Perfomance data from LiFePO4 (LFP) Battery

karrakkarrak Solar Expert Posts: 214 ✭✭✭
I have had an LFP battery installed in my Off-Grid system for around 20 months now. In September I put together a battery logger covered in this post http://forum.solar-electric.com/showthread.php?24630-Open-source-battery-monitoring-system-(BMS)-with-a-difference.

At the end of the post is the yearly data summary from the battery logger. This data is not actually for the whole year as the logger was only installed in October, the 'ah' readings are only for December and the end of November. This will be the baseline for future years.

In summary
The maximum Charge rate was 37.6 amps (~0.1C)
The maximum Discharge rate was 245.7 amps (~0.68C)
The maximum SOC was 104%. This should only ever get to 100%, this implies that the maximum error even without accounting for battery efficiency using coulomb/ah counting was only 4%
The minimum SOC was 25%, actually this was more likely 20% as I only ever charge the battery to around 95%
The average SOC of the battery was 76%
Minimum battery voltage was 24.7 volts
Maximum battery voltage was 27.86 volts
From the charge and discharge figures the battery coulomb/current efficiency is ~99.3%, this doesn't take into account the start and end SOC of the battery. Taking this into account we get an efficiency of ~98%

There are two glitches in the readings, cell 8 shows a minimum voltage of 2.584 volts which gives the high 'deltav' reading of .748 volts, the 'deltav' reading with the glitch removed should be around 0.1 volts, from looking at the daily summaries I found that it occurred on the 26th of December. Cell 2 shows a 'minnoload' of 3.099 volts, this glitch occurred on the 12th of November.

This summary I think just back up my experience of how good the LFP battery is from an operational point of view.

I can draw 6kW from a 9kWh battery with a voltage sag of around 1 volt, don't have to worry about the the rate the battery is charged at, or worry about keeping it at a high SOC.

The only maintenance I have had to do is a manual balance back in April. There is little evidence of any drift in battery balance. Cells 7 and 8 are drifting a little high but I think this is due to the Cellog 8 rather than the cells themselves. As my battery monitor seems to be working reliably I will retire the Cellog 8.

As far as I can see the major unresolved issues with these batteries are
  1. how long they will last when treated properly in an Off-Grid application. I am fairly confident of a figure of over ten years
  2. how long they will last if one charges them at temperatures below freezing.

I would be very interested to know other peoples experience with LFP batteries in Off-Grid system, especially if the battery has been in use for a longer period than mine.

Simon

Raw Data for 2014
timestamp, "20150101000005
maxvoltages, [3.463, 3.49, 3.465, 3.503, 3.462, 3.462, 3.521, 3.525, 27.86]
minnoload, [3.214, 3.099, 3.211, 3.2, 3.2, 3.193, 3.232, 2.584, 25.71]
minvoltages, [3.096, 3.086, 3.076, 3.085, 3.047, 3.103, 3.086, 2.584, 24.7]
deltav, [0.004, 0.748, 0.748]
amps, [-37.6, 245.7]
ah, [-14.29, 84.689088, 273.13, 47073, -2563.01, 2581.91]

KEY
'maxvoltages' is the maximum voltage measured over the time period of each cell and the pack as a whole

'minnoload' is the minimum voltage measured over the time period of each cell and the pack as a whole with a load of less than 10A

'minvoltages' is the minimum voltage measured over the time period for each cell and the pack as a whole

'deltav' is the difference in voltage between the highest and lowest cell in mV measured over the time period, the first reading is the lowest difference, the second in the maximum difference with a load less than 10A, the third is the maximum difference

'amps' is the maximum charge and maximum discharge current measured over the time period, negative is charge

'ah' is the DOD of the battery in Ah measured over the time period, my pack has a nominal rating of 360Ah, the first figure is the lowest DOD, with 0 being 'full', the second figure if the average DOD, the third figure if the maximum DOD 360 should be empty, the forth figure is the number of samples the average is taken over, the fifth figure total charge going into the battery in ah, the sixth figure is the total charge drawn from the battery in ah.

