by sightbroke | 2025-04-13 15:49:30+00:00
> From an electrical point of view, swapping batteries is fundamentally the same general problem regardless of whether they are large or small: you want to avoid arcing when the connector is plugged in, and you need to avoid exposing the user to stray voltage. Sure, there's added complexity to achieve that in a safe and cost effective manner when high voltages are involved, but it's a solved problem as the charge port does exactly this today.

The arcing is the problem AND generally when handling battery packs/modules requires high voltage safety equipment and precautions.

The charge port uses a low-voltage connection to "handshake" as I understand it before the high voltage is being supplied.

You can't, without a good bit more complexity to the battery module itself do that as the batteries terminals will just have the voltage of the battery itself (depends on their state of charge).

Plus the bus bar the module is connecting to also will have a voltage if there's existing modules connected to it.

You're down to having contactors and BDUs at every individual module.

> Current EVs on the market suffer from decreased maintainability compared to traditional ICE vehicles. The battery swapping skill set needs to be more widely available so that we don't see EV owners being dinged $40k for a battery swap. There are videos on Youtube showing people doing a battery swap themselves, and while it is challenging, it's not all that hard to do safely when the battery is not damaged given that the battery packs don't expose high voltage on the connectors when not enabled. Of course a damaged battery pack means that all bets are off on the safety front depending on the nature of the damage.

I'm not saying it can't be done. I am saying it's harder to make it actually safe for the average normal consumer to do as simply as plugging a battery into a power drill for example. In part because of the higher voltages involved.

> It a solved problem!!! Just put the charge port at the back of the vehicle and then use it for the add-on battery pack like the existing signal light connectors for trailers. You're done. The only added design constraints on the EV are on the location of the port and verification that it works while the vehicle is being driven. The F150 Lightning fails this today since the charge port is just in front of the driver side door, but relocating the charge port is not exactly rocket science.

This is a different concept than adding/swapping individual modules in the vehicle itself.

But regarding the concept of a trailer, I suspect that the high cost for the product for the minimum gain it not justifiable for the average consumer. That is you're trying to solve a problem in an inefficient and not profitable manner. (Who wants a trailer of batteries parked in their garage 99% of the time just to have a slightly lighter car?)

> Many EVs have already taken the step of making the charge port bidirectional so that the expensive battery in an EV can be used to provide power during an outage or to balance the load on the grid, and that is a far, far more complicated problem than accepting power from an external battery pack through the charge port while the vehicle is operating.

I understand that, but either you want a trailer or you want internal swappable/addable modules which both economically in my opinion seem of little benefit over engineering better cars with newer/better battery technology and stronger/lighter material.

Additionally, I didn't even mention the annoyance of engineering integrating the heating & cooling system for the modules themselves.

Better energy density batteries & better materials (or smarter manufacturing) make more sense to me than trying to make individual modules for a car swappable or asking people to drive around with a trailer they would use so infrequently that it would not justify the cost to them (not to mention most people don't know how to drive with one properly anyways).