Article #4

Understanding the Charging Process

When you press the start button and the charger starts its job, what can you expect over the next hour or so? Well let me give you the basics of the average charge cycle (assuming you are using a smart charger at a 1C charge rate, taking approx. 1 hour).

First, the ramp up…

Many chargers do not immediately jump to the specified charge rate when you start the charge cycle. Instead they ramp up slowly. Some chargers will do this over a minute and others will do it over just a few seconds. Assuming the charger can output the specified charge rate, it should settle pretty closely to this chosen rate and hold steady.

Phase 1/2 - The CC (constant current) phase
Once the charger has settled at the specified amperage it will hold this amperage for the entire phase, approx 45min for a 1C charge. If the charger is set to always balance then it will be working to balance all the cells during this phase. If you look at the individual cell info you should see the cells start off around 3.7-3.8V each (assuming an 80% discharged pack) and slowly raise until one cell, or all cells depending on the settings, is at 4.2V.

Important: The CC phase puts the most strain on your equipment, so this is the time to monitor how everything is handling their respective task. Many chargers will display the input voltage and charger temp, so don’t be afraid to check these numbers to make sure everything is as expected.

Phase 2/2 - The CV (constant voltage) phase
Once the cells get to 4.2V each during the CC phase, the charger will switch to the CV phase and hold the voltage at 4.2V for the remainder of the charge cycle. If your charger is set to CV Balance Only, then it will begin to balance during this phase and bring all the cells up to 4.2V. If you watch the amperage during this phase it should start off at the specified amperage and slowly drop off. The charger will stop the charge when 2 things happen. The first is that all the cells are balanced and second is that the charge amperage has dropped to a predetermined value. This predetermined value is decided by both the charger and the user settings, and can be anywhere from 0.1A to 1A. In other words, when your battery pack reaches this pre-determined voltage cutoff, it will end the charge process.

The beeping phase 🙂
Depending on your charger and user settings, the next phase will very likely be an annoying beeping with the screen displaying charge completed. This marks the completion of the charge cycle.

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Once finished
Here’s a tip: Don’t immediately unplug the pack or press any buttons after the charge cycle has completed. Instead examine the charger’s display and note a few handy pieces of information. This info can include total charge time, mAh replaced and even the pack and cell internal resistances (on some chargers). This is also a good time to make any notes about the pack if you are keeping a battery log (a very good idea)!