Reasons For Self-Discharge; Self-Discharge – Temperature Comparison; Checking Current Drain; Current Drain - Suzuki SV650/S Service Manual

3
Inspecting, Testing
and Charging

Reasons for Self-discharge

Batteries have a natural tendency to discharge. There
are a number of reasons why: self-discharge, high
temperatures, drain from electrical accessories on a
vehicle, and short trips that aren't enough to recharge
the battery.
Self-discharge Rate Characteristics at 77
Months on Storage Shelf
2 4 6
0
20
40
60
80
Lead-Antimony
100
Self-Discharge: Self-discharge goes on all the time.
It's a battery fact of life that they get weaker from "just sit-
ting." How rapidly batteries self-discharge depends, first
of all, on battery type. Lead-calcium batteries, such as
YUASA's CX, YT, YI, discharge more slowly than conven-
tional batteries. At room temperature lead-calcium dis-
charges at 1/300 volt per day. Conventional lead-anti-
mony batteries discharge at 1/100 volt per day.
Temperature: Outside temperature plays a big part,
too. As the mercury goes up, batteries discharge faster.
Particularly in hot climates, that can mean trouble: every
18°F doubles the discharge rate, so a battery at 95°F
discharges twice as fast as one at 77°F. And temperatures
Self-discharge – Temperature Comparison
From 100% Charged to 100% Discharged
0 100 200 300 400 500 600 700 800 900 1000
104°F
77°F
32°F
Lead-Antimony
8 10 12 14 16 18
Lead-Calcium
Days Stored
Lead-Calcium
of 130°F are battery-killing. Been in a closed-up garage
or storage building on a hot summer day recently? In
many parts of the country, it's no trick for inside tempera-
tures to reach that.
Accessories: Electrical accessories on some of today's
newer and bigger bikes – clocks and computer memory,
F
O
for example – will discharge the battery continuously,
even when the ignition's off. The drain can be consider-
20
able. You can find out the drain, in milli-amperes, by
disconnecting the negative terminal and putting a multimeter
in line. It should look like this:

Checking Current Drain

Motorcycle
Battery
Keep in mind that at the same time accessories are draw-
ing on the battery, the battery's self-discharging, too. The
charts below show how fast a battery is discharged by
self-discharge and by current drain:
Temperature
104°F
77°F
32°F

Current Drain

Discharging
Ampere
7 mA
10 mA
15 mA
20 mA
30 mA
13
Yuasa
Multimeter
Self-discharge
Approx. Number of Days From100%
Charged to 100% Discharged
Lead-Antimony Lead-Calcium
Battery Battery
100 Days 300 Days
200 Days 600 Days
550 Days 950 Days
(Y50-N18L-A)
Days From Days From
100% Charged to 100% Charged to
50% Discharged 100% Discharged
60 Days 119 Days
42 Days 83 Days
28 Days 56 Days
21 Days 42 Days
14 Days 28 Days
Negative
Battery
Cable