The following page discusses charging and discharging a Flooded Lead Acid
battery. The battery under test will be a U1L-3, more commonly known
as a garden tractor battery, the larger of the two that are typically
available. The ratings tag on this battery shows
CA of 335 amps and a CCA of 275 amps.
Performing a full charge on this battery resulted in an open circuit battery voltage of
12.82v prior to any load applied to the battery. A Victor battery
charger was used with a constant current (2 amps), constant voltage (14.4
volts) , then constant current charge cycle.
A RadioShack Digital multi-meter, with RS-232 output to allow
monitoring, was used to measure and log the battery voltage. The graph
below shows the battery voltage during the test.
Test Statistics
| Time |
Device |
Load (amps) |
Tot Load (amps) |
Voltage |
Ah |
| 3:22:01 |
Battery (U1L-3) |
0.000 |
0.000 |
12.82 |
0.000 |
| 3:22:21 |
Radio (FT-7100) |
0.320 |
0.320 |
12.76 |
|
| 3:43:31 |
Florescent Light (FL-8T5D, 1 lamp) |
0.570 (cold) |
0.830 |
12.60 |
|
| 6:42:41 |
|
|
|
|
2.573 |
| 7:22:56 |
|
|
|
|
3.126 |
| 10:48:16 |
|
|
|
|
5.931 |
| 11:06:01 |
|
|
|
|
6.169 |
| 11:06:21 |
Load removed |
|
|
|
|
| 11:10:46 |
2 amp charge applied |
|
-2.11 |
|
|
| |
Total charge |
|
|
|
6.045 |
Radio was in scan mode and the light current increased
after it was turned on but the timing was not monitored. This load
results in a C/40 - C/50 discharge rate (34/0.83=40.96, 40/0/83=48.2) which
is lightly loaded.
- - -
Load Test Set-up
Yaesu FT-7100, U1L-3, Astro Flight power monitor, RS Meter, Light
(room temperature test)
- - -
Voltage Profile
(5 second sampling rate)
- Click above graph to get an excel spread sheet -
- - -
Notes:
This battery has been excessively discharged several times
to well below 10.5 volts resulting is a reduced capacity. The only
data I have
been able to find was from
WindSun
showing a capacity of 34-40 Ah for the U1 size. Many articles warn against the usage in a "deep cycle"
application so I limited the discharge to 12.2 volts or about 50% of total
capacity (Battery University) but
it looks like 12.06 may be more reasonable as shown by
WindSun.
State of Charge (SoC)
| Open Circuit (V) |
State-of-Charge (%) |
| 12.65 |
100 |
| 12.45 |
75 |
| 12.24 |
50 |
| 12.06 |
25 |
|
11.89 or less |
Discharged |
|
Courtesy of
BatteryUniversity.com |
State of Charge (SoC)
| Open Circuit (V) |
State-of-Charge (%) |
| 12.7 |
100 |
| 12.5 |
90 |
| 12.42 |
80 |
| 12.32 |
70 |
| 12.20 |
60 |
| 12.06 |
50 |
| 11.9 |
40 |
| 11.75 |
30 |
| 11.58 |
20 |
| 11.31 |
10 |
| 10.5 |
Discharged |
|
Courtesy of
WindSun.com |
Windsun.com also has a nice chart for battery capacity:
|
U1 |
34 to 40 Amp hours |
12 volts |
|
Group 24 |
70-85 Amp hours |
12 volts |
|
Group 27 |
85-105 Amp hours |
12 volts |
|
Group 31 |
95-125 Amp hours |
12 volts |
|
4-D |
180-215 Amp hours |
12 volts |
|
8-D |
225-255 Amp hours |
12 volts |
|
Golf Cart & T-105 |
180 to 225 Amp hours |
6 volts |
|
L-16, L16HC etc. |
340 to 415 Amp hours |
6 volts |
Anderson PowerPoles on all connections.
Next project - voltage profile of my "marine" battery that is in between a
automotive starting battery and a true deep cycle.
- - -
Links:
http://www.batteryuniversity.com
If you have any questions or comments that could be added to this site
please send them along. I'll post and credit your information.
