How to Insert Batteries the Right Way. Aa batteries in series

Understanding battery capacity: Ah is not A

I used battery holders for eight “C” alkaline cells on my robot after not finding a 12V, 1A battery.

My earliest electronics projects and my first robot were powered by regular alkaline batteries, and I didn’t think about current or the capacity of those batteries. The batteries were prominently labeled “1.5V”, and I was happy in my understanding that putting four in a battery holder got me to 6 volts; when the motors slowed down, it was time for new batteries. When I began designing my second robot, I found some 12V, 1A motors (what a “1-amp motor” might mean is a topic for another post) and promptly wasted many hours dragging parents and teachers to Radio Shack and car parts stores looking for a 12V, 1A battery. No one understood that the batteries were labeled with capacity, not current, and since the smallest 12V motorcycle and alarm system batteries in town were 3Ah or 4Ah, I went home empty handed. I ended up using alkalines. Apparently, once the battery capacity wasn’t in my face, I forgot about my concern that they would force too much current into my motors.

I made many common mistakes in going about my battery selection:

  • Not understanding that my circuit would draw whatever current it wanted from the battery, as opposed to the battery forcing a given amount of current into the circuit.
  • Thinking that my motors would draw a fixed amount of current.
  • Confusing current and capacity.
  • Ignoring the “h” in “Ah”
  • Forgetting about a property, such as capacity, as soon as it wasn’t in my face.

The first two points are complex enough that further elaboration would merit their own posts; today I want to FOCUS on some technical details of battery capacity and current and touch on the sloppy attitude that leads to the last two mistakes.

A battery stores energy; the “capacity” is how much energy it can store. Energy is measured in joules, abbreviated J, but it can also be expressed in different units such as watt-hours, abbreviated Wh (for larger quantities, such as residential electricity use, kilowatt-hours (kWh) are used; a kWh is a thousand Wh). This is similar to the way area can be measured in acres or in square miles: there are units specifically for area, such as acres, but you can also arrive at a measure of area by multiplying length by length, to get mile-miles, or the less awkward square miles. (The hyphenation imposed by English grammar does not help matters since the hyphen looks like a minus sign when we are actually multiplying the units together.) Watts and watt-hours are generally good units for electronics since they are easily related to voltage and current and since typical batteries that you can hold in your hand will have a capacity of a few dozen watt-hours.

In the case of a typical battery, where we can assume a constant voltage, we can replace watts with volts multiplied by amps. A 12-volt, 1 amp-hour (abbreviated Ah) battery and a 6-volt, 2Ah battery each store 12Wh, but the voltage is usually a critical parameter for a battery, and once a voltage is selected, the capacity can be specified by the amp-hour rating. The value in using the amp-hour is that it makes explicit our multiplication of rate, the amp, and time, the hour: a battery rated for one amp-hour can provide a current of one amp for about one hour, two amps for about half an hour, or 0.1 amps for about ten hours. I say “about” because the exact capacity will depend on the current.

The current and capacity for a battery are like the speed and range of a car. If your car has a range of about 300 miles, you can go 30 miles an hour for ten hours, or 60 miles an hour for five hours. Your efficiency will get worse with speed, so by the time you go 60 miles per hour, you might run out of gas after only four hours, for a range of 240 miles. Going back to my battery search, looking for a 1-amp battery was like looking for a car with a speed of 60 miles: 60 miles isn’t even a speed, and even if I revised my search to a car that could go 60 miles per hour, it still wouldn’t be a useful specification to look for. Most batteries on the scale I was looking at can deliver one amp, just like most cars can go sixty miles per hour. The maximum available current, like the maximum speed of the car, might be a more reasonable specification to search for, though providing those kinds of specifications might make the respective manufacturers nervous.

It is reasonable, though, to consider the maximum current a battery can safely deliver. That value will depend on all kinds of things, including the chemistry of the battery, but the maximum discharge rate is almost always tied to the capacity. That means that given a particular technology, a battery with double the capacity can deliver double the maximum current. Batteries are often specified with a discharge rate in terms of C, where C is the capacity of the battery divided by hours. For example, for a 2Ah battery, C is 2A. If the battery has a maximum discharge rate of 10C, the maximum current is 20 amps. It’s good to keep in mind that a 10C discharge rate means a battery life of less than 1/10th of an hour, and with the loss of capacity that a high discharge rate generally causes, the battery life would be less than five minutes.

