Ever wondered what it means to connect batteries in series or in parallel? Ever wondered which is better…or if it matters or even what the difference is? Here is some basic information on how to get the most out of your batteries while preventing damage.

When talking about battery installation with multiple batteries you need to keep in mind the total capacity and total voltage. Capacity is rated in Amperage-hours (ah) and Voltage is rated in Volts (6V, 12V, 24V). There are generally two standard hour lengths used, 20 and 10 to allow consumers to compare apples to apples. Simply put, divide the stated hour metric into the AH rating to see what amperage load will last the rated hours. For example a 210Ah rating at 20Hr will run a 10.5Ah load for 20 hours. Amperage loads larger than this number will last for a shorter period of time and loads smaller than this number will last longer than the stated 20hrs. The 1:1 ratio will not continue as you deviate to either side of the standard amp hour rating. There is a mathematical curve that should be used to get precise measurements, but for estimating use the 1:1 ratio and add a little cushion for error.

Connecting batteries in series means that you are doubling the voltage but maintaining capacity. So pretend you have two batteries with a rated capacity of 210ah and rated voltage of 12V. If you connect the two batteries in series, you will have a total rated voltage of 24V and maintain a capacity of 210ah. Useful if powering a load that requires a voltage higher than 12V.

Connecting batteries in parallel means that you are doing the opposite as when you connect in series. In parallel, you are doubling the capacity while maintaining voltage. In the same example with the same 210ah 12V batteries, if you connect them in parallel, you will have a new rated capacity of 420ah while maintaining a voltage of 12VDC. With your load drawing 10ah, you will have roughly 42 hours of useful life.

How to Connect Batteries in Series

Connect the positive lead to the positive terminal on Battery A. Use a cable to connect the negative terminal of Battery A to the positive terminal of Battery B. Use another cable to connect the negative terminal of Battery B to the neutral terminal on the equipment you are powering. Easy, right? Two batteries on one load.

RELATED Article: How to Connect & Charge Batteries in Series / Parallel

How to Connect Batteries in Parallel

Connect the positive and negative cables to the positive and negative terminals on battery A. Using two additional cables, connect the positive terminal of Battery A to the positive terminal of Battery B. Use the other cable to connect the negative terminal of Battery A to the negative terminal of Battery B. Also pretty simple, right? Now you have a higher capacity for many loads that use one voltage.

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Some Precautions for Connecting Your Batteries

Be sure to read the owners manual of the equipment that you are powering. Some electric motors are not rated to receive more than 12VDC and will burn out if you power it with two 12VDC batteries in series. Parallel is the better option in this case. Also, use the same types of batteries when connecting in parallel or in series. Using two batteries with different chemistries can cause damage or fire.