Charging, Watering and Cleaning a Forklift Battery

Everyday large, heavy and expensive batteries power electric forklifts and inevitably need to be re-charged. Waiting too long or making the wrong connection can cost your organization time and money. To get the most out of your investment, machine operators should know and practice the proper care and maintenance of forklift batteries.

Houston native/Sailor uses a flow divider while fixing a forklift battery charging station in the hangar bay of USS Ronald ReaganMachine operators should monitor the percentage of charge on a battery, checking for a charge of 20 percent or less. Unlike cell phones or laptop computers, forklift batteries should not be connected daily to the charger as it will damage the battery’s ability to accept a charge. Batteries should only be placed on a charger when it has been discharged by 80 percent. Allowing a battery to go completely dead (unusable) will take over 72 hours of continuous charging to bring it back to full charge. In some cases it may even require service to restore it to a full charge.

Once the battery has been discharged to 20 percent or less, disconnect it from the forklift. And while it may sound obvious, insure that the forklift is turned off before doing so. Before connecting the battery to the charger, it’s critical that you make certain they are the same voltage. Connecting a battery to a charger that is a different voltage can cause serious damage. Connecting the charger to forklift instead of the battery is a common mistake that can result in damage to the charger and forklift. Be sure to take your time and pay close attention when making these connections. You want to connect the terminal from the battery to the terminal from the charger.

Set your charger to the “Equalize” or “Weekend” setting. Periodically giving your battery an equalizing charge will prolong its life. How often you should give your battery an equalize charge depends on the age of the battery. Newer batteries should have an equalize charge every 10 charging cycles while older batteries need an equalize charge every fifth charging cycle. Avoid making a habit of giving short charges during your lunch or break time as short charges constitute a “cycle” and will affect battery life and performance over time. Avoid interrupting a charge cycle if possible. Once a charge cycle is started it should be allowed to finish.

How often you water depends on your battery. For the first few years, new batteries will require water approximately every 10 charges while reconditioned batteries may only require water every 5 charges. Whether your battery is new or reconditioned, every 5 charges you should check 2 or 3 pilot cells, seeing if the water level is above the red perforated plastic Element Protector after it’s been charged. Element Protector color varies depending on brand. If the water is low, add only enough that it covers the Element Protector by 1/4 inch, leaving space for expansion while gassing at the end of a charge.

Understanding what’s necessary to clean a forklift battery is crucial. If your battery ever overflows, immediately rinse it with water to prevent corrosion both beneath and on top of the battery. Dilute the spilled acid with enough water that it’s not harmful to the environment. Spilled acid can generate additional heat during recharging. Clumps of conductive white corrosion can shorten battery life. Be sure to rinse your forklift batteries every spring and fall to remove acid residue.

Proper care and maintenance will extend your forklift battery’s life, helping you to get the most from your investment.

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23 thoughts on “Charging, Watering and Cleaning a Forklift Battery”

  1. i work for a large business and we have many battery powered lifts we always water before charging. we recently had someone come in with a charger other than what we normally use and we were told never to charge before always after where does your company stand on this

    1. There are two schools of thought on this one. The battery manufacturers & charger manufacturers will tell you to water after the charge. The main reason for this is to allow room for expansion of gases & even the acid itself. However, there is the other school of thought that if the battery is very low on water that you can burn a cell out during charging. However, that shouldn’t happen if the battery is being regularly checked. So, the simple answer is that if there is a proper watering schedule, you should only need to add water after the charge to top off the minimal amount that has dispersed since the last charge.

      1. well, that’s good to hear but will you not weak the strength of the battery if you water after charge?
        however, one of my batteries is working up to only two hours instead of the usual 6 or 8 hours, what should I do to regain it’s strength back? I will be glad to hear from you.

        1. The acid will mix with the water quickly and it won’t weaken the battery. The charge is between the plates not the acid.

          If you have a battery that is only lasting 2 hours and it has proper water levels, it’s likely either just old or has a bad cell. You can check each cell and see what voltage it is holding. Typically you’ll see something like 2.03v 2.02v 1.95v 2.04v…. etc. The one showing 1.95v would be the bad one because there is a large difference between the other cells. Make sure that you get a really good connection with your multimeter when testing, corroded terminals will give bad readings.

