M/HD Fleet EV Charger Maintainability – Critical to Charger Uptime

(Joseph Gottlieb, CTO, Tuesday November 17, 2020)

One thing that is certain about medium-duty and heavy-duty (M/HD) vehicles – they are EXPENSIVE.  Theaverage city transit bus costs roughly $300,000. Even with a 12-year service life, the purchase cost divided across the service life is $25,000 per year, or $100 per workday. When you figure in When they are down for a day, the average loss of revenue can be well over $1000 per day. If the vehicle is down for a week, the cost can be over $5,000. If you can’t charge an M/HD electric vehicle (EV), it will be down just as much as if the vehicle itself has a failure. That is why charger uptime is so important, and why charger maintainability is critical – the longer it takes to fix a charger, the more days that the M/HD EV is down. An interestingly, the cost of the charger has little to do with its maintainability – a cheap charger can take as long to fix (or more likely replace) as an expensive charger can.

Designing a product for maintainability is as much an art as a science. There are three factors that have a big impact on maintainability:

  • Accessibility: If you can’t access a failed component, replacing it takes a significant amount of time. The layout of the various components, mounting hardware, and cabling is critical to accessibility. That is why Rhombus chargers are designed for easy access to all components, with no unique tools required for disassembly.
  • Replacement Part Cost/Availability: Custom components may have a lot of capabilities, but they can be both expensive to replace, and difficult to come by. Rhombus selects parts not only to meet functional system requirements, but that minimize replacement costs.
  • Understanding Failure Mechanisms: All parts fail – the question is whether they fail during a product’s lifetime. Nearly all product failures are predictable, so if failure analyses are done correctly, failures can be predicted, and scheduled maintenance programs built around those failures. This is one of the areas that Rhombus’ experience provides value to our customers.

Rhombus has built high-power inverters for renewable energy such as “behind the meter” grid energy storage systems for several years. We have applied that expertise to the design of our latest-generation bi-directional EV charging systems (which are designed from the start for the needs of fleet operators) and bi-directional smart inverter systems for microgrids. Rhombus expertise in energy management system (EMS) software is also embedded in our VectorStat EMS controller and software which is embedded in our EV charging systems and smart inverters. Rhombus also excels in the design and testing of high-power electrical equipment to meet the requirements of UL and other certification organizations. We have built hundreds of V2G-capable high-power, high-reliability chargers and bi-directional smart inverters for a variety of different sizes and classes of EVs. Find out how we can help you by contacting us at sales@rhombusenergy.com, or by reading our Vehicle to Grid Solution Brief.