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.
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.
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.
What is a 9v battery?
A 9-volt battery is a battery with 9 volts of potential difference at two ends the positive and the negative. It was originally made for the introducti9on of the transistor radios. The 9-volt battery has a rectangular shape with smooth edges. They are used in smoke detectors, clocks, industrial electrical and electronic equipment, and even in walkie-talkies.
There are various dimensions of a 9v battery. You need to find out the right dimensions for your use and the gadget in which is to be fitted.
When we are generally talking about the 9v battery we are talking of the PP 3 batteries.
These are commonly used in all types of applications. PP stands for Power Pack and is a standard used to detect the size of batteries.
There are various types of batteries in the PP series itself. This includes the PP3 9v battery, PP4 9v battery, PP6 9v battery, PP7 9v battery, PP9 9v battery, and PP10 9volt battery.
Each of the batteries has a fixed dimension and that can be used for one specific task. It also has an mAH rating with itself which specifies the uses it can be put in without causing damage to both the device and the battery.
Before buying a 9v battery you need to measure the dimensions of the battery slot in your gadget and check the mAH specifications long with the correct load and voltage options.
Here we will give you an idea of the dimensions of each of the PP series batteries dimensions. This will help you to have an idea for reference while buying batteries for your gadget.
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Dimension For PP Series 9v Batteries
PP3 9v batteries with 4mAH have a depth of 17.5 mm, with a width of 26.5 mm, and a height of 48.5 mm.
PP4 9v batteries have a load rating of 0.9 mAH. It has a diameter of 25.8mm and a length of 49.8 mm to 41.5 mm ex contacts.
PP6 9v batteries give you a load rating of 1 AH. It is has a depth of 34.1 mm, a width having 35.7 mm, and a height of 69.9 mm.
PP7 9v batteries give you 2.5 Ah. The depth of the battery is 46 mm, a width of 46 mm, and a height of 63 mm.
PP9 9v batteries give you 5Ah. The dimensions of the battery are- depth having 51.5 mm, a width of 65 mm, and a height of 80 mm.
Pp10 9v batteries give you 15 Ah. Its dimensions are depth of 66 mm, a width of 65 mm, and a height of 267 mm.
Apart from this you also have the PP11 4 te3rminal batteries in which two physically isolated batteries are there with each one having a 4.5 v potential. It can deliver you 5 Ah. Its dimensions are- a depth of 51.5 mm, a width of 65 mm, and a height of 91 mm.
Apart from the pp3 9v batteries which are the most common, you will also see PP6, PP7, and PP 9 in a lot of industrial uses.
The 9v batteries are generally of two types the lithium-ion batteries and PP series batteries for their heavy-duty uses.
The alkaline batteries of 9v have 6 cylinders or cells connected in series to the two terminals. Sometimes welded tabs are also used to attach to the cells.
The rechargeable nickel-cadmium 9v batteries also have between 6 to 8 1.2v cells connected in series.
Low Temperature High Energy Density Rugged Laptop Polymer Battery Battery specification: 11.1V 7800mAh.40℃ 0.2C discharge capacity ≥80% Dustproof, resistance to dropping, anti. corrosion, anti. electromagnetic interference
Is it good for a battery to have a small dimension?
In the age-old times when the batteries were in the alkaline form and used carbon and zinc as the two positive and negative terminals, you could have said that the larger the electrode size and the more the volume of the electrolyte or alkaline material inside the more is the capacity of the battery and the longer it would run.
But this is not always true these days. The reason why the smaller AA sized or the PP 3 9v batteries have become most widely used is that they have almost the same alkaline material in them as a C or D shaped battery.
You can understand this if you lift the C and D sized batteries they are not relatively that heavier and cannot be justified due to their size.
And of course, it also costs you more to buy a C or D size battery.
The smaller ones like the PP 3 or AA batteries can be used in a series connection and add up to the voltage that you need. So why spend more on buying a heavier and bulkier c or D size battery.
And of course, on the usage front, it is much more convenient to store and replace the smaller sized batteries having smaller dimensions such as PP3 9v batteries and the AA sized batteries.
How do you choose 9v battery dimensions?
Now, as you might have understood by now that there are most important three things that you need to consider for buying the right sized 9v battery.
The first thing is to take note of the load ratings. You can check out the device specifications and find out mAH which is different for each device.
And of course, the dimensions of the battery slots also matter based on which you will be buying the right PP series batteries.
And the last thing is to note the voltage that you require. If you need 9 volts only then one will do. But in case you need more then you can buy that many batteries.
Комментарии и мнения владельцев
Looking for answers to technical questions?
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Hello, I have two questions about this Holder. What are its dimensions especially holes sizes and distances between them? Will it be good for arduino UNO power supply?
