Hybrid Vehicles
The Li-Ion In Winter: What Cold Weather Does To EV Batteries
A number of you will have bought your very first EV in the past 9 or so months (i.e., when the warmer weather began in spring through to autumn). Now that we’re heading into winter, there are some things that you will need to be aware of as the colder days roll around. This is because EVs don’t behave like ICE (internal combustion engine) vehicles.
You may well be glad that you don’t have to sit there and warm up the engine before you get going (although I have to say that most modern ICE vehicles don’t need you to do this – thankfully!). However, you may find the following scenario has happened to you:
You set out on a chilly morning as usual in your PHEV or BEV and head off on your normal commute. You had topped up the battery as usual the night before and you’ve got plenty of charge. However, this morning, you notice that the range seems to be much lower than usual, meaning that you have to plan for an extra stop to recharge. Because you’d planned your time according to what you normally do, you don’t have time to stop off and recharge right now if you want to be in time for work, so you plan for an extra stop on the way back home, meaning that you lose out on some family time. If you’re really unlucky, you have to limp into the charging station on the last dregs of the battery. You may wonder what on earth happened to drain your battery so quickly – and you will have a fair amount of time to stop and think about this as you wait at the charging station.
In fact, quite a few drivers have found that in cold wintery weather, battery range can drop by as much as 40%.
Now, one of the reasons why your battery may have drained more quickly in cold winter weather is obvious. If it’s a bit chilly, your natural instinct is to turn the heater on so you don’t arrive at work with a dripping red nose and chilly fingers. Obviously, the heat that comes through the climate control system in your EV has to come from somewhere, as the system can’t use the waste heat from the engine, as is the case in ICE vehicles. This heat has to be supplied by the battery, so that puts extra demand on it, meaning that you end up with less range and a battery that drains more quickly.
Now, you could always bundle up in an extra coat, a hat, a scarf and a set of mittens for your drive to avoid using the heater and spare your battery. However, there are other options. The first is to make the most of functions such as heated seats. Although these will also use the electrical energy stored in the battery, it’s a lot more efficient to heat your back and bottom with a heated seat than it is to heat the air enough to get you comfortable. With some models of EV, such as Tesla, you can also pre-warm your car while it’s waiting on the trickle charge so that it’s nice and warm when you get in, and the electricity used to heat things up hasn’t drained the battery as much as it would have if the car wasn’t plugged in.
However, this isn’t the only reason why your battery drains so quickly in colder weather. It’s an unfortunate reality that lithium ion batteries sulk when the temperature drops (it’s all to do with the electrochemical reactions going on inside the battery). You may remember from back in high school science days that you can speed up a chemical reaction by adding heat and slow it down by cooling things down, and the same applies to the chemical reactions that make the battery work. Because things inside the battery are sluggish, they don’t produce as much power, so your range goes down. Just to add to the insult, because of this slowed chemical reaction, regenerative braking doesn’t work as well, which also adds up to an extra reduction in the range.
Now, the designers of EVs have been smart enough to know that if things get too cold, the chemical reaction will stop altogether, so they have included a heating system in the battery pack – which, of course, runs off the battery’s own power. If you, like many others, have set your vehicle up on trickle charge overnight, you may find in the morning that you haven’t got as much charge overnight as you had hoped. This is because some of the energy has gone to heating the battery. Parking the car inside overnight while it charges can help overcome this problem, as this helps the battery stay in the Goldilocks Zone of temperature (not too hot and not too cold but just right).
Another reason why you may not have got as much charge as you had hoped is also a result of the sluggishness of lithium in the cold. In cold temperatures, the lithium is slow to release its charge and it’s also slow to receive charge as well (charging is just a reversal of the chemical process). This may mean that you have to allow more time to charge your battery, although it’s important to bear in mind that frequently using superfast chargers will shorten your battery’s lifespan.
Some aspects of winter driving are unavoidable. You probably will have to use the headlights more often in the darker days, along with the demisters to unfog your windows and the windscreen wipers. These will all put extra demand onto your battery. If winter in your part of the country means strong winds, these will also put an extra demand on your battery, as getting your vehicle up to speed means that wind resistance will have to be overcome. However, by following the advice in this article, you’ll be able to claw back a little extra range, so you see a drop of only ~10% rather than 40%.
To recap:
- Use heated seats and steering wheels rather than the climate control to stay warm.
- Preheat your vehicle while it’s still charging.
- Allow for extra charging time (and possibly more stops at the charging station).
- Park your vehicle inside overnight.
