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Battery Charger (Seal Lead Acid and Gel batteries) HoangThi Le October 11, 00 University of Rhode Island Kingston RI 02881 Biomedical Engineering Introduction: The main ideas of this project was designed a battery charger converter, which use for both Acid battery and Gel battery. Lead – Acid batteries are constructed of lead plates suspended in a container fill with a mixture of sulfuric acid and water. This fluid called the electrolyte reacts chemically with the lead plates to produce electrical current. Those batteries have deep cycle, the most satisfactory choice for most wheelchair users, even the power wheelchairs. In addition, to selection a deep cycle type battery is capacity of the battery. This is measure in ampere-hours, which is determined by number and size of the lead plates. The more and the larger plates the higher the ampere-hour rating. Different models of wheelchair, different patterns of use, and different users will require different battery capacities. But, In Zambarano hospital, they used a power wheelchairs, which operates 24 V, it means that they required two 12 Volt batteries. Another type of battery used in power wheelchairs is the gel cell battery. This battery operates the same as Lead Acid battery. The advantage of this battery is that person who travel by air are the most frequent users. The main disadvantage to gel cell batteries is that they have a lower ampere- hour rating resulting in less time operating time on a single charge. Design: we based all the information and knowledge we got from Internet, or technical support for battery charger. What we had been done: First, we drained the Acid and batteries by two cars headlights, and television. Then we measured the voltages drop between those two batteries: Acid batteries drained until 5-6 V, which completed drain. Beside that Gel cell batteries drained until 7- 8 V that fully drained. Second, we recharged them by a series connection, and then we measured the voltages of those batteries. The Acid batteries were got fully charge slower than the gel cell batteries. However, the Acid batteries weren’t complete charge as original, they charged up to 10- 11 V. This means the Acid batteries have leak resistant http://www0.delphi.com/disable/wheelchair.html http://www.4unique.com/battery/battery http://www.health-e-quip.com/tips/battery.htm http://www.mywebplace.com/batfaq.htm http://www.mywebplace.com/batinfo.htm http://www.usenergycontrols.com/chargerinstall.html http://www.sunpower-uk.com/battery_chargers.htm
occurs. So we need to refill the chemical in side a battery to get them full charge. Present: The best method is to slowly recharge Acid and Gel batteries using an external constant voltage, because the electrolyte has more time to penetrate the plates. A constant voltage “automatic” charger applies regulated voltages at approximately 14.4 volts and 10 ampere. But the “Seal Lead Acid” charger applied approximately 12 volts and 1.2 ampere. By charging different capacity battery, we need to change the circuit board of the Acid charger, based on Seal Lead Acid charging method. The Seal Lead Acid charger operates by float charging the battery to 13.65 Volts. This is the middle of the proper float voltage range at room temperature for most 12 Volt Seal Lead Acids. When the charger detects a charging current of greater than about 165 milliamps, it switches automatically into the "bulk charge" mode. In this mode, the charger attempts to pull the battery voltage up to 14.45 volts. This voltage is great enough to equalize the charge in the battery's cells. At all times, the charger limits the current output to 300 mA. When the battery becomes fully charged, its current drops off. When that current drops to less than 12 mA, the charger will switch back from the bulk mode to the float mode where the voltage will be maintained at 13.65 volts. Thus, when a battery that is slightly discharged is first connected, or power is applied to the charger, the battery will draw enough current to put the charger into the bulk charge mode. The battery will be charged, and its cells will be equalized. Then the charger will switch automatically to the float mode to maintain the battery's state of charge at precisely the correct voltage. Future Plan: Now, this project wasn’t worked, as we want, because we tried to get more information from people, who were technical support for battery charger. Accordantly, to what they told us that we need to either and more component to Acid charger circuit board or replace for a new devices. But where do we may get the replacement? If we can get a replacement, the Acid batteries charger will charge both Acid and Gel batteries. Ref: http://www.hepi.com/battery/battery http://www.nyquist.ee. Ualberta.ca/dcbat.html Lester Battery Charger Co. Technicians support: (402) 474-1769
US Energy Controls Corporation Technicians support: 408-274-5700
