Series and parallel circuits

Types of electrical circuits

A series circuit with a voltage source (such as a battery, or in this case a cell) and three resistance units

Two-terminal components and electrical networks can be connected in series or parallel. The resulting electrical network will have two terminals, and itself can participate in a series or parallel topology. Whether a two-terminal "object" is an electrical component (e.g. a resistor) or an electrical network (e.g. resistors in series) is a matter of perspective. This article will use "component" to refer to a two-terminal "object" that participates in the series/parallel networks.

Components connected in series are connected along a single "electrical path", and each component has the same electric current through it, equal to the current through the network. The voltage across the network is equal to the sum of the voltages across each component.[1][2]

Components connected in parallel are connected along multiple paths, and each component has the same voltage across it, equal to the voltage across the network. The current through the network is equal to the sum of the currents through each component.

The two preceding statements are equivalent, except for exchanging the role of voltage and current.

A circuit composed solely of components connected in series is known as a series circuit; likewise, one connected completely in parallel is known as a parallel circuit. Many circuits can be analyzed as a combination of series and parallel circuits, along with other configurations.

In a series circuit, the current that flows through each of the components is the same, and the voltage across the circuit is the sum of the individual voltage drops across each component.[1] In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents flowing through each component.[1]

Consider a very simple circuit consisting of four light bulbs and a 12-volt automotive battery. If a wire joins the battery to one bulb, to the next bulb, to the next bulb, to the next bulb, then back to the battery in one continuous loop, the bulbs are said to be in series. If each bulb is wired to the battery in a separate loop, the bulbs are said to be in parallel. If the four light bulbs are connected in series, the same current flows through all of them and the voltage drop is 3 volts across each bulb, which may not be sufficient to make them glow. If the light bulbs are connected in parallel, the currents through the light bulbs combine to form the current in the battery, while the voltage drop is 12 volts across each bulb and they all glow.

In a series circuit, every device must function for the circuit to be complete. If one bulb burns out in a series circuit, the entire circuit is broken. In parallel circuits, each light bulb has its own circuit, so all but one light could be burned out, and the last one will still function.

Series circuits

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Series circuits are sometimes referred to as current-coupled or daisy chain-coupled. The current in a series circuit goes through every component in the circuit. Therefore, all of the components in a series connection carry the same current.

A series circuit has only one path through which its current can flow. Opening or breaking a series circuit at any point causes the entire circuit to "open" or stop operating. For example, if even one of the light bulbs in an older-style string of Christmas tree lights burns out or is removed, the entire string becomes inoperable until the faulty bulb is replaced.

Current

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I = I 1 = I 2 = ⋯ = I n {\displaystyle I=I_{1}=I_{2}=\cdots =I_{n}}

In a series circuit, the current is the same for all of the elements.

Voltage

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In a series circuit, the voltage is the sum of the voltage drops of the individual components (resistance units).

V = V 1 + V 2 + ⋯ + V n = I ( R 1 + R 2 + ⋯ + R n ) {\displaystyle V=V_{1}+V_{2}+\dots +V_{n}=I\left(R_{1}+R_{2}+\dots +R_{n}\right)}

Resistance units

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The total resistance of two or more resistors connected in series is equal to the sum of their individual resistances:

R total = R s = R 1 + R 2 + ⋯ + R n . {\displaystyle R_{\text{total}}=R_{\text{s}}=R_{1}+R_{2}+\cdots +R_{n}.}

Here, the subscript s in

Rs

denotes "series", and

Rs

denotes resistance in a series.

Conductance

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Here, the subscriptindenotes "series", anddenotes resistance in a series.

Electrical conductance presents a reciprocal quantity to resistance. Total conductance of a series circuits of pure resistances, therefore, can be calculated from the following expression:

1 G total = 1 G 1 + 1 G 2 + ⋯ + 1 G n . {\displaystyle {\frac {1}{G_{\text{total}}}}={\frac {1}{G_{1}}}+{\frac {1}{G_{2}}}+\cdots +{\frac {1}{G_{n}}}.}

For a special case of two conductances in series, the total conductance is equal to:

G total = G 1 G 2 G 1 + G 2 . {\displaystyle G_{\text{total}}={\frac {G_{1}G_{2}}{G_{1}+G_{2}}}.}

Inductors

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Inductors follow the same law, in that the total inductance of non-coupled inductors in series is equal to the sum of their individual inductances:

L t o t a l = L 1 + L 2 + ⋯ + L n {\displaystyle L_{\mathrm {total} }=L_{1}+L_{2}+\cdots +L_{n}}

However, in some situations, it is difficult to prevent adjacent inductors from influencing each other as the magnetic field of one device couples with the windings of its neighbors. This influence is defined by the mutual inductance M. For example, if two inductors are in series, there are two possible equivalent inductances depending on how the magnetic fields of both inductors influence each other.

