200AH LiFePo4 Battery Test Results
A DIY Electric Car Member, david85, has been testing a 200 Amp-Hour LiFePo4 Battery for a few weeks now and has been keeping a public journal of the results. If you're not familiar with LifePo4, it's a fairly new battery technology that promises greater safety than Lithium Ion or Lithium Polymer while still holding a good energy density and a decent discharge rate. Many new LiFePo4 manufacturers are popping up in China and Japan and prices continue to get lower which is very encouraging for use in EVs. So far the test results are encouraging and while the battery hasn't been tested for a full 1000 amp load, it is apparently up to par with storage capacity. David says that as a general rule, the going rate seems to be about $0.50/ watt hour of capacity which is for the cells only, as in no charger, or BMS (battery management system). Test 1:
Voltage measured with no load at full charge: 13.43V
Voltage under load after
15 min: 13.16V
30 min: 13.14V
45 min: 13.13V
60 min 13.12V
Voltage after test:
5 min: 13.26V
10 min: 13.26V
15 min: 13.28V
Ambient temperature: 10 celsius
Test 2:
15 min: 13.12V
30 min: 13.09V
45 min: 13.08V
60 min: 13.08V
Voltage after test:
5 min: 13.25V
10 min: 13.26V
15 min: 13.26V
Ambient temperature: 7-10 celsius (test started and 7 and ended at 10)
Test 3:
15 min: 13.16V
30 min: 13.14V
45 min: 13.13V
60 min: 13.13V
Voltage after test:
5 min: 13.27V
10 min: 13.28V
15 min: 13.29V
Ambient temperature: 15 celsius (in direct sunlight, so battery was closter to 19)
I also turned the motor on and measured the voltage sag at each of the 5 settings:
no load: 13.43V
Setting 1 (10A): 13.38V
Setting 2 (15A): 13.36V
Setting 3 (25A): 13.3V
Setting 4 (30A): 13.27V
Setting 5 (62A): 13.07V (this setting is fun)
Test 4:
Amp draw reads 28 Amps on setting 4, but could be 30, I need to verify the specs of the motor and see what others are seeing with this motor.
Closed circuit voltage:
1:00 = 13.33 volts <<< I measured a voltage after 1 min to show initial voltage drop
15.00 = 13.04 V
30:00 = 13.03 V
45:00 = 13.02 V
60:00 = 13.02 V <<< I took measurements every 15 minutes only for the first hour to act as a control for previous tests, then every 30 minutes for the remaining 4 hours because I've got other things to do!
1:30:00 = 13.01 V
2:00:00 = 12.99 V
2:30:00 = 12.97 V
3:00:00 = 12.93 V
3:45:00 = 12.92 V <<< sorry, I was late checking the voltage.....(other things....)
4:00:00 = 12.91 V <<< ambient temperature 12.2
4:30:00 = 12.90 V
5:00:00 = 12.88 V
SHUTDOWN.......
Open circuit voltage after load:
5:05:00 = 13.08 V
5:10:00 = 13.10 V
5:15:00 = 13.10 V <<< ambient temperature 11.3
Test 5:
outside temperature: 9 Celsius
Battery open circuit voltage: 13.33 volts
Test begins....
1:00 = 13.11 V
15:00 = 13.05 V
30:00 = 13.04 V
45:00 = 13.03 V
60:00 = 13.03 V
1:30:00 = 13.02 V
2:00:00 = 13.00 V
2:30:00 = 12.96 V
3:00:00 = 12.94 V
3:30:00 = 12.92 V
4:00:00 = 12.91 V <<< outside temperature 11.5
4:30:00 = 12.89 V
5:00:00 = 12.88 V
Shut down....
5:05:00 = 13.10 V
5:10:00 = 13.11 V
5:15:00 = 13.12 V <<< outside temperature 13
Test 6:
Voltage before test: 13.60V
outside temperature: 9.5 celsius
Powersetting: 5 (62+amps)
Test starts:
1:00 - 12.79V
5:00 - 12.69V
10:00 - 12.69V
15:00 - 12.69V
30:00 - 12.68V <<< amp reading now shows 61 amps
Problem found......
There was a loose connection between two of the cells, instead of scrubbing the test I tightened the terminal bolt and carried on. You can see the voltage increace after I tightened the bolt.
36:00 - 12.76V
45:00 - 12.72V
60:00 - 12.70V
1:15:00 - 12.68V
1:30:00 - 12.68V
2:00:00 - 12.63V
2:30:00 - 12.55V
3:00:00 - 12.38V <<< outside temperature 10.5 celsuis
3:15:00 - 12.20V
3:20:00 - 12.07V <<< amp gauge now shows 60 amps
3:25:00 - 11.92V
3:30:00 - 11.72V
3:35:00 - 11.44V <<< I've been told by my contact that the lowest safe voltage is 9.2V
Shut down:
1:00 - 12.20V
5:00 - 12.48V
10:00 - 12.59V
15:00 - 12.63V
Test 7:
Voltage before test: 13.37V
Outside temperature: 9.5
Setting : 60 amps
1:00 - 12.82 V <<<62 Amps
5:00 - 12.78 V <<<61 Amps
10:00 - 12.77 V
15:00 - 12.75 V
30:00 - 12.73 V
45:00 - 12.68 V
60:00 - 12.66 V
1:30:00 - 12.62 V
2:00:00 - 12.50 V
2:30:00 - 11.95 V <<<60 Amps
2:45:00 - 11.08 V <<< 59 Amps
2:50:00 - 10.59 V <<<58 Amps
2:53:00 - 10.30 V <<< 50 Amps....test terminated (outside temp 10.5)
Here is the main testing thread which includes comments, photos and discussion.
Thanks to david85 for keeping a detailed journal of his tests.
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