Category Archives: Batteries

Batteries in Five Years

In Hypercritical Podcast #74, the topic of batteries came up, and it was asked what will batteries be like in five years (2017). Being a fan of the podcast and a battery geek I thought I’d write something up.

On the timeline, five years ago, the 18650 cell (the standard Li-Ion battery cell size, billions of cells manufactured annually) had a capacity of 2Ah. In 2012, the best 18650 cells have 3.1Ah of capacity. By 2017, I expect the standard 18650 cell to have a capacity in the range of 4.5-5.0Ah.

For lithium ion batteries the annual improvement rate in battery capacity is about 8%. This was pointed out publicly by Elon Musk, since he is running Telsa Motors I take his word for it (previously I’ve referred to this as Musk’s law, a la Moore’s law for integrated transistors). In 5 years you’re looking at 8% compounded, or about 47%. A laptop with the same sized battery will get almost 50% more battery life given the same power demands. This 8% annual rate might increase due to the tons of money being dumped into battery research and development, both public and private. Some forecasts have this annual rate increasing up to 18% starting in 2013 (page 16 of this PDF, which also has a lot of good information on the future of batteries).

But it is important to balance the energy supply from the batteries to the energy demand from the computer or handheld device to really understand what the battery of the future looks like.

Energy Supply

The capacity increase of the cells is driven by a few factors, the main two are manufacturing improvements and chemistry improvements. Chemistry improvements are the dominant factor and what everyone focuses in on. Large changes in chemistry (NiCad to Li-Ion) only come along once every 25-30 years. Meanwhile, smaller improvements in the chemistry occur throughout the interim until the next big shift happens.

In the next five years, a few technologies will come online that will improve energy storage capacity. Two specific improvements are the silicon anode (replacing today’s carbon anodes) and electrolyte improvements to allow for higher voltage batteries (4.5-5V, up from 3.7-4.2 today). These will contribute to the almost 50% increase in capacity mentioned above. In the long term, Li-Air batteries are looked upon favorably because their initial energy storage capacity will be about ten times today’s batteries (and possibly higher as time goes on), but they wont arrive until sometime in the 2020s.

Cycle life is dependent on the chemistry used to make the battery. Around 1,000 cycles that is probably the best we can expect for a leading edge battery. There are other formulations out there (Li-Titanate batteries) that can withstand 10,000 cycles, used for 8-10 years, and be recharged at super speeds, but they have less than half the capacity (per unit weight and per unit volume) of current Li-Ion batteries. If a vendor wanted to provide for more than 1,000 cycles they would need to reduce the depth of discharge of the battery to extend cycle life. This would mean oversizing a battery (100Wh instead of 75Wh) and artificially limiting the battery to operate between 15% and 90% full. Cycle life improves logarithmically with depth of discharge, so a battery that has a 75% depth of discharge would likely see its cycle life improved by 2.5x. But this battery oversizing takes additional space and weight…

Energy Demand

And therein lies the issue. I don’t expect anyone, let alone Apple, to keep the batteries the same size as they are now if the capacity is increased dramatically. Instead, I expect the battery size to be slimmed down to make that next generation iPhone, iPad or Macbook to be even thinner than the previous generation.

Likewise, I don’t expect the constituent parts of laptops, tablets and smartphones to consume more energy, rather less. One example is the pending switch to IGZO screens from LED LCD. IGZO screens let more backlight through the display, and reduce the power consumption of the device by reducing the power of the backlight. Figures estimate between 50-90% reduction in backlight power usage, which is one of the largest parts of the battery usage when it comes to mobile devices. The upgrade to the retina display for the iPad shows off how much power the backlight uses – the iPad 2’s non-retina display used about 2.7W of power, while the third generation iPad’s retina display used 7W of power for the backlight. By switching to IGZO screens, Apple could return to roughly the same power consumption level as they had before the retina displays. The resulting lower power draw would mean the fourth generation iPad for 2013 could return to a 25Wh battery found in the first two generations, instead of the larger and heavier 42.5Wh pack found on the third generation devices.

