Battery Reserve Capacity Explained: Time of Sustained Constant Loads. Automotive battery amp hours

What happens if I put a higher amp battery in my car?

Before answering this question, we are going to give some brief technical notes:

Every battery has two main characteristics: Voltage (V) and Capacity (Ah).

Voltage of a battery (V)

The voltage of a battery is the difference in potential or voltage that exists between its poles.

If we consider Ohm’s Law: Voltage = Intensity Resistance we have:

battery, reserve, capacity, explained, time

Resistance: It is the resistance offered by what we connect to the battery. If we connected a direct cable from one terminal to another, the battery would give its maximum current intensity. For this reason, it is very dangerous to connect any current conducting element between the two battery terminals. Be careful, therefore, with connecting a direct cable, putting something metallic between the two terminals, or even spilling water on the battery.Intensity: It is the force that the battery can provide at all times.Voltage: As the resistance of what we have connected to the battery is fixed, the higher voltage we have, the more current we can provide. Or put another way, the voltage will determine the current intensity and the higher the voltage, the more intensity we will give.Some conclusions can be drawn from all this:

In a car, everything that is connected to the battery is prepared to operate at a voltage of 12V. What would happen, therefore, if we could connect a 24V battery or 2 12V batteries in series? After all that has been seen, the answer is simple: if we double the voltage, the current intensity would also increase twice and we would run the risk of burning or damaging everything that is connected to the battery.

Likewise, if the battery were to discharge, the current intensity would decrease and the engine would not be able to start, some circuits would not receive enough energy to function correctly, etc.

Important: Never connect a higher voltage battery to the vehicle

battery, reserve, capacity, explained, time

Capacity of a battery (Ah)

On the other hand, the capacity of a battery, which is measured in Ah, represents the amount of electricity that a battery can provide. The more capacity (Ah) a battery has, the more electricity it can provide.

In theory, a battery that has 100Ah could give a current intensity of 100 Amps for 1 hour, an intensity of 1 Ampere for 100 hours, or 2 Amps for 50 hours. However, this is not always the case, as the faster a battery discharges, the more power it loses. Therefore, it is common to find batteries that have the following capacity:

Varta LA95 Battery Capacities
Ah 20hr 95Ah
Ah 10hr 90Ah
Ah 5hr 85Ah

That is, the same battery could give 4.75A for 20 hours (4.75A x 20 hours = 95Ah c20), 9A for 10 hours (90Ah c10) or 17A for 5 hours. If we did not have the power losses, the battery should have been able to provide 19A for 5 hours (95Ah) or 9.5A for 10 hours (95Ah).

  • The capacity of a battery is the energy that the battery can provide.
  • The more capacity a battery has, the more energy we can get from it.
  • The faster we discharge a battery, the less energy we can obtain from it.

Therefore, answering the initial question, if we replace a car battery with a higher capacity one, we will be able to leave the elements that depend on the battery in operation for a longer time. In addition, with the same consumption the higher capacity battery will discharge less, which in the long run will result in a longer battery life.

Is there a problem if we install a higher capacity battery?

Although this is not always the case, because the battery design can be different, a battery with a higher capacity will also have a higher CCA, which could be said to be the maximum intensity it can provide in an instant. That does not mean that he is able to provide it in all situations, only when the team needs it.

And this is where we can find the problem: if the equipment is faulty, has a ground problem or a short (connection of positive and negative), the battery with greater capacity will provide more intensity than a normal one and could damage part of the electronics ( although electronic systems are usually protected by fuses, precisely to avoid these situations).

But this effect will only be very apparent if the difference in CCA is considerable. For example, taking it to an extreme, the problem could occur if we try to start a motorcycle with a truck battery and we have some kind of ground or connection problem.

Under normal circumstances, there should be no problem installing a larger capacity battery. On the one hand, there is usually not enough space to install a battery with a large starting difference (CCA) and, on the other, by starting with a greater capacity (Ah) and starting force (CCA), we will increase the battery’s durability since both parameters degrade over time.

In short, if we install a higher capacity battery, we will increase battery life, improve starting and, in addition, we will be able to use the electronic equipment of our vehicle for a longer time.

However, what happens if we don’t have a space to install a larger battery?

For these cases, manufacturers usually manufacture batteries of different benefits for the same size. The most basic range usually has less ah and the highest range contains the highest performance, both in amp hours and starting capacity.

