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Scissor Lift Batteries & Chargers 101


Understanding and properly maintaining your Hy-Brid Lifts HB Series scissor lift’s batteries and charger is crucial to maximizing its performance and your crew’s uptime. All Hy-Brid Lifts authorized service centers and technicians that work on these machines should be aware of how these scissor lift batteries work, what makes them fail, and how to prevent them from failing prematurely. Here’s some important things you need to know about scissor lift batteries and chargers to get the most out of your fleet.

Scissor Lift Batteries

DISCLAIMER: Before handling a battery on any machine, make sure you’re wearing appropriate protection like gloves, safety glasses, clothing that covers your entire body, and closed toe shoes.

Battery Composition

All Hy-Brid Lifts HB Series scissor lifts use a group 27 lead acid battery made of plates, lead, and lead oxide. Inside the battery is a sulfuric acid and water mixture called electrolyte. The electrolyte solution in a battery should be approximately 35% sulfuric acid and 65% water. During normal operation, batteries “consume” water via evaporation. Since the majority of electrolyte is water, you should always add water if the electrolyte is low. You should never add sulfuric acid because this will change the pH level of the battery, leading to other issues and battery damage. If the battery is discharged, be careful to only add enough water to top off the cell without overfilling it. The water expands during charging, so overfilling a cell can create a dangerous boil-over condition.

Checking Specific Gravity

You can determine where a battery is in its charging cycle by measuring the specific gravity of the battery’s electrolyte. This test is performed with a hydrometer in three easy steps:

  1. Insert the hydrometer into one of the battery’s cells.
  2. Draw water into the hydrometer up to the level.
  3. Observe the measurement.

It should be noted that a fully charged 12V battery will read approximately 1.265 specific gravity, a fully discharged 12V battery will read approximately 1.12 specific gravity, and plain water will measure 1.0 specific gravity. Despite its low specific gravity, a discharged battery will still read approximately 10.5V. You should never drain a battery below 10.5V or 1.75V per cell as this drastically shortens the battery’s life and can even destroy the battery altogether.

Battery Failure: Sulfation

The most common cause of HB Series scissor lift battery failure is sulfation. Battery sulfation starts when the battery’s specific gravity falls below 1.225 per cell or when the voltage measures less than 12.4V per 12V battery. When this happens, lead sulfate crystals build up and harden on the battery’s plates, eventually destroying the battery’s ability to generate volts and amps. This is why it’s strongly advised that deep cycle batteries are never discharged below 1.75V per cell to prevent permanent battery damage and reduce the chances of shortening the battery’s life. Discharging a battery even slightly below its full discharge voltage can shorten its lifespan, while letting a battery discharge to 0 will destroy the battery.

There are numerous causes of battery sulfation, including letting batteries sit too long between charges, improperly storing batteries without an energy input, and undercharging batteries. To maximize battery performance, idle batteries should always be connected to a charge to maintain their charge. Undercharging to 90% capacity should be avoided as sulfation can occur using the 10% of battery chemistry not reactivated by an incomplete charging cycle. The bottom line is that when you’re charging HB Series batteries, ensure they’re fully charged before putting the machine into use.

Other Causes of Battery Failure

Heat is also a major contributor to scissor lift battery sulfation. When the temperature exceeds 100 degrees F, a battery will increase its internal discharge, meaning it drains faster than in moderate temperatures. Cold weather is also very hard on batteries. A battery will freeze solid in subzero weather. If you do come across a frozen battery, do not attempt to charge it until it has thawed completely, or an explosion may occur. Another notable cause of battery failure is low electrolyte. Battery fluid levels should be checked at least once a week and maintained above the battery’s plates to prevent sulfate build up on the plates.

Scissor Lift Battery Chargers

Let’s talk about battery chargers for Hy-Brid Lifts HB Series scissor lifts. It’s important to remember that you must replace the energy you use from a battery immediately because if you don’t, the battery will begin to sulfate, which affects battery longevity and performance.

Three-Step Regulated Charging

Batteries like to be charged in a certain way, especially if they’ve been deeply discharged. HB Series scissor lifts use a type of charging called three-step regulated charging via a Signa charger. The first step of the three-step regulated charging cycle is bulk charging. This is where 80% of the battery’s energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger. When the battery’s voltage reaches 14.4V, the absorption charge begins. Absorption charging is where the voltage is held at a constant 14.4V and the current amps decline until the battery is 98% charged. Next comes the float step where a regulated voltage of no more than 13.4V and usually less than 1 amp of current is used to bring the battery up to a 100% charge or close to it. The float charge will not boil the battery but instead maintains the battery at 100% readiness and prevents cycling during long-term inactivity.

Signa Battery Chargers

The Signa charger used with Hy-Brid Lifts HB Series scissor lifts will not charge deeply discharged batteries. For example, two batteries measuring 11.45V on a 24V system are severely discharged. Since the batteries are so discharged, there is a chance that the charger will not start. Before you condemn the charger, make sure your battery’s voltage is high enough to allow the charger to sense the current. If you plug a Signa charger into a lift with a deeply discharged battery bank, you’ll notice that the green lights on the front of the charger will continue to flash. This is known as a one-flash code and doesn’t necessarily mean that the charger is bad. Often times, this flash code means that the charger is not sensing battery voltage and will not start the charge cycle. Consider the following questions before tossing your battery charger:

  • Are the batteries dead or deeply discharged?
  • Is your power cord connected to the charger?
  • Is your power cord an appropriate length?
  • Is your power source the correct amperage and voltage?
  • Are all the charging connections clean and tight?

Charger Failure: Connections

Sometimes in the field, technicians will cut the wires and use splicing to form a new connection. However, this is not an acceptable solution because the splice will eventually corrode and cause a poor connection, giving you a false charger failure. Whenever you need to replace the charger in a Hy-Brid Lifts HB Series machine, make sure you always replace the wires completely. If you feel that you need to cut and splice the wires, always solder the wires together to ensure a proper connection.

Want more information on scissor lift batteries? Discover the benefits of AGM batteries and check out these four scissor lift battery maintenance tips to keep your machines running in tip top shape.