Other components in these devices will also become better at using less power, leading to a net drop in total energy use at the same time as batteries continue to increase in capacity. As discussed in the podcast, this means when companies make thinner and lighter devices that deliver the same usage time as the previous version, people will adopt. Those of us clamoring for 15 hour battery life on our laptops and iPads will be left wanting. The closest we’ll get is lighter and higher capacity secondary batteries.

Groundbreaking Battery Announcement? 400Wh/kg

I woke up this morning to read of the Envia energy company talking about how they had breached the 400Wh/kg battery barrier. While the average person has no idea what it means, lets just say thats 3-4x better than batteries available today in early 2012. These batteries wont be available until 2014 with smaller improvements between now and then (200-250 Wh/kg batteries available in late 2012-2013).

Extraordinary claims require extraordinary proof. 

Luckily, Envia seems to understand this. They’ve had the cells tested at private labs, and as well by the US Naval Surface Warfare Center. From the report’s conclusion.

The test results from the prototype cells tested at [NSWC] Crane were in line with the results obtained from the manufacturer. The claims of 400 Wh/Kg were substantiated through the cycling tests performed at Crane. This is a 160% energy density increase over the industry standard indicated in paragraph 5.1 [Panasonic’s 2011 year 18650-cell battery, 3.6Ah 245Wh/kg]

The cells are built around a cathode licensed from Arggone National Labs. The cathode was first licensed in 2007. The anode is developed using the new silicon nano-technologies used in other batteries (the new late 2012 Panasonic and Sony cells are supposed to use Si anodes and a significant boost to capacity).

The second big announcement is price – they tout a $180/kWh price tag for these cells. That is approximately 1/4 the price of batteries in 2010, and 1/2 the price of batteries today, and roughly the price expected for batteries in 2015 (around when the cells are set to hit the market). The recent stories about Tesla replacement batteries costing $40,000 for 53kWh (full pack price), this would be only cost about $10,000 (batteries only). If you look at the Tesla Model S incremental battery prices ($10,000 for 20kWh more), this dramatically undercuts those prices by roughly half – instead of $10,000 more for 20kWh, it could eventually be $5,000 more.

Battery Math

These batteries are very well suited for full EVs. A 300-mile pack for a Nissan Leaf style vehicle would be the same size and weight as the current pack and cost about the same as the initial cost of the pack in 2011. The five characteristics – capacity, power, weight, volume and cycle life – are sufficient for EVs — 85kWh, 250kW, 210Kg, similar to the current pack size, and 275,000 miles on the pack to 80% original capacity. This battery would yield about 275-300 miles per charge. A cut down pack that offers 150 miles would offer 150,000 miles, along with half the weight and power (but still enough for an EV).

For plug-ins, these batteries would probably need to be in up-sized packs based on power needs (the pack needs to be able to produce enough power to push the vehicle up steep mountain grades and pass on the highway). So a Volt pack might go from 16 to 20kWh. The bouns would be more extended range (from 35 miles to 40-45), and longer life on the battery, the battery would still be smaller, lighter and cheaper (welcome back 5th seat!) at 1/2 the size, 50kg, and only around $3,500 instead of $8,000 or so.

It isn’t really suitable for hybrids or small plug-ins (Prius Plug-in), not without an adjustment to the manufacturing to change the battery characteristics from high density to high power (you’d want to sacrifice energy storage for power/kg).

HARP 2.0 – Part 1: Getting your ducks in a row

I’m in a severely underwater mortgage (175LTV), and when Obama announced HARP 2.0 in late 2011, it was a way to shave some money of my mortgage payment (and the administration hopes I put that money back into the economy in the form of consumer spending). This and future blog posts under the HARP title will chronicle my progress of going through the process and hopefully help others who want to do the same thing. Its a departure from the tech stuff I normally talk about, but there is a dearth of information out there about going through HARP 2.0.

The HARP program is long and complex, and every bank and loan servicer I’ve talked to (Wells, Chase, Quicken Loans) seems to follow their own set of rules even though there are the rules the government sets out (the only thing they all seem to agree on is anything limited by the Fannie Mae/Freddie Mac software they must use to underwrite the loan).

