Best practices for opportunistic charging of Industrial battery solutions

by Gloria Philips Expert Blogger

Listed below are the guidelines that BSLBATT Lithium has developed to assist our customers in maximising their return on investment in Li-ion batteries and charging infrastructure. Opportunity charging has a multiplier effect on the positive return for adopting Li-ion batteries.

1. Understand the existing operational workflow of the operators/equipment/batteries to assess the available time per shift to connect to a charger. This can be established through a power study where the operator/equipment/battery activity is monitored for up to four weeks, and worst-case usage models should not be ignored. Based on the data, one can determine whether there are adequate opportunities for ad hoc (eg. coffee break) or scheduled (eg. lunch) charging throughout the shift. If there is no down-time for the equipment throughout the shift, then the batteries will need to be charged for an hour before the shift. Or, the operator's existing work flow can be modified so that there is some down-time made available for opportunity charging the equipment.

2. Single-shift vs. multi-shift operations can determine the value of opportunity charging for an enterprise. If the enterprise operates a single-shift operation, a fully charged Li-ion (or FLA) battery should power that vehicle through the shift. However, when a second (or third) shift is needed, then opportunity charging can be used to recharge that integrated battery in increments and ensure that the equipment is powered through all the shifts

3. Rather than charging FLA batteries in a centralised battery maintenance room, the enterprise can distribute the Li-ion charging stations near break rooms and heavy work areas. This will encourage and enable operators to charge their equipment when the operators have down-time or are not using their equipment. Decentralised charging stations eliminate the operators' travel time from their work area to the battery maintenance room as well.

4. Assess existing FLA chargers to determine if they are compatible with the Li-ion batteries. There are some charging parameters, such as voltage limits, that need to be aligned between the battery and charger. But most FLA chargers are typically compatible with Li-Ion batteries, enabling the use of the existing charging infrastructure for opportunity charging.

5. Assess the power output of the existing FLA and Li-ion charging infrastructure. As mentioned earlier, the conventional FLA battery charge regimen is a C/5 rate over an eight-hour period. With opportunity charging, the Li-ion battery should be charged throughout the shift at a 1 C rate for a total accumulated time of one hour. The implication is the power rating on the charger must be much higher when opportunity charging. As an example, a 48 Volt 500 Amp-Hour FLA battery could be charged with a 5 kW charger over an eight hour period, while a similarly-sized Li-ion battery would require a 25 kW charger for a one hour period.

6. Consider a multi-voltage battery if opportunity charging is desired but there is not adequate down-time within a shift. A multi-voltage battery has a power switching fabric within the battery electronics. The charger's charge voltage is set at twice the equipment's operating voltage, and the battery electronics then steps down the received power to the equipment's operating voltage. The charger delivers twice the amount of power when charging at twice the voltage, therefore the charge time is reduced by 50%. Multi-voltage battery options are available in 24 v (24/48), 36 v (36/72) and 48 v (48/96) battery configurations.

7. Consider the equipment/charger ratio. The best case for operators is a 1:1 ratio, so all operators can take their lunch together and each piece of equipment can be charged during this down-time. If the enterprise can stagger coffee/lunch breaks or run the fleet between 50-100% utilisation, then they can reduce this ratio down to 2:1 and still ensure that all equipment has unfettered access to the local charger.

8. Assess your operators' behaviour after you have introduced opportunity charging. Some Li-ion batteries have embedded Internet of Things (IoT) computing, WiFi transceivers and cloud-based applications so the enterprise can remotely monitor their operators' adoption and effectiveness with opportunity charging. One simple measure is monitoring the state of charge of each piece of equipment/battery throughout the day. Any operators/equipment consistently operating in the 5-20% state of charge range may need some retraining on opportunity charging.

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