Battery capacity, price and other details

Selecting the Best Battery for Embedded-System Applications article tells that non-rechargeable (primary) batteries find wide use in mainstream embedded-system applications. This category of batteries includes alkaline devices, which manufacturers typically fabricate using manganese dioxide and zinc powder with a caustic alkali of potassium hydroxide as an electrolyte. The nominal voltage of an alkaline cell is 1.5V, with a discharge voltage of 0.9V.

The capacity of an alkaline (regular) AA battery is typically approximated at anywhere between 700 and 3,000 mAH. “Heavy duty” batteries have much less powerful than alkaline batteries: for example Dynamic Energy Ultra AA say 258 mAh and Grunding Plus AAA 325 mAh.

BatteryIMG2

FAQ – Batteries tells that the Mallory charts give the AA size alkaline cell a capacity of about 2800 mAH, but that’s at room temperature, under light loading, with end of life at about 1.0 or 0.9 volt. But if you draw more current (over 500 mA) the alkaline really sucks, and dies after less than 900 mAH. Under similar conditions the NiMH are around 1500 mAH. Battery Life article give out tips how to get maximum battery life.

AA battery capacities from Wikipedia

  Zinc–carbon Alkaline Li-FeS2 NiCd NiMH NiZn
IEC name R6 LR6 FR6 KR6 HR6  ?
ANSI/NEDA name 15D 15A 15LF 1.2K2 1.2H2  ?
Capacity under 500mA constant drain 400-1000 mAh 1800-2600 mAh 2700-3400 mAh 600– 1000 mAh 2200– 2900 mAh 1500-1800 mAh
Nominal voltage 1.50 V 1.50 V 1.50 V 1.25 V 1.25 V 1.65 V
Rechargeable No No No[4] Yes Yes Yes

If you use lots of batteries you might wonder what is the most economical way to buy batteries. Are Expensive Batteries Worth the Extra Cost? That’s a good question that Are Expensive Batteries Worth the Extra Cost? article tries to answer. The writes tries to find out if cheap batteries from “dollar” stores are economically feasible or not. Here is a plot of the voltage vs. time for three different AA batteries: Energizer (Alkaline), Duracell (Alkaline), and DG (the one from the Dollar Store “heavy duty”).

You will see clearly that these cheaper batteries are not nearly as good as the more expensive ones. What about the energy per dollar? Really, you are paying for energy – right? Very interesting. So it seems that all three of these batteries have about the same money-energy density.

But there is a bit more to batteries than just the energy stored in it. Your battery selection also depends on what you are using it for. Because the voltage on cheap “heavy duty” battery drops quite quickly, it drops very quickly to value that is too low for electronics devices to work properly (what is the limit depends on device): Even through battery will still have energy in it, but when it won’t run the device correctly.

There are applications where cheap batteries can make sense. According to Are Expensive Batteries Worth the Extra Cost? article comments cheap batteries is the only way to go for kids’ toys when kids constantly leave toys running when not playing with them. Much better to let cheap batteries go dark that way than expensive batteries.

One Are Expensive Batteries Worth the Extra Cost? article comment points out that there is not one Duracell and one Energizer battery; each have a range of battery types/technologies at widely varying prices. Article comment also points out that the measured data is only valid when batteries are used continuously and then discarded when usable power falls beneath a set threshold. Usually the normal use is slightly different (dry batteries can have a certain level of re-activating the charge when in rest).

laptop_battery2

How about rechargeable batteries? A typical rechargeable NiMH is 1.2V 2.5Ah, so it would be a very close race in capacity with alkaline batteries and better capacity than “heavy duty”. The biggest problem with normal rechargeable batteries (NiCd and NiMH) is self-discharge, which means that after few months a flashlight tossed to drawer will be empty without any use. There are low discharge rechargeable batteries (for example Eneloop) that solve this self-discharge issue quite well.

Rechargeable battery vs regular battery article tells that most modern-day devices can compensate for minor differences in voltage (a common one is 1.2 and 1.5 V), but since there are so many “chemically different” regular and rechargeable batteries out there today. The simple solution: know how much voltage your device needs, then pick out the appropriate battery.

Rechargeable battery vs regular battery article says that when it comes to rechargeable batteries, though, you should keep in mind that the numbers indicated by the manufacturer are those seen under optimal conditions. Naturally, this varies depending upon the actual conditions of use. Factors like temperature and current-used have a large impact in determining just how long it will last. This applies to both rechargeable and to non-rechargeable batteries. Selecting the right battery article gives some more details on different battery types.