So the first step is to find out if your home loan is underwritten by Fannie Mae or Freddie Mac. Each one has tools on their website (FannieFreddie) to help you figure this out. If your loan is backed by either one and you haven’t missed any payments in the last 12 months, then you are eligible for HARP 2.0 (with a few other conditions). If its not backed by either one, then you might be eligible for HARP 3.0 or the upcoming settlement with the banks.

From this point, you can start the refinance process.

Your Steps

Start with your current mortgage servicer. Contact them about the HARP program, and go from there. Most institutions aren’t accepting HARP-based refinances from other banks as of the date this was posted. In my case, my mortgage servicer is not a lending institution but they referred me to a lending institution that picked me up and started the refi process straight away. If your loan is less than 125LTV you should be able to proceed now, if its at or above that amount (like mine), then you might be able to start getting your ducks in a row now, but nothing can officially start until March 15.

After March 15, it will be possible to “shop around” for HARP refinances, but it is still at the discretion of the lending institution as to whether they will accept loans serviced by other companies (HARP is itself voluntary, but refinancing to a lower monthly payment increases the likelihood people will stay in their home, so its in the bank’s interest to do it).

March 15, 2012

This date pops up a lot in the HARP program. Its the day Fannie and Freddie roll out the new version of their Desktop Underwriter (DU) software. This software update will allow institutions to evaluate loans from other institutions, and also for homes with greater than 125LTV to refinance. This is the day that refi applications like mine can be officially put into the system and the process started, and interest rates locked.

HARP 2.0 Flexibility

HARP 2.0 allows for a bit more flexibility than HARP 1.0 did. The two big features are the expansion of LTV ratios (to 300%) and the ability to shorten the term of the loan (you can go from 30 years to 20 or 15 years). An additional feature is not needing an appraisal of the house, they’re going to use a software algorithm to determine your home value based on comparable sales and foreclosures.

Paperwork

Things I needed to start the refi process (this is not a comprehensive list of what you might need, especially if you’re self employed, it may also vary from lender to lender).

  • W2/1099 forms
  • Recent bank statements (within the last 3 months)
  • Recent mortgage statement (within the last 3 months)
  • Pay stub (current)
  • Home insurance statement (current)

At this point I have all my paperwork ready except for the pay stub (it has to be the most recent one, so I wait). If I get it ready now, the loan will close quicker.

Battery Magnitude

Recently, there was news on a new formulation of lithium-ion battery using a Si-Graphene anode that would provide for 10 times the charge in 10 times the power capacity that current lithium-ion batteries in the same size (and I’m assuming the same weight). Now the standard three to five years disclaimer applies – in that it has to be brought out of a lab, commercialized and they have to figure out how to mass-produce them and not lose any of their stand-out characteristics.

But it didn’t immediately seem apparent to most observers that it would be useful because of rapid capacity fade – the battery would only last 150 cycles before it had only 50% of it’s original capacity, although that is still five times current battery capacity. Traditional lithium-ion batteries last 300 cycles to 80%, lithium-polymer (the battery in your iPhone and Mac laptop) last about 1000 cycles to 80%, and lithium-titanate batteries can last 5000+ cycles to 80%.

The difficulty with the Si-Graphene battery is managing the user experience. If a user were to go through their entire battery in a day, every day, in 5 months they’ll only have half the capacity. So the device developers have to oversize the batteries but artificially clamp the energy storage to keep heavy users from destroying the battery in a short time frame.

Consumer Electronics? Sure…

Putting this battery into a smartphone to replace the current lithium-polymer battery would let average users go 10 days between charges. However every 250 days (25-30 charges) the user would notice they’ve lost a day of use before it was time to recharge, so from 10 days to 9 days. Will users be upset that they lost a day? Will they even notice? Or will they beat down the door of the store where they bought it demanding an exchange on a perfectly good product? How can we avoid this? By artificially limiting battery capacity.