- Wear warm winter clothes inside the car so you don’t have to switch on the heater.
Extending The Life Of EV Batteries
One of the big questions that a lot of people have about making the shift from ICE (internal combustion engine) vehicles to EVs of any sort is the issue of battery life. In this context, battery life doesn’t refer to how many kilometres the batteries will take you (this is technically known as battery range) but the actual lifespan of the battery unit itself. If you’ve had any experience with any kind of rechargeable battery – which most of us have had – then you’ll know that even though you can recharge a battery a certain number of times, you can’t do it forever and eventually the battery will die, never to be recharged again.
Having said that, the lifespan of EV batteries is pretty good. In fact, the manufacturers claim that batteries can last for about 10–12 years, which is longer than the average lifespan of a whole car in some countries (although those who like second-hand cars or who are into classic cars may raise an eyebrow at this statistic). They’ve also got warranties to ensure that they last for a certain amount of time.
However, people researching rechargeable batteries don’t tend to measure the lifespan of batteries in terms of time (partly because no scientist in a rapidly developing field wants to spend 10 years running an experiment). Instead, they measure the lifespan of a rechargeable battery in charge–discharge cycles. To understand why they do this, we need to understand a bit about the science of a rechargeable battery. Don’t panic – I won’t get into too much detail, partly because I don’t have a PhD in it and can’t wrap my head fully around some of the minute details.
In any battery, an electrical current is generated when ions (particle with an electrical charge) move from the negatively charged anode through an electrolyte to the positively charged cathode. This keeps going until everything balances out and the electrochemical reaction stops. You can do this yourself with a copper coin (if you can find one these days), a zinc-coated nail and a lemon. Attach a wire to the coin and the nail, maybe connecting fairy lights in the middle, stick them in a lemon and watch the lights glow. However, in a rechargeable battery, this processed can be reversed, shuttling those ions back to the anode again.
In a rechargeable battery, every time the reaction comes to an end, i.e., complete discharge, that’s considered to be a full cycle. In the lab, to test a battery’s lifespan, researchers charge and drain and charge and drain and… until the material in the anode and/or cathode starts to deteriorate, which all things do over time. They also measure capacity decay. Over time, any rechargeable battery will lose the amount of charge it can store. Again, this is related to the number of charge–discharge cycles.
So what does that mean for EV batteries? Although the manufacturers measure lifespan in years, this figure is based the ideal battery user. If you charge your battery the right way and use it in the right way, then you’ll get the maximum lifespan from your EV’s battery pack. However, if you don’t, you’ll shorten the lifespan of the battery.
You can imagine the number of charge–discharge cycles in a battery as kind of like lives in a computer game. You’ve got a lot of them, but every time, you get those hit points down to zero and have to “respawn”, you’ve used up another life. However, unlike a computer game character’s life, hitting either extreme (full charge as well as full discharge) will shorten the lifespan because it puts stress on the battery – kind of like keeping a bow fully strung and at full draw most of the time, which, as any archer will tell you, isn’t good for the bow.
This means that ideally, you should avoid hitting these extremes. This means that exhausting your battery’s charge completely is a bad idea. However, so is topping it up to 100% all the time.
At this point, those of you who are familiar with rechargeable NiCad batteries will be scratching your heads because you’ve heard of “battery memory”. NiCad rechargeables (these are the sort that you buy to put in things that come with the label Batteries Not Included) do have a “memory”, meaning that if you are in the habit of recharging the batteries when they hit 10% charge, they’ll start acting as though 10% is the new zero. However, lithium ion batteries don’t have a battery memory effect, meaning that you won’t reduce their charging capacity if you top up the battery’s charge when it dips below a certain level.
In fact, what manufacturers recommend for preserving the life of a battery sounds rather like the principles used for managing blood sugar in Type 1 (insulin-dependent) diabetes. You don’t want things to drop too low, but you don’t want them to go too high, either. The ideal is to keep batteries between 80% charge (which is why the charging times given by EV manufacturers are usually the time taken to reach 80% charge) and either 20% or 40% charge. On top of that, rapid charges and rapid discharges also stress the battery.
In practice, this means the following:
- Don’t recharge your EV to overnight every night. However, you need to balance this against what you know about how and where you’ll be driving and where the accessible chargers are.
- Don’t let the battery drain too quickly. This means that you have to be very careful when it comes to things like towing, going uphill and running too many things that require electricity at once. In other words, if it’s a freezing cold rainy night when having the lights, wipers and heaters going is a must, then you have to decide if it’s really worth it to use the sound system as well.