When there are more than two inductors, the mutual inductance between each of them and the way the coils influence each other complicates the calculation. For a larger number of coils the total combined inductance is given by the sum of all mutual inductances between the various coils including the mutual inductance of each given coil with itself, which is termed self-inductance or simply inductance. For three coils, there are six mutual inductances M 12 {\displaystyle M_{12}} , M 13 {\displaystyle M_{13}} , M 23 {\displaystyle M_{23}} and M 21 {\displaystyle M_{21}} , M 31 {\displaystyle M_{31}} and M 32 {\displaystyle M_{32}} . There are also the three self-inductances of the three coils: M 11 {\displaystyle M_{11}} , M 22 {\displaystyle M_{22}} and M 33 {\displaystyle M_{33}} .

Therefore

L total = ( M 11 + M 22 + M 33 ) + ( M 12 + M 13 + M 23 ) + ( M 21 + M 31 + M 32 ) {\displaystyle L_{\text{total}}=\left(M_{11}+M_{22}+M_{33}\right)+\left(M_{12}+M_{13}+M_{23}\right)+\left(M_{21}+M_{31}+M_{32}\right)}

By reciprocity, M i j {\displaystyle M_{ij}} = M j i {\displaystyle M_{ji}} so that the last two groups can be combined. The first three terms represent the sum of the self-inductances of the various coils. The formula is easily extended to any number of series coils with mutual coupling. The method can be used to find the self-inductance of large coils of wire of any cross-sectional shape by computing the sum of the mutual inductance of each turn of wire in the coil with every other turn since in such a coil all turns are in series.

Capacitors

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Capacitors follow the same law using the reciprocals. The total capacitance of capacitors in series is equal to the reciprocal of the sum of the reciprocals of their individual capacitances:

1 C total = 1 C 1 + 1 C 2 + ⋯ + 1 C n . {\displaystyle {\frac {1}{C_{\text{total}}}}={\frac {1}{C_{1}}}+{\frac {1}{C_{2}}}+\cdots +{\frac {1}{C_{n}}}.}

Equivalently using elastance (the reciprocal of capacitance), the total series elastance equals the sum of each capacitor's elastance.

Switches

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Two or more switches in series form a logical AND; the circuit only carries current if all switches are closed. See AND gate.

Cells and batteries

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A battery is a collection of electrochemical cells. If the cells are connected in series, the voltage of the battery will be the sum of the cell voltages. For example, a 12 volt car battery contains six 2-volt cells connected in series. Some vehicles, such as trucks, have two 12 volt batteries in series to feed the 24-volt system.

Parallel circuits

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Comparison of effective resistance, inductance and capacitance of two resistors, inductors and capacitors in series and parallel

If two or more components are connected in parallel, they have the same difference of potential (voltage) across their ends. The potential differences across the components are the same in magnitude, and they also have identical polarities. The same voltage is applied to all circuit components connected in parallel. The total current is the sum of the currents through the individual components, in accordance with Kirchhoff's current law.

Voltage

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In a parallel circuit, the voltage is the same for all elements.

V = V 1 = V 2 = ⋯ = V n {\displaystyle V=V_{1}=V_{2}=\dots =V_{n}}

Current

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The current in each individual resistor is found by Ohm's law. Factoring out the voltage gives

I total = I 1 + I 2 + ⋯ + I n = V ( 1 R 1 + 1 R 2 + ⋯ + 1 R n ) . {\displaystyle I_{\text{total}}=I_{1}+I_{2}+\cdots +I_{n}=V\left({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}+\cdots +{\frac {1}{R_{n}}}\right).}

Resistance units

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To find the total resistance of all components, add the reciprocals of the resistances R i {\displaystyle R_{i}} of each component and take the reciprocal of the sum. Total resistance will always be less than the value of the smallest resistance:

1 R total = 1 R 1 + 1 R 2 + ⋯ + 1 R n . {\displaystyle {\frac {1}{R_{\text{total}}}}={\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}+\cdots +{\frac {1}{R_{n}}}.}

For only two resistances, the unreciprocated expression is reasonably simple:

R total = R 1 R 2 R 1 + R 2 . {\displaystyle R_{\text{total}}={\frac {R_{1}R_{2}}{R_{1}+R_{2}}}.}

This sometimes goes by the mnemonic product over sum.

