How to Calculate Amp Hours of a Battery Bank- Methods, Capacity and Cycle Life

Battery banks are so useful in our day-to-day activities. One of the most critical knowledge is on the battery's amp hour rating when assessing the battery. But most of us use the battery without knowing some essential issues about the batteries. If you are using a battery, there are several things about your battery that are very useful. One of those things formula of calculating the amp hours of a battery bank. 

Therefore, what do we mean by amp hours of battery bank? This is the rating used to tell consumers how much amperage a battery can provide for an hour. For small batteries such as those in personal vaporizers or AA sized batteries, the amp hour rating is labeled on the battery. It is given in milli-amp hours (mAh). For large batteries, the rating is abbreviated as Ah. 

Most deep cycle batteries give the Ah rating at multiple C ratings. The C rating gives the number of amp-hours the battery can offer for a certain period. For example, at C/5 battery bank can provide 26.8 amp-hours, which means that it can supply 26.8 amp for 5 hours without dropping off. Also, the same battery can supply 36 amp for a period 0f 100 hours.  

Calculation of amp hours is necessary because you can estimate your battery's time until it is fully discharged. If you need to perform a particular job, you will be sure that the battery you are using can take your through. Therefore, I will take you through the calculation of amp-hours in battery banks.

How do you calculate battery amp hours of a battery bank?

Let us take, for instance; you need to calculate the capacity of your battery bank. The information that you should have is the battery's voltage and the energy stored. Let's take, for instance, your battery is 12 volts, and the amount of energy stored in the battery is 26.4 Wh.

The battery amp hours is calculated as follows:

E=V *Q    where E is the power storage in the battery, V is the battery bank's capacity, and Q is the battery's amp-hours rating. 

Therefore, Q=E / V 

                       =26.4 / 12

                       =2.2 Ah

Thus the battery capacity is 2.2 amp hours. 

Calculations of amp hours can also be done at different ‘C’ rates. The calculation is as follows:

C rates are also known as hourly rates and are calculated based on the length of the discharge time. A C/20 rate shows that battery capacity is calculated based on complete discharge for 20 hours. Therefore, if you have a 1,000 amp-hours battery bank charging or discharging at 50 amps would be a C/20 rate (1000Ah / 50 A =20 hours).

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Battery capacity can be calculated at a given C rate using Peukert’s exponent for a battery. The formula is given as:

It = C x [C / (I x H)] k – 1; where

H = rated discharge time in hours.

C = rated capacity at that discharge capacity

I = actual discharge current given in amps.

K = Peukert exponent

It = significant capacity at the discharge rate "I."

Lead-acid batteries, that is, the flooded ones, have a Peukert exponent ranging between 1.2 and 1.4, while absorbed glass mat (AGM) batteries are between 1.05 and 1.2. But these figures change as the batteries age.

Peukert’s exponent can be calculated if the manufacturer provides the capacity ratings at two extinct discharge rates. This formula is a bit complicated, but you can get a helpful spreadsheet to solve it from the battery bank manufacturer.

How do we find the capacity of a battery bank?

The capacity of a battery bank is a measure of energy that a battery bank can store. It is essential to know how to approximate the amount of charge that your battery can store or provide. The solution is always given in watt-hours. For instance, let us take a 12 volts battery bank with a storage capacity of 105 amp-hours.

To find the capacity, multiply the volts (V) by the amp hours then divide the solution by 100.

Volts x Amp-hours /100 = Watt-hours

12V x 105AH = 1260 / 100 = 12.6 Watt-hours

This implies that you can power a 100-watt appliance for 12.6 hours on a fully charged battery. Thus when purchasing the battery bank, it is good to have in mind this calculation. This assists you buy a battery that can supply power to your various appliances.

Thus always calculate the battery capacity accurately so that you do not get stuck. Batteries capacity and the amp hours calculation will always give you peace of mind.

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How long will a 100 amp hour battery last?

The lifespan of 100 Ah battery can be easily determined if you know the load that the battery has to support, the type of battery, the discharge rate, and the voltage cut off. The amount of time the 100 Amp-hours rated battery will be known if the amount of current the battery is supplying is known.

To get a good point of view on this issue, let us say that the 100 Ah battery bank has to power a load rated with 10 amperes since we know that the battery capacity (BC) is calculated by finding the product of current (I) and time (T).

To determine the battery's lifespan, measured in hours is done by finding the quotient of capacity against the current. That is, 100 Ah / 10 amps = 10 hours. Therefore, the 100 amp hour battery will provide power to the load for 10 hours.  

Conclusion

You can now calculate the battery capacity comfortably. Thus before purchasing your battery, it is good to know the energy consumption of your appliances. It is also essential to know the time that your battery can support appliances that you are using. Hence, take your time to know the different essential issues that will help you have lovely moments with your battery bank.