Select the right battery fuel-gauge for smart phones and tablets article tells that a highly accurate battery fuel-gauge is needed in many electronics devices because it can can increase customer satisfaction, reduce battery costs, and extract the maximum run-time. Also the electronics needs to be designed so that it consumes as little power as possible. How Long Will My Battery Last? Standardized benchmarking methodology compares microcontroller power consumption in battery-powered applications informs you how to compare power consumption of different microcontrollers.

For many uses I can agree on the conventional wisdom used to be that most alkaline batteries have fairly similar energy levels. Alkaline Battery Shoot Out data seems to support that that the differences between most alkaline batteries in capacity are quite small (much smaller than price difference on shop). Based in that usually the best deal is finding the cheapest alkaline you could find. It is a good idea to avoid cheap “heavy duty” batteries that have low capacity and many seem to leak out too easily. I have tried to find cheap as possible “decent quality” alkaline batteries.

If you are shopping for rechargeable batteries for applications where the device is not constantly used, look for low-self-discharge rechargeable batteries. Even though their listed capacity is usually somewhat lower and price higher than other rechargeable batteries, in many cases they are worth of that. If you use rechargeable batteries all the time, then go for high capacity batteries that can be charged quickly using a smart charger.

15 Comments

  1. The Complete Battery Reconditioning Report - How to recondition a battery, battery reconditioning business, car battery reconditioning,lead acid battery reconditioning says:

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  2. AllenBaker says:

    Its perfect and superb informative blogging section which is giving the whole battery details. http://www.batterywarehouse.co.uk/type/silver-batteries

    Reply
  3. Tomi Engdahl says:

    Product How-To: Active balancing solutions for series-connected batteries
    http://www.edn.com/design/power-management/4410154/Product-How-To–Active-balancing-solutions-for-series-connected-batteries

    Large, high-voltage rechargeable battery systems are now common sources of power in applications ranging from electric vehicles to power grid load leveling systems. These large battery stacks are comprised of series/parallel arrays of individual battery cells, and are capable of storing enormous amounts of energy (tens of kilowatt-hours). Lithium polymer or LiFePO4 cells are common technology choices due to their high energy density and high peak power capability.

    As in single-cell applications, careful control of the charging and monitoring of the cells is essential to ensure safe operation and prevent premature aging or damage to the battery. However, unlike single-cell systems, series-connected battery stacks present an additional requirement: cell balancing.

    All Series-Connected Cells Need to be Balanced
    The cells in a battery stack are “balanced” when every cell in the stack possesses the same state of charge (SoC). SoC refers to the current remaining capacity of an individual cell relative to its maximum capacity as the cell charges and discharges. For example, a 10A-hr cell with 5A-hrs of remaining capacity has a 50% state of charge (SoC).

    All battery cells must be kept within an SoC range to avoid damage or lifetime degradation. The allowable SoC min and max levels vary from application to application. In applications where battery run time is of primary importance, all cells may operate between a min SoC of 20% and a max of 100% (or a fully charged state).

    Applications that demand the longest battery lifetime may constrain the SoC range from 30% min to 70% max. These are typical SoC limits found in electric vehicles and grid storage systems, which utilize very large and expensive batteries with an extremely high replacement cost.

    Reply
  4. Tomi Engdahl says:

    Ultimate rechargable AA batteries for Canon camera
    http://zapmaker.org/quick/ultimate-rechargable-aa-batteries-for-canon-camera/

    Canon cameras that use two AA batteries seem to be pretty much useless with normal NiMH rechargeables, as they last for about 10 shots or so, if you are lucky – that’s because they produce only 2.4 V.

    Solution: Use a single LiFePO4 3.2V AA cell coupled with a dummy cell.

    LiFePO4 is Lithium Iron Phosphate, a safer alternative to the usual Lithium Ion or Lithium Polymer. See http://en.wikipedia.org/wiki/Lifepo4

    Reply
  5. How To Recondition Old Batteries says:

    Valuable information. Fortunate me I discovered your website accidentally, and I’m stunned why this coincidence did not came about in advance! I bookmarked it.

    Reply
  6. Tomi Engdahl says:

    The battery question I really dread
    http://www.edn.com/electronics-blogs/power-points/4411385/The-battery-question-I-really-dread

    No, the question I dislike is not “what’s the story on those Boeing Dreamliner batteries, anyway?” And no, it’s not “are those lithium batteries I bought for my kid’s toys going to catch fire?”