- Although DC rapid charging is convenient, it does stress the battery, so reserve this for when you absolutely have to. DC rapid charging isn’t catastrophic for your EV’s battery and you can do it now and then without putting a serious dent in your lifespan, but it does put a bit more stress on it than slower AC charging, so don’t do it all the time.
- Extreme temperatures make the lithium in the batteries do funny things. Getting too hot is the most dramatic, but most modern battery packs (thank goodness!) have cooling systems to ensure that they don’t overheat (these systems use the battery’s own charge to operate). Getting too cold is also a problem, as the electrochemical reaction producing the charge is slowed right down, which translates to reduced range and slower charging times. Some battery packs, notably in Tesla vehicles, have systems that keep them at the ideal temperature – though at the cost of range. However, these can drain the battery more quickly, which shortens the lifespan.
- If your EV has to go into long-term storage, keep it on a trickle charger or a smart charger to ensure that it stays about half charged.
Plugging In A Plug-In
Like anything else with batteries, an EV of the PHEV or BEV type (i.e., plug-in hybrid EVs and full battery EVs), will need to be plugged in and charged. In my previous article, I talked about the different types of charger and the different charging speeds.
However, there’s more to know if you’re new to the world of EVs and plugging in instead of filling up. This is because different vehicles have different types of connectors or plugs. Obviously, you can only plug into something that has a compatible connector. This may sound confusing if you’re used to filling up a petrol or diesel tank, where one size fits all. However, if you’re used to negotiating all those different cables and chargers for Android phones, Apple phones, USB chargers and HDMI cables, then you will easily get the hang of the different connector types used in EVs.
There are a few basic types: Type 1, Type 2, CCS 2 and CHAdeMO. All of these have different pin patterns, meaning that you can’t plug the wrong one in by mistake (kind of makes you wish they had done something similar with ICE vehicles so that nobody put petrol in a diesel tank or vice versa).
Type 1 AC connectors are also known as J1772 or SAE J1772 connectors, or just J plugs. They are mostly found on older EVs and PHEVs. The connector has five pins that look a bit like a smiley face.
Type 2 AC connectors are also called Mennekes connectors after the German company that invented them. They look a bit like a mutant hair dryer. They are the standard connector in Australia and Europe found on most EVs sold in the country today. Type 2 Mennekes connectors is often found in combination with the CCS connector – if you look carefully, you can see that the “surprised face” circles in the top part of the CCS connector combo is hidden in the seven circles of the Mennekes connector.
Tesla connectors are based on the Type 2 connector to allow you to use it to charge a Tesla at home via AC charging but has a special lock-out design for the DC chargers, meaning that only Teslas can charge up from the dedicated Tesla DC ultrafast charging systems.
CCS stands for combined charging system. The bottom half of a CCS connector allows for fast DC charging from public outlets, while the top half is for AC charging. Although it is possible to find EV models that have Type 1 up the top and the DC connector down the bottom, these are very rare in the Australian market. Most EVs in Australia that have these CCS connectors (technically, these are CCS 2 connectors) will have a Type 2 pin arrangement up the top.
CHAdeMO connectors get their name from the French phrase “Charge de Move” (“movement using charge”). Rumour also has it that it was derived from the Japanese phrase “o cha demo ikaga desuka”, which means “How about a cup of tea?”, as the idea was that charging with a CHAdeMO charger would take as long as having a cup of tea. I don’t know how long it takes you to have a cup of tea, but I don’t think they’re referring to the full Japanese tea ceremony here, which can take up to four hours. However, the CHAdeMO connector is used for DC fast charging, which can take about half an hour. These connectors are mostly found on earlier Japanese models such as the Nissan Leaf.
When you buy an EV, it will probably come with at least one cable so you can plug it in and get started. However, it’s often a good idea to have a range of different cables with different connectors. For example, you can get a cable that can plug into a Type 1 outlet even though you’ve got a Type 2 input in your EV, or one with Type 2 at both ends for public charging stations where BYO cable is the expected way to proceed. If you’re anything like me when it comes to cables and remembering what goes in where, it might be a good idea to attach a label or colour-code the different cables if you have several, and to store them in separate bags.
Ready, Set, Charge!
If you are one of the many who has opted for an EV for whatever reason, then the time will come when you have to charge it up – just like you have to charge up your phone, e-reader or laptop. However, charging an EV is not quite the same as filling up a petrol or diesel tank, and if you’ve never done it before, there are a few things that you’ll have to get used to, especially regarding the different charging speeds.
