Question for the LFP Battery Users...

Mountain Don
Mountain Don Solar Expert Posts: 494 ✭✭✭
in Advanced Solar Electric Technical Forum #1
IF you are using a LFP battery bank that you assembled yourself....

Have you encased the cells in a "set" that is clamped / restrained by plates and bars? I gather this is usually done to maybe restrain swelling in case of an over charge.

Thanks
Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
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  • karrak
    karrak Solar Expert Posts: 326 ✭✭✭✭
    #2
    Re: Question for the LFP Battery Users...
    Mountain Don wrote: »
    IF you are using a LFP battery bank that you assembled yourself....

    Have you encased the cells in a "set" that is clamped / restrained by plates and bars? I gather this is usually done to maybe restrain swelling in case of an over charge.

    Thanks

    I have not clamped my cells. With the gentle charge and discharge cycles my battery has I have not noticed any swelling in about 20 months. Measured the end cells with a strait edge and they are slightly concave.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

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  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    #3
    Re: Question for the LFP Battery Users...

    A second question for the LFP users out there.... Many of you seem to be mobile users; RV's. Does that mean that the RV location is usually in a warm place, like a "snowbird"? A place where you do not have freezing temperatures? Or do you keep the batteries in a warm storage area in the RV? What the question comes down to is do you do anything to prevent charging in freezing weather? I have read in a few places (user manual for Genasun LFP batteries, for one) that LFP should not be charged under 32 degrees F.

    Thanks
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Question for the LFP Battery Users...

    The LiFePo's do not suffer from the low SOC/cold temp freezing issues of lead-acid; they're not full of water. Cold does slow down the chemical action (as it does with all chemical reactions) but not as significantly. This is one of the advantages.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #5
    Re: Question for the LFP Battery Users...

    Doing a little googling, different electrolytes have different freezing points... From -3C to -35C or so. But there are other issues that appear to possibly cause issues with low temperature operations (and perhaps, charging minimum voltage is different than discharging minimum temperature). From poster "T1_Terry):

    http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-224.html
    "Research on cathode material of Li-ion battery by yttrium doping,JOURNAL OF RARE EARTHS, Vol. 26, No. 2, Apr. 2008, p. 279 by TIAN Yanwen (田彦文)1, KANG Xiaoxue (康晓雪)1, LIU Liying(刘丽英)2, XU Chaqing (徐茶青)1, QU Tao (曲涛)1"

    Certainly its clear from that article that Y doping in LiFePo4 in certain amounts improves both initial discharge ability and also cyclic performance was improved. This is because Yttrium doping improves the conductivity of the cell over that of non doped Lifepo4 cathodes .

    Low temperature performance of LI cells, is still a matter of considerable scientific debate, but can be summarised as

    (a) reduced conductivity of the electrolyte and solid electrolyte interface on the elec- trod surface
    (b) limited diffusivity of lithium ions within graphite anode
    (c) high polarization of the graphite anode, ( as per (b)
    (d) substantially increased charge-transfer resistance on the electrolyte–electrode interfaces

    ( S.S. Zhang∗, K. Xu, T.R. Jow, Electrochemical impedance study on the low temperature of Li-ion batteries,US Army Research Laboratory, Adelphi, MD 20783-1197, US, Electrochimica Acta 49 (2004) 1057–1061.)

    Of this the primary factor has been to kinetics of Ion transfer at low temperature, and it has been shown that while discharge can occur at increasingly lower temperatures, the equivalent resistance of the cell reaction kinetics, increases with discharge at low termoperatures , making re-charging such cells difficult or even impossible at low temperature.

    So--It still appears that a person should not expect to operate a Li Ion rechargeable below 0C, and possibly not even below 5C.

    But they are so different than Lead Acid, there is just no similarities in operation/failures between the two chemistries.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Question for the LFP Battery Users...

    And of course this points out once again that not all lithium batteries are the same, and unlike with subtle differences in lead-acid the differences in lithium batteries are significant.

    In other words be sure you get the right ones; don't just buy after you read the word "lithium" in the description.
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  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    #7
    Re: Question for the LFP Battery Users...

    Genasun has been supplying LFP systems to the marine industry for many years. I found one of their user manuals online. In their user manual there is a section on temperature. Their battery packs are fitted with sensors in different locations throughout the pack. When the sensor reads 0 Celsius it turn off the charging buss. When the temperature sensor reads -20 Celsius it turns off the discharge buss. There is also a note that they offer a heater package that can be programmed to come on when necessary. See section 8

    Further reading about the lithium batteries in the Chevy volt finds that those battery packs have both a heating and a cooling system. Electric heaters that can operate while plugged in.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #8
    Re: Question for the LFP Battery Users...

    I don't know if one could assume that any of the 3-4 LiFeP04 battery Manufacturers use the same mix in their electrolyte. Believe anything you want, I guess, it's the Internet after all, you can throw up anything and see if it sticks.

    Here is what Winston says, not sure if I'd believe it.

    Attachment not found.
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  • RVTechnomad
    RVTechnomad Registered Users Posts: 5 ✭✭
    #9
    Re: Question for the LFP Battery Users...

    Hi all, I'm new and glad to find this forum.