As I tried earlier to recall what happened with my failed battery search, I was struck by the extent to which I ignored the “h” in the “Ah” specification and the ease with which I forgot about my critical “1-amp battery” requirement when I returned to the alkaline batteries. Unfortunately, this kind of carelessness or sloppiness is common, especially for beginners who might already be overwhelmed by all the information they need to sort through and who have not yet had the experience of losing time and destroying hardware because of inattention to details. I do not have any particular solution to this problem beyond reminding you to pay attention and think about how things should work before just hooking things up. Be on the lookout for contradictions; seeing “Ah” where you expect “A” should definitely make you very uneasy and lead you to reevaluate your expectations.

I will wrap up this article with some example battery capacities.

  • A typical alkaline or NiMH battery in the standard “AA” size has about 2000 to 3000 mAh (or 2 to 3 Ah). With a cell voltage of 1.2 V to 1.5V, this corresponds to 2 to 4 Wh per cell. When multiple cells are used in series, as with the use of a battery holder or most pre-made battery packs, the voltage goes up but the capacity in amp-hours stays the same: an 8-cell NiMH pack made of AA cells will have a 9.6 V nominal voltage and a 2500 mAh capacity. There can be quite a range in capacities depending on the quality of the batteries. For larger cells, such as C and D size, the capacity should go up approximately proportionally to volume, but some cheap units (they’re usually light) can have the same capacity as the smaller cells. Alkaline cells have a more pronounced drop in capacity as the current drawn out of them goes up, so for applications requiring several hundred mA or more current, NiMH cells of the same size could last significantly longer. For low-current applications that need to run for months, alkaline batteries can last much longer because NiMH cells can self-discharge in a few months.
  • 9V alkaline batteries can be convenient for their high voltage in a small size, but the energy density (watt-hours per given volume or weight) is the same as other batteries with the same chemistry, which means the capacity in amp-hours is low. In approximately the same size as an AA cell, you get six times the voltage, so you also get about six times less in the Ah rating, or about 500 mAh. Given the high losses incurred from discharging in anything under a few hours, 9V batteries are impractical for most motors and therefore for most robots.

Coin or button cell batteries.

  • Coin or button cell batteries vary in size and chemistry, but you can generally expect 1.5 to 3 volts with a few dozen to a few hundred mAh.

12V, 8Ah sealed lead-acid battery.

  • Lead-acid batteries are popular for larger projects since they are usually the lowest-cost option and are widely available. Sealed lead-acid or gel-cell batteries are available in 6 V and 12 V versions (other multiples of 2 can be found), with the 12 V versions weighing about a pound per amp-hour. 12 V car batteries store a few dozen amp hours, and they weigh a few dozen pounds.
insert, batteries, right, series

11.1V, 1800mAh Li-Po battery.

  • Lithium-based rechargeable batteries have around double the energy density of alkaline and NiMH batteries by volume and even better improvements by weight. These newer batteries are far less standardized in terms of battery size and shape, but since they are usually intended for applications where capacity or maximum battery life are important, these batteries usually have their voltages and capacities prominently labeled.
insert, batteries, right, series

Introduction to Jan’s blog

by Jan. 12 November 2010 My name is Jan Malášek, which is a Czech name, so the “J” is pronounced as an English “Y” (if you care, we can go over the last name in person, or.

Know your units

by Jan. 19 November 2010 How many volts of current are there in a bolt of lightning? That’s the kind of stupid question your local news anchor might ask while bantering.

2 Комментарии и мнения владельцев

Thanks for the article Jan!

It’s probably worth noting, particularly for lead-acid batteries, that the capacity is usually listed assuming that the battery will be discharged over a 20 hour period. If you’re using it in relatively high current applications (i.e. robotics or motors of any kind) then you can expect almost half of that. This is something that caught me out when I was looking at battery options.

Great comment; I’m sad that I neglected to mention that. Another variable to consider is how far the battery is allowed to discharge before being considered fully drained.

How to Insert Batteries the Right Way

This article was co-authored by Marvin Woo and by wikiHow staff writer, Devin McSween. Marvin Woo is a licensed electrician and the Owner of Woo’s Electrical Appliance based in East O’ahu. With over two decades of experience, he specializes in troubleshooting issues and maintaining residential electrical systems. Marvin is both licensed and insured to complete electrical work in the state of Hawaii.

There are 12 references cited in this article, which can be found at the bottom of the page.

This article has been viewed 326,241 times.

