than LA batteries. You can get by with a smaller lithium battery than LA battery for the same charge and discharge power requirements due to the lower internal resistance and larger daily charge cycling ability of lithium batteries.

Lithium has about twice the life span. of LA. 

Given the experience of people with offgrid systems  with LFP(LiFePO4) batteries up to seven years old I would say that a ten year lifespan is a minimum. Even though a lithium battery may loose 10%-20% of their capacity after 10 years unlike LA batteries there internal resistance remains low so they will remain usable well after they have lost 20% of their capacity.

Lithium can be discharged to 5-10% SOC without degradation as compared to about 50-80% SOC with lead acid which means more % of charge capacity is available per charge cycle.

My understanding is that lithium batteries will not last as long if you take them below 20% on a regular basis but using the 15% between 20% to 5% as a reserve which is only used now and again is OK. A few weeks ago I had my LFP battery down to ~12%. As far as I am aware charging LFP batteries above 90% is not a problem. It is a problem with other variants of lithium batteries.

Lithium has zero water maintenance.

Only maintenance for lithium batteries is to check the electrical connections and keeping the battery in balance. Balancing can either be done manually or you can get a BMS that will do it automatically. I would strongly recommend having some form of individual cell monitoring to make sure that all the cells in the battery remain in the safe operating voltage range.

I am assuming that my Xantrex 60-150 charge controller will charge Lithium batteries just fine using solar and the Xantrex XW6048 should work also?

After a quick look at the manuals for the Xantrex 60-150 and XW6048 I would say they are compatible with lithium batteries as you can manually set the bulk, absorb and float voltage and disable battery temperature compensation.

I noticed on the ones I have looked at that they list kw instead of a 20Ahr rating for some reason.

My logic would be to take:
Lithium Battery kw rating times 1000 times 0.9  = watts available
Watts available divided by 20 = watts available per hour for 20 hours
Watts available divided by volts = amps

Any thoughts out there on using Lithium batteries?

The 20Ahr rate is anachronistic to LA batteries as the amount of energy you can get out of an LA battery is dependent on the rate that you discharge it at, this is known as the Peukert effect. The Peukert effect is virtually non existent with lithium batteries. You can discharge them at the kW rating  continuously. For prismatic LFP cells from companies like Calb or Winston limiting the continuous charge and discharge rates to C/2 (battery capacity/2) and instantaneous rate to 1C will improve their lifespan.

I and others I know who have DIY LFP  offgrid systems have been very happy with the performance of the batteries. Operationally they are a huge improvement on LA batteries.

Simon

There are other options, think these are available in the US since the link is for North America but not 100% sure.

http://www.axitecsolar.com/us/storage-systems.html

Raj174

Hi mnittler,

I have had an LFP battery bank in service for over 10 months now. It consists of 16 195AH Hi Power prismatic cells in series. Total capacity is 10 kWh. The cells were top balanced and have been cycling daily. The system averages about 9 kWh per day. I cycle between 90% and 25% SOC. This bank is just large enough to get me through till morning, so I will probably replace these with 400AH cells when I can afford them.
As you know, there is no maintenance done on LFP cells, but I do check cell balance every few days. At present, they are all within 10 millivolts of each other. I know of a few, maybe 6 or 7 intrepid souls on the several solar power forums that I frequent that have LFP battery banks. However, a year ago that number was 2. For me going with LFP is a no brainer even at twice the cost of other chemistries. Let me know if you need more information.

Photowhit

karrak said:

Lithium batteries are more expensive than Lead Acid.

If you calculate the cost on the total amount of energy cycled through the battery over its lifespan lithium batteries work out comparable or cheaper than LA batteries. You can get by with a smaller lithium battery than LA battery for the same charge and discharge power requirements due to the lower internal resistance and larger daily charge cycling ability of lithium batteries.

Simon is a wealth of knowledge and generally well spoken, let me interject where I see things differently.