If we were to limit the battery capacity artificially to a value that the 80th percentile user will have after 2 years of usage, we can save the trouble of users noticing their battery doesn’t last as long as it once did. I’ll assume this number is 75% of capacity, that is the 80th percentile user will go through enough battery capacity in two years that will cause a 30% capacity fade (this also factors in an increase in usage due to the bigger battery). So the phone will be setup so the average user can go 7 days before hitting the 25% warning and then recharging. Using 4Wh/day the user will go through 36.5 full cycles per year, which represents a 12% capacity fade per year. After two years, the capacity fade will be 24%. So after two and a half years, the average user will start to experience the battery holding less energy, and probably notice it around the end of year three – about which time the user will need to buy a new phone anyways as this one will be long out of warranty. An 80th percentile use will probably start to experience capacity fade earlier, around 18-24 months. A 95th percentile user is likely to do crazy stuff with their phone like stream audio all day and go through one cycle per day, and run into capacity fade in 6 months. This last case could actually be accounted for in software – if the phone notices its being used heavily it could ask the user to plug it in while engaging in the heavy activity, or just nerf capacity in software in the name of getting out of the warranty period without having to replace the battery.

Below is a chart of a traditional Li-Polymer batter (5.3) and a new Si-Graphene battery (53). You can see that the new battery has much larger capacity, it also fades much quicker. If you were to limit the Si-Graphene battery at 40Wh (40) capacity, the battery would get to two and a half years of average use before the user experienced any capacity fade.

The downside to this approach over traditional batteries is that users might increase their phone use and suck down more battery power per day knowing they have a lot more energy available to them, which is all the more reason to artificially limit capacity in the name of having the battery last long enough to have a useful device for 2-3 years.

The same results from the smartphone situation above would also apply to tablets. Laptop computers would probably see more agressive artificial capacity restrictions, as users usually run out of battery on the laptop before they are done with whatever they were doing (like doing internet research and writing a blog post about batteries ಠ_ಠ), so the issue of using more energy per day and higher annual cycle counts would apply.

Electric Vehicles? Not so fast…

If the approach of limiting battery capacity in the name of extending its life sounds familiar, it should, as it is how the battery in the Chevy Volt is managed. So what would happen if you applied this to the battery in the Volt? Not much difference, and probably an increase in cost.

If you recharge the Chevy Volt once a day, 365 days per year, it is equivalent to 237 full battery cycles per year (10.4kWh used for 35 miles, 16kWh capacity), and the battery type they use is expected to have a life of 1500 cycles (without any depth of discharge reduction bonuses). But if you were to drop-in a replacement battery with this new technology (assuming same size, weight, etc), you’d have a 160kWh battery. Now that doesn’t mean you drive 10 times as far, rather you just use an increasingly small portion of the battery, specifically an initial depth of discharge of 6.5%, and a rate of 25 full cycles per year. By the end of year 10, or 250 cycles, the battery would have degraded enough where it will start to run into problems storing and producing enough energy (assuming they can last that long from a calendar standpoint). This doesn’t appear to be a significant change from the current battery regimen, where the battery is warrantied for 8 years or 100,000 miles (12,500 miles per year). The only benefit to using the Si-Graphene batteries would be the increased power output – a Volt’s 9-second 0-60mph times could improve dramatically, along with faster recharging times.

What would help

The problem with this is that batteries are predominately priced in $/kWh, which would make the above scenarios prohibitive. The fundamental question is would it be more appropriate to charge by mass and volume? Does it cost 10 times the amount of making traditional batteries to these batteries? I don’t think it will. They might be able to charge more than the highest end batteries, but the $/kWh would need to be discounted compared to other types of batteries that have higher cycle lives. The best figure to use when it comes to battery prices is $/lifetime kWh, or the amount of energy a given battery will output until its no longer usable for the specific application (e.g. smartphone, EV, etc). A battery might cost $700/1500 kWh lifetime, and it might not matter that its 1kWh of storage for 1500 cycles or 10kWh for 150 cycles for certain applications – assuming other factors are held constant (volume, weight, safety). In fact, the latter configuration helps in applications where power demand is high (e.g. a car).

So the most basic thing to help these batteries would be an increase in cycle life. Even a relatively small increase in cycle life would dramatically impact the usefulness and increase the impact these batteries can have.