For example, Varta for the same size has a battery of 70Ah, another of 74Ah and another of 77Ah. The lowest range is the 70Ah and the highest range is the 77Ah. In these cases, the manufacturer always recommends installing the highest-end (77Ah), especially if the car has a large number of electronic components.

Battery Varta E13 12V 70Ah: Size: 278x175x190 Battery Varta E11 12V 74Ah: Size: 278x175x190 Battery Varta E44 12V 77Ah: Size: 278x175x190

In short, whenever you have the opportunity to choose, install a battery with the highest possible capacity

Battery Reserve Capacity Explained: Time of Sustained Constant Loads

For those without extensive electrical experience, buying a battery can feel a bit overwhelming. With all the different styles, sizes, and brands, it can be easy to throw up your hands and buy the one suggested by someone else. But understanding the specifications of batteries can go a long way toward helping find the correct battery. One specification you may have seen is battery reserve capacity. Here’s why it’s so important to understand for your next battery search.

What Is Battery Reserve Capacity?

Reserve capacity is simply the time in minutes that a 12V lead-acid battery can sustain a 25 amp load and remain above 10.5 volts.

When evaluating batteries, it’s essential to make sure buyers are comparing apples to apples. That’s where battery reserve capacity (also called RC) comes in. The longer a fully charged battery runs before dropping below a specific voltage, the higher the battery reserve capacity. Most types of traditional lead-acid batteries display this measurement.

At a high-level reserve, capacity is a more accurate measurement of how long a lead-acid battery will last under a sustained load than its amp-hour rating. This rating will be much lower than the actual capacity of the battery primarily due to the Peukert effect.

Need a refresher before we dive in? Check out Amps, Volts, and Watts: Differences Explained in Simple Terms

What Do CCA and RC Mean on a Battery?

RC stands for reserve capacity and is commonly seen on deep-cycle lead-acid batteries. It’s critical to note that reserve capacity measurement is done at 80 degrees Fahrenheit — optimal temperature conditions for a battery.

CCA is a completely different measurement that is specific for vehicle starting applications. CCA stands for “Cold Cranking Amps”. As opposed to battery reserve capacity, CCA is measured in amps, not minutes. It shows how many amps a battery will deliver over 30 seconds at 0 degrees Fahrenheit without dropping below 7.2 volts. This is critical information to know when starting a vehicle to make sure the engine gets enough power from the battery to turn over in less than ideal conditions.

It’s important to note that CCA has nothing to do with battery capacity and will not indicate if a battery is useful for deep discharges. A starting battery is constructed very differently than a deep cycle and is intended for short bursts of energy only followed by an immediate recharge.

How Is Reserve Capacity Calculated?

Battery reserve capacity measures time so you will see it depicted in minutes. To calculate the RC of a battery, the battery has to have a full charge first. Then, manufacturers draw 25 amps of power from the battery at 80 degrees F until it drops below 10.5 volts. The number of minutes it takes for this to occur is the battery’s reserve capacity.

What Is A High Reserve Battery?

Much like the name implies, high reserve batteries are batteries that can provide reserve capacities higher than average. These batteries often produce a lower but still usable charge, meaning the overall capacity will last longer.

These are useful for those who consistently use large amounts of battery capacity between charges. They’re also good for those who may leave their batteries unused for extended periods. High reserve batteries are more likely to retain some energy even after sitting idle for a while. This helps avoid unexpected dead batteries.

Is Reserve Capacity the Same as Amp Hours?

No, these are separate measurements that reflect different things. For one, reserve capacity is a simple measure of time, while amp-hours measures the number of amps a battery can provide over an hour-long period.

However, these two measurements are related, and you can convert one to the other. Divide the RC by 60, and then multiply this number by 25 to obtain the amp hours. If you have the amp hours, divide this number by 25, and then multiply that number by 60 to find the battery reserve capacity.

Keep in mind that this doesn’t quite mean equal energy, as the measurements and conversions don’t take voltage into account.

Do Lithium Batteries Have Reserve Capacities?

Yes, lithium-ion batteries have reserve capacities, but they’re not typically rated or referred to that way. With lithium batteries, amp hours or watt-hours are the standards of comparison.

