How to perform a LiFePO4 capacity test?
Not all batteries are created equal and if you want to know how much juice your LiFePO4 battery, or any other battery for that matter, can really produce, read on.
In order to check the battery capacity, you need to fully charge the battery and then exhaust it until it reaches its cut-off voltage. This can be done in two different ways. The batteries are tested at a discharge rate of .2C, which is 20% of the battery capacity. For example, a 100-amp battery is typically discharged at 20 amps per hour (20 Ah) if it is a 100-amp battery.
This has to do with the Peukert effect and it is a bit beyond the scope of this article to explain how LiFePO4 batteries are more durable and can be discharged at a higher C rate without significantly changing the usable capacity.
THE ABILITY TEST LIFEPO4 IN REAL LIFE
In addition to the fact that real-world tests don’t cost anything, you can use just about any known charging source to do them, and they’re pretty reliable, there are several benefits to using them too. If you have an accurate amp rating of the load, they are reliable as long as you know exactly how much current they are drawing in, so you need to make sure you know exactly how many amps your load is drawing in.
In the downside of this test, it’s a fairly simple and enjoyable test, but there are some limitations. Apart from the fact that the battery should remain under close supervision at all times, you should be aware of the exact moment when it stopped producing power for calculations.
It’s very simple to follow these steps once you have this information.
- Fully charge the battery
- Take note of the time
- Use the device until the battery runs out
- Note the time again
Amperes x Time (hours) = Ampere hours, which is the formula used for this calculation
Then you’d be able to get 100 amp-hours (Ah) if you drew 20 amps for five hours, and 2 amps for three hours, so you’d have 7 hours of amps (Ah).
The results of such a test can be greatly affected by a number of factors, such as temperature, wire size, wire length, etc., all of which play a role in the actual results. If you want to know if you’re getting what you paid for and if there’s anything grossly wrong, you should investigate further. Real-world testing is a great way to find out if you’re getting close to what you paid for. They are usually the warm and fuzzy feeling that everything is going according to plan.
THE TEST ON THE BENCH
It’s usually more accurate to measure the number of amp-hours you get from your LiFePO4 battery using a Hall effect meter or a dummy charge capacity tester. These devices give you both the watts and amp-hours provided by the LiFePO4 battery.