For N equal resistances in parallel, the reciprocal sum expression simplifies to:

1 R total = N 1 R . {\displaystyle {\frac {1}{R_{\text{total}}}}=N{\frac {1}{R}}.}

R total = R N . {\displaystyle R_{\text{total}}={\frac {R}{N}}.}

and therefore to:

To find the current in a component with resistance R i {\displaystyle R_{i}} , use Ohm's law again:

I i = V R i . {\displaystyle I_{i}={\frac {V}{R_{i}}}\,.}

The components divide the current according to their reciprocal resistances, so, in the case of two resistors,

I 1 I 2 = R 2 R 1 . {\displaystyle {\frac {I_{1}}{I_{2}}}={\frac {R_{2}}{R_{1}}}.}

An old term for devices connected in parallel is multiple, such as multiple connections for arc lamps.

Conductance

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Since electrical conductance G {\displaystyle G} is reciprocal to resistance, the expression for total conductance of a parallel circuit of resistors is simply:

G total = G 1 + G 2 + ⋯ + G n . {\displaystyle G_{\text{total}}=G_{1}+G_{2}+\cdots +G_{n}.}

The relations for total conductance and resistance stand in a complementary relationship: the expression for a series connection of resistances is the same as for parallel connection of conductances, and vice versa.

Inductors

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Inductors follow the same law, in that the total inductance of non-coupled inductors in parallel is equal to the reciprocal of the sum of the reciprocals of their individual inductances:

1 L total = 1 L 1 + 1 L 2 + ⋯ + 1 L n . {\displaystyle {\frac {1}{L_{\text{total}}}}={\frac {1}{L_{1}}}+{\frac {1}{L_{2}}}+\cdots +{\frac {1}{L_{n}}}.}

If the inductors are situated in each other's magnetic fields, this approach is invalid due to mutual inductance. If the mutual inductance between two coils in parallel is M, the equivalent inductor is:

1 L total = L 1 + L 2 − 2 M L 1 L 2 − M 2 {\displaystyle {\frac {1}{L_{\text{total}}}}={\frac {L_{1}+L_{2}-2M}{L_{1}L_{2}-M^{2}}}}

If L 1 = L 2 {\displaystyle L_{1}=L_{2}}

L total = L + M 2 {\displaystyle L_{\text{total}}={\frac {L+M}{2}}}

The sign of M {\displaystyle M} depends on how the magnetic fields influence each other. For two equal tightly coupled coils the total inductance is close to that of every single coil. If the polarity of one coil is reversed so that M is negative, then the parallel inductance is nearly zero or the combination is almost non-inductive. It is assumed in the "tightly coupled" case M is very nearly equal to L. However, if the inductances are not equal and the coils are tightly coupled there can be near short circuit conditions and high circulating currents for both positive and negative values of M, which can cause problems.

More than three inductors become more complex and the mutual inductance of each inductor on each other inductor and their influence on each other must be considered. For three coils, there are three mutual inductances M 12 {\displaystyle M_{12}} , M 13 {\displaystyle M_{13}} and M 23 {\displaystyle M_{23}} . This is best handled by matrix methods and summing the terms of the inverse of the L {\displaystyle L} matrix (3×3 in this case).

The pertinent equations are of the form:

v i = ∑ j L i , j d i j d t {\displaystyle v_{i}=\sum _{j}L_{i,j}{\frac {di_{j}}{dt}}}

Capacitors

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The total capacitance of capacitors in parallel is equal to the sum of their individual capacitances:

C total = C 1 + C 2 + ⋯ + C n . {\displaystyle C_{\text{total}}=C_{1}+C_{2}+\cdots +C_{n}.}

The working voltage of a parallel combination of capacitors is always limited by the smallest working voltage of an individual capacitor.

Switches

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Two or more switches in parallel form a logical OR; the circuit carries current if at least one switch is closed. See OR gate.