Lead-acid batteries will see a lower reserve capacity due to the 25-amp draw and the Peukert Effect. The Peukert Effect shows how traditional lead-acid batteries see decreased capacity as the rate of discharge increases. High-quality lithium like our Battle Born line does not suffer significantly from the Peukert effect and the amp hour rating of the battery is the actual amount of charge you can get from the battery under most conditions.

There’s another important thing to note about maxing out battery reserve capacity levels in lead-acid batteries. Reaching the full RC will draw the battery down to 10.5 volts, which is lower than 50% of charge. This is a level that will dramatically shorten lead-acid battery life if reached regularly. Therefore, consider RC more of an upper limit than a target range.

While it’s not a published number you could say our 100AH battery has a 240-minute reserve capacity even though the battery will never go below 10.5 volts. The internal BMS would shut it off before then. It’s important to keep in mind that a 240-minute drain on a Battle Born will not harm the battery as it would with a lead-acid battery.

Why Is It Important to Know About Battery Reserve Capacity?

RC is important only when looking at lead-acid deep cycle batteries intended for use in a long discharge situation. For engine starting applications, RC has no benefit and CCA is the measurement that is more important.

When choosing a battery, it’s critical to know whether it’ll meet day-to-day needs and how far it can push in emergencies. Battery reserve capacity is one of the most valuable ways to quantify this with lead-acid. While different manufacturers and types of batteries may each promise confusing or unclear benefits, RC makes it simple to make an apples-to-apples comparison.

While both CCA and RC numbers are just a small part of choosing the correct battery (along with type, brand, size, and other considerations), it’s vital to understand their roles.

How Many Watts Are In A Car Battery?

If you’re like most people, you probably don’t think about your car’s battery very often. It’s there, it works, and that’s about it. But if you want to keep your car in top condition at all times—and if you want to make sure that one of the most important machines in your life (your car) can start whenever it needs to—then you need to know how many watts are in a car battery.

In this article, we’ll take a look at how many watts you need when starting a car, and how to pick the best car battery for your vehicle.

battery, reserve, capacity, explained, time

What is watt and how does your car’s battery work?

When you’re driving around, there’s a lot your car needs to do. From staying cool to keeping the engine running and everything in between, your car’s electrical system is responsible for a lot. But what is it that makes up an electrical system? How many watts are in a car battery? And most importantly: how does it all work together?

First things first, let’s see what a watt is: a watt is a unit of power. It measures how much energy is used in one second, and it’s equal to 1 joule per second. The more watts you use, the faster your battery drains. Watts can be calculated by multiplying amperage (amps) by voltage (volts).

How does it all work together?

A car battery is made up of six cells, each of which contains two plates made of lead. These plates are separated by an electrolyte solution of sulfuric acid and water. When you turn on your engine, the alternator charges the battery by sending electricity from one terminal (called the positive or POS) to another terminal (called the negative or NEG).

This makes electrons flow through the circuit from POS to NEG and back again. It’s this movement of electrons that powers all of your electrical devices in your car—including lights, radio, air conditioner, etc.—as well as powering the starter motor when you turn over your engine.

What’s the Car Battery Voltage?

The voltage of your car battery is determined by the number of cells in it. Your average 12-volt battery has six cells, which means it has about 66 volts. The higher the voltage, the more powerful your battery will be—and the more amps it will be able to pull out when you need it.

Now let’s talk about how long it takes for that energy to be released when you run down your car’s battery. The rule of thumb is that for every 1 volt of voltage in your battery, it will release 1 amp of current for every hour of discharging time. So if your car uses 12 volts, then it will release 12 amps per hour until it runs out of juice altogether.

How many watts does a car battery have?

This depends on what kind of car you have and how powerful your engine needs to be. The more powerful the engine, the more energy it uses—and the higher-powered batteries are needed to keep up with that demand.

A car’s battery is used to store electrical power. It powers the car’s electrical systems and is found in the trunk of the vehicle. A typical fully-charged automobile battery has a 12-volt capacity and a wattage range of 400–6000.

An automobile battery’s capacity is expressed in amp hours (Ah). Watt hours represent the amount of energy it takes to discharge one watt for one hour. So, if you have a 60 amp hour battery and are discharging it at 1 amp, it will take 60 hours to completely drain your battery.

