Buying Better Batteries: Part Two
Over the same wire, 48V batteries deliver four times as much power as 12V batteries
This action guide explores choices for batteries that are powerful enough to start car engines and operate tools. In each of our action guides, we cram crucial details for sustainability that you won’t find in the typical consumer guide. If you know anyone who needs to buy batteries (or just loves batteries), one easy step for sustainability is simply forwarding this fact-packed action guide to them!
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The “lead acid” battery sounds like an unsustainable scourge—a toxic metal in a caustic liquid—yet it is a paragon of persistence. First invented in the 1850s, lead acid batteries are still being sold in new cars more than a century and a half later. But a new contender—lithium ion—allows us to get the lead out when we buy batteries.
Part one of this “buying better batteries” series started with steps for small batteries providing a few watts of power and a few watt-hours of energy. This part two tackles steps we can take with bigger batteries up to around 10,000 watts of power and a thousand watt-hours of energy:
Remember, “reduce, reuse, recycle” applies to batteries, too: “no batteries required” is more sustainable than “batteries included.” For vacuum cleaners, lawn mowers, snow throwers, leaf blowers, chop saws, and other power tools, choose models with cords and without batteries whenever practical.
Prefer higher-voltage batteries (up to 50 V) over lower-voltage batteries. The higher the voltage, the smaller wiring can be to deliver the same power. But note that the Occupational Safety and Health Administration considers all voltages over 50 to be hazardous.
Look for “LFP” (also called “lithium iron phosphate”) batteries—these contain fewer toxic materials and last longer than other types of batteries.
Recycle old batteries.
Weekly Poll: Still Down with Lead?
Help! My friend has a really neat battery-powered vacuum cleaner, but I’m wondering how sustainable those batteries are.
Batteries are getting better—storing hundreds of watt-hours per kilogram instead of dozens, maintaining capacity for thousands of cycles instead of hundreds, and working well without toxic materials—but it’s still better for sustainability to choose power equipment without batteries if practical. Vacuum cleaners are an interesting example of some choices we now have as consumers—and other choices that are made for us by building codes.
By code, electricians in the United States are required to put in electrical outlets throughout homes so people can plug in vacuum cleaners and other electrical appliances safely. Just by buying or renting housing that meets electrical codes, you’re already paying for permanent electrical infrastructure that makes it reasonably convenient to use a vacuum cleaner with a cord.
For outdoor equipment, like a lawn mower, it’s possible to use a cord, but it's a lot less convenient because we don’t have as many electrical outlets on the outside of our homes as we have on the inside. So when choosing between corded or cordless tools, the sustainability calculation tips toward batteries being more necessary in outdoor equipment. Inside, the sustainability nod goes to using a cord because we’ve already paid for robust infrastructure (a convenient place in every room to plug in).
When we calculate the sustainability of a durable good like a vacuum cleaner, we consider the amount and type of materials in it. A vacuum cleaner with batteries doesn’t have a cord, but the rest is the same: it has a handle, a motor, attachments, etc. So, the comparison is between a battery pack and a length of electrical cord.
Price is a quick cheat to assess the sustainability of materials. It isn’t a perfect measure, but the price does reflect many environmental impacts. Let’s use replacement parts for Dyson vacuum cleaners as an example. One seller is offering replacement battery packs for between $69 and $165, depending on the model. Compare that to the cost of a replacement cord for Dyson vacuums, available from another seller for about $38. Battery packs are twice as expensive as cords, which strongly indicates that batteries have a more detrimental environmental impact. The higher price probably reflects at least some additional energy and raw material costs.
Another consideration is longevity. How long can we expect a battery pack to last versus a cord? Vacuum cleaner cords can last for decades—they work just fine right up to the moment they break. Batteries, on the other, degrade in performance daily. We’ll likely need to replace batteries more often than cords.
The inside of an electrical cord is copper or aluminum, surrounded by layers of insulation such as paper and plastic. Thanks to California Proposition 65, if an electrical cord contains toxic chemicals, it probably has a label with a warning. Most batteries in light-weight consumer electronics and appliances are now based on one of two lithium chemistries: Nickel Manganese Cobalt (NMC), which, as the name suggests, contains cobalt, a toxic and controversial metal; or Lithium Iron Phosphate (LFP), which does not contain any toxic metals and is considered less likely to catch on fire spontaneously than NMC cells.
There are some instances where using NMC lithium-ion batteries might improve your sustainability score (such as choosing an electric lawn mower to replace a gas mower), but choosing a battery-powered vacuum cleaner instead of one with a cord is not one of them. LFP lithium-ion batteries make it a closer contest. Perhaps in the future, battery technology will get so good that cordless tools will be more sustainable than ones that need cords, but today, “no batteries required” is a plus for sustainability.
