On battery swapping…

By Apoorv Shaligram

Apoorv Shaligram
4 min readMay 12, 2022
Credit: gogoro.com

An oft repeated question that I hear from people: Why can’t we have battery swapping and charging on the same vehicle? The answer to this question starts at the answer to Who owns the battery? Let us look at the possibilities:

  1. The vehicle owner owns the battery: Would you as a vehicle owner swap the battery for one which might be old and potentially in its last charge cycle? The answer is fairly obvious.
  2. The swapping service provider owns the battery: What if the vehicle owner never swaps and always charges at home (which is cheaper)? How do the service providers recover their investment in such a case? After all, their business is based on a pay per use model.

The only way to make this work would be a complicated model where the vehicle owner puts a deposit against which the battery is provided and the user has to complete x number of swaps in a given time period to recover the deposit, else it is forfeited. Would anyone agree to that? Is the cost-benefit analysis in the user’s and the service provider’s favor? It needs to be the favor of both for it to be an acceptable business model. Let us take a look.

From a user’s viewpoint, battery swapping sounds like a good idea. The advantages are obvious. However, it comes with challenges from both technological and economic perspectives. Without going into details of the tech challenges, let me just list them out:

  1. Since the batteries will be connected and disconnected multiple times, the connectors should have long fatigue life. Remember, the connector of a swapping battery gets used twice per cycle (once for connecting to charger, once for connecting to vehicle) as opposed to the fixed batteries (where battery connector is never disconnected, but the charger plug is connected to vehicle every cycle).
  2. Battery has to be designed to stand mechanical vibrations and shocks, since it will be repeatedly moved (manually for smaller batteries) and may be subject to abuse. The battery is literally a chain of electrical components in circuit and is only as strong as the weakest link.
  3. On a large swapping network, batteries from different vendors need to be standardized. This is a challenge from the tech viewpoint, but also from a quality and improvement standpoint. Standardization of battery packs is a death knell for progress of battery technology and gives every incentive for battery pack makers to churn out the minimum viable product.

Then comes the economics of swapping. To start with, a swapping solution needs more vehicles than batteries. This is obvious as there is one battery on every vehicle, plus few more at swapping stations. These idle batteries need to be amortized as well, which means that user pays for utilization of the battery on the vehicle plus the ones at the swapping station. Remember, that battery life is not purely arithmetic of number of cycles, but also has a calendar life component to it.

A non-obvious and counter-intuitive outcome of this is that economics of battery swapping depends on how fast the batteries can be charged. A drained battery that comes to the station can be put on a vehicle only after the time it takes to full charge. Thus, the faster a battery can be charged, the less is the need for idle batteries, and hence the cheaper will be the swapping solution. However, there are two more points that complicate the scenario.

  1. Batteries lose out on cycle life when fast charged repeatedly. Thus, amortization cost is higher than usual.
  2. The capex cost of fast chargers is higher than slow chargers. It is a trade-off between many slow chargers vs. few fast chargers with the total power delivery remaining more or less the same.

Thus, ironically, the economics of battery swapping totally depends on how capable is a battery of accepting fast charging and how well it maintains its life after repeated fast charging. When battery technology that allows superfast charging (say a 0–80% in 5 minutes) emerges, the economics of swapping may improve, but what about the added utility? How will that fare against a simple fast charger that charges vehicles directly in 5 minutes? Food for thought.

All this time, we are looking only at small batteries and manual swapping. The case of automated swapping for large batteries only becomes worse as there is need for costly automated systems to handle the swapping process. Again, looking purely at the economics and not even going into the technical challenges here! What else should we know about battery swapping… One added challenge, particularly in case of 2-wheelers and 3-wheelers is that with vehicle owners not owning the battery, the sense of responsibility to maximize the battery life and safety could be compromised. It just takes a few cases for creating a perception of poor UX and damaging the business model. On the plus side, a lot of idle batteries is essentially a stationary storage system, which can be put to use as a grid stabilizer and generating additional revenue for the swapping provider.

As of today, both battery swapping and fast charging have their challenges and need considerable work. IMHO, a 60+ minute charge does not qualify as fast. Both systems need a lot of work on improving fast charging capabilities of batteries as well as our understanding of battery life and safety. The answer to the question of swapping or fast-charging is not an easy one as of today. In the next blog, I will take a look at fast charging systems and the pros and cons of the same, before taking a stab at predicting the future of CI. For now, adios!

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Apoorv Shaligram

Co-founder & CEO, e-TRNL Energy Working on next-gen battery technology to kickstart the EV revolution…