OnTheRoadAgain
Solar Enthusiast
- Joined
- Feb 22, 2021
- Messages
- 643
So some of us buy and use MightMax batteries for various purposes.
I just bought some replacement batteries for the various battery backup devices I have in my office and tested at least one of them for capacity.
The battery in question was an ML9-12 common to APC and many computer battery backup devices.
The equipment used was a DL24P 180Watt Dummy Load Capacity Tester. Keep i mind that under real world use, backing up a computer and monitor alone, it would draw about 5 amps. This is important to know because of the advertised rating of 9 amp hours.
RESULTS
Test 1). At 3.00amp load, fully charged and discharged to 10.8volts, and too 1hour and 50 minutes to fully discharge = 5.58 amp hours capacity
Test 2). At 0.45amp load, fully charged and discharged to 10.8volts, and took 20 hours to fully discharge
Interpolating, I would expect about 1 hour of run time at a realistic 5Amp load. Lead acid batteries are often tested at a 20 hour rate.
It seems they are rated according to the industry standard 20 hour rating. Meaning at 0.45amp load, the battery will provide 9Ah over a 20 hour period. (Note: The battery could not even make it to the 20 hour mark at 0.45amps load and fell flat after only 17 hours.)
The problem is, I cant think of any real world scenario where you would only need half an amp of battery backup power.
This battery only provided 7.6Amp Hours at the 20 hour discharge rate. Perhaps it would provide 9Ah at a 30 hour rate?
But then, that's totally unrealistic for the application it is intended.
Conclusion - The battery I received is over rated and lacking in capacity. Hopefully there is a better choice than MightyMax batteries.
I just bought some replacement batteries for the various battery backup devices I have in my office and tested at least one of them for capacity.
The battery in question was an ML9-12 common to APC and many computer battery backup devices.
The equipment used was a DL24P 180Watt Dummy Load Capacity Tester. Keep i mind that under real world use, backing up a computer and monitor alone, it would draw about 5 amps. This is important to know because of the advertised rating of 9 amp hours.
RESULTS
Test 1). At 3.00amp load, fully charged and discharged to 10.8volts, and too 1hour and 50 minutes to fully discharge = 5.58 amp hours capacity
Test 2). At 0.45amp load, fully charged and discharged to 10.8volts, and took 20 hours to fully discharge
Interpolating, I would expect about 1 hour of run time at a realistic 5Amp load. Lead acid batteries are often tested at a 20 hour rate.
It seems they are rated according to the industry standard 20 hour rating. Meaning at 0.45amp load, the battery will provide 9Ah over a 20 hour period. (Note: The battery could not even make it to the 20 hour mark at 0.45amps load and fell flat after only 17 hours.)
The problem is, I cant think of any real world scenario where you would only need half an amp of battery backup power.
This battery only provided 7.6Amp Hours at the 20 hour discharge rate. Perhaps it would provide 9Ah at a 30 hour rate?
But then, that's totally unrealistic for the application it is intended.
Conclusion - The battery I received is over rated and lacking in capacity. Hopefully there is a better choice than MightyMax batteries.
Last edited:
