In a previous post, it was shown that a 16-hour bot factory workday is possible just by leveraging standard break schedules, only using a battery pack. No umbilical cord. No swappable battery packs. No induction pad charging.
However, what is the maximum workday possible? The bot needs to charge after all. So what is the optimum charge schedule to minimize disruptions to production? The break schedule is the optimum, since it is already used to accommodate the humans, and bots and humans will be working side-by-side initially. A 16-hour day is typically a two-shift schedule. For a longer day, a three-shift model is needed.
A three-shift model is challenging, because the schedule is very compressed. The time between shifts is tight, and there is no off-shift to leverage for charging to full. Hence, the day starts with less than 100% charge. Normally a shift will include two short breaks and a meal break for a total of about one hour of breaks. This is a 21-hour workday. To get more productivity, the breaks need to get shorter.
Assumptions:
As in the previous post, the bot will be functioning at maximum drain of 500 W with 7 kW charging and a 2.3 kWh battery pack.
Plot One shows that a 20-hour workday is easily achievable. There are ample breaks, and sufficient time between shifts. 15-30-15-20 breaks per shift.
Plot Two shows that a 21-hour workday is also achievable. There are reduced breaks, and truncated time between shifts. 10-30-10-10 breaks per shift.
Plots Three shows that a 22-hour workday is challenging, but possible. The breaks are reduced from 15 to 5 minutes, and meal breaks from 30 to 20 minutes, and 10 minutes between shifts. 5-20-5-10 breaks per shift
Plot Four eliminates the breaks in exchange for a 30 minute meal time, resulting in full discharge. The long stretch between charges causes the full drainage, demonstrating the sensitivity of achieving a 22-hour day at full power. 0-30-0-10 breaks per shift.
While the 22-hour workday is possible with only 2 hours of charging strategically spaced, it pushes the limits of the battery pack. But this is worse case assuming a maximum discharge rate. At 400W or less the reserves improve. Still for financial models of the bot, a maximum of a 20-hour workday is recommended.
Thanks to @CernBasher for help with the plot formatting. Thanks to @LimitingThe for help with the charging curves.