One Outlet, Many Cars
Public EV charging infrastructure is improving, but home charging — the dominant mode for most EV owners — faces practical constraints that a new General Motors patent aims to address. The core problem: most homes have one or two Level 2 charging capable circuits, but multi-EV households are increasingly common. When two or three electric vehicles need charging overnight, managing that load efficiently with existing infrastructure requires manual coordination or expensive electrical upgrades.
GM's patented "daisy chain" charging system connects multiple vehicles through a single power supply unit, with intelligent power distribution that routes charging current to each car based on its needs. The system is designed to optimize the order and rate of charging across connected vehicles, minimizing total charge time while staying within the power limits of the circuit.
How the Daisy Chain Works
In the standard configuration, one primary charger unit connects to the electrical panel and communicates with a network of secondary charging nodes, each connected to a vehicle. The primary unit monitors the state of charge, voltage requirements, and thermal conditions of each connected vehicle and dynamically allocates power accordingly.
The "daisy chain" architecture means secondary nodes connect not just to the primary unit but potentially to each other in series, allowing the power path to be reconfigured based on which vehicles need charging most urgently. A vehicle with a nearly depleted battery might receive the full available current until it reaches a safe state of charge, after which power redistributes to the other vehicles.
GM's patent describes algorithms that determine optimal charging sequence and rate allocation, taking into account factors including user-entered departure times, current battery temperatures, and each vehicle's voltage compatibility.
The Multi-EV Household Problem
The patent addresses a real and growing challenge. As EV adoption accelerates, households with two or more electric vehicles are becoming common — particularly in the US, where car-dependent transportation means most households need at least two vehicles. A typical US residential panel supports 200 amps of service. A single Level 2 charger at 48 amps represents a significant fraction of that capacity. Running two simultaneously can stress the panel and risk tripping the main breaker. The daisy chain system allows multiple vehicles to share a single high-power circuit intelligently rather than competing for current.
Implications for Home Installation Cost
One of the practical benefits of the daisy chain approach is that it could significantly reduce the electrical work required for multi-EV households. Currently, adding a second or third EV charger typically requires running additional circuits, potentially upgrading the panel, and incurring several thousand dollars in electrician fees. A daisy chain system allowing multiple charging nodes to share a single circuit reduces both installation complexity and cost.
Home charging infrastructure cost is a documented barrier to EV adoption, particularly in older housing stock where panel upgrades are expensive. Simplifying multi-vehicle charging installation removes a friction point for buyers considering their second or third EV.
Patent to Product Timeline
Patents represent future possibilities rather than confirmed products. GM files hundreds of patents annually, and only a fraction become commercial products on predictable timelines. However, the daisy chain charging system addresses a problem that is growing in practical importance as EV adoption rates rise, making it a commercially plausible application rather than speculative technology.
If GM brings the technology to market — either as a GM-branded home charging product or through licensing to charging equipment manufacturers — it would add a meaningful practical capability to the EV ecosystem. The broader trend toward intelligent home energy management means this kind of dynamic load distribution is likely to appear in the market in some form, whether from GM or a competitor.
This article is based on reporting by Jalopnik. Read the original article.
