Preparing the Batteries part 2:

Having rescued the most discharged batteries using parallel charging, it is time to prepare the bulk of the batteries to be assembled as a pack. The goal is to have all the batteries fully charged before assembling them as a 385 volt pack. This way, when we start cycling them (discharge and charging them), all start equally charged.

Since parallel charging six at a time for 48 hours will take a while, we start sorting the batteries of about equal state of charge (based on resting voltage) and charging them as 24 volt series. With 180 batteries, it is easy to find 12 batteries within a couple of hundreds of a volt of each other.

Each battery is labeled using a permanent marker and then connected using the battery connectors we fabricated November 11. Our 24 Volt charger allows 3 strings to be charged in parallel, which is 36 batteries at once.

Each Batteries history including resting voltage, time spent charging, final voltage are recorded in an Excel spreadsheet.

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