    I have lithium batteries in my RV and they came as 12 volt batteries with stainless steel straps and aluminum plates on either end. I heard it was for the reason you asked, to restrain swelling.

    About temperature, the dealer that installed my Li-ion battery is Starlight Solar in Yuma az. He made sure I understood that if the cell temperature goes below 32° that my solar controller and battery charger will stop working until the temperature goes up. But, I can still use the power, just not charge below 32°. They do have a battery heater but because my bay has heat I chose not to install it. My battery is 360Ah of LFMP which is different than LFP but I don't understand much more than that. They installed my solar system a few years earlier and did a great job. Here's some info about the battery i bought: http://www.starlightsolar.com/RV_Lithium_Battery.html
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  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    #10
    Re: Question for the LFP Battery Users...

    Thanks for your response. The "M" is for manganese which is that manufacturers "enhancement"... still basically an LFP. That appears to have a comprehensive management system at the cell level. Cool!.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
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  • RVTechnomad
    RVTechnomad Registered Users Posts: 5 ✭✭
    #11
    Re: Question for the LFP Battery Users...
    Mountain Don wrote: »
    Thanks for your response. The "M" is for manganese which is that manufacturers "enhancement"... still basically an LFP. That appears to have a comprehensive management system at the cell level. Cool!.

    Hi Don,

    I wish the manufacturer would publish WHY they use mangenese and what the benefit is. I do know that these batteries are smaller than LFP batteries of equal capacity.

    Yes, all my battery cells have EMS to control of many things. No cells ever over charge because each cell will begin to shunt current to allow other cells to charge until all are equal. I really liked this feature and the fact that it came with a computer so I don't have to do anything. What is really cool is the dealer connected the computer to my TV's. If I want to monitor the SOC or temperature or any other data about the battery, I just hit "Video 2" on my TV's and the data is there.

    Stuart
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #12
    Re: Question for the LFP Battery Users...

    Interesting chart of comparison....

    Do you have a 12 V system with 2 batteries or just one 12V LFMP? What are the loads you run regularly (daily)? amount of solar capacity? etc..
     
    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,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • RVTechnomad
    RVTechnomad Registered Users Posts: 5 ✭✭
    #13
    Re: Question for the LFP Battery Users...

    Hello Westbranch,

    I have 24 cells, 360AH @ 13 volts. My PV solar system is about 1400 Watts, 2 outback controllers. No temperature compensation; Li-ion does not need that. The alternator charges to 13.9 volts with amperage about 100 amps. Loads are computers, lights, fans, water pump and various small loads. Occassional ham radio operation with 500 Watt RF amplifier. My use varies but up to 250AH discharge on the high side which the PV solar quickly replaces.

    I did my own battery comparrison: 440AH of Lifeline battery was $1400 installed. If I remove 200AH per night from the lifeline battery, they will last for about 1500 cycles. $1400/1500 cycles is $0.93 cost per cycle. The LFMP bank was $3629. They will last for at least 4000 cycles at the 200AH or 55% DoD. $3629/4000 is $0.91 cost per cycle. So the Lithium battery will cost less to own plus I get all the features and benefits of the Lithium system. If they last 11 years, about 4000 cycles, I will be pleased because of the incredable performance I am getting.



    Stuart
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
    Re: Question for the LFP Battery Users...

    And if they don't last for 4000 cycles?
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #15
    Re: Question for the LFP Battery Users...
    RVTechnomad wrote: »
    Hello Westbranch,
    I will be pleased because of the incredible performance I am getting.
    Stuart

    Hi Stuart, can you tell us about your observations that make you so happy with the LFMPo4 battery.

    If I understand correctly:
    You have 3 parallel 120Ah 12V batteries and charge while driving and top/finish off with PV or fully PV if docked? (even though you do not need to get 100% SoC);

    A 3 hr drive would /should fill 'er up if down to ~ 30%SoC (250A for 1 hr), right?
     
    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,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • RVTechnomad
    RVTechnomad Registered Users Posts: 5 ✭✭
    #16
    Re: Question for the LFP Battery Users...
    Cariboocoot wrote: »
    And if they don't last for 4000 cycles?


    Well...I'll chock it up to the cost of living on the leading edge of technology. As a TechNomad, I have always sought out new and useful technologies to work for me. This is just part of that quest.
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  • RVTechnomad
    RVTechnomad Registered Users Posts: 5 ✭✭
    #17
    Re: Question for the LFP Battery Users...
    westbranch wrote: »
    Hi Stuart, can you tell us about your observations that make you so happy with the LFMPo4 battery.

    If I understand correctly:
    You have 3 parallel 120Ah 12V batteries and charge while driving and top/finish off with PV or fully PV if docked? (even though you do not need to get 100% SoC);

    A 3 hr drive would /should fill 'er up if down to ~ 30%SoC (250A for 1 hr), right?

    Actually I have six 60Ah batteries, 24 cells, 6 parallel strings. The things I like best are no voltage sag under load, higher voltage and thus lower current and heat, extremely fast charging, takes full advantage of opportunity charges, and of high importance to me, no requirement and struggle to reach 100% SoC to prevent sulfation from damaging the battery. With lead acid, that was always a chore. Lower weight is also a plus since I use petroleum to move my house around.
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