You should look at the summary for the Uno on Arduino’s website, it’ll help you figure out what’s compatible with it.
In case anyone needs it, this looks like the right datasheet: http://www.memoryprotectiondevices.com/datasheets/BH9VPC-datasheet.pdf
The BH9VPC product described in the data sheet doesn’t have a barrel jack. Instead, it has two leads out the bottom, spaced.5 inches. I was looking for something I could use on a PCB.- the BH9VPC looks just about perfect and is available on DigiKey. So, thanks for posting that link!
Sweet. One of these, a couple rechargeable and a charger would make for a much more compact and simple system than AAs or even LiPo bars and chargers.
Customer Reviews
3.3 out of 5
4 of 4 found this helpful:
not as depicted
about 8 years ago by Member #421207 verified purchaser
Once again, SF delivers a product that is not accurately portrayed. I ordered a bunch recently; all are missing the last 2 inches of insulation. This is a deal-breaker for my application. Yeah, I could beef it up myself. But the point is that you should deliver what you depict. C’mon SF.
If you look in the second photo (box detail) at the top near the wire, you can see that this gap was depicted in the original image. It’s just not very easy to notice.
Hi, Sorry for the change in part. You are right, these are now shipping with about 2 inches of wire from the box end showing before the main shielding starts.
1 of 1 found this helpful:
Does what it is supposed to.
about 6 years ago by Spacecase544 verified purchaser
Holds 9V battery securely, connects to and powers Arduino board. Don’t know what else one would want from it.
1 of 1 found this helpful:
Great holder, if a bit tight.
about 6 years ago by MoviesColin verified purchaser
Great battery holder, solid construction and wires. Only complaint is the tab at the bottom. it broke on one of my holders and with the tab there, 9V batteries are very difficult to remove. But on the other hand, it’s also nice to know that the battery isn’t going anywhere. especially if you have a mobile project or if it gets dropped.
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Best 9V Batteries: Reviews and Recommendations
Best Overall: Energizer Ultimate Lithium 9V Battery
Why They Made The Cut: Energizer’s Ultimate Lithium 9V battery delivers consistent power for longer than any competitor, has greater shelf life, and can withstand extreme operating temperatures.
— Type: Lithium-Manganese Dioxide — Capacity: 750 milliamp hours (mAh) — Pack Sizes: One, two, 12, 24
— Market-leading performance — Suitable for all weather conditions — 10-year shelf life
— Expensive — Not rechargeable
Energizer has been one of the leading developers of advanced lithium battery chemistries that provide better performance for longer and in more extreme conditions. Their 9V battery uses lithium-manganese dioxide and offers class-leading consistency in terms of power delivery, and provides a shelf life of up to 10 years.
The Energizer Ultimate Lithium 9V battery is certainly expensive. It’s disposable, yet costs more than most rechargeable 9V batteries. On the other hand, the unrivaled durability means it’s the ideal choice for important, high-drain security apparatuses, Smart home devices, or personal medical equipment. It is extremely reliable, and the extended run time makes it especially good for equipment that is awkward to reach, thus reducing how often batteries need changing.
These batteries are also the optimum solution for outdoor use. Alkaline versions lose charge rapidly as the temperature drops, but the Energizer Ultimate Lithium 9V battery can function anywhere from minus 40 degrees Fahrenheit to 140 degrees Fahrenheit.
Best Budget: Amazon Basics 9V Performance Battery
Why They Made The Cut: For many ordinary household gadgets and toys, the money-saving 9V Alkaline batteries from Amazon Basics are a convenient, and perfectly adequate solution.
— Type: Alkaline — Capacity: Not given — Pack Sizes: Four, eight, 24
— Great everyday value — Five-year shelf life — Leak-free design
— Not for high-drain devices — Poor in cold weather
For household devices that have modest power demands, lithium 9V batteries are overkill. 9V alkaline disposable batteries, like these Performance Batteries from Amazon Basics, are a reliable, affordable alternative.
These shouldn’t be confused with cheap, bargain-store 9V batteries. Amazon doesn’t reveal who makes them (and we were unable to find a mAh rating), but they are a quality product that comes with a solid, leak-free construction and a five-year shelf life.
While not designed for high-drain equipment, Amazon Basics 9V batteries will still run a high-drain gadget for a limited period. So, as well as having them for everyday use, they can be kept as an emergency backup in case more powerful alternatives run flat unexpectedly.
Amazon Basics 9V alkaline batteries have limited cold weather performance, but that’s a drawback with the chemistry, rather than this particular model. While they come in a plain cardboard box that Amazon calls ‘frustration-free’ packaging, each does have a plastic wrap that some find awkward to remove.
