Charging Batteries in Series
Charging Batteries in Series
If you want to get the most life out of your battery pack it is important to
maintain them properly. Having the right charger for your pack is only part of the
When you charge batteries in series, you are charging the entire group of them all
at the same time. The charger will stop charging when the entire group reaches a certain
voltage. If the batteries are not each at the same voltage, this means that one battery
is charging higher than the rest, and one is not charging as high as the rest. This will not
give you the most usable capacity out of the pack, and will likely lead to one or more of
the batteries reaching the end of their usable life sooner than necessary.
How to balance your pack
To make sure that all of your batteries are at the same voltage, the easiest way is
to put them all in parallel and charge them all at the same time at the individual battery
voltage. For instance, if you plan on using a 48v pack that is comprised of (4) 12v
batteries, you will initially charge them all at 12v to make sure they are all completely
full. Even better is to put them all into parallel while balance charging making one big 12v
battery. Make sure that your 12v charger is rated for the type of batteries you're
using, like sealed vs. flooded. *Note that a “12v” battery will charge to approx. 14.7v
total, and then float around 13.5v.
After your 4 12v batteries are all topped off, take them out of parallel and wire
them in series. This means you have a fully charged 48v battery pack with each battery
at the same state of charge.
Over time it is good to check your individual batteries with a voltmeter. It's best
to check at the very end of a charge cycle as this will show the biggest difference in
voltage, if there is one. The easiest way to fix a voltage difference is to charge the pack
fully, then bring up the lowest battery with a 12v charger placed on just the lowest
battery. You do not need to disconnect the series connections to do this as long as you
can access just the lowest battery.
Next time you charge, you should
see the batteries are then closer in
voltage at the end of the charge
For a plethora of information
including important safety
information see
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