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EV Battery Packs Have It Easy Compared To Home Batteries\u00a0<\/strong><\/p>\r\n It has been two weeks since I laid down the heavy news that out of the 26 home batteries given a whirl by the Canberra Battery Test Centre, only two worked as they should without suffering a fault or excessive capacity deterioration.\u00a0 This sad news has caused some people to wonder if electric car battery packs will have similar poor performance. <\/p>\r\n Fortunately, on this topic, I’m the bearer of good tidings.\u00a0 I’m hauling so many high-quality tidings my back hurts.\u00a0<\/p>\r\n The best tiding I have is:<\/p>\r\n This chart illustrates the difference (you’ll have to read on to see my working):<\/p>\r\n I also have another tiding that isn’t exactly good, but it does improve the odds of EV battery packs having fewer problems:<\/p>\r\n I’ll explain further below, so read on if you want to learn why electric car battery packs should mostly survive well beyond the end of their warranties and provide years of additional driving.\u00a0 If you’d like to read the Canberra Battery Test Centre article that caused this consternation, you can do that here<\/a>.<\/p>\r\n EV batteries aren’t expected to supply anywhere near as much energy, per kilowatt-hour of usable storage, as home batteries<\/a>.\u00a0 Their warranties make this clear.\u00a0 Fortunately, some companies sell electric cars<\/a> and home battery systems, making the comparison easy.\u00a0 Two that operate in Australia are…<\/p>\r\n I’ll focus mainly on Tesla.\u00a0 While both companies have sold many home batteries here, Tesla has sold a lot more electric cars, and I have better information on them.\u00a0 But I will compare the warranties of BYD’s home batteries and their Atto 3 EV, which should now be available in Australia.\u00a0<\/p>\r\n The Tesla Powerwall 2 warranty<\/a> says it will last for 10 years when it’s exclusively used for home use.\u00a0 If put to any other additional purpose, such as being part of a Virtual Power Plant (VPP), the warranty is for 10 years or until it supplies 37,800 kilowatt-hours of stored energy.\u00a0 Whichever comes first.\u00a0 In either situation, the warranty promises it will retain at least 70% of its original capacity by its end.<\/p>\r\n When a new and fully charged Powerwall 2 is discharged of all usable energy, it can supply 13.5 kilowatt-hours.\u00a0 If a battery is fully charged and then fully discharged1<\/a><\/sup>, that is called one full cycle.\u00a0 I’m going to use this term to refer to the maximum amount of energy a home battery or EV battery pack can normally provide when new.\u00a0 Batteries slowly decline in capacity with use, but I’m not taking this into account when I talk about full cycles.<\/p>\r\n For a Powerwall 2 to supply the 37,800 kilowatt-hours its warranty allows when not used exclusively for home use, it will need to be fully cycled 2,800 times.\u00a0 This is far more than the number of full cycles Tesla’s EV battery pack warranties cover.<\/p>\r\n Going by sales, the most popular EV in the world2<\/a><\/sup> is the Tesla Model 3 Standard Range Plus — or Model 3 Rear Wheel Drive, as it’s called now.\u00a0 It has a battery pack of around 60 kilowatt-hours capacity, with 57.5 kilowatt-hours of usable storage.\u00a0 Its warranty lasts for 8 years or 160,000 km — whichever comes first.\u00a0 Like the Powerwall 2 warranty, it also promises it will retain at least 70% of its original capacity.<\/p>\r\n To work out how many full cycles 160,000 km represents, we’ll need to know the average amount of energy it consumes per km.\u00a0 I know from fun earned experience<\/a> that Tesla’s figures for range can’t be trusted3<\/a><\/sup>, but the EV Database<\/a> says it gets around 7.75 km per kilowatt-hour in mild weather.\u00a0 Using this figure means the battery pack warranty only covers around 359 full cycles before it hits its km limit.\u00a0 That’s only 13% as many as the Powerwall 2 warranty allows.<\/p>\r\n There are a couple of reasons to expect actual energy use per km driven to be higher than the EV Database figure I used.\u00a0 These are:<\/p>\r\n Australians are a pretty soft bunch.\u00a0 If you burn down their house, they complain bitterly. If their local cafe serves them a nice bowl of broken glass and rusty nails, they ask to see the manager.\u00a0 For this reason, I expect electric cars here will use a considerable amount of heating in winter and a lot of air conditioning in summer.\u00a0<\/p>\r\n Unfortunately, the EV Database is European and doesn’t give figures for air conditioner consumption.\u00a0 This is despite the fact I’d expect Europeans to be using a lot of air conditioning at the moment, considering the River Loire has all but dried up.<\/p>\r\n Vampire drain occurs when the car isn’t in use, either because it’s thinking about stuff<\/a>, updating software, or simply monitoring the battery.\u00a0 In some situations the EV may heat or cool the battery pack in order to protect it.