Most car batteries nowadays are 12-volt 105 AH batteries, which can deliver 12 x 105, or 1260 Watt-hours (1.26 kWh). When you’re starting up your engine, it kicks on instantly to make sure that you can get going as soon as possible. To get things moving, you’ll need a power of at least 1,000 Watts.

How much power does a car battery store?

We know how many watts your battery can have, but the power in its storage depends on some other factors. The majority of batteries are either rated at a 10-hour rate or a 20-hour rate. This battery can handle that many amps for 20 hours (or 10 hours) before its voltage declines to the point where it is no longer useful, at around 11 volts.

The average type of battery has a 50 amp hour capacity if it can sustain 5 amps for 10 hours. That is approximately 600 WH.

How do you pick the car battery?

When you’re looking for a car battery, it’s important to understand how much power your vehicle needs. There are two different types of car batteries: standard and deep cycle. Standard batteries are designed for vehicles that run on a lot of electricity—like trucks, buses, and heavy equipment. Deep-cycle batteries are made to handle heavy work (like construction), but they also work well in cars that need less power.

The quantity of amp-hours you require is one of the most important considerations when selecting a car battery. This is dependent on the application and your geographic location. You should think about getting batteries with a capacity that can handle more than twice the projected outage.

To calculate the needed amp-hour, divide your average daily use by the battery’s voltage. Consider the scenario where you use a 48-volt power system at a rate of kWh per day. 48 divided by 5000 results in 105 AH.

Since you don’t want to deplete the battery below 50%, you will require at least 210 Ah.

When should you change your car’s battery?

A battery usually stops working because it can no longer maintain a charge over a period of time. The battery’s lead plates degrade, making it impossible for them to sustain current. The battery will have to be changed in this case.

You can also notice when the life of your battery is close to an end when you see the headlights getting less bright and the “Check Engine” light illuminates.

If your vehicle is not starting correctly or has trouble starting in cold weather (below 32 degrees Fahrenheit), then it may be time to replace the battery. You can also tell when it’s time to change your battery by looking at its voltage level; if it drops below 12 volts while running, then that’s another sign that it needs replacing.

Things to consider when picking a new battery

Here are some tips for picking the right battery for your car:

  • Know what kind of car you have. Different types of vehicles require different kinds of batteries, so make sure you get one that fits your needs. For example, some cars use lead-acid batteries while others use lithium-ion or lead-calcium batteries. These differences can affect how long they last and how much weight they add to your vehicle.
  • If you live in a colder climate and use your car only for short trips around town, then an AGM battery may be best for you. If you live in a warm climate and drive long distances frequently, then an absorbed glass mat (AGM) battery might be best for you.
  • If you live in an area that has frequent downpours during the rainy season but very few snowstorms during winter months (or vice versa), then a deep cycle battery may be best for your needs.
  • Look at the appropriate cell power. The size of your battery is important, as you’re searching for items that can fit in your automobile. If you don’t do this, you could have to buy many trial batteries, which will cost additional money.
  • Check the battery name. The brand of your battery is still another crucial factor, so buy from trusted brands, as they guarantee performance and safety.


For most people, car batteries are pretty straightforward. You know when they’re low on power and need to be charged, and you know when they need to be replaced. But there are some situations where you might have a hard time figuring out whether or not your battery needs to be replaced, and that’s when you need information about its watts, voltage and power.

This can help to know what factors affect the performance of your car battery over time. That way, you’ll be able to tell when it’s time for a replacement—and when it’s not! And if you have more questions, don’t hesitate to let us know in the Комментарии и мнения владельцев.

How to Convert Cold Cranking Amps (CCA) to Amp Hours (Ah)

There is a very straightforward reason why the conversion between Cold Cranking Amps (CCA) and Amp Hours (Ah) is not exact: Amp Hours (Ah) refers to the capacity of the battery and its ability to produce a specific current for, typically, 20 hours, whereas Cold Cranking Amps refer to the ability of the battery to provide significant currents required for starting/cranking of internal combustion engines, typically for 30 seconds. So, how do you convert cold-cranking Amps (CCA) to Amps hours (Ah)?

There are many requirements for car batteries that you should be aware of. You must purchase the proper battery for your vehicle because modern cars require a lot of technological components. The CCA to Ah conversion is useful for figuring out whether a battery will suit a particular car or not.

