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Figure 2-2 Model 946 Lead-Acid Battery
T h e l e a d - a c i d b a t t e r y o f f e r s h i g h e r c a p a c i t y t h a n t h e
nickel-cadmium battery at a lower price. However, fewer
charge-discharge cycles are generally possible. If your experience
has been with the nickel-cadmium battery, please study the fol-
lowing before using the lead-acid battery.
• Do not run an instrument to complete discharge
of the battery. Total discharge of gelled-electrolyte
batteries can cause cell reversal, and this can ruin the
battery. One manufacturer recommends 10.5 VDC,
loaded at 400 mA, as complete discharge of a 12-volt
battery.
• Although it may appear that there is still much
power left when the battery voltage drops to 10.5
VDC, in fact, there is very little. Trying to use all
remaining power from a battery will cause cell reversal.
The weakest cell is the first to fail in a battery. The first
cell depleted will be forced into reversal by the rest of
the battery, if the load is still connected.
• Recharge lead-acid batteries as soon as possible
after use. Unlike nickel-cadmium batteries, if you leave
lead-acid batteries partially or fully discharged for any
period of time, they may not recharge to full capacity.
Eventually they will not accept or retain a charge at all.
• Battery life is related to the depth of the
discharge cycle. One manufacturer specifies that you
can expect only 200 cycles at 100% discharge for each
cycle. With a 50% depth of discharge, this number
increases to over 400 cycles. With a 30% depth of
discharge, cycle expectancy increases to over 1,000.
• Avoid the use of lead-acid batteries in subfreezing
environments, especially where you expect deep
discharge. One manufacturer recommends that you
use them above 5
lead-acid battery will withstand cold temperatures, a
discharged battery can freeze if the temperature is low
enough, and that can ruin it. If frozen, the battery could
Power Products Guide
Section 2 Batteries
o
o
F (–15
C). While a fully-charged
2-9
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