I was reading a post in the RV-10 section and need to provide some correction to that post.
I've been dealing with large, grid-scale batteries for a very long time and have currently just installed a 200MWh Lithium chemistry based battery in the California grid; I assure you, that if that battery did not meet the discharge specs, I would not have signed off on the final test.
I'm not sure where the poster got the "PB equivalent" ratings from, but they are not in the National Electric Code, nor does it jive with either IEEE consensus on battery discharge rate nor the manufacturer specs for the batteries I've dealt with, which are many. There are suspect manufacturers that use a phony "pBeq rating", but it's just that, a made up rating to justify a poor quality battery performance.
In order to have an 18Ah rating, a battery must be able to discharge at 18A for one hour without dropping below minimum voltage. I pulled up EarthX's discharge curve for my battery, an ETX900 (attached below), to provide a reference.
The linked post states, "My 18Ah SLA battery will only give me about 10-11 amps for an hour and a PB equivilancy is 1/3 of that." This is a good example of a failed battery. Amp-hour ratings are based regardless of the battery chemistry. Note that if the battery does not pass the annual test, the battery is failed and should be replaced.
Test your batteries annually folks...if you don't have a manual for your battery, I've provided a good test to use below that mirrors most reputable battery vendor tests.
This is an excerpt from EarthX's manual 2020 edition designated 111017_Y
Battery Inspection and Testing
The ETX hundred series battery is a maintenance free battery. Charging is only required as needed (see charging section in this manual). Inspection or testing is not needed for 24 months after purchase, and thereafter the following is recommended annually:
• Visually inspect the battery for signs of damage; plastic case is warped or swollen.
• Test the fault indicator: to test, touch the fault wire output of the battery to ground –
the internal battery LED should on as well as the cockpit indicator.
• Ensure the terminal screws are tight (properly torqued)
For electrically dependent aircraft the following annual battery capacity testis recommended: To test the battery capacity (should be done at near room temperature, 23DegC):
a. Fully charge the battery with an appropriate charger
b. Turn on all electrical loads for flight operation and start a timer.
c. Measure and record the battery’s discharge amps using a DC clamp-on
current meter at the positive terminal of the battery.
d. Using the measured amps in the previous step and the battery’s nameplate
rated capacity (in Ah), calculate the time to discharge the battery to 80%. Time to discharge 80% (Hours) = ���������� ���������������� ���� ��h ∗ .8
For Example (16 Ah Rated Capacity, 5 amp measured discharge rate) Time to discharge 80% = 16 ∗ .8= 2.56 hours
5
31
���������������� ��������h�������� ��������
ETX SERIES LITHIUM BATTERIES
e. Terminate the test after the number of hours calculated in the previous step has expired or if the battery is over-discharged (shuts off discharge current). If the battery is still supplying power at the termination of the test, then the battery’s capacity is greater than 80%. If the battery’s capacity is greater than 80% of it rated or capable of supporting the aircraft’s emergency load for the required amount of time, then the battery has passed the test.
f. Fully charge the battery with an appropriate charger.
I've been dealing with large, grid-scale batteries for a very long time and have currently just installed a 200MWh Lithium chemistry based battery in the California grid; I assure you, that if that battery did not meet the discharge specs, I would not have signed off on the final test.
I'm not sure where the poster got the "PB equivalent" ratings from, but they are not in the National Electric Code, nor does it jive with either IEEE consensus on battery discharge rate nor the manufacturer specs for the batteries I've dealt with, which are many. There are suspect manufacturers that use a phony "pBeq rating", but it's just that, a made up rating to justify a poor quality battery performance.
In order to have an 18Ah rating, a battery must be able to discharge at 18A for one hour without dropping below minimum voltage. I pulled up EarthX's discharge curve for my battery, an ETX900 (attached below), to provide a reference.
The linked post states, "My 18Ah SLA battery will only give me about 10-11 amps for an hour and a PB equivilancy is 1/3 of that." This is a good example of a failed battery. Amp-hour ratings are based regardless of the battery chemistry. Note that if the battery does not pass the annual test, the battery is failed and should be replaced.
Test your batteries annually folks...if you don't have a manual for your battery, I've provided a good test to use below that mirrors most reputable battery vendor tests.
This is an excerpt from EarthX's manual 2020 edition designated 111017_Y
Battery Inspection and Testing
The ETX hundred series battery is a maintenance free battery. Charging is only required as needed (see charging section in this manual). Inspection or testing is not needed for 24 months after purchase, and thereafter the following is recommended annually:
• Visually inspect the battery for signs of damage; plastic case is warped or swollen.
• Test the fault indicator: to test, touch the fault wire output of the battery to ground –
the internal battery LED should on as well as the cockpit indicator.
• Ensure the terminal screws are tight (properly torqued)
For electrically dependent aircraft the following annual battery capacity testis recommended: To test the battery capacity (should be done at near room temperature, 23DegC):
a. Fully charge the battery with an appropriate charger
b. Turn on all electrical loads for flight operation and start a timer.
c. Measure and record the battery’s discharge amps using a DC clamp-on
current meter at the positive terminal of the battery.
d. Using the measured amps in the previous step and the battery’s nameplate
rated capacity (in Ah), calculate the time to discharge the battery to 80%. Time to discharge 80% (Hours) = ���������� ���������������� ���� ��h ∗ .8
For Example (16 Ah Rated Capacity, 5 amp measured discharge rate) Time to discharge 80% = 16 ∗ .8= 2.56 hours
5
31
���������������� ��������h�������� ��������
ETX SERIES LITHIUM BATTERIES
e. Terminate the test after the number of hours calculated in the previous step has expired or if the battery is over-discharged (shuts off discharge current). If the battery is still supplying power at the termination of the test, then the battery’s capacity is greater than 80%. If the battery’s capacity is greater than 80% of it rated or capable of supporting the aircraft’s emergency load for the required amount of time, then the battery has passed the test.
f. Fully charge the battery with an appropriate charger.
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