Well, in this article, we’ll be discussing the answers to the following questions:

  • What are Cold Cranking Amps (CCA)?
  • What are amp hours (Ah)?
  • Why do you need to convert Cold Cranking Amps (CCA) to Amp Hours (Ah)?
  • What is the difference between cold cranking amps (CCA) and amp hours (AH)?
  • How do I convert Cold Cranking Amps (CCA) to Amp Hours (Ah)?

Ok, let’s dive in!

What are Cold Cranking Amps (CCA)

The term “cold-cranking amps” refers to a rating system that describes a battery’s capacity to start or crank an engine in cold weather. In other words, Cold Cranking Amps (CCA) is a measurement of the amount of current a battery can deliver at a temperature of 0°F (-18°C) for 30 seconds while still maintaining a voltage of at least 7.2 volts. In essence, it evaluates a battery’s capability to start an engine in a cold environment.

Whether on land or in the water, starting your engine is one of the biggest issues when it comes to cars, and not all batteries perform at their best in more severe weather. Some people, especially those who live in persistently cold regions, require more energy to start a car or boat battery than those who reside in warmer climates.

than anything else, a CCA rating will let you know how many amps are required to ensure that cold weather won’t make it difficult for you to start your engine. The CCA rating provides information on the number of amps produced by a charged battery during a 30-second period while sustaining at least 7.2 volts at a temperature of 0°F (-18°C) to help consumers choose the best battery.

What are amp hours (Ah)?

Ampere-hour (Ah) is a standard unit of electrical charge for assessing a battery’s capacity. When a current of one ampere (1 A) is flowing, it is defined as the volume of electrical charge that moves across a circuit in a 24-hour period. A battery with a 10 Ah capacity, for instance, has the ability to deliver a current of 1 A for 10 hours or a current of 5 A for 2 hours.

When comparing the capacity of batteries of various types and sizes, ampere-hours are a useful unit of measurement. It’s vital to remember that a battery’s real runtime will also depend on other elements, such as the effectiveness of the device it is powering, the temperature, and other operational circumstances.

Why do you need to convert Cold Cranking Amps (CCA) to Amp Hours (Ah)?

There are two distinct ways to measure a battery’s capacity: Cold Cranking Amps (CCA) and Amp Hours (Ah). While Ah represents the amount of energy a battery can store and provide over a longer period of time, CCA assesses a battery’s capacity to start an engine in cold weather.

If you wish to compare the capacity of various batteries that are rated in various units, you might want to convert CCA to Ah. It is necessary to convert the CCA rating to Ah in order to fairly compare, for instance, a vehicle battery with a CCA rating to a deep cycle marine battery with an Ah rating. The conversion from CCA to Ah is not exact since it makes assumptions about the battery’s discharge profile. It still allows you to get an idea of how much power a battery can hold and deliver over time.

What is the difference between cold cranking amps (CCA) and amp hours (AH)?

CCA is the ability to supply power for a brief amount of time (bursts) as was mentioned above for car starting, whereas Ah is the ability to deliver power for a prolonged period of time.

Note: Amp Hours (AH) is a measurement used largely for deep cycle batteries used in applications like RVs, boats, and renewable energy systems. Cold Cranking Amps (CCA) is a measurement used mostly for lead-acid starting batteries used in vehicles.

How do I convert Cold Cranking Amps (CCA) to Amp Hours (Ah)?

Since there is no correlation between CCA and Ah, there is no straight conversion from one to the other. However, as a general guideline, you can calculate Ah by dividing the CCA by 7.25. For instance, a battery designated 1450 CCA stands for 200 Ah. A battery with this rating ought to deliver 8 amps of power for 25 hours.

Even if you simply have the CCA statistics, knowing your rate of use and voltage level will help you choose the proper battery. In contrast, you may calculate the CCA measurement to see how well your battery can start your engine in cold weather if you know the Ah values on it.

CCA to Ah FAQs

How do you convert cold cranking amps to Ah?

By utilizing the formula CCA/7.25 = Ah, you can calculate the Ah value from CCA. As a result, converting a battery with a 725 CCA rating to Ah will result in 100 Amp-hours. This indicates that your battery can operate at ten amps of voltage for up to ten hours.

How many CCAs is a 35Ah battery?