Cost vs Capacity is an on going theme, many would not dare have an off grid system without alternative charging. But for those of us who dare. We need the extra capacity! It won't be used often. A 16Kwh forklift battery can be drawn down to 20% SOC even if you normally don't use more than 2Kwh's a day. It can NOT be replaced with a 8 or even 10 Kwh Lithium battery bank without the added expense of a generator!

karrak said:

Lithium has about twice the life span. of LA. 

Given the experience of people with offgrid systems  with LFP(LiFePO4) batteries up to seven years old I would say that a ten year lifespan is a minimum. Even though a lithium battery may loose 10%-20% of their capacity after 10 years unlike LA batteries there internal resistance remains low so they will remain usable well after they have lost 20% of their capacity.

I think if the comparison was against large traction batteries, HUP and Forklift batteries, the life span will be similar, I personally hope they last 30+ years, but after a recovery of a poisoned cell this fall, I'm beginning to believe in the longevity of forklift batteries.  I have a more generic forklift battery, but this is what Northern Arizona Wind & Sun says about Crown Forklift batteries;

Northern Arizona Wind & Sun said:

These batteries are designed for extremely heavy usage. In a typical solar electric system they will normally last for about 20 years or more. We have been selling these for over 25 years and have the utmost confidence in their reliability. Fork lift batteries have a slightly different plate composition from smaller deep cycle batteries

I do think Lithium will be the chemistry of the near future. I'm even intrigued by the power wall, though I have always had issues with several parts of their sales model. It will be a very high voltage, and appears to have integrated inverter and charge controller. If it ever gets to a point where they publish a spec sheet and price list, things will be easier to figure out. It may be that I skip over switching to a 48 volt LA battery and inverter and go directly to a power wall (likely 2) but that will be a good bit of my of my savings.

nickdearing88

Don't know if anyone has worked with Battleborn Batteries from Reno, NV but they are the most affordable Lithium solution I've found ($899 USD for 12v 100Ah). I emailed with some questions regarding charging profiles and pricing for large-scale purchases (10, 20, 30 Kwh banks) and they replied back in a few hours with friendly, detailed answers. They also stated to reach out to them for quotes on larger purchases.

Currently only 12v 100Ah configurations are available but they are developing other profiles with larger Ah capacities/lower voltage for better series use. However, they also noted that large parallel strings (5-7 series of 4 for 48 volts) were not a problem for Lithium, like it would be for Lead Acid. I assume this is because of the BMS system.

I intend to purchase one or two so I can play around and test them prior to a future large-scale project.

https://battlebornbatteries.com/

jonr

In case it's not clear, this is a packaged system with balancer and protection devices included in the case.   But I see no way that such circuitry can balance between multiple units in parallel.   Calendar life is unclear.  About 2.7x more expensive than a couple of T105RE lead acid batteries (which should last for ~1800 cycles at the same AHs).   IMO, weight and ability to handle fast, partial charges are the primary advantages.

nickdearing88

jonr said:

In case it's not clear, this is a packaged system with balancer and protection devices included in the case.   But I see no way that such circuitry can balance between multiple units in parallel.   Calendar life is unclear.  About 2.7x more expensive than a couple of T105RE lead acid batteries (which should last for ~1800 cycles at the same AHs).   IMO, weight and ability to handle fast, partial charges are the primary advantages.

Yes, that's true, it is a packaged system. I don't have any personal experience but I intend to ask if they have any customers I could contact to share their reviews. Depending on their volume discounts, that could bring a more reasonable cost. Perhaps there is some communication between the BMS on parallel strings. I'm not sure, I didn't get that detailed yet.

I would add no/little maintenance to the pros list also. For me partial SOC is a huge seller, along with very little voltage drop throughout discharge.

jonr

Good point - no issues with adding water, equalizing or stratification.  Also much better resistance to heat.

Estragon

For me, not being able to charge at temps below freezing would be a deal killer for the cabin.

