Transcript Batteries
Batteries User Brianiac (2003), Batteries [photograph]. Retrieved from https://commons.wikimedia.org/wiki/File:Batteries.jpg Clinical Use Primary: Single use Alkaline, mercury, zinc air etc. Secondary: Rechargeable Lead acid/gel cell Nickel Cadmium (Ni-Cd) Li-ion NiMH Common Problems: All rechargeable batteries have a life span; Typically # of charge cycles The specification varies with technology Heat & discharge cycles limit lifespan Caring for Wet Lead Acid: Minimum cell voltage is 2V Hydrometer is the best test 1.23Kg/L density Rechargeable batteries lose capacity when stored-lead acid are no exception Trickle charge regularly when stored Charging Rechargeables: Rule of thumb; Non-current limiting charger-set voltage to nominal +20% If an ammeter is not available-check repeatedly for excessive heat Current limiting charger-set volts +20%, set current to max charge limit, check for excessive heat By Andrevruas (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons Rejuvenating Batteries: Procedure; Only if cell does not respond to normal charging! Never leave cells unattended! Set current limiting supply to nominal +20%V Set current limit to 20% of Ahr rating Increase voltage until max current flows Check cell heat-warm is acceptable, hot is not Reduce voltage while current flow is maintained Note: This is a temporary repair, new batteries will be req'd. Substituting Chargers: Important Specs; Line voltage O/P voltage Max current o/p Physical dimensions/mounting Connector Some wall units are AC o/p Bridge rectifier can change to DC Any customized charger should be permanently attached to the equipment it is used with Battery Substitution • One can replace rechargeable cells for one use batteries if: - The equipment does NOT have an internal charger! • If the charger delivers excessive charge, then the cells and device may be damaged Substitution Example • You make a pack of 12, 600 mAh, 1.2 V, NiCd cells connected 4x3: – 3 sets of 4 batteries in series 1.2 V x 4 = 4.8 V – 3 sets in parallel 600 mAh x 3 = 1800 mAh • You have created one, 4.8 V, 1800 mAh battery! Substitution Example • To charge your pack, use Trickle charge: 1800/100 = 18 mA for a few days Max charge: for NiCd=C=1800 mA (1.8 A)! Minimum Testing: Check battery volts; Nominal typically needs no adjustment Corrosion; clean if present Capacity testing; use equipment it supplies Check cables Check insulation Monitor voltage during charge from built in charger – fast rise typically Ok Acid Batteries • Hydrometers are available in auto parts stores for acid batteries • If the electrolyte level appears low or the acid level is too high, add distilled water By Palagiri (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons Safety • Acid batteries - Hydrogen gas may build up if proper venting has failed: EXPLOSION • 12.7 volt lead-acid battery can destroy a finger if a ring shorts the terminals Questions