Your new TV is all plugged in and ready to go when you realize the remote doesn’t have batteries installed. Fitting your batteries into the remote can feel like a puzzle, leaving you unsure where each battery end goes. Luckily, there are easy ways to remember how to insert batteries that work for all kinds of devices. In this article, we’ll tell you where to find your device’s battery compartment and how to install AA, AAA, C, D, 9-volt, and button batteries. If you’re ready to pop in those fresh batteries, read on!

  • For AA, AAA, C, and D batteries, slide the flat, negative end of the battery against the spring. Then, push the raised, positive end into the flat side of the compartment.
  • For a 9-Volt battery, hold it at a 30° angle to line it up with the connector snaps. Press it into the connectors and then push it into place.
  • For coin or button batteries, place the positive side facing up unless otherwise directed.

Locating the Battery Compartment

Examine the device for a small battery symbol or a plus and minus sign. Most battery compartments are on the back or bottom of the device, so check there first. Depending on the device, the compartment might be on the front, sides, or top of the device. The compartment is typically marked with either a small battery-shaped symbol or a “” or “-” sign, indicating the polarity of the battery. [1] X Expert Source

  • Some devices have a clasp or a lever that releases to open the compartment door.
  • The battery compartment may also be held shut by one or more small screws.
  • If the screw is stuck, you may be able to remove it using a screw extractor.
  • In you’re changing a watch battery, you may need to use a special tool, like a small flathead screwdriver, to remove the back of the watch.
  • AAA, AA, C, and D batteries are all 1.5V batteries, but the different sizes produce different currents, or the amount of power that comes out of the battery at once. AAA is the smallest traditional 1.5V battery, and is usually used to power small electronics. D is the largest 1.5V battery and usually charges larger items like flashlights.
  • A 9V battery looks like a small box with snaps on top, and it’s often used to power devices like smoke detectors and walkie-talkies. [2] X Research source
  • Coin and button batteries are small and round, and they’re used to power very small devices like watches, hearing aids, and computer components. [3] X Trustworthy Source United States Environmental Protection Agency Independent U.S. government agency responsible for promoting safe environmental practices Go to source

Installing AA, AAA, C, and D Batteries

Look for a plus symbol on your battery. The polarity of batteries is what helps them supply current to a device. [4] X Expert Source

  • The negative end of the battery is completely flat. It may or may not be marked with a minus, or “-,” symbol.

Find the positive and negative symbols on your device. Inside most devices, you’ll see one side of the compartment has a spring, and the other side is flat. Many devices mark a plus and minus sign on each side, telling you which direction the battery needs to go. [6] X Expert Source

insert, batteries, right, series
  • If the polarity isn’t marked on your device, you may need to consult the manufacturer’s instructions.
  • On devices with vertical compartments, like flashlights, see if the bottom is flat or has the spring. If the bottom has the spring, the flat, or negative side, of the battery goes in first. If the bottom is flat, the raised, or positive side of the battery goes in. [9] X Research source
  • If there are symbols, simply match the “” on the battery to the “” in the compartment, and the “-” on the battery to the “-” in the compartment.
  • On some devices, like flashlights, you’ll stack batteries directly on top of each other. In cases like these, the batteries face the same direction so the opposite polarities touch. If the negative side of the battery went in first, its positive end is facing up. So, place the next battery in with the negative side facing down. [12] X Research source
  • Some devices that use multiple batteries may continue to function if one battery is installed incorrectly, but you can damage the device or shorten the life of the batteries by doing so.

Putting in a 9-Volt Battery

  • The smaller, circular snap is the male connector, while the hexagonal or octagonal snap is the female connector.
  • It’s obvious when you put in a 9V battery incorrectly, as the connectors will bump against each other and the battery won’t snap into place.
  • These types of batteries can be a little hard to install sometimes. If it doesn’t go in the first time, try again with a little more force.

Inserting Coin and Button Batteries

  • Usually only the positive side of the battery is etched. The negative side typically doesn’t have any markings at all.
  • In some button-style batteries, the positive side is slightly raised.
  • If you inserted the battery backwards in a device with a battery door, like a hearing aid, you’ll likely have difficulty closing the door.
  • If you’re installing a coin cell battery on a computer’s motherboard, for instance, there may not be any markings to indicate which way the battery should go, but the positive side should face upward.
  • If you’re still not sure how to install the battery, consult the device’s user manual.

