When four of the 5 LEDs light up, this indicates that the battery in that bay is charged to approximately 80%. The user can then take the battery out of the bay for use and doesn’t have to wait for the top off cycle to finish.
I interpreted this to mean that, with multiple batteries on the charger, you need to watch for the LEDs to indicate 80% charge capacity, which is the approximate cut-off where fast charging switches off to slow top-off charging.
Fast-charging to 80% and then a slow top-off charge seems like a convenience.
Then, a reader suggested that we got it wrong – Bosch’s charger worked much differently than the impression we were given.
We asked Bosch for clarification, asking more specific questions about how the charger works. This is what they said:
The charger will finish the first cycle of charging at 80% and move counter clockwise to the next battery until each battery on the charger has reached 80%.
The charger will then circle back around and top off each battery to 100% for a second cycle of charging.
The LED indicators are necessary as they show the current status of each battery. This feature allows the user to visually see what stage of the charging phase each battery is in. For example, 1 light indicates 20% charge, 2 lights indicates 40% and so on.
What if you need to recharge several batteries, and you want one particular battery charged to 100%? I guess you could charge one battery and then connect the others to the charger, or maybe find a second charger for that lone battery. Or, if you want long enough, all of the batteries should charge to 100%.
I still think this could have been an opportunity for Bosch’s “Connected” system, but that probably would have just driven up the cost for the benefit of few users.
Charging all batteries to 80% and then all to 100% seems like a convenient feature, and helps to make up for this being a sequential charger. As a sequential charger, it can only charge one battery at a time.
This is a nice touch, that in my opinion makes the charger quite a bit more appealing.