The reduction of the charging time for long-distance trips is one of the major levers for improving the acceptance of electric vehicles (EVs). Today, some passenger EV models already propose relatively low charging times thanks to an 800V system for their battery architecture. That battery architecture enables to charge with a higher power (350 kW) than the one permitted by most EV models on the road today with a classic 400V system. However, if EVs can handle higher charging power, the infrastructure should be adapted accordingly. As installing ultra-fast charging points (350 kW) generates higher costs, we can wonder to what extent the gain of time induced by an 800V-system battery and high power infrastructure is worthwhile compared with the additional cost of the adapted infrastructure. To answer that question, we tuned the share of 800V-system EVs travelling on the highway and, for a given percentage, we determined, thanks to a differential evolution algorithm, the Pareto-front that compares the cost of the charging infrastructure built and the time saved with that infrastructure layout. At an identical or even lower cost, increasing the percentage of 800V-system EVs reduces significantly the average time spent at stations. The Pareto curves show that the optimal results are reached for the vehicle fleets with 100% of 800V batteries. Indeed, for those fleets, we can find solutions where time is reduced by 47% while guaranteeing a 27% decrease in the infrastructure cost compared with the optimal solution presenting the lowest cost in the situation today (with barely 1% of 800V EVs on the road).