Community QA

This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

When you’re stacking batteries, the positive end of one battery touches the negative end of the other, and vice versa. So with coin cell batteries, insert the first battery with the positive side face-up. Then, stack the second battery with the negative side facing down (and positive side facing up) so the negative side rests on top of the first battery’s positive side.

Thanks! We’re glad this was helpful. Thank you for your feedback. As a small thank you, we’d like to offer you a 30 gift card (valid at Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy! Claim Your Gift If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even 1 helps us in our mission. Support wikiHow

I have a very small cylindrical flashlight that takes 4 button batteries, stacked. Should all the batteries have the negative side against the positive side of the adjoining battery?

This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

Yes, this is correct. When you stack batteries, the negative end of one battery touches the positive end of the other (and vice versa).

Thanks! We’re glad this was helpful. Thank you for your feedback. As a small thank you, we’d like to offer you a 30 gift card (valid at Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy! Claim Your Gift If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even 1 helps us in our mission. Support wikiHow

I have a device that takes 4 AA batteries but there are no markings inside. The bottom only contains springs, so does that mean the compartment terminals are positive or negative?

This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

The spring side of a device’s battery compartment is the negative end, while the flat side is the positive end. When you insert batteries, just match the negative end to the spring and the positive end to the flat side. In this case, you’ll place the negative, flat sides of the batteries against the springs.

Thanks! We’re glad this was helpful. Thank you for your feedback. As a small thank you, we’d like to offer you a 30 gift card (valid at Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy! Claim Your Gift If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even 1 helps us in our mission. Support wikiHow

Start Simple with Alkaline AA Batteries

I thought I’d whip up a circuit to run exclusively on solar power. Growing around solar-powered electronics like desktop calculators, I knew it was a solved problem. But after running into obstacles, I have been humbled by the challenges involved and decided to fall back to battery power. A lot of solar power projects have a rechargeable battery somewhere in the mix, and I’m going to follow that precedence in the hopes of simplified energy management.

But as an intermediate stepping stone, I will adapt my circuit to run on batteries without worrying about the charging circuit just yet. I have the components I need on hand: a pile of alkaline AA batteries and a tray for 5AA batteries in series.

A fresh AA alkaline battery has an open-circuit voltage just over 1.5V, and four of those in series would deliver more than 6V. Plenty for an ESP8266, but I’m not using fresh batteries for this project. My fresh AA batteries go into devices with motors or other high drain use. Once those devices complain the batteries were too weak, I move them into purely electronic devices with lower amperage demands. (TV remote controls, Hackaday badges, Xbox wireless controllers, etc.) When they are deemed too weak again, they go into my pile of AA batteries awaiting Joule thief LED duty. Open-circuit voltage for veteran batteries in this pile hover around 1.1V, thus I needed five of them in series instead of just four.

These 5-ish volts are too low to activate my modified MP1584 buck converter, which would no longer activate until input voltage of at least 13V. But that’s not a problem, because the Wemos D1 Mini clone board I’m using could run on 5V USB power. These batteries are pretty close to that voltage level, so I bypassed the MP1584 and connected the battery tray to existing “5V” pin on this module and used its onboard voltage regulator (which I didn’t trust to handle solar power directly) to deliver 3.3V to the ESP8266 and INA219. This worked pretty well.

thoughts on “ Start Simple with Alkaline AA Batteries ”

9V cells are also pretty spiffy for low current demands – if you’re replacing them every spring and fall in your smoke/CO2 detectors (okay, yea, who is actually doing that?) you could have a stockpile of them. Paired with a 9V connector cable and a good compact switchmode regulator, those second purposed 9V cells can power a variety of much lower voltage (and current) devices Like Liked by 1 person

In my home I’ve switched over to smoke detectors with builtin non-replaceable 10 year life batteries. The upside is that I no longer need to remember to replace 9V batteries on a regular basis, the downside is I no longer have a steady source of 9V batteries to repurpose. Like Liked by 1 person

Do the batteries still sustain a usable charge when you combine a bunch of semi dead ones? Or do they all just die right away? I like recharging my dead alkalines for use in remotes or other low value/low power draw devices. There’s risk of spilling, but I’m willing to take that gamble over wasting new batteries in cheap low draw situations Like Liked by 1 person

It all depends on how power is drawn. This specific experiment had relatively high draw (Wi-Fi) but only for a few seconds, followed by several minutes of near-zero draw allowing battery recovery. This pulsed pattern may work better than a constant low draw for certain batteries near end of life. Like Liked by 1 person

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

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.

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.


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.


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.


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.


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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