Battery charging

Plucka
Plucka Registered Users Posts: 130 ✭✭
Best setting for charging lithium batteries -gel -flooded or sealed?

Comments

  • Wheelman55
    Wheelman55 Registered Users Posts: 233 ✭✭✭
    Plucka...what are the charging specs for the battery that you want to charge?  That will tell you how many volts you can use.  There are AC chargers as well as PV charge controllers made specifically for 12 volt lithium batteries.  Lithium batteries have a unique charge regimen vs LA.
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    My understanding is absorb voltage should be adjustable (for the lithium chemistry and cell configuration used) as should absorb time (typically very short for lithium vs L.A. gel/agm/flooded).  A L.A. preset probably isn't ideal.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Are the settings you are referring to basic selections in a basic controller?
    Details of the battery are important, such as if it has a built-in BMS or if it a DIY system.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • DJJ
    DJJ Registered Users Posts: 7 ✭✭
    Hi everyone  Is there a way to connect 6-6volt batteries and maintain 24 v.
  • DJJ
    DJJ Registered Users Posts: 7 ✭✭
    Is the 6-6 v batteries a good idea or not?
  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    edited June 2019 #7
    I have an LDSolar 12/24 mppt charger that gives a choice of  the 3 battery types and supplier says okay for lithium. but he is shut today.Yes it has a commercial BMS> .This is just too difficult for a 75 year old.Found something.Battery type --sel  ---gel-------fld                                                                                                                                                                                         Boost       14.4    14.2      14.6                                                                                                                                                                                  Float        13.8    13.8       13.8                                                                                                                                                         The rest of the figures are the same for all 3 batteries and the default is Sel
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    I don't see how you connect 6 x 6v batteries in a 24v bank.  4 x 6v = 24v bank.  8 x 6v = 2 parallel strings of 24v each.  6 doesn't work for 24v.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Generally speaking a BMS is designed to protect the battery from overcharge, over discharge and various other parameters which may differ depending om naked or model. The maximum charging voltage for a 12V nominal lifepo4 battery  is typically 14.4V or 3.600 volts per cell, or cell block, the 12V will have 4 in series.

    For the purpose of off grid, often  a lower voltage is utilized to prevent charging to 100%, the intention is to extend lifespan by preventing the cells from stress near the fully charged state. Usually a voltage of ~3.450 to 3.500V per cell (VPC ) is used or 13.8V to 14V for a 12V battery, this is not an issue because the capacity above 3.450 VPC represents a tiny fraction of the overall capacity. 

    Lithium batteries do not charge like lead acid, there is no absorption stage where current drops as the battery nears full capacity, they accept all available current until terminal voltage is reached. Should there be no way of regulation the voltage would runaway, damaging the cells, this is where the BMS steps in to drop the current as the voltage nears the target value  to very low values, otherwise the voltage would climb too fast.

    There are differing schools of thought regarding float voltage, or the use of float at all, in applications such as electric vehicles there would be little need for float since the self discharge is negligible. Off grid solar use is different because there generally are loads which would deplete capacity over the course of the day if all charging were terminated, meaning there would be less capacity overnight.

    The best values from the ones listed would be the lowest available 14.2V, the unknown however is what determines the transition to float, with more advanced charge controllers this can be programmed, since it appears the LD Solar has no specific lithium setting it may not be compatible, so I would not recommend using something without specific charging algorithms for lifepo4. The manufacturer may claim it will work for the application, but the only way I could see this being the case is if the voltage is set to 14.4V,  the BMS terminates charging and  the algorithm transitions to float based on current drop, way too much guessing.