    Instead, it’s when someone hands me a couple of basic cells (AA, AAA, C, or D) and asks this simple question: “Hey, is there any life left in these?” Somehow, they expect a clear answer: “Yes,” “no,” or “some,” end of discussion.

    But they don’t want to be told that it is a fairly complicated question, depending on the battery chemistry and the intended use.

    Back in the old days, when carbon-zinc was the only battery chemistry in widespread portable-product consumer use (with some alkalines as well, and lead-acid in cars and fixed installations), you could check a battery by measuring its no-load, open-circuit potential, and come up with a reasonably accurate answer.

    But for today’s more advanced chemistries, especially the many variants of lithium-based cells, the output is fairly close to nominal – until they lose most of their charge.

    The flat-output characteristic of new chemistries has had an effect on OEM product design, as well.

    Reply
  7. keyword retriever says:

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  8. Tomi Engdahl says:

    What’s your battery shelf-life experience?
    http://www.edn.com/electronics-blogs/power-points/4414616/What-s-your-battery-shelf-life-experience-

    I came to this conclusion because unlike lithium batteries, whose terminal voltage remains relatively flat even as they discharge, alkaline cells have a steady drop in voltage versus capacity. So I wouldn’t have seen full-output voltage unless the remaining amp-hour capacity of the cells was at least reasonably good.

    Why should we care about shelf life? Shelf life is not only for batteries which are not in use. With many of today’s extremely low-drain applications (milliamps or even microamps), the battery is close to being unused even in actual use, so it is an important and relevant factor.

    What’s been your experience with shelf life of various cell chemistries, such as lead acid, alkaline, lithium, and even old-fashioned carbon zinc? Have you used them near the end of the official life? What about using them way beyond that date?

    Reply
  9. Tomi Engdahl says:

    Helping batteries last longer
    Dave Freeman – July 31, 2013
    http://www.edn.com/electronics-blogs/dave-s-power-trips/4419155/Helping-batteries-last-longer

    How long should things last? I think it depends on what you are willing to tolerate.

    While I used a dollar-per-day of ownership to target the replacement of my laptop, there are other targets. You may want to keep the equipment until the embedded battery no longer can support the run time expectations. I do appreciate the embedded battery strategy as long as the battery life meets my level of tolerance for truly portable operation. As a side note, I have an electric razor that has had the same battery for 8 years.

    Battery degradation is a popular topic or complaint. Most portable users just accept the phenomena. They live with it by purchasing a replacement battery, if their battery is replaceable, or replace the entire device. A colleague of mine, Yevgen Barsukov, presented on this topic of battery degradation at this year’s International Battery Seminar and Exhibit.

    Just knowing the kinetics of battery degradation can help determine actions that can reduce the rate of the phenomena. For example, temperature accelerates degradation and higher state charge further increases the reaction rate. So charging your device to full and then leaving it in your car in the summer, can take weeks off your battery’s life.

    Battery degradation occurs in two areas: Coulomb losses and impedance increase. Coulomb losses are due to loss off active materials such as Lithium or cathode material. This loss is due to the material not being able to participate in energy cycling. Impedance increase reduces the rate capability of the battery, causing the battery to produce lower terminal voltages during discharge and slower recharge cycles.

    Barsukov addressed Lithium plating as one component of capacity degradation. This component results in the loss of Coulomb capacity.

    Figure 1 shows the results from Barsukov’s paper using multi-level charging compared to the traditional constant-current, constant-voltage charging (CCCV).

    Although you may not be able to recover the degradation once it occurs, it seems that you can keep some of the components from happening. In doing so, the life of the portable equipment with embedded batteries can be extended. In the end, batteries do wear out. You replace them when they are removable, or replace them along with the entire portable device when they are not.

    Reply
  10. Tomi Engdahl says:

    Now there seems to be rechargeable lithium-ion 9V batteries on that market with considerably higher capacity than Ni-MH batteries. For charging them generally you need a special charger suitable for the Lithium Ion Rechargeable Batteries. Here is some info on those:

    Information Article about 9 Volt Lithium Ion Rechargeable Batteries and Chargers
    http://www.megabatteries.com/9_volt_li-ion_batteries_and_chargers.html

    The power out of these 9 volt rechargeable batteries ranges between 400 – 600 mAh (milliampere-hours), and will power your 9 volt device(s) for longer periods of time (called run-time) than NiMh (Nickel Metal Hydride) chemistry batteries.

    See the difference: 9 volt NiMh’s are rated from 250 -300 mAh, clearly making 9 volt Lithiums twice as strong with twice the power (run time)!