\u00a0 Various features, such as Tesla’s “Sentry Mode” security system and heating or cooling the cabin before you get in, can greatly increase vampire drain.<\/p>\r\n Here we see vampire drain sapping the proletariat of the will to resist their aristocratic masters.<\/p><\/div>\r\n As a mildly educated guess, I’d say climate control and vampire drain may add an extra 15% to average energy consumption per km driven4<\/a><\/sup>. This increases the number of full cycles that will occur before the warranty’s km is hit, but this adjustment only means the battery pack will be fully cycled 15% as much as the Powerwall 2 warranty allows instead of 13%.<\/p>\r\n There’s also a reason to think that electric cars will use less energy per km than the EV database figure suggests.\u00a0 This is because it’s for a combined driving cycle that assumes the EV will be driven 50% on highways and 50% in town.\u00a0 In practice, the majority of km will be done on town and city roads and — unlike internal combustion engine cars — EVs require less energy per km for urban driving than on the highway.<\/p>\r\n I’m not going to try to adjust for this for three reasons:<\/p>\r\n If I use the EV Database figure for energy consumption but bump it up 15% to account for climate control and vampire drain, then the Tesla Model 3 Rear Wheel Drive will fully cycle its battery around 422 times before its km limit is reached.\u00a0 This is only 15% as many full cycles as the Powerwall 2 warranty allows.\u00a0<\/p>\r\n The battery pack warranties for most other Tesla vehicles allow them to be driven more km, as you can see here:<\/p>\r\n But because most other models have larger battery packs, it doesn’t make much difference to the number of full cycles their warranties allow.\u00a0 Below I’ve listed approximately how many times the battery packs of different Tesla electric vehicles can be fully cycled before they reach their warranty’s km limit.\u00a0<\/p>\r\n I’ve used the EV Database energy consumption figures for mild weather driving and bumped them up by 15%.\u00a0 I’ve also given kWh figures, which are how many usable kilowatt-hours of battery storage the EV Database says these vehicles have – but note Tesla can vary the capacity of battery packs.\u00a0 The EV Database doesn’t have information on the Model Y Rear Wheel Drive, so it’s not included:<\/p>\r\n Their warranties only cover from 14-19% as many full cycles as the Powerwall 2 warranty.\u00a0 The Model X is a full three percentage points ahead of the other Tesla vehicles thanks to having the highest energy consumption per km.<\/p>\r\n The warranty of BYD home batteries lasts for 10 years or until they supply around 3,050 kilowatt-hours of stored energy for every kilowatt-hour of usable storage capacity.\u00a0 A new BYD HVM home battery with 13.8 kilowatt-hours of usable storage can provide 42,690 kilowatt-hours of stored energy in total before hitting its warranty limit.\u00a0 This is 3,093 full cycles and 10% more than the Powerwall 2 warranty allows.<\/p>\r\n However, the BYD warranty only promises a minimum battery capacity retention of 60%, rather than Tesla’s 70%, so I consider BYD’s warranty to be worse for typical households.\u00a0<\/p>\r\n While BYD hasn’t sold many electric cars in Australia, they may sell a considerable number of their new Atto 3<\/a>, as the standard range version will have an on road cost of around $45,000 or less.\u00a0 That’s not cheap, but it is cheaper than plenty of other cars, whether EV or conventional.\u00a0<\/p>\r\n The warranty for the Atto 3 battery pack is similar to the one for Tesla’s Model 3 Rear Wheel Drive, as it has…<\/p>\r\n But the warranty requires the vehicle to be serviced at least once per year, and this makes it worse than Tesla’s warranty.<\/p>\r\n The EV Database doesn’t have information on BYD vehicles, but — as far as I can tell — the Atto 3 appears to use around 19% more energy per km than the Tesla Model 3 Rear Wheel Drive.\u00a0 The battery pack of the extended range Atto 3 is similar in size to that of the Tesla vehicle and, using the same same assumptions for climate control and vampire drain, can be fully cycled around 490 times before reaching its warranty’s km limit.\u00a0 This is only 16% as many full cycles as the warranty of a BYD home battery allows.\u00a0<\/p>\r\n The standard range Atto 3 has a 17% smaller battery pack and can be fully cycled around 590 times before reaching its warranty’s km limit.\u00a0 This is still only 19% as much as a BYD home battery.<\/p>\r\n On average, Australians drive private cars around 13,000 km a year.\u00a0 For a Tesla Model 3 Rear Wheel Drive, this represents around 34 full cycles.\u00a0 That’s an average of under one full cycle every 10 days.\u00a0<\/p>\r\n A Tesla Powerwall 2 home battery<\/a> that’s only used for home storage and isn’t part of a VPP<\/a> may be fully cycled an average 0.8 times a day by a home with well above average electricity consumption.