Cells and batteries

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If the cells of a battery are connected in parallel, the battery voltage will be the same as the cell voltage, but the current supplied by each cell will be a fraction of the total current. For example, if a battery comprises four identical cells connected in parallel and delivers a current of 1 ampere, the current supplied by each cell will be 0.25 ampere. If the cells are not identical in voltage, cells with higher voltages will attempt to charge those with lower ones, potentially damaging them.

Parallel-connected batteries were widely used to power the valve filaments in portable radios. Lithium-ion rechargeable batteries (particularly laptop batteries) are often connected in parallel to increase the ampere-hour rating. Some solar electric systems have batteries in parallel to increase the storage capacity; a close approximation of total amp-hours is the sum of all amp-hours of in-parallel batteries.

Combining conductances

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From Kirchhoff's circuit laws the rules for combining conductance can be deducted. For two conductances G 1 {\displaystyle G_{1}} and G 2 {\displaystyle G_{2}} in parallel, the voltage across them is the same and from Kirchhoff's current law (KCL) the total current is

I eq = I 1 + I 2 . {\displaystyle I_{\text{eq}}=I_{1}+I_{2}.}

Substituting Ohm's law for conductances gives

G eq V = G 1 V + G 2 V {\displaystyle G_{\text{eq}}V=G_{1}V+G_{2}V}

G eq = G 1 + G 2 . {\displaystyle G_{\text{eq}}=G_{1}+G_{2}.}

and the equivalent conductance will be,

For two conductances G 1 {\displaystyle G_{1}} and G 2 {\displaystyle G_{2}} in series the current through them will be the same and Kirchhoff's Voltage Law says that the voltage across them is the sum of the voltages across each conductance, that is,

V eq = V 1 + V 2 . {\displaystyle V_{\text{eq}}=V_{1}+V_{2}.}

Substituting Ohm's law for conductance then gives,

I G eq = I G 1 + I G 2 {\displaystyle {\frac {I}{G_{\text{eq}}}}={\frac {I}{G_{1}}}+{\frac {I}{G_{2}}}}

1 G eq = 1 G 1 + 1 G 2 . {\displaystyle {\frac {1}{G_{\text{eq}}}}={\frac {1}{G_{1}}}+{\frac {1}{G_{2}}}.}

which in turn gives the formula for the equivalent conductance,

This equation can be rearranged slightly, though this is a special case that will only rearrange like this for two components.

G eq = G 1 G 2 G 1 + G 2 . {\displaystyle G_{\text{eq}}={\frac {G_{1}G_{2}}{G_{1}+G_{2}}}.}

G eq = G 1 G 2 G 3 G 1 G 2 + G 1 G 3 + G 2 G 3 . {\displaystyle G_{\text{eq}}={\frac {G_{1}G_{2}G_{3}}{G_{1}G_{2}+G_{1}G_{3}+G_{2}G_{3}}}.}

Notation

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For three conductances in series,

The value of two components in parallel is often represented in equations by the parallel operator, two vertical lines (∥), borrowing the parallel lines notation from geometry.

R e q ≡ R 1 ∥ R 2 ≡ ( R 1 − 1 + R 2 − 1 ) − 1 ≡ R 1 R 2 R 1 + R 2 {\displaystyle R_{\mathrm {eq} }\equiv R_{1}\parallel R_{2}\equiv \left(R_{1}^{-1}+R_{2}^{-1}\right)^{-1}\equiv {\frac {R_{1}R_{2}}{R_{1}+R_{2}}}}

This simplifies expressions that would otherwise become complicated by expansion of the terms. For instance:

R 1 ∥ R 2 ∥ R 3 ≡ R 1 R 2 R 3 R 1 R 2 + R 1 R 3 + R 2 R 3 . {\displaystyle R_{1}\parallel R_{2}\parallel R_{3}\equiv {\frac {R_{1}R_{2}R_{3}}{R_{1}R_{2}+R_{1}R_{3}+R_{2}R_{3}}}.}

If n components are in parallel, then

R eq = ( ∑ i n R i − 1 ) − 1 {\displaystyle R_{\text{eq}}=\left(\sum _{i}^{n}{R_{i}}^{-1}\right)^{-1}}

Applications

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A common application of series circuit in consumer electronics is in batteries, where several cells connected in series are used to obtain a convenient operating voltage. Two disposable zinc cells in series might power a flashlight or remote control at 3 volts; the battery pack for a hand-held power tool might contain a dozen lithium-ion cells wired in series to provide 48 volts.