Help! I’m seeing ads about tools having more power with higher-voltage batteries, but I thought power is measured in watts, not volts. What voltage battery should I buy, anyway?
You’re right; power is measured in watts, but volts are half the equation. Watts are volts times amps. The physical size of a battery cell (number of molecules in it) determines amps, but the chemistry of the molecules in the cell (how attracted to or repelled by each other they are) determines volts. Battery packs can now also include a microelectronic battery management system to adjust volts and amps.
To avoid making costly mistakes—or hurting yourself and others—when using batteries (or any other kind of electricity), it is vital to understand volts and amps. Volts measure how much resistance a battery can overcome to send current, which is measured in amps. Higher voltages can force more amps across a resistance.
Before connecting a battery to equipment, make sure you have the right voltage. If a battery provides a higher voltage than the equipment is designed for, you can cause damage by sending too much current through it. If a battery provides a lower voltage than required, not enough current will go through the equipment to make it work.
Human bodies have an internal resistance of about 500 ohms. At about 50 volts, batteries can start forcing enough current through our bodies to cause harm. Below 50 volts, the electrical resistance of our bodies limits electrical currents to safe levels.
Whatever the Volts, Watch Out for Metal Around Batteries!
Electricity doesn’t have to flow through our bodies to hurt us; touching jewelry to both electrodes of even a 12 volt battery can cause serious burns.
Case 1
A 50-year-old auto mechanic was referred to hospital suffering from a circumferential electrical burn around his left ring-finger. The patient was working on a car electrical system with a metal spanner which touched the positive pole of the battery, the wedding band and the solenoid metal housing, causing a short circuit through the ring.
Case 2
A 32-year-old schoolteacher tried to help her husband start his car, which had a flat battery, by using her car battery and jump leads. She operated the starter and while she was adjusting the jump starting cables, her wedding ring shorted across the battery.
Discussion
Both of these patients demonstrate the potential problem of wearing metal jewelry around electrical current. The perspiration underneath a wedding ring serves as an excellent conductor for the current. [T]o confirm that a car battery could indeed cause a severe burn[, a] gold ring was connected to a 24 V battery; within 1 to 2 seconds the temperature of the ring was above 1000 'C and it started to melt. [Even] a 12 V battery can cause the same hazard. If a car battery is short-circuited by metal jewelry the energy produced can therefore cause a local deep second-degree burn.
—Circumferential Electric Burns Of The Ring Finger, Annals of the MBC
If we were just concerned about human safety, we’d limit every battery and electrical circuit to 50 volts. That would make them safe to touch (unless we’re wearing metal jewelry). The issue with keeping voltage that low is that it keeps power low. If voltage only goes to 50, to get more power, we would have to increase amps.
Why can’t we just increase amps? If we try to squeeze too many together, they get hot. A direct metal connection between battery electrodes (a “short circuit”) allows so many amps to crowd in that the metal can vaporize. That is the principle behind fuses: if too many amps go through the fuse wire, it melts, which stops the flow of current before something else in the circuit melts. To let more amps through safely, we need to give them more room to flow—a larger diameter wire. That can get expensive and at some point impractical since bigger wires weigh more and cost more.
So, let’s put all this knowledge together so you can make well-informed decisions whenever you shop for batteries for yourself, your family, or your friends. To calculate power, just multiply volts by amps: that product is called watts. Batteries with higher voltages will probably deliver more power for the same weight.
Volts up to 50 are considered safe but always watch out that you don’t directly connect the positive and negative electrode of a battery with a piece of metal. There should be no exposed metal on any battery pack with a voltage higher than 50. Because higher voltages provide more power using less copper wire, there is a sustainability argument for going above 12V or 24V, and even above 50V. But there is a strong countervailing safety argument for sticking around 50V for safety.
An up-and-coming battery type that may become a new standard is a 48V battery pack with LFP lithium-ion cells. This provides four times more power over the same gauge wire as a 12V battery. We might see 48V become the new standard in cars and trucks, finally replacing the 12V standard and allowing vehicles to save weight by reducing the amount of copper wiring by a factor of four. Unfortunately, it will be difficult to retrofit older cars to the new 48V standard; they’ve already been built with the larger diameter wire necessary for 12V power.
Help! I’m confused about SLA, AGM, NiCad, NiMH, lithium, lithium-ion, NMC, and LFP batteries. What’s the difference, and which one is the most sustainable?
Determining which type of battery is most sustainable is a case where price is not the best guide. The bottom line is that LFP scores as the most sustainable type of battery on the market for five main reasons: 1) you can store more energy using less material; 2) you get more recharge cycles before a battery needs to be recycled; 3) you avoid hazardous metals like cadmium, lead, and cobalt; 4) you are less likely to start a battery fire; and 5) you can use the full capacity of the battery and leave it fully or partially charged without shortening its useful life.