          Or you can have a battery service come out and inspect your battery and do some load testing. They can even balance the acid. Usually, they can refurbish a battery for less than a new battery. However, it may not be worth it if the battery is already 5 or more years old because that’s about the expected life of the cells with average usage.

  2. Is 80 percent considered a full charge. Would taking it off the charger once it has reached that point kill battery fast. The charger has a light come on at the 80 percent point

    1. No, 80% is just what it says. What you likely have is an opportunity charger. What is happening is that the charger will stop charging to allow the battery to cool down. This extends the life of the battery. It will after a period continue to charge to the full 100%. However, 80% is considered a good enough charge to use the lift for a half shift.

  3. I work for a large warehouse as the battery tech. The chargers in the building are all set up to equalize all the time. Can this harm the charge capacity?

    It is a large warehouse with about 40 36 volt getting changed about 3-4 times a shift.

    1. Honestly, I’ve never heard of a situation like this. However, here’s my thought process on the matter.

      An equalize charge does two things through what is really just a forced overcharge. First, it brings all of the cells to a near equal voltages. Second, it helps to shed sulfation that occurs from low charge conditions.

      Now, I do see an issue with method being used by your warehouse mainly because the batteries are constantly being overcharged. This can have a number of repercussions. During overcharging, excessive current causes the oxides on the plates of the battery to “shed” and precipitate to the bottom of the cell and also heat the battery, thus removing water from the electrolyte. Once removed, this material (which represents capacity) is no longer active in the battery. In addition, the loss of water from the electrolyte may expose portions of the plates and cause the exposed areas to oxidize and become inactive, thus reducing additional capacity. On top of all of this, an equalize charge is typically a longer charge. So, you need to let the battery cool down for the same amount of time as it has charged. Thus, the batteries will (should) have an extended down time, which can affect productivity.

      For your information, the typical recommended usage of the equalization charge is every 6 months or 20 cycles.

    1. It doesn’t hurt to wait a day, but generally, the charging process itself does a the job of mixing the contents of the cells due to the bubbles rising. Just make sure that you didn’t fill them too high or you’ll have battery acid flowing everywhere half way through the charge.

  4. Hi Sir,
    How to properly mix the Sulfuric acid and Distilled water to pour in a completely dry cell . i’m asking because one of the Forklift battery gravity showing around 1125 and 1150 range . So i can i boost the gravity? should i first completely remove the electrolyte or directly pouring the Sulfuric acid in each cell.

    1. We aren’t in the business of restoring batteries. Thus, I don’t feel that we can give a proper answer to this question. One thing I do know is that you should add acid to water and not water to acid (when the acid is in it’s pure form and not diluted like in a battery). Otherwise, the acid will react violently with the water and will splatter. Draining the cells seems optimal for the most accurate mixture, but once again, we don’t refurbish batteries. Thanks for your question.

  5. This damage can compromise the structural integrity of your battery case or even cause your cables to overheat, melting the insulation and shorting your battery connector.

  6. Hello, if doing opportunity charging, does the battery need to be completely dead before eqaliuze charging?

  7. Hi
    Thank you for the attention
    I am from Libya
    I have experience in the field of maintenance of acid and alkaline batteries .. 12 volts from 40 ampere to 225 ampere. I can disassemble it and install it again. This is for this type of battery
    But for forklift batteries, I don’t have a complete idea.
    Can you tell me some information on this. Cells. I mean, is it possible that I can repair these cells
    And thanks ..

    1. They are repairable, however, that isn’t a part of the business that we are in. So, unfortunately, there isn’t much we can say on the subject.

  8. This comment is very greatfull. If doing opportunity charging, does the battery need to be completely dead before equalize charging?

    But how many times do I have to clean the water? I didn’t get the direction section of your content please describe me with full details.

    1. The whole idea of opportunity charging is that the battery doesn’t need to be dead before charging. Equalize charging can be done to a battery at almost any level. The water doesn’t need to be cleaned, just added to as noted in the article.

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