Series circuits were formerly used for lighting in electric multiple units trains. For example, if the supply voltage was 600 volts there might be eight 70-volt bulbs in series (total 560 volts) plus a resistor to drop the remaining 40 volts. Series circuits for train lighting were superseded, first by motor-generators, then by solid state devices.

Series resistance can also be applied to the arrangement of blood vessels within a given organ. Each organ is supplied by a large artery, smaller arteries, arterioles, capillaries, and veins arranged in series. The total resistance is the sum of the individual resistances, as expressed by the following equation: Rtotal = Rartery + Rarterioles + Rcapillaries. The largest proportion of resistance in this series is contributed by the arterioles.[3]

Parallel resistance is illustrated by the circulatory system. Each organ is supplied by an artery that branches off the aorta. The total resistance of this parallel arrangement is expressed by the following equation: 1/Rtotal = 1/Ra + 1/Rb + ... + 1/Rn. Ra, Rb, and Rn are the resistances of the renal, hepatic, and other arteries respectively. The total resistance is less than the resistance of any of the individual arteries.[3]

See also

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References

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1. a b cResnick, Robert; Halliday, David (1966). "Chapter 32". Physics. Vol. I and II (Combined international ed.). Wiley. LCCN 66-11527. Example 1.

2. ^Smith, R. J. (1966). Circuits, Devices and Systems (International ed.). New York: Wiley. p. 21. LCCN 66-17612.

3. a b

   Costanzo, Linda S. Physiology. Board Review Series. p. 74.

Further reading

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Understanding the difference between wiring batteries in series vs. parallel is critical if you have a multiple battery system. How you connect your batteries will determine how they perform in different applications. Let’s look closer at how to wire batteries in series vs. parallel and when each method is appropriate. 

These two batteries are wired in series

What’s The Difference Between Wiring Batteries in Series Vs. Parallel?

The main difference in wiring batteries in series vs. parallel is the impact on the output voltage and the capacity of the battery system. Batteries wired in series will have their voltages added together. Batteries wired in parallel will have their capacities (measured in amp-hours) added together. However, the total available energy (measured in watt-hours) in both configurations is the same.

For example, wiring two 12-volt batteries with 100 Ah capacities in series will output 24 volts with a 100 Ah capacity. Wiring the same two batteries in parallel will output 12 volts with a 200 Ah capacity. Thus, both systems have a total available energy of 2400 watt-hours (watt-hours = volts x amp-hours).

Additionally, batteries wired in series and parallel configurations should all have the same voltage and capacity rating. Mixing and matching voltages and capacities can lead to problems that may damage your batteries.

Wiring Batteries in Series

To wire multiple batteries in series, connect the positive terminal of each battery to the negative terminal of the next. Then, measure the system’s total output voltage between the negative terminal of the first battery and the positive terminal of the last battery in series. Let’s look at two examples to make this clear.

The first example is two 100 Ah batteries wired in series. As you can see, the positive terminal on the first battery is connected to the negative terminal on the second. Thus, the total system voltage is 24 volts, and the total capacity is 100 Ah. 

The second example is wired the same way but with a third battery. The voltages of all three batteries add together, resulting in a system voltage of 36 volts, but the capacity remains at 100 Ah.

Advantages

The power a device consumes is equal to its operating voltage multiplied by the current it draws. For example, a 360-watt device operating at 12 volts would draw 30 amps (12 x 30 = 360). That same device operating at 24 volts would only draw 15 amps (24 x 15 = 360).

Wiring batteries in series provides a higher system voltage which results in a lower system current. Less current means you can use thinner wiring and will suffer less voltage drop in the system. 

In addition to power draw, charging works the same way. Consider an MPPT solar charge controller rated at 50amps. a 50A x 12V controller could only handle 600 watts of solar, but at 24Vx50A it could handle 1200 watts!

In general, operating larger power systems can see big benefits in running batteries in series at higher voltages.

Disadvantages

In a battery system wired in series, you cannot get lower voltages off the battery bank without using a converter. Either all equipment needs to function at the higher voltage or an additional converter is needed to use 12V appliances on the system.

Wiring Batteries in Parallel

To wire multiple batteries in parallel, you connect all of the positive terminals together and all of the negative terminals together. Since all of the positive and negative terminals are connected, you can measure the system output voltage across any two positive and negative battery terminals. Let’s look at two examples to make this clear.