There is a minute between samples.
Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
Homemade BMS https://github.com/simat/BatteryMonitor
 

«13

Comments

  • gww1gww1 Solar Expert Posts: 963
    Re: Perfomance data from LiFePO4 (LFP) Battery

    If you went to the outback tech forum and pm gorden Lunbaunm. I really did not spell his name correctly. He is an advocate and I believe he has ran his battery longer then you and may "it I remember correctly" have good data recording equiptment.
    There was another lipo user that posted but I can't remember his name at all.

    http://outbackpower.com/forum/index.php?sid=2f1ec936ec7eb584c9f67f32b723e85a

    I hope this gets you what you are looking for. I believe there is only one gorden on that site so you won't get it wrong if you pm him.
    gww
  • karrakkarrak Solar Expert Posts: 214 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    gww1 wrote: »
    If you went to the outback tech forum and pm gorden Lunbaunm.

    Thanks for the information, he is another Australian, lives on the opposite side of the continent. Looks like he installed his LFP battery in December 2012 about four months before I installed mine. Impressive that he has been off-grid since 1991.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    Performance Data is nice to have. In the case of LiFep04 cells it's impossible to expect a long cycle life without it. The hang up with LiFeP04 is the cost. While each chemistry has it's pluses and minuses, different DOD factors and cost, one should weigh each one to see what fits their use and best overall ROI. LiFeP04 does not have enough data available to prove it can do that overtime. No one knows if the foil envelope packs inside will last that long ( 10 years ).

    Cost per Amp Hr @ 12 v. Prices are current street price with shipping costs on the Roll's and LiFeP04.

    GC-2's = $.76 per amp hr, 3-5 years ( Sams pick up price )

    Rolls Premium = $1.92 per amp hr, 5-7 years

    LiFeP04 = $4.80 + per amp hr, 10 Years ( maybe, but not proven yet )

    Karrak deserves a round of applause, he's walking the talk and plowing the ground for us all.

    .
  • inetdoginetdog Solar Expert Posts: 3,121 ✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    Performance Data is nice to have. In the case of LiFep04 cells it's impossible to expect a long cycle life without it. The hang up with LiFeP04 is the cost. While each chemistry has it's pluses and minuses, different DOD factors and cost, one should weigh each one to see what fits their use and best overall ROI. LiFeP04 does not have enough data available to prove it can do that overtime. No one knows if the foil envelope packs inside will last that long ( 10 years ).

    Cost per Amp Hr @ 12 v. Prices are current street price with shipping costs on the Roll's and LiFeP04.

    GC-2's = $.76 per amp hr, 3-5 years ( Sams pick up price )

    Rolls Premium = $1.92 per amp hr, 5-7 years

    LiFeP04 = $4.80 + per amp hr, 10 Years ( maybe, but not proven yet )

    Karrak deserves a round of applause, he's walking the talk and plowing the ground for us all.

    .
    This is great information, but if I understand your numbers correctly, anyone looking at a battery system for off grid use will also have to adjust those prices for the fact that the three different battery types will require a different AH rated battery pack for the same design daily load and days of autonomy. (Blackcherry's different DOD comment.)
    For LiFePO4 it will not be enough to bring the price to parity with lead acid, but it does reduce the difference in total battery cost and gives room for other considerations to influence the decision.
    A common suggestion, from people I find reasonable, is to operate the LiFePO4 bank between a maximum charge of about 80% and a minimum of about 40% on a daily basis and depend more on generator for autonomy. The fast charging of Li can reduce the required generator run time and increase efficiency when you need to use it.
    SMA SB 3000, old BP panels.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    LiFeP04 costs could definitely be mitigated with properly sized charge equipment and charge regimen. With high fuel costs and cheap PV it's hard to know what direction works out best. Doing the 70 - 80% DOD makes sense if you can work out the sun hours and PV size. Another area to exploit is the 100% recharge factor, of course anything you take out in amp hrs has to be returned at some point or the capacity goes away.
  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    A common suggestion, from people I find reasonable, is to operate the LiFePO4 bank between a maximum charge of about 80% and a minimum of about 40% on a daily basis and depend more on generator for autonomy. The fast charging of Li can reduce the required generator run time and increase efficiency when you need to use it.
    Cost per Amp Hr @ 12 v. Prices are current street price with shipping costs on the Roll's and LiFeP04.

