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Jumbo Battery System

Used on electric patient lifters and electric patient beds.

Maximizing Jumbo System Battery Life

The batteries used in the LINAK Jumbo system are sealed lead–acid gel cells requiring no user maintenance (other than regular charging). When new a Jumbo battery pack has a nominal voltage of 24V, and a capacity of 2.9Ah. With use, both these values will decrease, resulting in fewer lifts on each charge. Some simple precautions, though, can dramatically improve the life of the batteries.

Unlike nickel–cadmium rechargeable batteries the lead–acid cells used in the Jumbo system should never be fully discharged. In fact deeply discharging these batteries will significantly decrease their useful life. The following graph illustrates the lives of three batteries. The first, battery A, is completely emptied every cycle. The second, B, is discharged to half full every cycle, and battery C is discharged by only 30% between each cycle.


As can be seen from the figure, after roughly 180 cycles battery A, which was discharged to empty every cycle, is not able to maintain any charge. Batteries B and C, however are still able to retain close to 100% of the capacity of a new battery. After 400 cycles battery B is dead, but battery C still retains 95% of the capacity it had when new, and it does not become unusable until after nearly 1200 cycles.

In order to increase the longevity of your Jumbo batteries it is recommended that you take the following steps:

  • Discharge the batteries as little as possible between charges
  • When not in use, especially over long periods, store batteries on the charger. With the Jumbo system charger it is not possible to overcharge a battery.

Jumbo System Battery Charger Diagnostics – Charger Reference

Type: Switch Mode Power Supply (SMPS)
Input Voltage: 100–240VAC
Output Current: max. 650mA
Charging Time: 4hrs for BAJ1 ⁄ BAJ2 battery pack
Indicator Lights: Green: ON – charger is connected to mains power
  Yellow: ON – battery is charging
  OFF – battery is fully charged

Jumbo System Battery Charger Diagnostics – Charge Profile

The following figure illustrates the charge for a very empty battery, showing the three distinct stages of a typical charge.


  1. Constant Current at 650mA: If a battery is empty it will accept current at a rate far higher than the charger can safely supply. To prevent damage the charger will limit its output to 650mA (approximately C/4). The battery is charged at this rate until it reaches a voltage of 29.4V.

  2. Constant Voltage at 29.4V: If it were to continue charging at 650mA the battery voltage would rise very quickly and damage from overcharging would result. To avoid this the charger continually reduces its current to maintain a constant voltage of 29.4V for the remainder of the charge.

  3. Trickle Charge at 27.6V: Once the current drops below 50mA the charge is essentially complete. The yellow light goes out to indicate this, and the battery can be removed from the charger and put into use. If the battery is left on the charger a very small trickle current of around 20mA maintains the battery voltage at a constant 27.6V. This keeps the battery ready for use over an indefinite period, and improves the battery’s long term cycle life by counteracting self–discharge.

Jumbo System Battery Charger Diagnostics – Testing the Charger

If you suspect that the charger is not functioning correctly perform the following tests:

  1. Measure the voltage across the charger terminals with no battery present. It should be 27.6V±1.4V.

  2. Short circuit the charger terminals with a 100ohm resistor (this gives a charger current of roughly 300mA). The voltage across the terminals should read as 29.4V±1.5V.

If the charger fails either of these tests it is faulty and should be replaced.

Jumbo System Battery Charger Diagnostics – Testing the Battery

Unfortunately the capacity of any battery does diminish with use. The following tests can help determine whether a battery has reached the end of its useful life.

  1. Measure the voltage across the battery terminals. A full battery will read above 24V, an empty one less than 20V. Anything below 18V should be considered very empty and it is very bad practice to allow batteries to drain so low. A reading of 0V across the terminals indicates that the battery has been shorted circuited and its internal safety fuse has blown.

  2. Place the battery on the charger and wait for the yellow light to go out. The voltage across the terminals should measure around 26V immediately after being removed from the charger. A voltage of less than 24V indicates that the battery should be replaced.

  3. Connect the freshly charged battery to a lifter and lift a load up and down once. The voltage should be above 25V, anything else and the battery should be replaced.

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