The first example is two 100 Ah batteries wired in parallel. The positive terminal on the first battery is connected to the positive terminal on the second. Likewise, the negative terminals of both batteries are also connected. The total system voltage is 12 volts, and the total capacity is 200 Ah. 

The second example is wired the same way but with a third battery. The capacities of all three batteries add together, resulting in a total capacity of 300 Ah at 12 volts.

Advantages

The main advantage of wiring batteries in parallel is that you increase the available runtime of your system while maintaining the voltage. Since the amp-hour capacities are additive, two batteries in parallel double your runtime, three batteries triple it, and so on.

Another advantage to wiring batteries in parallel is that if one of your batteries dies or has an issue, the remaining batteries in the system can still provide power. 

Disadvantages

The main drawback to wiring batteries in parallel vs. series is that the system voltage will be lower, resulting in a higher current draw. Higher current means thicker cables and more voltage drop. Larger power appliances and generation are harder to operate and less efficient when operating at lower voltages.

How Many Batteries Can You Wire In Series?

The limit on how many batteries you can wire in series typically depends on the battery and manufacturer. For example, Battle Born allows up to four of their lithium batteries to be wired in series to create a 48-volt system. Always check with your battery manufacturer to ensure you do not exceed their recommended limit of batteries in series.

How Many Batteries Can You Wire In Parallel?

There is no limit to how many batteries you can wire in parallel. The more batteries you add in a parallel circuit, the more capacity and longer runtime you will have available. Keep in mind that the more batteries you have in parallel, the longer it will take to charge the system.

With very large parallel battery banks comes much higher current availability as well. This means the proper system fusing is critical to prevent accidental shorts that could have catastrophic consequences with so much current available.

Can You Wire Batteries in Series and Parallel?

You cannot wire the same batteries in series and parallel as you would short the system, but you can wire sets of batteries in series and parallel to create a larger battery bank at a higher voltage.

The photo below wires two batteries in series to get 24V then that set is wired in parallel to another set of 24V batteries. Think of each set of series batteries as one battery. You must “create” another set of batteries equal to the voltage of the first to wire them in parallel.

Here is another graphic of our heated lithium batteries wired in a series-parallel configuration. This setup would yield a 24V 200AH bank. While the amp hour is smaller, the power is the same because of the higher voltage.

Charging Batteries in Series Vs. Parallel

Besides making sure you have the correct voltage charger, batteries in series vs. parallel charge the same way. For batteries wired in series, connect the positive charger cable to the positive terminal on the first battery in series and the negative charger cable to the negative terminal on the last battery in the series. For even charge across a parallel bank, connect your charge in the same fashion: positive connect to first battery, and negative connected to last battery.

Optionally, a multi-bank battery charger may provide faster charge times for series and parallel battery banks. As always, refer to the manufacturer’s recommendation for the best way to charge your batteries. 

➡ Also be sure to read our article on Charging Lithium Batteries: The Basics.

FAQ: Do Batteries Last Longer In Series Or Parallel?

Series connections provide a higher voltage which is slightly more efficient. This means that batteries wired in series can last marginally longer than batteries wired in parallel. However, batteries connected in series vs. parallel will provide roughly the same amount of runtime. Let’s take a look at a quick example that explains why this is true.

Two 12-volt batteries with a 100 Ah capacity are powering a 240-watt device. These two batteries wired in series will provide 24 volts and 100 Ah of capacity. The current draw of the device will be ten amps (24 x 10 = 240). The theoretical runtime of the series system is 100 Ah divided by ten amps, which is ten hours.

Conversely, the same two batteries in parallel provide 12-volts and 200 Ah of capacity. The device’s current draw in this setup is 20 amps (12 x 20 = 240). The theoretical runtime of the parallel system is 200 Ah divided by 20 amps, which is also ten hours. 

Batteries in Series Vs. Parallel: Which Is For You?

Deciding between connecting your batteries in series vs. parallel is often dictated by the needs of the devices you’re powering. For general boat and RV applications wiring batteries in parallel provides the simplest wiring and common voltage, however, for large applications beyond 3000 watts of power, using higher voltage series connections might be best. Now that you understand how each wiring configuration works, you can determine the best option for your needs and proceed with confidence. 

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