Might work on the boat if parallelling works though.

jonr

Of course you can always measure amps and adjust cables to get parallel operation fairly well balanced.  

westbranch

The AXITEC has a 10 year replacement guarantee.... bottom of Home Page....  just don't know what price

mike95490

Lithium has ZERO forgiveness.   Overcharge them once (like forgetting to disable temperature compensation) ruins them, deeply discharging them once, ruins them.
If you have already dialed in your system with lead acid, it might be a move to consider, but I think the price for Li is still too high

Dave Angelini

That is what Skybox does for Outback systems and the Bridge does for Schneider systems. They both take all of these variables that the user can screw -up (or lightning/surge system glitches)  and remove them from the loop through firmware specifically made for the exact battery.

They give state of charge %, battery health or life left, exact battery temp in multiple key places.
 Over/under voltage, temp, current and BMS comms. The troubleshooting for imbalance and how well the BMS is correcting feeds back into battery health. All of this to protects the battery and using the interfaces already there from Outback/Schneider.

It can go out to the web or just stay local to you on your mountain top 

There really is not reason that Li can't be alot cheaper, or even more available, but hang in there.
 I agree with you Mike if you are dialed in with LA, wait it out.

mnittler

Thanks for the wealth of information.  I would like to here from a few more that have experimented with the Li batteries for renewable.

I agree with McGivor to keep SOC at at least 20% unless they say otherwise and actually have a valid replacement warrangee.

I am current looking at the new Tesla Powerwall 2 14kw system with integrated inverter and charge controller. If I do this then I will move the Xantrex XW6048 and T-105's to my shed. I must admit that XW6048 is a piece of versatile work and has served me well and still purring like a kitten.  Most of the Powerwall installations that I have found online are from Australia and they are the original 7kw & 10kw powerwall battery paired with a Solar edge inverter.

Tesla claims a 10 year warrantee but no description of what the warrantee is.  Tommy Boy and his brake pad guarantee comes to mind. I figured that they have dealt with LI for awhile now on their cars so that might count for something. Tesla is building a $5 billion 35 Gigawatt battery facility in Nevada so maybe they are just trying to edge into the battery market and keeping all avenues open. They are currently installing a 12 megawatt battery system on the island of Kawai, Hawaii (saw this online) so they are doing things on a grand scale.  But, if this pans out for them then it looks like they have bet the entire farm on Li batteries. I think that one new factory they are building in Nevada is equal to or larger than the current Li battery annual capacity in the world.

I got my hands on a spec sheet for the Powerwall 2 but what I wanted was a programming manual and wiring diagram which is not available yet.. I think about 9 of these can be connected together.
From what I understand:
They only sell the Powerwall 2 installed for a one time flat fee no matter how many times they have to come back and how many are initially purchased (I think limit of 9)? The guy I talked to said they originally come do a site survey then return to do the install.
Specifications from specification sheet that I downloaded are as follows:
AC voltage: (208v, 220v, 230v, 277v, 100/200v, 120/240v single or split phase, 50,60 hz.
13.2kwh
Real 5kw continuous charge and discharge
Real 7kw discharge only
continuous 5.8kva
apparent power 5.8kva continuous
apparent power  peak 7.2kva discharge only
Load imbalance 100%
Internal battery DC voltage 50V
round trip efficiency 89.0%
Depth of Discharge 100% (This probably leaves some wiggle room since I think they install more Kva that advertised?)
warranty 10 years (But does not say what the warranty is)
Operating -4F-122F
Nema 3R (indoor or outdoor) IP67-Battery & electronics, IP56-Wiring
Mounting Floor or wall
269 lbs
45.3" x 29.7" x 6.1" (So a pretty small footprint)
Ul1642, UL1741, UL1973, UL9540, and a bunch of others

Connectivity WiFi, Ethernet, 3G
AC meter revenue grade
Modularity Supports up to 9 AC-Coupled powerwalls (This seems interesting)
There is no mention if this unit can supply power without the grid present or not and that could put a damper on the project.
In some of their literature they discuss using the powerwall for power failures but it is a bit fuzzy if they are referring to the original or the 2.

