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Thread: question on 12v,40ah battery

  1. #1
    Junior Member
    Join Date
    Feb 2009

    Default question on 12v,40ah battery

    hi everyone. i want to know can 12v,100w solar panel recharge 12v, 40ah? will the battery over-charging?if the battery over-charging, what the suitable battery do i need to use? and another question is how long can the solar panel fully recharge the battery?

  2. #2


    Quote Originally Posted by farhannna View Post
    hi everyone. i want to know can 12v,100w solar panel recharge 12v, 40ah? will the battery over-charging?if the battery over-charging, what the suitable battery do i need to use? and another question is how long can the solar panel fully recharge the battery?
    you need one regulator to control the solar panel and battery. Then the regulator can help you the protect the battery over-charge or deep discharge.

    how long time depends on the capacity of the battery and the Ah you get from your solar module.

  3. #3
    Solar Skipper
    Join Date
    May 2009
    Jakarta [Lat:06:08South Long:106:45East] Indonesia

    Default Need one regulator

    Quote Originally Posted by indalecio.feng View Post
    you need one regulator to control ...
    ... regulator can help ...
    ... time depends on the capacity of the battery and the Ah you get from your solar module.
    Last edited by MarineLiner; 05-25-2009 at 12:39 AM. Reason: 40 / 8 = 5

  4. #4

    Default Overcharge, Overdischarge, Overcurrent, Short Circuit, Over Temperature protection fu

    Dear Sir:
    for your 12V40AH battery, you can use the BMS ( Battery management system), because we are the LiFePo4 battery manafacture in China, Shangdong Hipower Batteries is the pioneer of Lifepo4 battery manufacturer with 6 years of mass production expriece which is 3 years earlier than other companies. With an investment of USD 48Million and a production base of 520,000 square meters, we are now the biggest lifepo4 battery maker. our LiFePo4 battery exporting volumn in 2008 accounted for more than 1/4 that of total China.
    Here’s a list of all the advantages of LiFePo4 batteries:
    1. Safe technology — will not catch fire or explode with overcharge, the only 100% safe lithium battery till now ,High thermal stability of phases up to 500C.
    2. Extraordinary Long Cycle Life: Over 2000 discharge cycles life compared to typically around 300 for lead acid
    3. Double the usable capacity of similar amp hour lead acid batteries
    4. Virtually flat discharge curve means maximum power available until fully discharged (no “voltage sag” as with lead acid batteries)
    5. High discharge rate capability, 10C continuous, 20C pulse discharge
    6. Unlike lead acid batteries, can be left in a partially discharged state for extended periods without causing permanent damage
    7. Extremely low self discharge rate (unlike lead acid which will go flat quite quickly if left sitting for long periods)
    8. Does not suffer from “thermal runaway”
    9. Can be used safely in high ambient temperatures of up to 60C without any degradation in performance
    10. Maintenance free for the life of the battery
    11. Can be operated in any orientation
    12. Does not contain any toxic heavy metals such as lead, cadmium, nor any corrosive acids or alkalies thus making LiFePO4 batteries the most environmentally friendly battery chemistry available
    13. LiFePO4 cells are of solid construction — there are no fragile/brittle plates made of lead which can be prone to failure over time as a result of vibration
    14. Can be safely rapidly recharged — when fully discharged can be brought to a state of over 90% fully charged in 15 minutes
    15. Wide working temperature range : From -25

  5. #5

    Default Why LiFePo4 battery for solar s ystem ?

    Advantages of LiFePo4 battery in Solar industry
    Ⅰ. Charge factor :
    1. Absorbency of LiFePo4 battery is very strong . for the LiFePo4 battery , we have 2 types, one is normal, and another is high capacity power. For the Normal one, we can reach to 3C charge ability, and if you have any special demand, you can use our high capacity power battery, they can reach to 10C charge ability .
    And for the Lead Acid battery, if we use the good qualiy, they only have charge ability at 0.2C . when under the weak sunshine, the Lead Acid can not absorb the solar energy, and for the LiFePo4 battery, still can absorb, that because the LiFePo4 battery is at lower volt (just more higher than3.5V/Cell) which still can charging.
    The charging rate of LiFePO4 can reach 3C.if any special requirement,it can withstand 10C charge rate.while for the high quality of lead acid battery,the maximum charge rate is only 0.2C.
    when under the weak sunshine, the Lead Acid can not absorb the solar energy.but LiFePo4 battery still has strong capability of absorbing energy even under weak sunshine. Moreover,the charging voltage is relatively lower,only if the voltage is over 3.5v,the batteries can be charged and its available charging time is longer.

    2. For the Lead acid battery, they only can charge (0.2C charging ability) , if over charging which will affect the lifetime of the battery, (for the LiFePo4 battery, we will design for the BMS system, which means they will prevent the over-charging and discharging which can protect the battery pack, and LiFePo4 also has the balacing function,which can keep as consistency for every battery all the time .) and here is 2C charging ability for the LiFePo4, that means its charging ability is ten times of Lead Acid battery. This characteristic plays an important role in designing of Solar modules.

    For example, most strong sunshine is at noon time, if the Solar module can convert as 10A charging current, Then we need at least 50AH lead acid battery that can completely absord the charging current of 10A(since lead acid battery has only 0.2C charing capability).
    However the battery lifespan is two years and it also decays during usage,then we have to add 40% more of the capacity .therefore we need at least 70ah lead acid battery to ensure it has the ability to abosorbing 10A charging current within two years.meanwhile for this 70ah lead acid battery,it can not be fully charged after a whole day’s sunshine.but without such large capacity of 70ah,it can not absorb the current that is produced by solar pannel during its highest efficiency.thus it is a waste of energy and cost from this point.

    means if you use Lead Acid battery, the lead aicd battery must have 50A current ability which can absorb the 10A current from the solar modules(Charging ability). But we deduct the lifetime 2 years for the Lead Acid battery, and we also must take attenuation into consideration, means we must add 40% current , so we must need 70A current lead acid battery, can reach to our requirement which can have ability for 10A charging current about in one year time.
    But after whole day’s sunshine, it can not be charged fully in the Lead Acid battery. But if you not use so big current which can not absorb the best current under best efficiency from the solar modules, so it is waste a lot.
    Lead acid battery can only withstand no more than 0.2C charge rate.when over 0.2C,they are like to get damaged.while LiFePO4 battery can be charged with 2C,that is to say the charging capacity of Lifepo4 is as ten times as that of lead aci battery

    3. But if you choose the LiFePo4 battery, you don’t need to consider the charging ability at all, you just need to consider how much current and power can get from the solar modules. For example, most strong sunshine is at noon time, if the solar modules can convert as 10A charging current, so it can storage 30A current at most, that means you just need a 30Ah LiFePo4 battery and no need to consider how high or low of charging current
    Totally not to need to consider the problem of charging current, and for the 30Ah LiFePo4 battery, its charging can reach to 90Ah which will not affect the life time or get hot.
    4. from above we can conclude that,when selecting what capacity of battery you need, you have to consider charging current for lead acid battery,while for LiFePO4 battery, you only need consider charging capacity
    Ⅱ. Lifetime factors:
    1. The solar modules usually are installed the remote places where is not so convenient to get the electricity power. If you need to replace battery every 2 or 3 years, do you think it is troublesome or not ? moreover, the lifetime of the solar modules are 20 years, so you can calculate how many times you need to replace the lead acid batteries?
    2. After 2000 times cycling test under 1C discharge condition in the lab, there only 8 percent of the capacity has been reduced for LiFePo4. If take a normal battery lifetime as a standard, the lifetime of the LiFePo4 is far more long as expected, at least fifteen years. (There is a criterion in battery industry.it says that the battery life is end when its capacity remains less than 60%)
    3. Also check the Hipower discharge curve at 0.5C
    Testing result:
    The voltage keeps 98%, and the capacity resumes 98%
    Store the fully charged battery under room temperature (55℃

  6. #6
    Join Date
    May 2009
    off grid retirement in Northern Calif


    hipowercandy - re your LiFePo4 battery. What is required to manage the charge for it. I doubt very much, that a standard lead/acid controller can properly charge it. You state the charge current does not matter - it can accept up to C2 rates. What happens when the battery is "full" ? how is charge current regulated then?

    what about internal resistance. Suppose there is a 30A load on the battery, and a large motor is turned on. The inverter will call for several 100A to supply starting current for the motor, for up to 5 seconds. Is the internal resistance low enough to supply the starting surges too ?
    Since the dawn of time it has been mankind's dream to blot out the sun.
    Montgomery Burns

    "Always listen to experts. They'll tell you what can't be done and why. Then do it."

    spreadsheet based voltage drop calculator:


    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,
    battery lugs http://tinyurl.com/LMR-BigLug
    Setting up batteries http://tinyurl.com/LMR-NiFe

    gear :
    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

  7. #7

    Default what is the resistance for the LiFePo4 battery ?

    Reply Mike:
    LiFepo4 is the Newest Technology in the world now.
    We will have a BMS with the whole battery pack (Battery Management system), Regarding BMS, it has at least six functions. Overcharge, Overdischarge, Overcurrent, Short Circuit, Over Temperature protection functions and balancing. the balancing also is very important for the battery pack, you know the battery consistncy is the key point of the lifetime.
    yes, the internal resistance low enough to supply the starting surges too . LiFePo4 can stand the big current charging (Our engineer suggest 1C, but LiFePo4 can stand 2-3C charging) and discharging (8C, even 15C discharging rate)

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