    GC-2's = $.76 per amp hr, 3-5 years ( Sams pick up price )

    Rolls Premium = $1.92 per amp hr, 5-7 years

    LiFeP04 = $4.80 + per amp hr, 10 Years ( maybe, but not proven yet )

    Another factor that just came to mind is the lack of need to bring a LiFePo4 battery to 100% SoC daily or even weekly, as previously notes.

    Assuming similarly bank(s) of batteries with equivalent autonomy/capacity included.

    What if we look at this over a longer time period say a month to several years?

    With lead chemistry batteries we fret over needing a 100% charge at least weekly , or maybe a little longer depending on the degree of discharge, BUT with the LiFePo4 that is not an issue, so what is the added cost, particularly in the dead of winter here in the cold North of bringing my lead battery up to full charge once weekly?

    In my case I would say (est) at least 4 hours of run time on a Eu3000i, at current prices of gas, at least $10/$15 a week..So about $40 /$60 per month.

    Assuming the same run time or less the total is reduced to once per month or less so $11/$15 per month.... YES?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    That ain't how you compare things, boys. It's like saying "assuming an application which LiFePo batteries are better suited to than lead-acid, the LiFePo batteries are a better choice".

    The difficult bit is coming up with a cost value for the other LiFePo factors which may or may not be required in any given application. The higher energy density, for example, isn't much of an issue for most off-grid applications where weight and space are not significant limitations. In a mobile system they can be. The partial SOC resistance to failure is usually not an issue either, but if the particular system in question may run into this often it could be.

    In short the two chemistry types are not 100% interchangeable. The advantages and disadvantages to each, including cost, must be taken into consideration according to the needs of the system. It's not a case of "this one is better because ..." is that 'because' isn't a factor in the application.

    Regrettably the high capital expense of LiFePo is a severely limiting factor at this time. Its advantages rarely outweigh that immense extra cost. Hopefully with more people will to shell out the megabucks for it to begin with prices will come down and available real data will go up.

    But at this point it certainly isn't something Joe Beginner should shell out his hard-earned spondoolicks on, especially considering the ease and frequency with which first batteries can be destroyed.
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    Balqon has drop in LFP battery packs of various sizes that are designed for solar off grid systems. Apparently, they have built in BMS and they state that they work seamlessly with most leading charge controllers and inverters. User just has to ensure charge voltage doesn't go above 28.8 volts (for a 24 volt pack). Price is reasonable as well at about $2.70 per watt hour. They use Winston LiFePo4 cells.

    I did a cost calculation comparing them to long life FLA batteries and overall cost factoring in cycle life works out to be about the same. As coot mentions there are advantages and disadvantages going with a different battery chemistry, and an LFP battery may be more suitable in some applications than in others.
  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    I know they are expensive...I just looked at their website and I came up with a comparable 24V LFP battery (18KWh) to my
    21,KWh AGMs and it is $7560 and that works out to $.42 per Wh before shipping. Its 450pounds so I am thinking ~$500 for shipping max.
    I dont know how Northerner calculated that $2.70 / Wh http://www.balqon.com/hiqap24_18kwhr/
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    westbranch wrote: »
    I know they are expensive...I just looked at their website and I came up with a comparable 24V LFP battery (18KWh) to my
    21,KWh AGMs and it is $7560 and that works out to $.42 per Wh before shipping. Its 450pounds so I am thinking ~$500 for shipping max.
    I dont know how Northerner calculated that $2.70 / Wh http://www.balqon.com/hiqap24_18kwhr/

    I didn't factor in cycle life with that calculation but is just the price/battery capacity. Here is a comparison of costing I did recently and posted on another site. It is based on recommended average DOD's for each battery type. Of course one could figure out the costing with your own average DOD:

    Here is the costing comparing battery types and factoring in cycle life:

    Trojan L16 is $809/4000 cycles = $0.202 per kwh @ 20% DOD

    Balqon 5.2 kwh module is $1417/7000 cycles = $0.202 per kwh @ 35% DOD

    Aquion S20 stack is $962.5/6000 cycles = $0.160 per kwh @ 50% DOD

    Rolls 5000 series is $1314.5/5000 cycles =$0.263 per kwh @ 20% DOD
  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    Interesting. I see on this page http://www.balqon.com/hiqap24_18kwhr/ that they state 3000 cycles to 70% DOD so that is ~ 9 years, and 5 yr prorated warranty....?? hm .... So if you only go to 35% DoD it moves up to 7000 cycles..?

    So even though you can go to 80% DoD, if you did that regularly it that would take it below 3000 cycles , to maybe 2000 or less, so that is a significant negative, to me at least... not that I am planing to go there, it is like going below 50% DoD with a FLA... as it's NOT recommended!
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    westbranch wrote: »
    Interesting. I see on this page http://www.balqon.com/hiqap24_18kwhr/ that they state 3000 cycles to 70% DOD so that is ~ 9 years, and 5 yr prorated warranty....?? hm .... So if you only go to 35% DoD it moves up to 7000 cycles..?

    So even though you can go to 80% DoD, if you did that regularly it that would take it below 3000 cycles , to maybe 2000 or less, so that is a significant negative, to me at least... not that I am planing to go there, it is like going below 50% DoD with a FLA... as it's NOT recommended!

    Balqon (they use Winston cells) posts their cycle life versus depth of discharge curve for the batteries here: http://www.balqon.com/wp-content/uploads/2013/07/35_35balqon_battery_2013.pdf

    One must realize to that if your going with a deeper depth of discharge (ie daily average), your getting away with a smaller battery than if you went with a lesser depth of discharge. I haven't figured it out, but it could be fairly linear as far as cost goes (up to a point)? If you go with an average daily depth of discharge of 35%, that would give you about 2 days of autonomy as well.

    Also, I didn't factor in battery efficiency with the cost comparison. You would actually gain about 10% or so with LiFePo4 over FLA and AHI batteries.
  • Mountain DonMountain Don Solar Expert Posts: 493 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    I take a lot of what Balqon says with some skepticism. Reason: On their web pages, in the specs area, they list the operating temperature range as having a low end of -40 or - 45 F (I forget which and didn't feel like looking it up). That is a half truth. The LFP cells can be discharged at temperatures that low, but they can not be charged below 32 F. That little tidbit of info took more digging. They also do not respond well, or at all, to email inquiries. There are other LFP vendors that do acknowledge the minimum charge temperature openly. You really can not take everything a manufacturer or a reseller says as absolute truth. Sad, but so true.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    All my planning has been using a 25% DoD for 3 days (max 75%) on my current batteries and I like it as it leaves me with more flexibility , IMO... and as I am not set up for AGS yet, it gives us a bit of a comfort zone.

    Looking at that graph (Thanks for the link.) 25% /day keeps one in that safe zone, if you go a bit heavy on use in days 1 & 2, there doesn't need to be a late night run to the gen shed...
    From that graph, 80% DoD = 2200 cycles, 90% = ~ 1600 cycles and 100% = ~1000 cycles
    55% appears to give ~ double the cycles of 80%DoD, coming in at ~= or> 4200cyles, and it is a reasonable 2 day usage...

    The more I read about them the more I see that they would be a good fit for us...

    Don, I agree with you one rusting publication of data, still sitting on my wallet. 8)
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    It's the Internet, full of Smoke Blowers and Fan Boys touting something they know very little about.