Now, let’s sort out all those acronyms:
SLA (Sealed Lead Acid) and AGM (Absorbed Glass-Mat) are rechargeable lead acid batteries. AGM is a type of SLA battery designed to keep sulfuric acid inside the battery, with no maintenance required. Older lead acid batteries required periodic refilling with distilled water, so they were not sealed. AGM batteries provide performance benefits compared to regular “flooded” lead acid batteries, helping lead acid batteries hang on a little longer against competing chemistries.
NiCad (Nickel Cadmium) and NiMH (Nickel Metal Hydride) are two types of nickel-based rechargeable batteries that were developed to compete with lead acid batteries. NiCad batteries contain toxic cadmium and have other drawbacks compared to NiMH batteries, which do not contain toxic metals.
Lithium batteries come in a wide variety, including non-rechargeable (single-use) lithium batteries and many types of rechargeable lithium-ion batteries. Of the rechargeable lithium-ion batteries, NMC (Nickel Manganese Cobalt) and LFP (Lithium Ferro-Phosphate, also called Lithium Iron Phosphate and often abbreviated LiFePO4) are the two most common chemistries.
Now that you’ve had a tour of battery acronyms, you’ll start noticing more and more LiFePO4 (LFP for short) batteries being advertised. LFP batteries are starting to be introduced to replace 12V car starting batteries and making inroads in all sorts of other battery markets traditionally served by lead acid batteries. Rechargeable lithium-ion batteries in cell phones, laptops, power tools, and some outdoor equipment often use NMC or other chemistries; you may have difficulty determining exactly which type. For most consumer products, you may not have any choice but to use the type of battery the manufacturer offers. But if you have a choice, LFP stands out as offering more environmental benefits with fewer harms.
Help! I’ve noticed over the years the batteries in my lawn mower are holding less and less charge, and now I think I need to get new ones. What should I do with the old ones?
We should recycle old batteries. In fact, being able to recycle the metals in batteries forever is one of the biggest sustainability reasons to “electrify everything.” Here’s how to become superbly sustainable by recycling batteries:
Get a multimeter and learn how to test the voltage and amperage of batteries by putting one lead on the positive electrode and the other on the negative electrode. Checking the volts and amps a battery can produce is how to determine when it needs to be recycled.
Get some plastic tubs and label them “batteries to recycle.” Use them to store batteries that need to be recycled.
Optional (for safety): If you use 12V batteries, build a simple DIY “light bulb battery drainer” from the following parts:
A 12V light bulb (the higher the wattage, the better). This makes a nice resistance load you can watch to see when the battery can no longer produce current.
A pigtail socket to hold the light bulb.
EC5 connectors to connect the pigtail socket to jumper cables.
A set of jumper cables to connect the light bulb to the battery.
Optional (for safety): If you have batteries with higher voltages than 12, consider building a battery drainer with the correct resistance.
Optional (for safety): Batteries that still have a charge can start fires. If you have a battery drainer, attach it to a dead or dying battery until the current stops flowing. After that, use your multimeter to test the voltage. Once you can no longer detect voltage between electrodes, the battery is ready to be recycled.
Use the Call2Recycle drop off locator to find where to drop off your batteries for recycling. Use their store for batteries that are not safe to drop off.
Next time you shop at an auto parts store or home improvement center, ask them about their recycling programs. Many of them accept batteries.
Offer to help family, friends, and neighbors recycle their batteries. Many people have a drawer full and don’t know what to do with them.
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What’s Still Ahead on the Pathway…
Earlier this year, we explored the pathway to sustainable movement; now, we’re exploring the related pathway to sustainable energy. What are the best ways to save, use, and make energy? Stay with us on the journey to sustainability as we take action to have a positive impact on the world.
References and Further Reading
Guarding requirements for 50 volts or more DC, US Department of Labor Occupational Safety and Health Administration
Battery Cell Comparison, epec Engineered Technologies
Electrical Code Requirements for Outlets in the Home, The Spruce
Cancer Warning Labels Based on California's Proposition 65, American Cancer Society
Lithium-ion Battery (LFP and NMC), Pacific Northwest National Laboratory
The Environmental Impacts of Cobalt Mining in Congo, Earth.Org
How are LiFePO4 batteries safer than other lithium batteries?, Relion
Circumferential Electric Burns Of The Ring Finger, Annals of the MBC
48-V Systems: What You Need to Know as Automakers Say Goodbye to 12 V, ElectronicDesign
What Is an AGM Battery and What's the Big Deal?, Interstate Batteries
NiCad vs NiMH Batteries, EVS Supply
A lithium-ion upgrade for your car, but not the one you’re expecting, Ars Technica
Choosing Marine Batteries: Lithium vs Lead Acid, Island Fisherman Magazine
5 Best Multimeters (2023 Guide), This Old House