The battery has a 315A Cold Cranking Amp (CCA) rating. The nominal capacity of this battery is 35Ah at a 20-hour pace. The battery will take 20 hours to reach the end of discharge voltage of 10.5 V if you discharge it at a current of 1.75Amp from a completely charged condition.

Is cold cranking amps the same as Ah?

The short answer is no! While Ah is able to give power over a long period of time (think endurance applications such as mobility scooters where the battery is utilized for several hours), CCA is able to deliver power over a brief period of time (bursts, as stated above for car starting).

How many CCAs is a 60Ah battery?

The DL 60Ah is a fantastic option for high amp demand applications like starting engines, golf carts and electric cars, deep cycle applications, or any electronics that need a lot of power at once thanks to its 1,000 cold cranking amps (CCA) and high continuous discharge rate.

How do you calculate amp hours from cranking amps?

CCA (Amps) = Capacity (Ah) x 100

These batteries reduce weight significantly and enhance engine starting and cranking, although they are typically more expensive than lead-acid batteries.

How many amp-hours is a 1000 CCA battery?

Built for dual-purpose performance, the DL 12V 135Ah battery offers 1,000 cold cranking amps (CCA) and a high continuous discharge rate, making it a great option for high amp draws applications like starting engines, car audio, heavy machinery, golf carts, or any electronics that need a lot of power at once.

How many amp-hours is a 12v car battery?

However, not everyone is aware of the vehicle’s ampere rating. The majority of us believe the car battery is in the 12 volts category. A typical automotive battery can provide 1 amp for 48 hours, 2 amps for 24 hours, etc. when completely charged. It has a capacity of about 48 amp hours.

How do you calculate the Ah of a car battery?

To calculate the total ampere hours, use a battery tester and the automobile battery’s ampere. By dividing the recorded volt by the ohm rating, one can calculate the ampere-hour. The battery’s ohm rating is also required to measure ampere-hour.


It is necessary to perform some simple mathematical calculations and comprehend the relationship between these two units of measurement in order to convert Cold Cranking Amps (CCA) to Amp Hours (Ah). Although it is not a direct conversion, it is possible to calculate a battery’s Ah capacity using the formula CCA/7.25. It is crucial to keep in mind that this conversion only gives a rough idea of the real Ah capacity, which might change depending on a number of variables. For precise information on the capacity and performance of a battery, it is, therefore, advisable to refer to the manufacturer’s specifications.

That is all for this article where we looked at how to convert Cold Cranking Amps (CCA) to Amp Hours (Ah). Nonetheless, we got to discuss the answers to the following questions:

  • What are Cold Cranking Amps (CCA)?
  • What are amp hours (Ah)?
  • Why do you need to convert Cold Cranking Amps (CCA) to Amp Hours (Ah)?
  • What is the difference between cold cranking amps (CCA) and amp hours (AH)?
  • How do I convert Cold Cranking Amps (CCA) to Amp Hours (Ah)?

We hope it was helpful. If so, kindly share it with others. Thanks for reading; see you around!

Volt, Amps, Amp-hour, Watt and Watt-hour: terminology and guide

We understand that all this terminology can be a bit confusing at times but once you know how it works it is quite simple. Below we will try to explain what it all means.

Volt or Voltage (V):

The number of volts is the amount of energy given to an electronic circuit. By a circuit we mean, for example, an electronic device. With a 12V device, 12 volts are always “given” from the battery. A battery always has a fixed voltage (e.g. 12, 24, or 36 volts) and a device always works at a certain voltage. For example, a device that works on 12 volts obviously needs a battery that also supplies 12V.

Current – Ampere (A):

When we talk about amperes (or amps), we are talking about how much electricity “flows” per second. If the number of amps goes up, then current flowing through the device per second also goes up. An electrical device usually works on a fixed voltage, but the amount of amps it draws can vary depending on, for example, the position of your trolling engine (a trolling engine at full throttle draws more amps than in half throttle for instance).

Example 1: Suppose I have a Minn Kota Endura C2 50 LBS that I am running on gear / speed setting 2. The trolling engine runs on 12V and currently draws 15A. I decide to go a little faster and I switch to gear / speed setting 4. The engine still runs on 12V but now pulls 25A. The voltage has remained the same but the number of amps has gone up.

Power – Watts (W): :

Power is the voltage multiplied by the number of amps, or W = V x A. This is the amount of energy consumed by a device and therefore an indication of how powerful it is. This goes up when the number of amps also goes up.