This is what interested me about Li. 
I am guessing here that they probably have some sort of logic imbedded that will not let the system die below a critical level.  Like the XW6048 low voltage cutoff.  I had heard that their cars will call home (Tesla) if they are abandoned and dying and a mechanic is dispatched to assist with a battery charge as not to kill the battery. 
I doubt that this battery system would have that but they do want you to connect the system to the internet if possible in order to use their Tesla App.
Weather it works or not I cannot tell. But they said the powerwall 2 includes charge controller, inverter, and 14kw Li battery.
I could not even get a wiring diagram.

What kind of Li batteries do you all use and where do you get them?

The above specification intrigued me enough to ask you guys what you thought.

Raj174

This is a pic of the system with the 10 kWh LiFePO4 battery bank I posted on earlier.

Dave Angelini

The OP here can keep his system and add this. Take a look at this thread and you will not have to depend on Elon.

http://forum.solar-electric.com/discussion/351297/conext-bridge-for-xw-li-ions-from-lg-and-hoppecke-announced-for-2nd-half-2017#latest

jonr

Raj174: are you checking balance at both the top (fully charged) and at the bottom (when the low voltage cutoff activates)?   Balance at one point says little about the other - but either one can kill a battery.

Raj174

Yes, at top (float, 90% SOC) 1 to 2 millivolts between cells and at 25 to 30% SOC, 9 to 10 millivolts between high and low cells. Readings have been pretty consistent. I check it two to three times a week. 

jonr

Sounds like they are well balanced.  How old are they?  Have you had to manually re-balance them (ie, how long do they stay balanced for)?

Raj174

The cells were manufactured 2/2014. I bought them new In November of 2014. Had them in A/C storage at 50% SOC for about 15 months giving them a little charging every few months. Top balanced all to 3.6 volts before installation on May 18th 2016. I have not had to rebalance them so far. How long do they stay balanced? They appear to be staying in balance, but I would consider rebalancing if they were maybe 3 or 4  hundredths of a volt out of balance. As you can guess, rebalancing is easy and only takes about 8 hours. I think there is a lot of hype out there about LFP and balance issues. I believe this is from the EV industry because they routinely discharge the cells at 3 to 5C. That's enough to cause an imbalance and require a BMS, however when charging and discharging at C3 or less I just don't see it happening to any significant degree. I have found LFP to be quite resilient. I especially like getting 99% of the power that goes into them back out to the loads.

Rick

westbranch

this made me think out loud...EV industry because they routinely discharge the cells at 3 to 5C.

It occurred to me that HEAVY discharges would accentuate any 'irregularities' in the manufacturing of the prismatic cells, (probably in any format?) and that these anomalies would tend to 'degrade(?)' a bit faster or take less charge once 'highlighted' by the first heavy discharge... 

Does that make any sense?

Dave Angelini

It makes sense to me.

 It is not just the deep discharge that one has to be concerned with for battery life, it is just as important for long life to not over-current the battery. Both LG and Tesla have warranty issues with big loads and it is logged. Big loads = shorter life.

Raj174

You are quite right about this accentuating the irregularities in the manufacturing of the cells. LFP cells of a nominal size, say 200AH are not all exactly 200AH. They can vary as much as 5%. That's as much as 10AH, and putting a 5C load on a 204AH cell and a 196AH cell for 30 seconds could leave them at different voltages even though they were initially the same.

EV manufacturers that use prismatic cells usually buy the cells in bulk and match sets according to capacity to get around this problem. But, the average Joe EV guy has to buy his cells individually on the market and gets slightly mismatched cells. Thus the need for top or bottom balancing. It helps, but it does not cure the capacity problem at high amperage draws, thus the need for a BMS. As far as any degradation goes, many of these cells are made to output 3 and 5C for short durations without damage. So I don't know if that is the case.   

westbranch

Yes, it looks like that short duration is SHORT!  I have some specs for a 6.8 kWh batt. and they read: 
Continuous  @ 25*C                       60A
Peak Pulse Current at 10 sec     < 300A
Peak Pulse Current at 100 msec < 500A

You really do want to have a BMS if there is the slightest CHANCE of a Peak Draw over the continuous rate!!

