One could say that the battery is the heart of the forklift. Just as the human heart beats to circulate blood throughout the body, the battery is circulating energy through the forklift. It is important for a forklift operator to understand how the battery works, how to maintain it, and when to know that a replacement battery is needed. He should also understand what accessories are necessary to have on hand to assure that the battery performs well.
Regarding the question of whether it’s safe to leave your forklift battery plugged in, the answer largely depends on what type of battery it is. For a lithium-ion battery with a low maintenance charging procedure and battery management system, it’s perfectly fine and better than leaving them discharged for long periods. For other types of batteries, not so much.
In this article, we’ll go over some common FAQs for forklift battery charging, discuss the differences in charging procedures for different types of batteries, and lay out what users need to keep in mind both for safety precautions and proper battery maintenance.
A battery’s SoC or state of charge is the level of charge of an electric battery relative to its capacity - so 0% is empty and 100% is full. The inverse form of this metric is DoD or depth of discharge, in which 100% is empty and 0% is full.
The term ‘battery SoC’ usually refers to a battery’s state while it is in use, whereas the term ‘battery DoD’ typically refers to how much of the overall battery capacity has been discharged.
There are several ways to measure SoC that apply to different types of batteries. Lead acid batteries with a liquid electrolyte can be measured chemically with a hydrometer, while most other batteries, including lithium-ion, are measured by their open-circuit voltage.
Measuring a battery’s voltage must be done after it has been resting in the open-circuit state for at least a few hours, or else the reading will be affected by the battery’s current and temperature and will be inaccurate.
Very simply put, the industrial battery charger takes AC power from the utility company, changes it to DC power, controls the DC power going into the battery, reverses the electro chemical process that occurred during the discharge cycle. The charger forces the acid that has penetrated into the plates during discharge back out into the electrolyte.
There is a strong misconception that an oversized charger will simply recharge the battery properly in a shorter time period. A battery is designed to absorb a charge at a controlled rate. If it is charged at a faster rate, the energy that it cannot absorb is converted into heat. Cell temperatures rise, and the battery, in effect, “cooks in it’s own juices”.
If the charger is not large enough to reverse the electro chemical reaction in the battery within the allotted time, some of the acid will remain in the plates. The battery will not perform in accordance with it’s ampere-hour rating capacity. More serious is the permanent loss of capacity resulting from repeatedly leaving acid in the plates. The results you would experience would be an 840 ampere-hour battery performing like a 400 to 500 ampere-hour battery if it is continually undercharged (50% or more loss of shift time).
Overcharging occurs when a battery is charged to a higher than specified voltage. It can be very damaging to forklift batteries and, if not controlled, dangerous for the users.
The right charger for your battery is crucial to prevent overcharging; the charger must match the battery in terms of output voltage and Ah rating.
It’s easier to avoid overcharging in lithium-ion batteries because they can receive a partial charge or be charged intermittently.
Lead acid batteries have a more complicated process for charging and must receive a full charge each time they are plugged in; for this reason, it’s easier to accidentally overcharge.
Lead acid batteries only last about 1,500 charging cycles on average, so it’s not a good idea to charge them partially - you should do it completely every time to prolong the battery’s lifespan.
Along that same line, it’s also a waste of battery lifespan to start charging a lead acid battery with more than 50-60% of its capacity left. Each charging cycle, no matter the SOC, is still considered one cycle. So, the more often a lead acid battery gets charged, the shorter its lifespan will be.
If undercharging is combined with over-discharging the effects are intensified. Strictly speaking, a battery is not overdischarged at any rate unless more than its capacity at that rate has been taken out. Nevertheless, it is highly undesirable to take out anything approaching 100% of its rated capacity on a regular basis.
While the capacity of a traction battery is increased somewhat at higher temperatures, heat also has other adverse effects and all practical means should be employed to keep the battery temperature normal. Higher temperatures also increase the charging current and may result in a considerable overcharge. This means increased water usage, greater ‘formation’ (corrosion) of the positive plate spines and a shorter battery life. Any tendency for battery temperatures to rise above 45°C due to operating conditions, should be minimised by:
● Avoiding over-discharge
● Charging in a cool location
● Supplying ample ventilation during charge by opening the battery compartment and circulating air by fans if necessary
● Note: For every 10 °C rise in average battery temperature, the service life of lead acid batteries is reduced by approximately 50%.
In a lithium-ion battery, overcharging can create unstable conditions inside the battery, increase pressure, and cause thermal runaway.
Lithium-ion battery packs are required to have a protection circuit to prevent excessive pressure build-up and cut off the flow of ions when the temperature is too high.
Most lithium-ion battery packs also contain a battery management system to monitor their state of charge and cut off the current when the limit is reached.
Lead acid battery overcharging will corrode the cathodes, cause increased water consumption, and increase the temperature inside the battery. At best, this will lead to reduced capacity and shortened life cycle, and at worst this could cause thermal runaway. Additionally, lead acid batteries can emit harmful, toxic gases if overcharged.
Lithium-ion batteries use a constant-current constant-voltage method for the first stage of their charging process. After reaching peak voltage, the battery enters the saturation charge stage. Altogether this process only takes about 1-2 hours.
Lithium-ion batteries can be used until 20% of their capacity remains. Unlike lead acid batteries, it won’t damage the battery to utilize opportunity charging, which means a user could plug the battery in during a lunch break to top off the charge and finish their shift without the battery getting too low.
Many industrial lithium-ion battery packs come with the chargers integrated within the pack that can be plugged into regular electrical outlets, which means the batteries don’t even have to be positioned near an installed wall charger to charge the batteries.
If your warehouse operates on multiple shifts, the simplified charging process of lithium-ion batteries offers a huge advantage. Forklift operators can opportunity charge lithium-ion batteries while on break or in between shifts, and the batteries are available in just 15 to 30 minutes to return to service, even if not fully charged yet.
Equipment downtime can be costly, so the fact that a forklift operator can connect the battery to the charger without having to waste time on removing the depleted battery and reinstalling a charged battery will improve warehouse productivity.
Plus, eliminating the need to transfer thousand-pound batteries between forklifts and charging stations greatly reduces the safety risks for workers.
BSLBATT lithium batteries significantly reduce operating costs of your warehouse trucks. The benefit becomes obvious: Real world example in Chicago, IL: using lithium batteries on 29 truck fleet for a 6 day-per-week operation, will save nearly $400K over 4 years. Reduction of costs is driven by:
Lithium battery packs let you have only one battery per truck (vs 2 or 3 in traditional lead acid battery setup) this is possible through opportunity charging and consistent full charge times of less than 2 hours.
BSLBATT Lithium battery lifetime is twice as long as that of lead-acid and gel batteries.
No battery room or maintenance. Savings on equipment of battery room, wages for maintenance personnel and outsource maintenance contracts.
If you use equipment more than 5-8 motor-hours a day, with a traditional setup you need 2 lead-acid batteries. With Lithium you only need 1! BSLBATT lithium battery does not require additional investments in battery room or battery maintenance personnel. In addition, lithium batteries are more power-efficient and use 35% less electricity. Because a much smaller lithium battery can handle the same workload, properly sizing a lithium battery can further increase your cost savings.
To select the right battery for you our sales managers need detailed information about the facility and nature of operations in which you plan to use the new batteries. Just call us and together we will select the ideal battery and a charger.
