Great Tips For Care Of Lithium Batteries

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A recent thread by World of Engineering on Twitter gives a lot of good, basic advice to anyone who owns a lithium-ion battery (or a few hundred/thousand). Sharing this information periodically is a great idea because many people have no idea that lithium batteries require any kind of care at all.

Everything you need to know about Lithium-ion batteries 🪫🔋

As an electric car owner, laptop and smartphone user, you have choices how to prolong battery life.

Let’s go 🧵

— World of Engineering (@engineers_feed) September 22, 2022

Many readers probably already know about all this, but I’ve seen on many internet forums, Facebook groups, and Twitter conversations that people are skeptical and even hostile toward advice on this topic. “You know better than the engineers?” they ask. The prevailing counterargument to care of batteries is that the designers of laptops, solar generators, and electric cars must have considered it all, and owners don’t need to do anything.

While it’s true that designers and engineers did consider battery safety and longevity, that doesn’t mean you, as the owner and user/driver, can’t do things to make them last even longer.

With that out of the way, let’s look at the thread. I’ll add some explanations and additional information along the way.

The important takeaway here is that lithium-ion batteries aren’t like older rechargeable battery designs that have “memory” problems. It’s perfectly OK to run them only part-way down and then charge them back up again. In fact, the less you discharge them, the more charge-recharge cycles you’ll get out of them. Keep that in mind for the next part.

Specifically, what they’re talking about here is how much of the battery you use between recharging it. If you always charge it to full, and then run it to dead (100% depth of discharge, or DoD), you’ll get far less life out of the battery than you would if you only use half of the battery or even less.

The relationship of depth of discharge to cycle life isn’t linear, either. Being just a little more conservative with the battery’s usage can lead to outsized gains in battery longevity. So, if you’re one of those EV drivers who only plugs the car in once every week or two and then charges it up to full like you would with a gas car at a gas station, you’re not going to get as much life out of the car as some one who plugs it in every night.

But, there’s more to it than how much you use.

How full you charge the battery is another very important factor in how long your battery will last. The voltage numbers above probably aren’t very relevant to readers who don’t build their own battery packs, so I’ll explain this a bit further.

A laptop computer might have only a few cells, and they’re wired together to add the voltages up to whatever voltage the computer needs to run. Larger devices like electric bikes, solar generators, and neighborhood EVs have higher voltages using more cells wired to add that voltage up. Full-sized electric vehicles usually have 400-volt or 800-volt battery packs, again put together by wiring the individual cells described above to get that high voltage power.

So, it’s best to translate those numbers into percentages. Good manufacturers won’t let the cells ever charge up to 4.2 volts or higher. They usually program in a “buffer” that keeps you from ever getting to a true 100% charge, for battery life. But, they have to balance this with cost and how much energy storage the customer gets to use out of what they paid for. So, charging up to what the manufacturer lets you charge to is still more harmful than charging to 80-90%.

This keeps the individual cell voltage closer to that 3.92 volts (depending on the specific battery cell, of course).

Most EVs have some way for you to limit how high it charges. If you can, it’s best to set that to 80% on routine days when possible, and only charge to 100% on days that you really need all of that range. Then, add in that you don’t want too much depth of discharge, so try to never go below 10-20% unless you really need to do that to get where you’re going.

As many of us probably already know, temperature is another important factor in battery longevity.

For laptops, power stations, e-bikes, scooters, and other things that you can keep indoors, it’s best to not let them get too hot or too cold. Keeping portable devices at room temperature in your home is best. Leaving them in a hot car, or leaving batteries in an e-bike outside is a bad idea from a battery life perspective.

For EVs, you’re best off to buy an EV with an active coolant system, usually liquid cooling. This greatly helps the batteries last. If you want or need to buy an EV without liquid cooling (the Nissan LEAF is the most common one that doesn’t), live in a mild climate and/or keep it in a garage. Even with liquid-cooled and/or refrigerated batteries, you also need to keep the car plugged in in some cases to keep that cooling system running.

Let’s apply all of this to EVs. In a nutshell:

Try to stay as close to 50-60% as you can.

Drive between 40% and 70%, or 20% and 80%. You won’t kill your battery off if you occasionally go to 0% or 100%, but keeping the battery there for extended periods of time is very bad for it. You have to strike a balance here between longevity and making the car or device fit your needs.

Sure, you could store an EV at 60% charge in refrigerated storage for a decade and never drive it, but what good would you get from it? It really comes down to doing the best you can.

Keep the car plugged in and in as cool a place as you can when parked.

Plugged in, charging only to 80%, and in an air-conditioned garage is ideal, but not always possible. Sitting at 50% in the shade in the parking lot at work is better than sitting at 100% in the Phoenix sun all day every day. Once again, do the best you can given your needs.

Take it easy on the battery pack (avoid high charge and discharge).

Like any vehicle, stomping on the accelerator every time you take off from a light will be harder on the batteries than hypermiling. Nobody can hypermile all the time, and few even want to. So, just try to take it easy and drive normal. The same goes for regenerative braking (don’t do it all right before a stop), and DC fast charging (don’t use DCFC unless you need to do it to get somewhere).

Don’t take any of this too far.

You bought whatever device or vehicle you have to do things with it, and maybe even have some fun. So, don’t let battery car advice get in the way of getting things done or having a little fun. 

Need to drive a Nissan LEAF in the heat? Do it.

Want to step on the skinny pedal and have some fun here and there? Go for it!

Need to charge to 100% to make it somewhere? Don’t get yourself stranded!

All of these battery tips have to be used when you can to fit them around your life. Making an EV battery pack last 50 years probably wouldn’t do you much good anyway, because by 2072, EVs are going to be wildly better than they are today. The same is probably true for 2032. So, do what you can when you can to get a few more miles or years out of your car, but don’t take it to extremes.

Featured Image: A prototype battery pack for the upcoming Aptera. Image provided by Aptera.