Intelligent Juggling Game Behind Battery Swapping

Arun Sreyas Dec 07, 2022

Battery swapping – a concept where instead of charging your batteries, you swap out the discharged battery with an already pre-charged one to get an instant full charge in your EV. Think of the old days of phones which came with removable batteries, and you could carry one extra to simply swap for a full charge. You needed this extra battery since you had a heavy usage of your phone, maybe you were a jet setter, or perhaps you just wanted to play Snake - a lot of it.

This extra battery you would carry is called a ‘Float’. Similarly, for EVs, if the vehicle requires one battery to power it and one spare battery for swap, then the float is 100 per cent. Suppose the same battery in float can power swaps to happen across two vehicles, then the float is 50 per cent, i.e., total batteries outside of vehicles at any point of time divided by total batteries in all vehicles.

Float is an essential parameter for the scale of a battery swapping business. The lesser the float, the lesser you have to invest in batteries which are the most expensive component in an EV.

How does a swapping player optimise the float? The basics are very simple. The battery in float is the one that is being charged. Let’s assume it takes three hours to fully charge a battery. Let’s also assume that a typical commercial vehicle’s battery lasts for a day’s worth of range, i.e., 24 hours. In an ideal situation, one can circulate this one extra battery across eight vehicles in a day, achieving a float of 1/8 or 12.5 per cent.

Notice two things here:

Firstly, the charge time is critical for the float. If we have a 15 min charge time, then a single battery in float can be circulated across 96 vehicles, achieving an impressive float of just 1 per cent.

Contrary to popular belief, this is the number one reason why fast charging and swapping aren't competing with each other. Swapping players are going to be the first to deploy fast charging technology.

Secondly, this is an ideal scenario. In a practical situation consider 18 hours in a day where swaps would happen and a gap of 30 min to 1 hour between swaps for the same battery - effectively circulating this one extra battery across five vehicles, taking the float to over 20 per cent. Factoring in the cooling that most advanced swap stations deploy to preserve the battery life, the float increases further. Factor in the network irregularities, i.e., some stations will have high demand and some won’t, the float increases even further.

It doesn’t stop just yet. Most drivers prefer to swap around the morning or evening rush hour; this is not unique to swapping but also for petrol, diesel, or gas. Factor in the variable electricity prices that most DISCOMs offer; you would want to charge the batteries at an off-peak time. All of this pushes the float up.

We’ve only talked about one side of swapping. The other side of swapping is the ‘Grid’. Each swapping station is essentially a battery storage unit plugged into the centres of a city. Several of these swap stations can work together to solve several grid related issues – a concept known as Battery-to-Grid (B2G), which is an adaptation of Vehicle-to-Grid (V2G), but with better control over batteries.

These factors are just the tip of the iceberg to optimising the float and the network. To truly optimise the network, technology is key. Starting with just collecting the correct data to build great algorithms advancing into ML, tech will be a key player in ensuring the best margins for a swapping operator.

Bringing the float from around 40-50 per cent to an ideal 1 per cent - battery swapping has a long way to go. We have barely scratched the surface of the potential of battery swapping.

It’s been around over 30 years since the introduction of the mobile phone and approximately 15 years since the introduction of the smartphone. Yet, spare batteries continue to exist – just as power banks now. Battery swapping solves this fundamental problem for high usage EVs and today’s jet setter – the gig worker – the cab driver, the rickshaw driver, and the food delivery guys.