So, what does it take to build a battery? What makes a good battery? And does ‘good’ always mean the same thing?

Batteries are, in many ways, the ultimate black box. Power in, power out. So long as it works — no need to know how — everyone’s happy.

This status quo has remained largely unruffled, while most of our encounters with battery tech have involved sliding a cylinder into a TV remote or juicing a smartphone overnight. Electric vehicles (EVs) have required a bit more attention (spurred by the quest for longer range and fast charge times, if nothing else).

But as batteries become the backbone of the grid, our industry will need to invite a greater degree of transparency about how all this stuff works.

That suits me just fine. Personally, I’ve always aspired to be open with our data and what it means. That’s why I’m happy to go into detail when explaining why we run our batteries so hot, or sharing our test results.

At a basic level, I’m proud of what we’re achieving — and want to show that off. More importantly, though, I believe that greater transparency is better for the planet. A more informed industry means a more informed customer base, allowing the best tech to win out — which means the planet will win too.

So, what does it take to build a battery? What makes a good battery? And does ‘good’ always mean the same thing?

Broadly, there are three things to consider and yes, I’ll be showing my working.

First of all, you need to have a battery that can cycle a lot of times (one cycle is counted as going from charged, to empty, to fully recharged). There are many novel sources of batteries. Many promise plentiful availability at low cost, but cheaper is only good if what you’re building lasts a decent amount of time. There’s no point making a battery which is half the price— if you need to replace it four times as often as the alternative.

All batteries are going to degrade a little bit over time, as they’re charged and drained and refilled. Your smartphone’s declining battery life after a year of use will be a familiar indicator of this. The same is true on a grid scale, but these batteries are designed to last much longer. To demonstrate how well a battery performs, we charge and discharge it 80% many times, and measure the maximum remaining capacity every 10 cycles. By observing how the remaining capacity ‘degrades’ over time we can predict the ‘cycle life’ of the battery.

Below is an example of one of those tests. In this test, the average degradation is 0.002%/cycle or 10,000 cycles until; 80% of the capacity remains. Of course, this is only one way of testing cycle-life and we pair it with other tests such as ‘accelerated degradation’ where we run harsher and faster cycles over months and months to demonstrate retained capacity.

The second factor to consider is energy density. This has long been considered the holy grail of battery tech, and essentially refers to how much energy you can pack in per unit. Calculating energy density is very easy – you simply take the energy of the cell and divide it by the mass or volume. One of our Gen 1 cells has a capacity of 8.32 Wh and a weight of 64.7g, equating to an energy density of 129 Wh/kg.

Energy density has typically been synonymous with EVs, and how far you can drive without needing to recharge. This has delivered an agreed wisdom that energy density should always be as high as possible.

However, when it comes to the grid, energy density isn’t such an important metric. You’re not moving anywhere, for a start, and you don’t have the space and weight restrictions that stuffing something under a car bonnet imposes.

That doesn’t mean you should forget about this metric entirely, because higher energy density ultimately means you’ll need fewer batteries — because you’re getting more energy per battery — which in turn means a lower cost.

It’s easy to get bedazzled by the race for energy density. Early on at LiNa, we made the mistake of chasing this metric. We spent time on a sole mission to push our Wh/kg higher and higher. But as time progressed, getting reliable batteries into prospective customer hands was more important – and ultimately, with more testing, we settled on a first generation of cells with a lower energy density (130 Wh/kg) and better cycle life. Making these types of mistakes and discoveries is simply part of the deeptech journey.

Power density — or C-rate — is the third factor. A battery’s C-rate refers to how quickly you can get the power in and out of each unit. Again, EVs have dominated the conversation around this, as C-rate impacts how quickly you can do things like accelerate.

In the stationery storage world, power density requirements will flex depending on your use case. Are you trying to trade a lot of energy in a short window to maintain frequency, or are you trying to shift hours and hours of renewable energy generated in the middle of the day to be used in the evening or overnight?

Bigger is not always better here: it’s better to choose what you want from your battery, and then build around that. LiNa’s batteries are capable of high C-rates, but that won’t help with our goal of meeting energy demand spikes that occur in the morning and evening. The best battery is the one that does the job you want it to do efficiently and time-and-time again.

Getting all of these factors lined up is, of course, just the first part of the challenge.

When building an effective deeptech company, you’re ultimately defined by your ability to get your tech in someone else’s hands — and by them wanting more of it. That’s the exciting part of the journey we’re now beginning at LiNa. We have our first system operational out in India, and future outposts planned for the Middle East, Europe, and then Australia.

This stage requires transparency too. In deeptech circles, we speak less of customers and more of partners, because these relationships are less purely transactional: we need partners who understand and are committed to innovating with us.

Transparency means being honest and accountable on what that journey is going to look like. It takes hard work and the best and most determined people — but we’re doing things the right way, because the rewards at the end is definitely worth it: impactful technology, deployed at scale.