    The best I can suggest is get a controller that is programmable, lithium batteries need more specific settings than flooded, sealed or gel, this is my opinion, others may differ. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    Plucka, If you are going to invest in lithium do buy a controller with specific lithium settings, any thing else will probably destroy the lithium batteries and you will be burning money...
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    • The regulator is only suitable for lead acid batteries: OPEN,AGM, GEL
    • It is not suited for nickel metal hydride, lithium ions or other batteries Just found this new instruction on their web site.
  • DJJ
    DJJ Registered Users Posts: 7 ✭✭
    Estragon  I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?  
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,040 ✭✭✭✭✭
    DJJ said:
    Estragon  I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?  
    You can but then you have a 24 volt bank and a 6 volt bank.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    DJJ,

    I you mean build two series strings of 4x6 batteries for 24 volts, then connecting those 2 strings together in parallel (for 2x more AH capacity) for a total of 8x 6 volt batteries in series/parallel--Yes you can.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    DJJ said:
    Estragon  I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?  
    You can with 8 batteries, but not with 6.  The parallel strings need to be the same voltage (otherwise the higher voltage string would discharge into the lower one).

    You could parallel first, then put the paralleled batteries in series, but then 1/2 of the string is 1/2 capacity vs the other 1/2, so the smaller capacity will be drawn down to a lower relative SOC than the larger.  Both the large and small will fail early from under/overcharging. Also bad.

    In other words, for 24v you need 4 or 8 x 6v batteries.  6 doesn't work.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,040 ✭✭✭✭✭
    Any word on your battery bank wiring?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • DJJ
    DJJ Registered Users Posts: 7 ✭✭
    Estragon said:
    DJJ said:
    Estragon  I realize 4x6=24v but can't you hook 4 in series and 2 in parallel?  
    You can with 8 batteries, but not with 6.  The parallel strings need to be the same voltage (otherwise the higher voltage string would discharge into the lower one).

    You could parallel first, then put the paralleled batteries in series, but then 1/2 of the string is 1/2 capacity vs the other 1/2, so the smaller capacity will be drawn down to a lower relative SOC than the larger.  Both the large and small will fail early from under/overcharging. Also bad.

    In other words, for 24v you need 4 or 8 x 6v batteries.  6 doesn't work.
    Thanks Estragon
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    edited June 2019 #18
    People do have a 24 volt (for example) battery bank, then try to take 12 volts off of 1/2 the battery bank.
    Don't do it.
    You end up with 1/2 the bank under charged (where the 12 volts is tapped off), and the other 1/2 over charged.
    It just does not work well.
    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SDCacti
    SDCacti Registered Users Posts: 9 ✭✭
    edited June 2019 #19
    Thank you for the info, my apologies if it takes me a bit to wrap my head around some of these concepts. I work in an instrumentation/process control/SCADA field and am only a couple years into my career so by no means an expert and have much to learn about electrical systems. I built this little system one piece at a time for that purpose so advice is appreciated.
    Question-
    So i cant afford to go out and buy a whole new set of batteries now, so what is my best bet for using these 12 volt batteries? using just 8 of them? I looked em up and they are Duracell Ultra 12v high rate AGM SLA batteries (82ah) my panels are 2x 270wt Renogy (poly) and i have two 100 watt 12v renogy poly panels. As I mentioned a outback flex 60 amp controller and 3000 watt aims inverter. all in an enclosure w breakers and such.. basically what is the best way to set this up for my equip to get the most from it?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    SDCacti,

    After I finish this post, I am going to split your discussion into its own thread... It is easier to understand/follow your needs and address them, rather than mixing with the Original Poster (OP) and his questions.

    With solar, it works best if you have some "fixed thing" to design around... Generally, the idea is to measure/understand your loads, and then define the battery bank... Then design the solar array to a) charge at 5% to 13% or so rate of charge, and b) to keep up with your loads and hours of sun per day.

    However, in this case... You have the battery bank, so we figure out how much energy the bank can produce, and then design the solar array to do 1) and 2).

    The first past is just a simple back of the envelope/paper design process. Don't care about "exact hardware" and such until we have the basics down. Once we have a paper design, we can then size/pick/price the hardware that will support your needs.

    The neat thing about the paper design is that if something does not meet your needs, it is very quick to reconfigure... Like you start with 8x AGM batteries. If the system does not meet your needs, we adjust (more/fewer/different batteries/etc.). Then we figure out the rest of the system hardware. This is all trying to design and build a "balanced" system (right size battery bank, right size inverter, right size array, etc.).