    I thought this was interesting. If your buying something it's nice to know what is inside that your paying for. Fancy on the outside doesn't mean much.

    http://liionbms.com/php/prismatic_cells.php
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    I take a lot of what Balqon says with some skepticism. Reason: On their web pages, in the specs area, they list the operating temperature range as having a low end of -40 or - 45 F (I forget which and didn't feel like looking it up). That is a half truth. The LFP cells can be discharged at temperatures that low, but they can not be charged below 32 F. That little tidbit of info took more digging. They also do not respond well, or at all, to email inquiries. There are other LFP vendors that do acknowledge the minimum charge temperature openly. You really can not take everything a manufacturer or a reseller says as absolute truth. Sad, but so true.

    I absolutely agree. I myself am looking at an alternative to FLA batteries, and the more we know about a product, the better off we are. I was just pointing out a product out there that is drop in ready for an off grid system. I don't know of any other company that has put packages such as this together. I do know that Winston cells have been around for a while now, but I haven't seen much feedback about them?
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    It's the Internet, full of Smoke Blowers and Fan Boys touting something they know very little about.

    I thought this was interesting. If your buying something it's nice to know what is inside that your paying for. Fancy on the outside doesn't mean much.

    http://liionbms.com/php/prismatic_cells.php

    So what are you saying? Are you saying that LiFeP04 cells are not reliable or safe?
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    northerner wrote: »
    So what are you saying? Are you saying that LiFeP04 cells are not reliable or safe?
    No one can say that, they havn't been around long enough to know. I said you ought to at least know what they look like inside.
  • PhotowhitPhotowhit Solar Expert Posts: 4,280 ✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    It would be easy to figure out what the best battery is if every day was the same, They aren't...

    YOU CAN NOT COMPARE BATTERIES USING POTENTIAL!

    IN OFF GRID SYSTEMS YOU MUST WASTE POTENTIAL IN ORDER TO SECURE CAPACITY!

    Sorry for shouting, but I have to rerun peoples numbers so they can understand how off grid systems work, I've done it in a half dozen LFP past threads. Hope people will read this and try to understand. I don't own a generator yet and don't intend to, though I wouldn't pass up a bargain...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    I did find this short circuit test of a Winston 160 ah cell. Interesting video!

    http://gwl-power.tumblr.com/post/70017866727/test-the-winston-lifepo4-cell-160ah-short-circuit
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    Here is a Winston cell that looks like someone cut open for a Demo and covered with Plexiglas. Looks like it has many small pouch cells. One thing if you lose a few you'd never know it.

    Attachment not found.
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    I found a bit more info about the Winston cells which have Yttrium here:

    http://www.diyelectriccar.com/forums/showthread.php/whats-difference-between-lifepo4-and-lifeypo4-56271.html

    Apparently, the addition of Yttrium at the cathode improves cold weather performance.
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    One more consideration if deciding on using LFP batteries for off grid storage is the fact that actual calendar life of the batteries is still not known, as others have alluded to. Even though a company may claim a 6000 (16 year) or 8000 (22 year) cycle life at a certain daily average DOD, the battery may have a shorter calendar life. From the research I have done, some figure around 10 years, and perhaps longer, but really nobody knows at this point. Something one may consider if deciding to go this route!
  • westbranchwestbranch Solar Expert Posts: 4,873 ✭✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    The fact that there are other 'new' chemistries, like the addition of Yttrium for cold weather performance, coming out tells me they still think (know?) that the cells can/must be improved on for the average Joe to be happy with the performance, think DreamLiner and fire...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    Since we know that a LiFeP04 Prismatic Battery is a plastic case with a bunch of Pouch / Envelope cells paralleled inside it might be a good time to do some research about them. It's easy to see why the charging perimeters are so critical. How many cell phone batteries does it take to run a off grid system ??

    http://batteryuniversity.com/learn/article/pouch_cell_small_but_not_trouble_free
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    A area of concern that I have is internal corrosion cause by the failure of one pouch that releases it's electrolyte into the battery case. Based on the picture on the web site I posted that battery had a massive failure from a leak ( maybe ). It had to be there long enough to dissolve the foil clamps. It's not hard to see the pouches have been compromised from it also. Can one leaking pouch take the whole battery out ?? So much for longevity if thats the case. Of course there is no way to know the history of this battery.