    When sourcing these batteries, always be sure to buy from a trustworthy and reliable supplier. One who delivers proper technical information to you PRIOR to your purchase

    Charging Lithium-ion
    http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

    Achieving the Most from Your Rechargeable Batteries
    http://www.horizonbattery.com/ansmann-pro-audio-division/tips-for-successful-recharging

    Anyone tried 9v lipo batteries?
    http://www.eevblog.com/forum/reviews/anyone-tried-9v-lipo-batteries/10/?wap2

    kaptain_zero:
    I just got one of the 9V batteries from DX
    I charged it up in my 9V Lithium/NiMH/Nicad charger and then used one of my iChargers to discharge and measure the capacity. Peak voltage after charge was just over 8.4V,

    I ended up getting 484mAh total when the internal battery protection circuit kicked in at ~6.25V

    So… if using these types of batteries, there are a few quirks one must be willing to accept.
    1. Low voltage vs primary cells. Many devices will be quite happy to run on 6.x to 8.x, but not all.
    2. If using the cell until it goes dead, be aware that it goes dead *suddenly* when the protection circuit kicks in.
    3. Lithium Ion chemistry is not the best for little used devices. A fully charged Lithium cell will deteriorate faster than one that is partially charged
    4. Compared to NiMH, LiIon has a shorter lifespan and does not store well.

    5. LiIon with it’s low internal resistance can cause problems should the battery short out by contacting something conductive by accident, and this could result in a “vent with flames” event. I do not know if there is short circuit protection in the internal protection device. All that is mentioned on the battery is that one should not draw more than 0.5A in use.
    6. Cell balance. This is an issue unless the internal circuit manages it. Unlike NiHM or Nicad where trickle charging is used to bring the cells into balance, trickle charging is unsafe with Lithium based cells.

    For me, too many downsides to switch to this type of cell. Yes, the capacity is nice

    NiHaoMike:
    The rechargeable lithium batteries, if they’re for consumer use, should have overcurrent protection built in. However, older NiMH batteries have no protection whatsoever and will supply very large currents to short circuits. (Some newer ones have built in PTCs.)
    Some devices use the very high current capability of NiMH AAs

    Reply
  11. Tomi Engdahl says:

    Detroit losing MILLIONS because it buys CHEAP BATTERIES – report
    Man at hardware store was right: name brands DO last longer
    http://www.theregister.co.uk/2014/08/16/detroit_parking_meter_batteries/

    The debate over which battery brands work best is almost as old as dry cells themselves, but one US city has learned that it’s definitely not a good idea to skimp when it comes to powering important municipal equipment.

    the discount batteries that Detroit is using now don’t do the job as well as the name-brand alkaline cells the city used before budget cuts took effect.

    As a result – according to the office of the emergency manager, whose thankless job it is to oversee the city’s ongoing fiscal crisis – on any given day, nearly half of Detroit’s parking meters aren’t working.

    Dead meters mean Detroit loses more than just coins. Legally, the city can’t give parking tickets to cars parked at broken or nonfunctioning meters.

    Consider that, the next time you’re shopping for batteries for your smoke alarm.

    Reply
  12. Tomi Engdahl says:

    EEVblog #508 – Can You Test Battery Charge By Dropping It?
    https://www.youtube.com/watch?v=PRf9JTg3QwA

    Can you determine the charge of an alkaline battery by simply dropping it and see how high it bounces?

    Reply
  13. Tomi Engdahl says:

    An Obsessively Thorough Battery (and more) Showdown
    http://hackaday.com/2014/09/05/an-obsessively-thorough-battery-and-more-showdown/

    There are a number of resources scattered across the Internet that provide detailed breakdowns of common products, such as batteries, but we haven’t seen anything quite as impressive as this site.

    This page is about flashlights, batteries, chargers and sometimes other stuff.
    http://lygte-info.dk/

    Reply
  14. Tomi Engdahl says:

    The Reason Dead Batteries Bounce
    http://hackaday.com/2014/09/05/the-reason-dead-batteries-bounce/

    For the last few years, very well-informed people have been able to tell if an alkaline battery is good or not simply by dropping them. When dropped from an inch or two above a hard surface, a good battery won’t bounce, and will sometimes land standing up. A dead battery, on the other hand, will bounce.

    the reason dead alkaline batteries bounce is due to the electrolyte. [Lee] cut open a few AA cells and found the electrolyte in a good battery was a mushy mess of chemicals. In the dead battery, this same electrolyte hardened into a solid mass.

    Reply

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