Example 2: Suppose I have a 24V Minn Kota Terrova 80 LBS bow motor that draws 30 amps. So the power consumption is 24 x 30 = 720W.

Example 3: Suppose I have another Minn Kota Endura C2 50 LBS that I am running in gear / speed setting 2. The engine runs on 12V and draws 15A and thus has a power consumption of 180W (12 x 15). When I switch to gear / speed setting 4, the engine draws 25A and still runs on 12V. The power consumption of the trolling motor is now 300W.

Capacity – Amp hours (Ah):

Battery capacity is measured in Ah, or Amp-hours. As the name suggests this means how many amps the battery can deliver in an hour. For example, a 12V lithium battery with a capacity of 100Ah can deliver 100A to a 12-volt device for one hour. The same 100Ah battery could supply power for 4 hours (100/25=4) to a 25 ampere device. If a battery has 12V50, this means that the battery works on 12 Volt and has a capacity of 50Ah. A 24V100 battery works on 24 Volt with a capacity of 100 Ah etc. In practice for lead-acid batteries the nominal capacity (how many Amps hours the battery can deliver according to specifications) differs greatly from the effective capacity (how many Amps the battery can actually deliver during use). We explain how this works in our article discharge and battery capacity.

Example 4: I run my Minn Kota Endura C2 50 LBS in gear / speed setting 2, drawing 15A at 12V. I have a 12 volt battery of 70 ah. My total run time is now 70 / 15 = 4.7 hours. When I switch to gear / speed setting 4 the engine draws 25A. My total runtime is now 70 / 25 = 2.8 hours.

Capacity – Watt-hour (Wh):

Another way to measure the capacity of the battery is in Watt-hours (Wh). Wh is calculated by multiplying the number of Amps with the battery voltage. For example, a 12V100 (a 12 volt battery with a capacity of 100Ah) has a capacity of 12 x 100 = 1200Wh. A 24V50Ah battery has a capacity of 24 x 50 = 1200Wh. So these batteries have the same capacity, only one works on 12 volts and the other on 24 volts. In practice you will notice that these batteries will be around the same dimensions and weight.

Example 5: I have a 600W trolling motor and a battery with a capacity of 1200Wh. My runtime at full throttle is 2 hours with this battery (1200 / 600 = 2). I do not even need to know how the trolling engine or battery voltage to calculate this (as long as they work at the same voltage obviously).

The attentive reader notes that the runtime of a battery with a device can be calculated in two ways. Either by dividing the number of Amps of the battery by the power draw in A of the trolling motor or by dividing the number of Wh of the battery Wh by the number of W of the trolling engine.

Connecting batteries: in series and parallel

Batteries can be connected together to achieve a higher voltage or higher capacity. This is done by connecting the battery terminals of the batteries with cables.

Connecting in series: higher voltage, equal number of Ah

When we say that we connect batteries in series, we connect the plus terminal of one battery to the minus terminal of another battery. This means that you still have a minus terminal available on one battery and a plus terminal available on the other battery. The electrical device should be connected to these two available battery terminals. If we connect batteries in series, the voltage goes up, and the capacity measured in Ah remains the same.

In the picture above we see two 12V50Ah batteries. As you can see the two batteries are connected in series: the minus and plus terminals are connected together. You have created a 24V50 battery : 24V (due to series connection) with 50Ah capacity (number of Amps remains the same). If we measure the capacity in Watt-hours, the total capacity is now 24 x 50 = 1200 Wh.

Connecting in Parallel: equal voltage, higher number of Amps

When connecting batteries in parallel, we connect the minus terminal of one battery to the minus terminal of the other battery and the plus terminal of one battery to the plus terminal of the other battery. We connect the minus wire of the electrical appliance to one of the minus terminals and the plus wire to the plus terminal of the other battery (see the picture below). The same voltage is now supplied but the number of Amps has increased.

In the picture above, the minus terminals of both batteries are connected and the plus terminals are connected. So the battery is connected in parallel. There is still 12 Volt but the number of Amps has increased from 50 to 100. We have now created a 12V100Ah battery. If we measure the capacity in Watt-hours, the total capacity is now 12 x 100 = 1200 Wh.

So the number of watt-hours always remains the same, whether you connect them in series or parallel.

