E-Mobility Engineering 019 | In conversation: Stephen Lambert l WAE EVR l Battery case materials focus l Quality control insight l Clipper Automotive Clipper Cab digest l Optimising battery chemistries insight l Powertrain testing focus

54 May/June 2023 | E-Mobility Engineering new components to existing mounting points,” he says. “Obviously the brakes and steering are now electrically powered, but the system is still the same and we don’t go over design loads. We are only 70-100 kg heavier than the original TX4, which is well within the design load, so the suspension and drum brakes are fine, but we have regenerative braking as well.” The TX4’s standard hydraulic steering system is retained, for example, but it now has an electric pump driven by a Vauxhall Astra steering motor. Although Clipper Automotive’s modifications comply with the existing type approval, the company also puts each electrified cab through the Individual Vehicle Approval (IVA) process, which involves an inspection by the UK’s Driver and Vehicle Standards Agency (DVSA). Many local authorities require either type approval compliance or an IVA, but Clipper has chosen to go down both routes for extra assurance. “We have made a point of painting everything we have added in quite bright colours so that when you look at it, especially when somebody inspects it, they can see exactly what we have put in,” Medwell says. Also, the cab has to have a high- voltage ticket from the UK Vehicle Certification Agency (VCA), which involves testing to make sure there is no danger to anyone inside or outside the vehicle. While most of the electric powertrain is unmodified with respect to the Leaf or E-NV van fromwhich it came, Clipper makes its own front and rear battery boxes to contain the original cells from the Nissan pack because of the limitations presented by the TX4’s structural architecture. That means all the connections between the cells inside the boxes, the HV and BMS connections between the boxes and from the battery to the inverter have been engineered by Clipper. The original Nissan 3 kWonboard charger has been replaced by a 7 kWTesla unit. Although Clipper repackages the original cells into two boxes, it follows the Nissan connection scheme between cells in themodules, and betweenmodules in the pack. That’s done to preserve the capacity and voltage, and to ensure it performs as designed, particularly when controlled through the Leaf’s BMS. New BMS wanted A newBMSmight be on the cards for later production vehicles, however, in order to simplify the battery pack wiring and to gain extra efficiency, Medwell says, as the split pack makes the BMSwiring more complicated. There are effectively two battery packs, so either the sensing cables have to run between themor theremust be two BMSs in a primary- secondary configuration, he explains. The present set-up runs the BMS cabling and HV power cabling in extended looms between the front and rear battery boxes. The extra lengths of cable cause a very small voltage drop, but not enough to affect range or management tasks such as cell balancing. “We will probably go down the route of two BMS units, because of the complexity of those extended looms,” Medwell says. He adds that the BMS is also very important for getting themost range for the capacity and in thermal management, and believes there are better BMSs on themarket. “There aremany companies developingBMSs that are approaching5% more efficiency than theOEMunits, so it will be quite interestingwhenwe come to do that. Someonemight want tomake a bespoke BMS for us, but it could also be an off-the-shelf system,” he says. “Also, we have HV cabling running the length of the cab and those extended BMS looms as well; we want to get rid of that, basically. In terms of cost, we are spending over £1000 per cab on connectors alone, so if we can take two to four of those away it would be a big saving.” The battery capacity of 40 kWh gives the cab a range of about 120 miles in city traffic, which Medwell says meets the needs of most city taxi drivers. If a taxi driver lives in central London within its low-emissions zone, they will be driving between 50 and 80 miles a day, he says, noting that most people commute into the city from the vicinity of the M25 orbital motorway, which would bring daily mileages to between 100 and 120. In London, that is enough most of the time, he reckons, while acknowledging that for some a 20-minute lunch stop at a fast charger might be required, which can add 40 or 50 miles. Talks with drivers outside London revealed daily mileages approaching 150 to 160, which would require 30-40 minutes on a fast charger. Schematic showing the split battery pack with HV, HV sensing, 12 V and CAM connectivity plus motor, inverter, AC and DC chargers, DC-DC converter and charging connectors Digest | Clipper Automotive Clipper Cab