Percent recharge unit permits each cell of a rechargeable battery to be charged to a preset capacity of the cell. The unit automatically monitors and controls a rechargeable battery subjected to charge-discharge cycling tests

Baer, D.

Ford, F. E.

English

NASA Technical Reports Server

August 1968	 Brief 68-10273 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Recharge Unit Provides for Optimum Recharging of Battery Cells 
Digital 
Voltmeter 
Power 
Supply 
Recorder 
Digital	
Current Battery under Formation 
Integrator	 Cycler	 Test 
Since the voltage slope of a rechargeable battery 
is very small near the upper preset voltage limit, 
voltage sensing is not the ideal way of determining 
when charging of individual cells in the battery should 
be cut off. A "percent recharge unit," which has been 
developed, permits each cell of a rechargeable battery 
to be charged to a preset percentage value of the dis-
charge ampere-hour capacity of the cell. This preset 
percentage value is set on the front panel and has a 
range of 100 percent to 199 percent in 1-percent incre-
ments. This unit operates in conjunction with an auto-
matic formation cycler, a current integrator, a digital 
recorder, a digital voltmeter, and a power supply for 
battery charging. The entire system automatically 
monitors and controls a rechargeable battery sub-
jected to charge-discharge cycling tests. Without the 
percent recharge unit in the system, the formation 
cycler would monitor the voltage of each cell in the 
battery and automatically remove a cell from the bat-
tery when its voltage reached an upper preset limit
during charge or a lower preset limit during discharge. 
With the percent recharge unit in the system, the 
process begins by connecting a fully charged battery 
(containing up to 20 cells) to the formation cycler. 
The fully charged battery is discharged into an internal 
load in the formation cycler, with the current time 
integrator monitoring the ampere-hour discharge ca-
pacity. During this discharge mode, pulses which are 
generated by the current integrator are counted by 
20 discharge counters located within the percent re-
charge unit. Each cell of the battery has its own dis-
charge counter. When a cell is removed from the bat-
tery by the formation cycler because of a low preset 
voltage limit, the cell control relay located in the 
formation cycler applies an inhibit level to the cell 
counter gate, preventing the integrator pulses from 
being applied to the discharge counter representing 
that cell. Therefore, at the end of the battery dis-
charge cycle the digital information stored in each 
of the 20 discharge counters represents the discharge 
(continued overleaf) 
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ampere-hour capacity of each of the corresponding 
battery cells. 
During the battery charie mode, pulses from the 
current integrator are applied to a single charge 
counter within the percent recharge unit. Therefore, 
the digital information in this charge counter repre-
sents the ampere-hour charge applied to the battery. 
The percent recharge unit sequentially multiplies the 
ampere-hour discharge capacity stored in each cell 
counter by the percentage value set on the front panel 
and compares this product to the ampere-hour value 
accumulated in the charge counter. If this product is 
equal to or less than the value in the charge counter, a 
signal is sent to the formation cycler which causes it to
bypass that cell. Cell identification, voltage, and 
ampere-hour capacity are recorded by the printer each 
time a cell is removed from the battery. 
Note: 
Complete details may be obtained from: 
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B68-10273 
Patent status: 
No patent action is contemplated by NASA 
Source: D. Baer and F. E. Ford 
(GSC- 10688) 
Brief 68-10273	 Category 01


Recharge unit provides for optimum recharging of battery cells

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