    Attachment not found.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery

    Actually they aren't pouches. In a large prismatic, between the anodes and the cathodes is the leafed separator material, and the electrolyte is a thin layer coating them.

    The pic above shows what happens when you let a lifepo4 sit too long at an extremely low voltage - far lower than what you run normally. The copper anode gets eaten away, gassing, and swelling the case if it is not constrained. A secondary damage comes from recharging the battery in this abused condition with full current. Double whammy.

    On the opposite end of high voltage, held over time, lithium plating occurs and damage comes that way.

    Solution - don't do that. Much like not charging your lead acid at 18v, nor letting it sit and sulfate at 1v for a decade in your garage. The damage is different but the solution is to just maintain the battery properly.

    As for cellphone batteries - different chemistry, and much more volatile requiring extreme maintenance methods not applicable to our application.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    westbranch wrote: »
    The fact that there are other 'new' chemistries, like the addition of Yttrium for cold weather performance, coming out tells me they still think (know?) that the cells can/must be improved on for the average Joe to be happy with the performance, think DreamLiner and fire...

    The addition of small amounts of yttrium to the lifepo4 (LiFeYpo4) mix is supposedly to improve the cold weather performance. GBS on the other hand, used a very small amount of manganese (LiFeMNpo4) to improve it's performance. CALB doesn't add any other chemicals, but refines the anode and cathode material to sustain huge current demands. Take your pick if that is important to your needs.

    The Dreamliner did NOT use lifepo4. Also, like other reports of fire, nobody asks to see if the actual charger or poor infrastructure wiring set it off, and not the battery per se. High resistance terminal and interconnects are common for shade-tree installations. If you do it, you do it right regardless of chemistry. Makes for good sensationalist news-bytes though. Nobody is interested in the under-hood lead-acid explosions from a bad setup - that is accepted and taken for granted. Battery blows up but nobody investigates the charger nor the wiring infrastructure that may have lead (pardon the pun) up to it.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    PNjunction wrote: »
    Actually they aren't pouches. In a large prismatic, between the anodes and the cathodes is the leafed separator material, and the electrolyte is a thin layer coating them.

    The pic above shows what happens when you let a lifepo4 sit too long at an extremely low voltage - far lower than what you run normally. The copper anode gets eaten away, gassing, and swelling the case if it is not constrained. A secondary damage comes from recharging the battery in this abused condition with full current. Double whammy.

    On the opposite end of high voltage, held over time, lithium plating occurs and damage comes that way.

    Solution - don't do that. Much like not charging your lead acid at 18v, nor letting it sit and sulfate at 1v for a decade in your garage. The damage is different but the solution is to just maintain the battery properly.

    As for cellphone batteries - different chemistry, and much more volatile requiring extreme maintenance methods not applicable to our application.
    Sounds like a good guess on your part, keep up the good thinking.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Perfomance data from LiFePO4 (LFP) Battery
    northerner wrote: »
    I did find this short circuit test of a Winston 160 ah cell. Interesting video!

    http://gwl-power.tumblr.com/post/70017866727/test-the-winston-lifepo4-cell-160ah-short-circuit

    What it really demonstrates is that nobody in their right mind does a direct short like that on purpose - however, even under these conditions of total abuse you witness the electrolyte cooking off and the battery itself doesn't catch fire. Later, what DOES cause the battery to catch on fire and melt is the HIGH RESISTANCE STEEL BOLT which melts the battery and the wiring infrastructure.

    Ironically, although at first totally dramatic, it demonstrates that lifepo4 is not a firecracker unlike the chemistry of most laptop batteries. The fire department is standing by and instead of applying extinguishers to the whole mess, a fan is used to disperse the cooked electrolyte vapor.

    Essentially, there is no defense for shoddy installation schemes that have no fuses or other safety features to help safeguard against these type of accidents no matter the chemistry.

    A far better video of capacity testing under *normal* conditions:
    https://www.youtube.com/watch?v=oJ8AfJsOhsM

    Now we're talking.
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