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8.8.2 Sequential Charging Strategies
Although up to four dispensers can be connected to one charger, only one dispenser can actively
charge an EV. If there are more than one EV plugged into the dispensers, the EVs will be placed in a
queue to wait for their turns to be charged. The following rules are followed when processing the
order of the queue:
1.
Bulk charging takes precedence over trickle charging.
An EV that needs bulk charging will always take precedence over an EV that needs trickle charging.
This will ensure that all EVs are sufficiently charged in the fastest time possible. When a bulk charge
EV with a battery that is below 85% SoC is connected to a dispenser, it will be placed in the queue
ahead of all the EVs waiting for trickle charging. If there is an active dispenser that is trickle charging
an EV, then that active charging process will be terminated and the bulk charging for the incoming EV
will be started. This is illustrated in the following example (see Table 8.1 – Sequential charging
example for three dispensers below).
2.
All EVs are assigned equal duration of time for trickle charging.
The charging current decreases as the battery approaches full SoC. The trickle charging process takes
significantly longer to get to full SoC as compared to bulk charging. It is not practical to wait for one
EV to complete a trickle charge to full SoC before moving on to the next EV. Instead, every charger is
allocated a fixed amount of time in trickle charging.
3.
Trickle charging takes place continuously to "top off" the EV batteries.
A fully charged EV can still drain battery through auxiliary circuits. As a result, an EV battery needs to
be topped off continuously. The EV triggers a charging request through the CP relay continuously at
fixed time intervals. If the battery is fully charged, the EV will cut the current demand to only maintain
the battery auxiliary circuit running to avoid overcharging.
SICHARGE UC uses state B1 to indicate that the EVSE is not ready to supply energy by not turning on
the oscillator.
State B1 is used by the EVSE to maintain the current charge session during sequential charging; in
other words, it is used to keep the vehicle in the queue. This state may last for an extended period of
time.
The vehicle may enter a sleep mode during this state and wake upon detection of the EVSE turning on
the oscillator and entering state B2.
The EVSE will stay in state B1 until the time to allow charge, and then move to B2. The vehicle would
initially wake up, see state B1, time out, and go to sleep until B2 is obtained, where it would wake up
and then move to state C to allow charge.
The EVSE triggers a new charging session in trickle charging using the BEB toggle. It is required for the
vehicle to be able to start a new charging session by detecting a B1/B2 transition on the CP line only
without PP connection status change.
Installation and Operations Manual | SICHARGE UC 150 UL Plug-in Dispenser
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