Attention: always check whether batteries are suitable to connect together. Only connect identical batteries (same type/model, age and charge status) and use cables of the correct thickness and length. We recommend that you do not connect 12 volt Rebelcell batteries in series but instead select a Rebelcell 24 volt battery. Rebelcell 24 volt batteries can be connected in series up to 48V without any problems.

Other terminology relating to batteries

The technical specification for batteries often includes many other terms. Below we will try explain what the most important ones mean.

Voltage: this is the voltage that the battery delivers on average. As explained above, the battery starts with a higher voltage than when it is partially discharged. With this we mean the average of this progression or the nominal voltage.

Chemistry: this indicates what kind of lithium battery technology is used.

C1, C5, C20: this indicates battery capacity when discharged in a certain number of hours. C20= 100Ah means that the battery can deliver 100 ampere hours if it is discharged in 20 hours (with 5A). Lead batteries have a lower capacity if they are discharged faster. For example, a lead-acid battery can deliver 100Ah if it is discharged in 20 hours (C20=100), but if the same battery is discharged in 5 hours it will only deliver 70Ah (C5=70). With Rebelcell batteries it doesn’t matter if you discharge them in 20 hours, 5 hours or 1 hour, they always deliver the same capacity. That is why we always refer to our capacity as Capacity (C1-C20). Read more about this in our article about effective battery capacity.

EqPb: this stands for ‘equivalent lead battery’. By this we mean that this battery can be compared to a lead battery with the indicated capacity when used in combination with an electric motor. Often a lithium battery with a much lower Ah can in practice deliver the same amount as a lead-acid battery with a much higher Ah. In practice, for example, the Rebelcell 12V50 can be compared to a 105Ah semi-traction battery in terms of operating time for an electric motor. This also has everything to do with the usable battery capacity.

Nominal energy: this is the battery capacity measured in watt-hours (see above for explanation).

Maximum continuous discharge: this is the maximum number of amps the battery can continuously deliver. Suppose a battery has a maximum continuous discharge of 30A, then you cannot connect a device that draws more than 30A. The higher the capacity of the battery, the higher the maximum continuous discharge.

Peak discharge (10 milli-sec): this is the maximum number of amps the battery can deliver for 10 milli-seconds. This is always higher than the maximum continuous discharge. Some equipment has a short peak discharge when starting up (so called ‘inrush’ currents). This is for example the case when you go from zero to full throttle in one go with an electric outboard engine. At that moment, the motor requires more amps than the rated maximum for a short time.

Lifespan (#charges) (@80%DoD): this indicates how often you can discharge and recharge the battery up to a certain percentage. For example, if it says “Lifetime (#charges) (@80%DoD): 1500” it means that the battery can be discharged to 80% for 1500 times (i.e. with 20% capacity left). For example, if it says “Lifetime (#charges) (@100%DoD): 1000” then the battery can be fully discharged 1000 times.

Energy density: with this we measure the number of Watt-hours per kilo of battery. Energy density is much higher for lithium batteries than for lead-acid batteries. A high energy density means that you can store more energy in the same space. And this results in a lighter and smaller battery.

Bandwidth voltage: see explanation of the discharge and capacity of batteries. This gives the minimum voltage (at 0%) and the maximum voltage (at 100%) of the battery.

Charge temperature: this gives the minimum and maximum temperature at which a battery can be charged.

Discharge temperature: this indicates the minimum and maximum temperature at which a battery can be discharged.

Storage temperature: This indicates the minimum and maximum temperature at which a battery can be stored safely.

Maximum charge current: This gives the maximum current in A at which the battery can be charged. The higher this number, the faster the battery can be charged (with the right battery charger).

battery, reserve, capacity, explained, time

Integrated cell balancing: part of the Battery Management System. The cell balancing feature ensures that the voltage of individual lithium battery cells is equalised, so the cells all have the same charge status / voltage. This is necessary for optimal use and performance of the battery.

Temperature protection: part of the Battery Management System. The battery is switched off when the temperature becomes too high or too low. This is a protection to prevent damage.

Maximum discharge current protection: part of the Battery Management System. The battery is switched off when the power draw of your equipment is higher than is allowed. This is a protection to prevent damage.

Overvoltage protection: part of the Battery Management System. The battery is switched off when the voltage becomes too high and the battery is overcharged. This is a protection to prevent damage.

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