Home  Sources  Part descriptions  Electrical parts  Passive components Resistors Resistor part codes Capacitors Capacitor part codes Batteries Batteries compared  Semiconductors  Integrated circuits  Packages  Mechanical parts  Misc. parts Assembly descriptions   BEAM Pieces is a BEAM Reference Library site.		Batteries, compared AAA, AA, 9V; Carbon Zinc, Alkaline, NiCd, NiMh The purpose of this page is to go into a bit more depth on commonly-used batteries -- hopefully, as a helpful guide in your decisions about what to use in your 'bots. Here, I'll concern myself with the 3 most-common small battery packages -- AAA, AA, and "9V." Note that other package types are too numerous, and too ill-documented for me to do much with in any global sense. At the very least, when you find a pager or cordless phone battery that you're considering for use in a BEAMbot, you can use the data on this page to "rank" it, and see if it's worth the bother and cost (vs. some standard battery package). Let's start with basic phisical data about the packages themselves: Package Diam (mm) Height (mm) Width (mm) Depth (mm) Volume (cm3) AAA 10.5 44.5 N/A N/A 3.8533 AA 14.5 50.5 N/A N/A 8.3391 "9V" N/A 48.5 26.4 17.5 22.4070 While you'll be interested in the different packaging from the standpoint of deciding what will fit on your 'bot, it's not the end of this battery selection story. There are a number of different battery chemistries available for our use; while most likely, we'll be interested in rechargeable batteries (NiCd or NiMh), I'm also including Carbon Zinc and Alkaline data for comparison purposes. Note that this is presented as "representative" data, most derived from the Eveready web site, and so may not (most likely will not) be precisely what other vendor's batteries will live up to. Battery Chemistry Package Mass (gm) Volume (cm3) Nominal Voltage Capacity (mAh) Mass Charge Density (mWh/gm) Volume Charge Density (mWh/cm3) Carbon Zinc AAA 9.3 3.8533 1.5 540 87.10 210.21 Carbon Zinc AA 15 8.3391 1.5 950 95.00 170.88 Carbon Zinc 9V 37 22.4070 9 400 97.30 160.66 Alkaline AAA 11.5 3.8533 1.5 1150 150.00 447.67 Alkaline AA 23 8.3391 1.5 2850 185.87 512.65 Alkaline 9V 45.6 22.4070 9 595 117.43 238.99 NiCd AAA 11 3.8533 1.2 250 27.27 77.86 NiCd AA 24 8.3391 1.2 700 35.00 100.73 NiCd 9V 26.9 22.4070 7.2 150 40.15 48.20 NiMh AAA 12 3.8533 1.2 700 70.00 218.00 NiMh AA 27 8.3391 1.2 1200 53.33 172.68 NiMh 9V 41 22.4070 7.2 150 26.34 48.20 You'll note a couple of things in this table. First, "9V" batteries don't always output 9 volts -- rechargeable batteries run at voltages 20% lower than do their non-rechargeable cousins. Second, while battery capacity (on the "nameplate") is specified in mAh (milli-Amp hours), I think we need to look at power (vs. current) storage in order to get a valid battery comparison -- so my charge density measures are in terms of mWh (milli-Watt hours, just mAh * nominal battery voltage). Third, you'll want to be concerned about both battery size and weight -- both will determine just how small your 'bot can get. But enough with the preliminaries -- let's see what this data looks like when plotted. First, let's look at raw battery capacity: Here you can see why rechargeable batteries are not more widely-used -- they still can't store the amount of power that an alkaline battery can. But looking just at the rechargeables, we can see that "9V" batteries aren't a universally good thing -- they can store just a bit more power (and in the case of NiMh, less power) than AA or AAA batteries. This result really came as a surprise to me. But this chart only tells us part of the story. To get a good handle on 'bot design, we also need to know how our battery capacity will be impacted by size and / or weight limits. Note that the following charts over-state the storage "efficiency" of 9V batteries, since we can't run our 'bots at 9V (and so, these charts should ideally take into account losses involved in regulating a 9V battery's output down to 5V). From these plots, we can conclude a few things with respect to battery selection and energy storage density: For NiMh batteries, AAA batteries are king For NiCd batteries, AA batteries are a better choice (being about 30% better than AAAs) For any battery chemistry, "9V" batteries are only a good choice when battery (physical) size is a more important consideration than storage density or battery capacity (i.e., battery life). For more information... For copious details on commercially-available batteries, you might want to consult Eveready's "Index of Active Battery Types." Note that this includes few NiCd batteries; these seem to be in the process of being phased out (in favor of NiMh batteries, which have higher storage capacities and fewer disposal issues). All good things come to an end. When your rechargeable batteries no longer take a charge, don't throw them away, dispose of them responsibly -- see here for recycling locations in the U.S. and Canada.
Sitemap  Search  Legalities   Page author: Eric Seale This page was last updated on This work is licensed under a Creative Commons License.