Deep breath required here. There will be maths.
With all types of charging, the exact amount of time you’ll need to charge the battery will depend on the voltage of the outlet and the battery capacity. The formula for working it out is:
E = P × t
Makes you feel a bit like Einstein, saying that. E is energy, P is power and t is time. Rearrange this and you get t = E/P or, in plain language:
Your EV’s battery capacity (in kWh) ÷ power output of the charger (in kW) = hours of charging time
This equation, however, mainly applies to charging to 80% rather than 100% (and this is the charge time figure that you’ll see in specs and stats from the manufacturers of EVs). This is because charging isn’t a linear process and it slows down as the battery gets closer to full charge. It’s a mechanism that helps prevent overheating. If you want to charge to 100%, bear in mind that doing so will take a bit longer.
The thing that most people are concerned about is the charging speed. In fact, the charging times are one factor that can put people off purchasing an EV, especially an all-electric BEV or a PHEV. Here in Australia, we have reasonably sensible names for the different charging speeds, unlike in other countries, where you have to ask a few questions to be sure what you’re talking about during a discussion of fast charging – you’ll hear some people talk about fast charging as something different from rapid charging (I feel sorry for those who don’t speak English as their first language because – well, you try explaining the difference between fast and rapid!). Here, we keep things straightforward, calling the two most common charging speeds Level 1 and Level 2, with only the fastest type being called “DC fast charging”.
Level 1 charging is simplest type of top-up charging that you can do at home or anywhere else you can access a standard common or garden power socket. It seems very simple but the trouble is that this type of charging is very, very slow. Recharging a completely drained battery will take at least a whole day, as in a 24-hour day. It could even take 48 hours, which is fine if you’ve got the whole weekend to recharge your car’s batteries as well as your own and don’t have to go anywhere. On the other hand, if you find yourself at a relative’s place in the country and not enough charge to get you home, you can just plug in and recharge enough to get you home again, or at least to the nearest public charging station (it would be nice if you compensate your relative for the power you’ve used, same as if they let you have a jerrycan of petrol if you’d run out). You may hear this referred to as trickle charging.
Level 2 charging is the sort of charging you do with one of those wall boxes in your home, and Level 2 chargers are what you’ll find in typical public chargers of the kind you’ll see at the supermarket, mall or gym and, if you’re really lucky, at work. Typically, you get around 7.2 km of mileage for every 10 minutes of charging with a 7.2 kW unit, or 22 km of mileage for every 10 minutes with 22 kW charging. (Is anybody else getting flashbacks to the sorts of word problems we had to solve at school?)
However, remember that these mileage figures are approximate and are under ideal conditions. If you have a heavy load, if you have to go into a headwind, or if you want to run the lights or heaters or play music, you’ll reduce the range.
Commercial outlets will often provide chargers not just for their customers’ convenience (although this is certainly part of their motivation) but also as a marketing ploy. If you need to ensure that you’ve got enough charge in your battery to get you home again after work and shopping, then you may need a couple of hours to charge the battery to the right level. However, it may take you only one hour to do your workout at the gym or to pick up your groceries, leaving you with time to kill. Chances are that you’ll spend time in the gym cafeteria or that you’ll spend a bit longer in the supermarket browsing the shelves to fill in the time and will thus spend more money, which is what the commercial outlets are hoping for. Just be aware of this little ploy and budget for it, develop some iron self-discipline and a healthy bit of patience, or take a book. Just don’t make the mistake of sitting in your car doing things on your phone or laptop with your device plugged into the charger in the car!
Speaking of budgets, a home wallbox will have to be bought separately when you buy a new EV. It’s a good idea to buy one, as otherwise you’ll be relying on super-slow trickle charging or public charging stations to top up the battery. It will also need to be installed by a professional electrician, like your oven or hot water cylinder and for the same reasons. You’ll also have to factor the cost of labour in as well. This is something to keep in mind.
DC fast charging (aka rapid and ultra-rapid charging) uses DC electricity, whereas Levels 1 and 2 use AC electricity. The best known DC chargers are the Tesla superchargers even though, ironically, the original Nikola Tesla promoted and popularized the use of AC electricity. How fast this type of charging will be will depend on the battery, but charging can be done in less than an hour, depending on the kW rating and the type of car. Some EVs charge faster than others. It has to be remembered that not all EVs are compatible with DC fast charging; this is often the case with PHEVs. This is something to check and think about when you buy an EV.
It’s also important to understand the different types of connectors or plugs, but that’s another story for another time.