Raj174

This is the spec sheet on my cells, notice the 10 second discharge current rating of 975 amps and the very low internal resistance. 

sub3marathonman

OK, my situation may not be typical for all Li batteries, but I think it is fairly typical when you understand I purchased them from Balqon, a group who at one point may have been fine, but along the way and definitely in the end left a lot of unhappy customers.  I think they should be prosecuted, and importation of Winston batteries stopped until Winston rectifies what their representative did to customers, but that is another story.

In theory, Li is spectacular.  And when I first got the 700ah Thundersky batteries, I was assured by Mr. Samra that even though they had been stored several years, they would be fine.  He was supposed to be a battery expert, so I foolishly believed this illogical statement.  I was desperate to get my system working again, as the previous PbA batteries had self-destructed due to a guy at the company not tightening the inter-cell connections in one battery.  But that is another story too.

My system is the XW6048. the MPPT 60-150, and the 16 Thundersky batteries.  So for about a year they worked as theoretically they should.  After that things started deteriorating.  Then, and this is one thing people don't think about, as I was depending on their BMS, one of the little cell monitors had a problem, and one cell was discharged deeply.  As was stated, that isn't good.  And the problem is compounded by the fact that even though there are 15 other cells, it doesn't work without 16 cells.

Now, I'm left with apparently very limited capacity, and basically I'm trying to stretch their life by using them strictly for floating, instead of supplying backup power, so the inverter and PV panels can still work.  I suspect that when Mr. Samra heard I was with a grid-connected PV system, he figured these batteries would be good enough to use for floating and a rare discharge, but I was using them to offset demand during peak periods, so they were being cycled five days per week.  If I was off-grid, I'd be in major trouble. 

I don't know if any of the Li battery experts have any helpful suggestions for my situation.

As I and Nissan found out too, with a different Li chemistry though, the batteries don't hold up well in the heat without a temperature monitoring system.  I lost over 50% capacity from the LEAF is four years.  People in Phoenix and other hot places had batteries going bad in two years.  Nissan, to their partial credit, although it was part of a court settlement, stepped up and introduced a proper warranty for their batteries, and I have actually gotten mine replaced as part of that settlement.

Now it seems as if the price of Li is on the downward trend, although if you purchase from Battle Born batteries or some of the other similar groups that isn't true.  You pay dearly for their system, as opposed to the Li cells, and in fact at $900 for 12V and 100ah, my battery bank would cost over $25K.

So I have had two negative (pardon the pun) experiences, one with PbA, and one with Li.  However, with the PbA, it would be easier to recover from, as availability is much greater, and the price at least in the short term is still much better.

Some are attempting to use salvaged LEAF or even Tesla batteries, but this is highly experimental.  There is supposed to be a promising situation with Aquion batteries, but here a few years later and they're pretty much in the same situation as I remember back then.  There are NiFe batteries too, but good luck getting any of them, and the efficiency is poor, so there goes much of your PV capacity.

The one benefit, if it really is a benefit, is that the federal government covers 30% of the risk when you're using them with a PV system.  So theoretically, if you could find a battery that would last 100 years and cost 10 times PbA, that would be the thing to get.  However, in practice, at least at the moment, I'm thinking that PbA is still the only real mainstream choice.

karrak

sub3marathonman said:
My system is the XW6048. the MPPT 60-150, and the 16 Thundersky batteries.  So for about a year they worked as theoretically they should.  After that things started deteriorating.  Then, and this is one thing people don't think about, as I was depending on their BMS, one of the little cell monitors had a problem, and one cell was discharged deeply.  As was stated, that isn't good.  And the problem is compounded by the fact that even though there are 15 other cells, it doesn't work without 16 cells.

When you say one cell was deeply discharged, do you know what voltage it got down to, for how long and how many times?

Do you know how much usable capacity is left in the damaged cell and in the other cells in the battery?

Looking at some of your old posts I see that the battery has a "Clean Power Auto" BMS and balancing system. As far as I am aware this system has a reasonable reputation. What makes you think it is one of the BMS modules that has caused the problem?

One major flaw with that BMS is that it does not send the voltage readings to the outside world so you have no idea what is happening with the individual cells.

If there was only one cell damaged you can just replace it with a new one.

Simon