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Connecting Batteries in Series and Parallel

Powering equipment via batteries often means connecting them together in a battery bank to gain a higher voltage or amp hour rating.

Batteries can be connected in two ways, series or parallel.

Divide

Series

Connecting two batteries of the same voltage together in series effectively converts them into one bigger battery doubling the voltage rating of the battery bank, but keeping the same amp hour rating.

e.g. Connecting two 6 volt 30 Ah batteries together in series, will give you one big 12 v battery with a 30 Ah rating.

Connecting three together in series will give you an 18 volt battery with a 30 Ah rating.

Below is an example using 3 x 12 volt batteries with 100 Ah ratings.

Connecting in Series

Connecting In Parallel

When connecting batteries of the same voltage and amp hour rating together in parallel, the amp hour ratings of the batteries are added together, and the voltage across them stays the same as an individual battery.

e.g Three 12 volt 100 amp hour batteries connected in parallel would give us one large battery bank of 12 volts and 300 amp hours.

Connecting in Parallel

As you can see, both circuits still kick out the same amount of power – 3600 w.

As the equation for power P = VI shows, connecting in series or parallel affects the voltage and current ratings across each circuit. They are inversely proportional to each other.

Be aware when connecting batteries together in packs. It is always advised to connect batteries with the same voltage and amp hour ratings together so as to keep their voltages and rates of discharge as even as possible. This avoids voltage drops across one battery affecting the others, prevents strain on the pack, improves battery life and and keeps the system balanced.

For time and legal reasons I don’t answer reader’s questions on calculations or individual set up’s, but if you need to know anything about creating your own power set up or need advice on calculations, make sure you fully read through my battery guide and posts on inverters, battery calculations and battery connections.

There you should find all you need to know to help you get started.

Other Posts of Interest

Batteries
Battery Calculations
Busking & Gigging Power – Outdoors
Inverters

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13 comments to Connecting Batteries In Series & Parallel To Increase Voltage & Power Capacity

  • Joe

    Thank you so much! This webpage help me tremendously with my physics lab. I can never remember which one increases volts/amps. I know how to hook up parallel vs. serial but I cant remember which does which.

    Thank you!

  • a/kadir

    hi thank u for your great deal of time and effort in setting up this website
    i want you help me if i can connect two banks of baterry which has different amppere
    and if not why?

  • Hi, Although the same mathematical rules apply, if you read my post you will see we don’t recommend connecting two batteries of different specifications.

    “Be aware when connecting batteries together in packs. It is always advised to connect batteries with the same voltage and amp hour ratings together so as to keep their voltages and rates of discharge as even as possible. This avoids voltage drops across one battery affecting the others, prevents strain on the pack, improves battery life and and keeps the system balanced.”

    I hope that helps a little.

  • E.Eddie

    thanks man,it was for my Electronics Coursework Essay

  • sergio

    thanks very useful and well explained, am tring to make a battery charger 36v 60A for forklift with inverter can you give me ani hint about it. Thanks a lot. Sergio

  • Baris

    Pls I need to be clear on something:
    what happens if my inverter of 1.4KVA/24V is connected with just 12V battery?

    And:
    I want to connect four 200AH/12V batteries in parallel so that I can have max capacity (800AH) but obviously by that, I would be getting only 12V entering my 1.4KVA/24V inverter…. anything wrong in that?
    In summary:

    what is the disadvantage of installing battery banks with voltages less than the rated voltages for the inverters?

  • Baris

    I havent recieved my answer yet…. what happens when u connect your inverter with a battery bank not upto the specification in voltage?
    For instance what happens if I connect my i.4kva/24v inverter with just a battery bank of only 12v… pls urgent, thank u!

  • Baris

    No reply yet??

  • Baris,
    What I would do is connect two sets of 2 batteries in series to equal 24v. Then run the two sets in parallel with each other to increase your AH. The

    To further clarify,
    12v + 12v = 24v for your inverter. Run two banks of 24v in parallel to icrease your amp hours. Refer to the diagram above on connecting parallel and series.

    Never run an inverter on power its not designed for. You will either overload the circuits or Just not get enough voltage to convert.

  • One more thing, that setup will yield 24v @ 400Ah. In order to achieve 24v at 800AH, you will need to double your batteries. 8 12v 200AH batteries will be needed. To connect them, you will need 4- 24V banks running in parallel ( 4 pairs of 12v batteries connected in series )

    Hope that helps !

  • Rick

    If I connect 3- 12v deep cycle batteries with 210 Reserve capacity in series to get 36 volts, will I still have the same reserve capacity. This is for a golf cart which normally would take 6-6 volt batteries, but they are too expensive and rarely last more than a year. This cart is never used for more than 45 minutes at a time, could I get by with 3 deep cycles wired in series? This cart is equipped for hunting with an 8hp motor.

  • farrukh

    thanks for my help

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