MAX rate of charge for Flooded Lead Acid Batteries?

ligwydligwyd Registered Users Posts: 168 ✭✭
My 630 amp hour battery bank (3 strings of 4-12volt batteries) is currently set at 10% MAX charge rate. So 63 amp MAX in bulk.

The labels on my 12 volt batteries state 10-15 amps Bulk.

So, according to my battery labels the max charge rate should be 45 amps max for all three strings, however I realize that with solar you have to make hay while the sun shines and get the batteries charged up as fast as you can with the avail sunshine.

My question is what max charge rate is common for FLA banks? I know it is a ballpark question, relative to many other factors, however just looking for some feedback none the less......

I have read that 10-13% (of 20 hour capacity) max charge rate is a min recommendation. If I have enough solar could you go higher and if so what is the highest some have safely and successfully used?

Comments

  • mike_smike_s Registered Users Posts: 128 ✭✭
    ligwyd said:

    I have read that 10-13% (of 20 hour capacity) max charge rate is a min recommendation.
    What does that even mean? If they thought higher was good, they'd spec 10-25%, or whatever.

    Trojan is quite clear - 13% "Maximum Charge Current" (for FLA), with the note "If charging time is limited contact Trojan Technical Support for assistance."  But different manufacturers have different recommendations, and you haven't bothered mentioning which batteries you have.
  • Raj174Raj174 Solar Expert Posts: 787 ✭✭✭✭
    edited March 2020 #3
    That would be true if the batteries were 100 amp hour, but they are 210 amp hour, right, so up to 81 amps (13%) should be ok for bulk charging.

    3600W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH LiFePO4, Kohler Pro 5.2E.
  • BB.BB. Super Moderators, Administrators Posts: 31,433 admin
    Usually, it is GEL type batteries (at least in the USA) that end to have a 5% or C/20 limit on the rate of charge.

    Another issue could be is if the capacity (AH) of the battery bank is defined at C/100 discharge rate (makes tattery appear larger AH capacity vs the normal C/20 discharge rate battery capacity number we use).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Marc KurthMarc Kurth Solar Expert Posts: 842 ✭✭✭✭
    The best source of information regarding how far you can push something - is from the manufacturer. Yes, there is a huge amount of field experience here, but a decent guess cannot be offered without knowing what you have. All flooded batteries are not the same.
    I always have more questions than answers. That's the nature of life.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,805 ✭✭✭✭✭
    Fast charging for offgrid is a balance of the manufacturer and a lesser amount that will often yield the longest life. What is the rush? Go for a walk or a boat ride :)
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • ligwydligwyd Registered Users Posts: 168 ✭✭
    edited March 2020 #7
    Pic of the batteries used in this application and pdf of the spec sheet. C20 discharge rate of 630Ah (210 Ah per string).
    I'll fire off an e-mail to the vendor and manufacturer and post what I find.
    Any other feed back is appreciated.
    Thanks.

  • mike95490mike95490 Solar Expert Posts: 9,247 ✭✭✭✭✭
    The recurring story I've heard, is that flooded and AGM lead acid, can take a pretty beefy charge rate, well above normal rate, till the battery is about 80% full.  Then you must reduce to factory specs or heat damage occurs .
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Marc KurthMarc Kurth Solar Expert Posts: 842 ✭✭✭✭
    Discover put the specs on the battery label for a reason so I would let them tell me what they want and why.
    I realize that you know this, Mike, but for less experienced people I will point out that around 80% to 85% SOC is where the battery naturally increases in resistance and starts reducing its current draw on its own. That is the definition of going into the Absorb phase of the charging cycle.
    I always have more questions than answers. That's the nature of life.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,805 ✭✭✭✭✭
    It is actually the opposite of what Mike said and reducing this huge current is what can make a battery last well past warranty.

    If there is not a rational reason to hit a battery with all of the power you have, you can lessen the thermal shock of internals and get longer life.

    I really have never had a FLA not last long past 10 years and the only reason to replace was loss of capacity. I also am not just talking about my 30+ years but hundreds of clients offgrid.

    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mike95490mike95490 Solar Expert Posts: 9,247 ✭✭✭✭✭
    It's all about a balance of available sunlight, loads and generator fuel.  When the battery gets warm, slow down.

    And of course, the factory specs are very important. 
    And maybe late at night I inverted my logic and memory, so the rest of the innertubes will set you straight when I foul up.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • ligwydligwyd Registered Users Posts: 168 ✭✭
    Thanks for you all comments. Very much appreciated. Love this forum. My system is up and running and in service and performing well:)
  • mcgivormcgivor Solar Expert Posts: 3,724 ✭✭✭✭✭✭
    ligwyd said:
    Pic of the batteries used in this application and pdf of the spec sheet. C20 discharge rate of 630Ah (210 Ah per string).
    I'll fire off an e-mail to the vendor and manufacturer and post what I find.
    Any other feed back is appreciated.
    Thanks.



    This is a link to a cut away of that battery   https://forum.solar-electric.com/discussion/353896/tubular-lead-acid-battery-cutaway
    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.
  • mike95490mike95490 Solar Expert Posts: 9,247 ✭✭✭✭✭
    Label says to me, 15A max
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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