Sealed Lead Acid (SLA) Battery
Battery Health Evaluation Process
With the use of sealed lead acid batteries in our mobile computing and auto relocking medical carts, Capsa
recommends replacement every 12 to 18 months under normal use for healthcare environments. This ensures
maximum battery stability and a safe battery condition.
With heavy use, it may be necessary to replace the batteries at an earlier interval based on depleted battery life.
If a cart’s battery life is experiencing a noticeable reduction in run time, it is likely in need of replacement.
To evaluate the battery, a simple condition check can be performed to determine the general condition of the battery.
In addition, to thoroughly evaluate the battery and determine remaining capacity, a run time test should be
performed to thoroughly assess the health of the battery.
Cart and Battery Condition Check:
• With the cart plugged in and fully charged, test the voltage of the battery.
• The battery voltage with the charger attached should be between 13.5 and 14.5 volts.
• Unplug the cart from AC power
• After unplugging for 30 - 45 seconds, check the battery voltage.
-If the battery voltage remains above 12.5 volts, the battery is OK and does not need to be immediatley replaced.
NOTE: This does not indicate the battery run time will be acceptable; a full run time test must be completed to determine run period. This measurement simply indicates the battery is functioning correctly.
-If the battery voltage drops below 12.5 volts, the battery should be replaced and removed from use.
• While the cover is removed, examine the battery and record the warranty install date on the sticker to determine the age of the battery.
• Examine the battery, and look for excess swelling on the sides. Slight swelling is normal, anything that seems excessive indicates the battery should be replaced.
Battery Run Time Test:
• Charge the cart for a minimum 12 hours.
• Measure the voltage on the battery with the cart still plugged into AC power. The voltage should be between 13.5 and 14.5 volts. If the voltage is outside of this voltage range after the 12 hour charge, contact Capsa Solutions for further information.
• Turn on the cart and all attached peripherals, and record the time.
• Let the cart run with the peripherals on until the cart Low Battery alarms are activated. Record the time the Low Battery alarm starts and when the cart shuts down the peripherals. The cart will shut down when the battery voltage falls to approximately 11.6-11.8 volts. NOTE: After shut down, the voltage may rise above this level, and this is considered normal.
• Subtract the shut off time from the start time to determine the cart’s actual run time.
• Compare the cart run time with the new cart run time estimate (see below) to determine if the battery health has depleted beyond the recommended level.
How to calculate new battery run time estimate for SLA batteries:
• A new battery run time can be calculated using the following formula. + / - 15%:
- Cart run time hours = (battery size AH x 0.75 ) / (average load current)
- If the actual run time is less than 60% of the calculated runtime, the battery should be replaced.
• Load current should be measured from the battery power lead with a clamp style current meter, or depending on the cart model, can be read directly from the cart. If the load Watt rating is known, the load current can be estimated by dividing the watts by 12. It is recommended to measure actual load as listed loads on equipment are generally maximum ratings and will potentiall give inaccurate results.
Example, 50AH battery, 2.5 amp load:
- New runtime = (50AH x .75) / 2.5
- = 15 hours + / - 15% (11.75 -17.25 hours)
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© Capsa Solutions, 2014
Form C-283