When your business depends on lift trucks for throughput, battery charging deserves careful analysis. Many operations have adopted fast charging and opportunity charging, two similar — but distinct — alternatives to conventional battery charging practices.
Advocates of these technologies note that a well-implemented fast/opportunity charge plan will improve lift truck efficiency by reducing or eliminating the need to change forklift batteries between shifts. There is, of course, a tradeoff, which we’ll discuss later in this article.
While the terms are often used interchangeably, as a general rule, fast charging refers to a charge process that uses starting charge rates of 25-50 amps per 100AH of the battery’s capacity. Opportunity charging uses lower charge rates of up to 25 amps per 100AH.
The starting charge rate is important because lift truck batteries are charged on a curve — to reduce the time spent on charging, the battery needs to receive more current at the beginning of the charge cycle. Both charging processes gradually slow down during the charge.
Opportunity charging typically ends when the battery is at about 80 percent of its capacity. Batteries resist a charge when past this point, and charging procedures are optimized with the 80 percent figure in mind. Some fast chargers take the state of charge to 100 percent, but require built-in charge times (opportunity charging can take place whenever a lift truck is not in use, for instance, during breaks or when workers are occupied with other tasks).
The advantages and disadvantages of each technology will vary depending on the design of the batteries and the work schedule of the lift truck fleet. Generally speaking, administrators will need to keep the following factors in mind when considering either approach:
Reduced Battery Lifespan – Per Toyota Material Handling, fast-charge batteries typically last for three years or less, as compared to the five-plus-year lifespan of a conventionally charged lift truck battery. Opportunity charging can also reduce battery lifespans, though less significantly.
As lift truck batteries can cost more than $6,000, any reduction in lifespan merits careful consideration. Put simply, conventional charging strategies often save money in the long term.
Overheating – Fast chargers and opportunity chargers can further reduce battery lifespan by overheating batteries during the first phase of the charge cycle. A higher starting charge increases the chances of overheating — and to keep workers safe, managers need to be aware of the possibility. Workers will need to be trained to address overheating and other issues before the new charging equipment is put in use.
Availability of Equipment – Opportunity charging equipment is far more common than fast charging equipment, and finding affordable fast chargers for certain batteries can be difficult. With either technology, administrators need to weigh the benefits of the charging equipment with the cost of the equipment and the expected reductions in battery life.
For most operations, standard battery chargers (and a well-outfitted battery room) are still a better long-term approach, but opportunity/fast charging technologies can be useful in some applications. Facilities with particularly large forklift fleets often use a combination of traditional, opportunity, and fast charging. Calculating the feasibility can be difficult on a case-by-case basis, but proper battery handling equipment can help to limit some risks while optimizing any type of battery charging strategy.