Forklift Batteries: Conventional Vs. Fast Vs. Opportunity Charging

by Bill Parks on July 13, 2017
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forklift batteries conventional vs fast vs opportunity chargingWhat's the difference between the conventional method of charging a forklift battery versus fast-charging and opportunity charging? Generally speaking, conventional charging is best for single-shift operations. Multi-shift facilities can save time and money with fast or opportunity charging. In this post, we’ll review the pros and cons of each method and special considerations like truck modifications and the cost of new chargers. 

Conventional Forklift Battery Charging

Charge time: 8-10 hours
Charges to: 100% SOC (State of Charge)
Cool down time: 8 hours
Charged at: 16-18A / 100 Ahrs

BEST FOR: Conventional charging is best-suited for single shift operations and is the easiest on the battery. You run it during the day, re-charge it in the evening and by the next day it's cooled down and is ready for use.

CONS: For multi-shift operations, you'll need to buy at least two batteries per truck. Your staff must take the time to change batteries between shifts which requires equipment and is a potential chemical hazard.

Fast-Charging

Charge time: 10-30min + weekly equalization charge
Charges to: 80-85% SOC
Charged at: 40-60A/100Ahrs (3-4x greater than conventional)

BEST FOR: Three-shift / heavy use operations. The battery can partially charge up in ten minute spurts during breaks or in-between shifts. This eliminates the need for extra batteries and for battery change-outs between shifts. Operations with limited space will also benefit from fast-charging as you no longer need battery change-out rooms.

CONS: Fast-charging is extremely hard on the overall life of the battery and warranties are reduced. So the battery will have to be replaced more often versus conventional charging.

SPECIAL CONSIDERATIONS:
Fast-charging keeps the battery at a 40-80% SOC (state of charge). However, it’s important to charge the battery to 100% at least once a week (this is called equalizing) and it is typically done over the weekend.

Your lift trucks will need to be modified slightly to have permanently-mounted connectors and dual battery cables routed to the rear of the vehicle. Optional modifications include fans or vents to cool the battery and reduce heat under the hood.

Fast-charging also requires special chargers:
- With a multi-vehicle charger, multiple vehicles get charged  at the same time with one  AC input. The power is shared, so this is better for light-duty equipment like utility trucks, small forklifts, etc.
- You can also have dedicated chargers where only one vehicle charges at a time and gets the full power output. This is better for mid-sized forklifts and larger capacity lift trucks.

Will fast-charging save you money?
After the initial investment, most multi-shift operations end up saving money. Here’s a hypothetical:

A multi-shift operation has 50 trucks
- With conventional charging, they’ll need at least 100 batteries (2 batteries per truck), but with fast-charging, only 50 batteries are needed - a 50% savings, roughly $250k.
- The company also needs 50 chargers and battery extraction and changing equipment (approx $150k).
- The fast chargers cost approx $550k, however, each year, the company saves roughly $300,000 in labor costs (based on $25/hour) because the batteries won’t need to be changed out every shift.

So even though the company is spending $400k more on fast chargers initially, they’ll make up the cost in less than a year because they’ll buy fewer batteries and lower their labor costs.

CONS: Fast-charging requires built-in time to charge the equipment throughout the day. If the only time to charge is between shifts, that won’t be enough. Also, 24/7 operations may find it hard to find time to do a 100% charge once a week. Lastly, a fast-charge battery generally lasts 3 years or less as compared to a conventional battery than can last up to 5 years.

Opportunity charging Charge time: 10-30min  + weekly equalization charge
Charges to: 80-85% SOC, 100% overnight
Charged at: 5A /100 Ahrs

Opportunity charging is best for two-shift operations where you can keep the battery going just long enough to get through the second shift by charging  during breaks and lunchtime.  An opportunity charger brings  the battery up to an 80-percent state of charge. Once a week, the battery must be fully charged to equalize. Opportunity charging  can also extend the run time of aging batteries. 

BEST FOR: Companies with multi-shift operations and space to install strategic charging stations.

CONS: An opportunity charger will shut off at 80-percent SOC and allows the battery to cool down. Even if you can squeeze in a full hour of charging, the opportunity charger won't take the battery to 100% ( a fast charger will). 

SPECIAL CONSIDERATIONS:
You’ll need to buy opportunity chargers, conventional chargers aren’t designed for opportunity charging and can damage the battery. Also, to ensure staff charges equipment during breaks, it’s smart to install chargers near break rooms and work areas to make sure your trucks get charged throughout the day. Lastly, as with fast-charging, the forklift’s battery must be fully charged to 100% each week to equalize. This may be challenging for around-the-clock operations.

Before you invest in additional batteries or new charging equipment, do a one-week survey to determine which forklift battery charging option is best for your operation. Some questions to ask:

- When and for how long can staff find time to fast or opportunity charge?

- Can you schedule time for a weekly 100% charge?

- How many chargers do you need and where might they be installed?

We’ve helped numerous material handling operations find the right battery charging option for their facility - which is sometimes a combination of the options above. Please contact us with any questions; we look forward to earning your business

Further Reading:
Forklift Battery Replacement, Watering and other FAQs 
How to Extend Electric Forklift Battery Life

Forklift Battery Questions

Topics: Electric Forklifts, Forklift Battery FAQs

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