Best Rechargeable: LP 9V Rechargeable Battery Charger Pack
Why They Made The Cut: The LP 9V rechargeable pack contains four high-performance lithium-ion batteries and a Smart charger that can individually manage each charge level.
— Type: Lithium-ion — Capacity: 600 mAh — Pack Sizes: One, two, four
— Up to 1,200 recharge cycles — Low self-discharge rate — USB-powered charger
— expensive than NiMH — Not compatible with all chargers
Although rechargeable 9V batteries are more expensive initially, they can be a very affordable choice over their entire lifetime. That’s especially true of the LP model. which can be recharged up to 1,200 times. Even taking into account the price of the included charger, that works out at a very low unit cost.
It is also a more environmentally friendly approach than disposable batteries. While 9V alkaline batteries are relatively easy to recycle, unfortunately, many still find their way into landfill.
The 600 mAh capacity of the LP 9V is also impressive, giving a consistent performance for a variety of security and testing devices. They are also one of the best for guitar use and other sound equipment. These are low self-drain batteries, retaining up to 75 percent of charge over a three-year period.
The charger itself can be powered by any device with a micro USB port and has a microchip that allows it to control each charging port individually. We recommend this option because the LP batteries might fail to charge fully on some other chargers.
Best Alkaline: Duracell CopperTop 9V Battery
Why They Made The Cut: Duracell claims to be the world’s most trusted battery brand, and has a long-standing reputation for reliable performance at a reasonable cost.
Things to Consider Before Buying a 9V Battery
The key difference between types of 9V batteries is the chemistry used to store the electrical charge.
Alkaline
Alkaline 9V batteries are the budget option. They provide proven, reliable technology best suited to low-performance devices (often called low-drain) like radios, clocks, or hand-held remote controls. Alkaline 9V batteries are not rechargeable.
Lithium
There are a number of variations in lithium battery chemistry, and it is an area of ongoing development. 9V batteries are often simply called lithium (Li), or maybe lithium-manganese dioxide (LiMnO2). Lithium 9V batteries are recommended for high-drain devices like medical or testing equipment where reliability and stability are of prime importance. Lithium 9V batteries are more expensive than alkaline and many types are not rechargeable. The exception is lithium-ion (Li-ion) 9V batteries, which are rechargeable.
Nickel Metal Hydride
9V NiMH batteries are a popular rechargeable option. In both performance and price terms, they usually sit somewhere between alkaline and lithium. The fact that they can be recharged hundreds of times means they are economical in the long run. The drawback with NIMH 9V batteries is that they lose charge over time and new batteries may need to be charged before use. Some are low self-drain (LSD), meaning this problem is much less pronounced.
Capacity
Even when two 9V batteries share the same chemistry, there can be differences in how long they can supply their power. The figure used is milliAmp hours (mAh), and it’s often compared to the amount of fuel in a car’s gas tank. For example, if one 9V battery is rated for 400 mAH, and another for 600 mAH then the latter will continue to deliver its charge when the former has run flat. Maximizing 9V battery mAh is important for devices that need to run unattended for long periods.
FAQs
Q: What are 9V batteries used for?
9V batteries are used in a variety of small electronic devices including smoke and carbon monoxide detectors, circuit testers, blood pressure monitors, walkie-talkies, portable radios, and more.
Q: When should I replace my 9V battery?
In most devices, a significant drop in performance or failure to operate will indicate you should replace your 9V battery. Alarms usually have a recommended replacement of six or 12 months.
Q: Do 9V batteries last longer than AA batteries?
Much depends on the equipment being powered, but typically AA batteries have a higher milliamp-hour (mAh) rating, so tend to last longer than 9V models.
Q: How long does it take to recharge a 9-volt battery?
Much depends on the battery and the charger. Our research shows charging times vary considerably from a low of around three hours to eight hours or more.
Q: How long does a 9V battery last in a smoke detector?
While it’s possible they may last more than a year, most smoke alarm manufacturers recommend that they are replaced every six months.
Q: At what voltage is a 9V battery considered dead?
Advice varies. While some say 9V batteries should be considered dead at 8V or below, numerous devices (typically meters and measuring equipment) will still function at 7V or even 6.5V.
Final Thoughts on 9V Batteries
Energizer’s 9V Ultimate Lithium batteries are head-and-shoulders above the competition in performance terms. They store longer, run longer, and function at greater temperature extremes. They are undeniably expensive, but if you want a battery you can rely on in harsh conditions these are the ones to choose. At the other end of the scale are the Amazon Basics All-Purpose Alkaline. cheap 9V batteries that are more than adequate for dozens of everyday gadgets.
This post was created by a non-news editorial team at Recurrent Media, Futurism’s owner. Futurism may receive a portion of sales on products linked within this post.