    Battery bank. 8x AGM 12 volt @ 82 AH batteries for a 24 volt battery bank. Note, that will be 2x batteries in series (2x12v= 24 volts) and 4x parallel strings (4x82ah=328 AH). Note--I am not a big fan of paralleling a bunch of small batteries in parallel--I like larger AH rated batteries and fewer parallel strings... 1-2 is probably ideal, and I would try to avoid going over ~3 parallel strings (more wring, more costs, more connections/batteries/cells to fail). But--You have what you have.

    All these calculations are starting from a rule of thumb design for a full time off grid system... Anything you have questions about , please ask. Any assumptions/guesses I made that are wrong or different--please change.

    Generally suggest 2 days and 50% maximum discharge for battery bank usage (full time off grid/best overall performance)--For emergency and weekend RV/Cabin, using 1 day of storage and 50% max discharge can work.
    • 24 volts * 328 AH battery bank * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 1,673 Watt*Hours per day (2 days of "no-sun")
    Next, need to figure out the size of solar array to have a 5% to 13% rate of charge--For "solar" systems, 5% rate of charge can work for emergency and weekend/sunny weather systems. For full time off grid, use 10%+ rate of charge.
    • 328 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 618 Watt array minimum
    • 328 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,235 Watt array nominal
    • 328 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,606 Watt array "cost effective" maximum
    And then there is sizing your system to support your loads--Assuming you charge during the day and use power at night, that would be ~1,673 WH from your battery bank that needs to be recharged.

    I have no idea where you are at--Let's assume somewhere in Southern California. Fixed array facing south. 
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    San Bernardino
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 56° angle:
    (For best year-round performance)

    JanFebMarAprMayJun
    4.64
     
    5.02
     
    6.28
     
    6.73
     
    6.70
     
    6.65
     
    JulAugSepOctNovDec
    6.43
     
    6.42
     
    6.25
     
    5.77
     
    5.07
     
    4.55
     

    In So Cal, there is a lot of sun even in the winter... December is 4.55 hours "average" sun--So if we use that number, you may have to run a genset/conserve power during bad weather in winter:
    • 1,673 Watt*Hours from battery bank * 1/0.52 off grid AC system efficiency * 1/4.55 hours (Dec) sun = 707 Watt array minimum for "December" break even power
    For your system assuming it is more of a backup/seasonal usage, somewhere between 707 to 1,235 Watt array would work pretty well... If this was a full time off grid system, then 1,236 to 1,606 Watt array would be nicer (and cut genset runtime to near zero except for a few days of bad weather).

    For your system, I would normally recommend 250 to 500 Watt inverter per 100 AH of 24 volt battery bank:
    • 328 AH * 250 W / 100 AH = 820 Watt AC inverter "nominal"
    • 328 AH * 500 W / 100 AH = 1,640 Watt AC inverter "on the large side"
    And if you wanted to predict the "average" harvest for a larger array (1,606 Watt @ 13% rate of charge) and different month (June, the equation would look like this:
    • 1,606 Watt array * 6.65 hours of sun * 0.52 off grid system eff = 5,554 Watt*Hours per day
    • 5,554 WH per day - 1,673 WH overnight battery power = 3,881 WH for "day time" loads
    The above is based on flooded cell lead acid batteries... You have AGM which can surge 2x (or more) current vs FLA batteries... However, for a balance system design, oversizing the AC inverter is not a great idea... Too large of AC inverter will "burn extra power" just being turned... A very large inverter only make sense if you have high power / short term loads (well pump, machine tools, etc.)--Not just power computers/lights/cell phone chargers etc...

    The above "brackets" your system based on the present battery bank... And down the road, you could for example, replace the12x AGM batteries with 4 or 8 6 volt @ ~200 AH "golf cart" batteries in series parallel configuration (4x 6 volts = 24 volts; 1 string or 2x parallel strings) and the rest of the system (solar panels, charge controller, AC inverter) would all be the same.

    Looking at the above... What works/does not work for you (location, cost of solar panels, more/less battery power than you need, emergency vs "off grid" living, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset