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What is the C Rate for AGM & LiFePO4 Battery?

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We can always see terms like 0.1C, 0.5C, 1C, C1, C10, C20 on some battery packages, labels, specifications, and manuals, then what do they mean?

Firstly, for 0.1C, 0.5C, 1C, and others with a number before the symbol C, we refer to the current. C refers to the value of the battery capacity.

For example, 12V100Ah battery, C is 100. “1C discharge” means 100A as discharge current. And just like that, 0.1C is 10A, 0.5C is 50A, which equals the number before C multiplied by the C value.

In the case of a number after the symbol C, we generally refer to the capacity.

For example, 12V100Ah C10, we mean that the capacity of this battery is 12V100Ah at 10 hours rate. It means this battery can support 0.1C (10A) current discharge for 10 hours constantly.

Especially for deep cycle AGM batteries, please note that the actual capacity will be different apparently at different hour rates.

Small batteries (below 24Ah) take C20 as the capacity standard, while large capacity batteries above 33Ah take C10 as the standard.

In some special industries and applications, because the operating current is really high, there are also cases that require a one-hour discharge or even a five-minute discharge, such as UPS, and some power tools.

In the present solar industry, the C100 standard is also very popular.

I don’t really understand why C100 is used. As in my understanding, the battery bank of solar system’s discharge cycle should be around 10 to 20 hours. If you are knowledgeable about this, please contact me, thank you!

C-Rate of Deep Cycle AGM Battery

Just as mentioned above, we generally choose C10 as the capacity standard for large batteries. In our Deep Cycle AGM Battery, we also use C10 as the capacity standard. In the case where C is not mentioned, e.g. 12V100Ah battery, we refer to 12V100Ah C10.

The actual capacity of the battery changes with the hour rate.

The higher the hour rate, the higher the actual capacity. The lower the discharge current, the higher the actual capacity.

Low current is more suited to release the remaining energy inside the battery.

The following table shows the discharge specifications of our 12V100Ah battery.

Table-01 12V100Ah Discharge Current & Voltage

We can see that at 10 hour rate, the discharge current is 10A and the end voltage is 1.80V/cell, i.e. 10.80V for 12V battery.

In the case of 20 hour rate, the discharge current is 5.36A, and the actual capacity of C20 is 107.2Ah.

At 5 hour rate, the current is 17.1A and the actual capacity is 85.5Ah C5.

If the manufacturer does not provide a specific discharge table, the actual capacity can be estimated approximately according to the following ratios (Only for reference, it can be different sometimes).






If you want to know more about our deep cycle AGM battery, please click the button below.

C-Rate of Small VRLA Battery

SLA, VRLA, AGM, are actually the same type of battery, but described in different ways.

SLA is Sealed Lead Acid Battery, which is described in terms of sealed container. VRLA is Valve Regulated Lead Acid Battery, which is described in terms of its valve-regulated structure. And AGM is a battery that uses AGM as a separator.

The classic model of small battery 12V7Ah is used in many applications, such as UPS, such as small energy storage systems, such as security systems, such as mobile audios, etc. Its capacity standard is normally C20, which means that it can support 0.05C (0.35A) discharge for 20 hours.

The following table shows the discharge specification of our 12V7Ah battery, please check.

Table-02 12V7Ah Discharge Current & Voltage

For special applications, such as UPS, we can see that the discharge current can reach 26.8A for 5 minutes. It means that it can support about 321.6W (12V*26.8A) of electrical appliances for 5 minutes.

Here we set the end voltage as low as 1.60V/cell because the battery voltage could be really low under high discharge current, and it will recover quickly once disconnected from the load.

For more information, you may check my another post, AGM Battery Voltage & Capacity.

This post describes in detail how the battery voltage performs differently under different conditions.

If you want to know more about our small VRLA battery, please click the button below.

C-Rate of LiFePO4 Battery

As the new generation of energy storage battery, LiFePO4 battery has the features of much longer cycle life, much higher constant power, much better high-temperature performance, much more stable, and more eco-friendly (Cobalt Free).

In power applications, LFP batteries can be discharged at currents up to 3C, 5C.

In energy storage applications, a discharge current of 1C is sufficient for most cases.

In home solar applications, a current discharge of 0.2C to 0.3C is most common. For example, for a 5kWh home solar battery, the discharge power is usually between 1kw and 2kw.

In the case of air conditioners with higher power, a 10kWh home solar battery can support more than 5kW power.

If you want to know more about our deep cycle LiFePO4 battery, please click the button below.

Hi, I’m Andy. Since the year 2015, I’ve been working in SunOn Battery, a manufacturer in China that makes various batteries for 15 years now. The purpose of this article is to share with you the knowledge related to batteries and energy storage solutions from a Chinese supplier’s perspective.

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11 Responses

    1. OK, yes, we will have different capacities in Ah based on different C ratings, such as C10, C100, etc.

      And when it is for a 12V100Ah battery, 1C is 100A.


    1. Hi Kirk,

      Most LiFePO4 batteries are supported for charging at 1C current.
      To avoid charge over temperature, it is recommended to charge under 0.5C.


  1. Hi Andy,
    I will need to replace my four old 12v 130Ah lead acid in-series batteries to power my Minn Kota 36V EM101 (101lb of thrust) trolling motor. I am debating whether, autonomically and economically, I should purchase three 12V or one 36V LIFEo4 batteries to be delivered to your local Canadian authorized agent or to my door at J8T 7G3, Canada.

    1. Thanks, Jacques,

      For trolling motors, there may be a high starting current required.
      Lead acid battery can offer a super high instant current easily, but for LiFePO4 battery, there is an over current protection. Common LiFePO4 battery pack is not able to offer a high instant current.

      At the moment, we don’t have such a type of LiFePO4 battery supporting starting purpose.


  2. Just dropped by here for whatever reason…
    That Minn Kota EM 101 thruster is rated for 46 A at maximum speed, and so it’s stall current will be ≈3x such figure, which is 138 A but let’s say 150 A to round it up.
    LiFePO4 is excellent in power delivery or discharge rate, and so 150 A should be an easy job even for a small 50 Ah battery pack. A 100 Ah battery pack made with three “12.8 V” 4S battery packs in series should not even ruffle its hair for powering such thruster.
    If the BMS boards inside the packs cannot deal with that current (they should) you can swap them for higher current BMSs, this should be an easy job unless the manufacturer has done shenanigans to the battery cases to prevent tampering.
    In all honesty, a 100 Ah LiFePO4 battery pack should at least use a BMS capable of delivering 200 to 300 A CONTINUOUS without effort.

    1. Hi Salvador,

      You are right about part of the lithium battery cells.
      For those EVs, the allowed discharge rate of the lithium battery can be 5C – 6C, or even higher because of the specific cells.

      But for common applications and energy storage, most of lithium battery cells are only allowed to be discharged at 1C.
      Instant current can be higher, but constant current is not allowed to be over 1C.
      (C equals the value of battery capacity, 100Ah battery is 100A.)


  3. In response to the question on powering a 36v Trolling Motor with LFP (LiFePO4, aka Lithium Iron Phosphate) … the answer should always be ONLY go with a single 36V LFP (if it will fit!).

    Why? Because this battery will have a single BMS (Battery Management System) guarding all the cells as a single system; whereas if you opted to externally connect 3 x 12v LFP batteries then each BMS will operate independently. And that’s not good for the long term health of each battery! Sure it works but just not as well in the the term.

    And why was there no difference when connecting multiple 12v AGM batteries? Because these batteries don’t have a BMS!

    Another thing to be aware of is that due to the discharge cycle of LFP chemistry and how it can maintain higher voltage for longer (it’s not just about Amps because Volts matter too), you may find that when replacing AGM with LFP that you may not require a 36v/100Ah LFP battery.

    For example many are opting for a single 36v/50A LFP battery to power the very latest brushless trolling motors (e.g. the latest from Power Pole, etc).

    And this is critical … a brushless motors in combination with an LFP battery is highly efficient which means can opt for a battery with less capacity and still run all day.

    However because old fashioned “brushed” trolling motors (e.g. the now superseded tech used by Minn Kota & MotorGuide, etc) are less efficient, an LFP battery with more capacity will be required to get the same run-time/range.

    Bottom line: with LFP always go for a single battery if possible and also consider whether you can downscale the Ah rating (aka capacity). Either way, LFP is vastly superior to AGM which is something you will notice from the get-go no matter what tech the trolling motor or how you opt to get the required volts.

    1. Quite impressive!

      Only one more thing, watch out of the max power/current and instant power/current.
      Unlike lead acid batteries, the BMS of LiFePO4 battery has current limit.


      1. Thank you Andy for that timely warning to those new to LFP batteries.

        What you say is true for appliances such as compressors, air conditioners, winches, some power tools and also many typical kitchen appliances like induction cook tops, fridges, freezers, etc.

        However it isn’t so for devices like trolling motors.

        Why? Because modern brushless trolling motors incorporate a “soft-start” circuit which ensures there is no excessive start-up current placed on the BMS (and so the cells).

        Old fashioned brushed motors typically do not have a soft-start feature, however there is often adequate protection against instantaneous overload because the motor must be started at the slowest speed and then gradually increased.

        But this isn’t always so because when “paused” some trolling motor controllers will re-start at what ever setting they were at prior to being interrupted. Thus users are cautioned against pausing and re-starting their trolling motors at near maximum speed.

        Most trolling motors (or more accurately the power cables from battery to motor) are also protected by an inline fuse or circuit breaker which provide double end-to-end protection – and of course this was essential with otherwise unprotected lead/acid batteries where a short circuit could spell doom.

        In any case, no harm will be done to the LFP cells because it’s the job of the BMS to protect them. So, if the instant load (or even a prolonged constant load) is too high then the BMS will kick in and cut all power for a few seconds or maybe longer.

        However, since prevention is always better than cure, any prospective buyer of an LFP battery should always check the technical specification (sometimes called the data sheet) of the battery under consideration and compare that with the current draw (often stated in watts and amps) of the device they intend to power.

        The data sheet will always list the continuous maximum constant discharge current (which typically will be equal to or greater than 1C) and sometimes there will be several figures stated over various periods of time, as well as the “pulse current” (which is sometimes incorrectly referred to as the surge, inrush or start-up current).

        For example: the spec sheet for an LFP battery with a nominal capacity of 100A may read something like this:

        Max discharge current (constant) 50A (0.5C)
        Max discharge current (40 min) 100A
        Max discharge current (2 min) 150A
        Pulse current (3 sec) 200A

        For a trolling motor with a maximum nominal draw of approx 40-50A at full speed, obviously one would not choose this battery because the maximum discharge rate (constant) is only 50A, and that’s cutting it just a bit fine even if not intending to run at maximum speed for very long.

        As with all batteries no matter what the chemistry, not “red lining” the battery is best for performance and longevity.

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