\u00a0 That comes to 292 full cycles a year.\u00a0 This is 8.6 times more full cycles per year than the EV. \u00a0<\/p>\r\n After 8 years, which is the maximum time period the EV battery pack warranty will last, the number of full cycles each will have undergone will be:<\/p>\r\n That’s a huge difference in the amount of work they’re expected to do.\u00a0 After 8 years the EV battery pack discharges less than 12% of the full cycles of a Powerwall 2.\u00a0 The more a battery is fully cycled, the more likely it is to develop a problem. The relatively low number of cycles required from EV battery packs greatly improves their chances of reaching the end of their warranty without issue.<\/p>\r\n If the Model 3 Rear Wheel Drive battery pack delivered as many full cycles as the Powerwall 2 warranty covers, it could drive over one million<\/a> km.\u00a0 That’s enough to get to the moon and back<\/a> and nearly get to the moon again5<\/a><\/sup>.<\/p>\r\n EV battery packs have it easy compared to home batteries in terms of the number of full cycles their warranties cover, but their lives aren’t entirely a bed of roses.\u00a0 Additional challenges they face include:<\/p>\r\n Because home batteries have it far easier in these areas, optimising them for durability is easier.<\/p>\r\n The biggest difference between an EV battery pack and a home battery is how much power they’re expected to provide per kilowatt-hour of energy storage capacity.\u00a0 (Here’s an explanation of the difference between power and energy<\/a> if required.)\u00a0<\/p>\r\n Ignoring minor DC to AC losses, a Powerwall 2 normally never discharges more than 5 kilowatts of power.\u00a0 At that rate, it would discharge 37% of a full cycle in one hour.\u00a0 A Model 3 Rear Wheel Drive may have to supply 208 kilowatts for brief periods.\u00a0 If maintained for an hour — which is impossible — it would represent 360% of a full cycle.\u00a0 The Model 3 Performance EV can briefly draw up to 377 kilowatts, and if maintained for an hour, that would be 500% of a full cycle.\u00a0<\/p>\r\n This high power draw puts the batteries under considerable strain and is a major reason their warranties don’t cover as many cycles or years as home batteries.<\/p>\r\n When high power is used to fast charge an EV<\/a>, it also puts the battery pack under strain.\u00a0 This is why EV manufacturers normally recommend limiting fast charging.<\/p>\r\n High power drain heats batteries, and parking an EV in the sun can also raise its temperature.\u00a0 The hotter lithium batteries get, the faster they degrade.\u00a0 Most EVs have active cooling systems that can protect the batteries if necessary, but if the EV isn’t charging, it’s Catch-22<\/a>\u00a0because energy used to cool the battery pack has to come from the battery pack.\u00a0 Home batteries also have to deal with high temperatures in summer, but as they’re not likely to be driven hard and then parked in the sun, the problem isn’t as extreme.<\/p>\r\n EV battery packs are also exposed to a lot more vibration than home batteries.\u00a0 It isn’t as bad as you may think because most of the vibration in conventional cars is the result of engines that run off explosions<\/a>.\u00a0 But Australian roads are not smooth, mirror-like surfaces. \u00a0Even with decent suspension, this means an EV battery pack will be exposed to far more vibration than a home battery.\u00a0<\/p>\r\n The lighter an EV battery pack is, the better since it has to be driven around; but weight isn’t a major problem for home batteries.\u00a0 A lightweight battery isn’t necessarily less durable than a heavier one but, generally speaking, it’s going to be easier to design a durable battery if you don’t also have to worry about how heavy it is.<\/p>\r\n Car manufacturers have reputations based on their vehicle’s reliability.\u00a0 Some have better reputations than others…<\/p>\r\n\r\n
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Home Batteries Work Far Harder<\/h2>\r\n
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Tesla Powerwall 2 Warranty<\/h2>\r\n
Tesla Model 3 EV Warranty<\/h2>\r\n
Climate Control & Vampire Drain<\/h2>\r\n
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Climate Control<\/h2>\r\n
Vampire Drain<\/h2>\r\n
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Combined Cycle<\/h2>\r\n
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Other Tesla EV Models<\/h2>\r\n
![\"Tesla](\"https:\/\/www.solarquotes.com.au\/blog\/wp-content\/uploads\/2022\/08\/easy_tesla_warranties.png\")
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BYD Batteries<\/h2>\r\n
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Full Cycles In Actual Use<\/h2>\r\n
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It’s Not All Easy For EV Batteries<\/h2>\r\n
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High Power Draw<\/h2>\r\n
Temperature Extremes<\/h2>\r\n
Vibrations<\/h2>\r\n
Lightweight<\/h2>\r\n
It’s Easier To Screw People Over With Bad Home Batteries<\/h2>\r\n