JLG X20JP - X600AJ Service Manual - Manual (Page 139)

SECTION 3 - CHASSIS & TURNTABLE
3121623 – JLG Lift – 3-115
If one cell goes under a specific voltage level, BMS reduce
the speed or stop completely the machine interrupting the
feed to the internal contactor. The same happens in case
of other voltage problems on the cells or in case of over-
temperature inside the battery pack.
CHARGING PROCESS
BMS controls the charging process too.
Charging operation is critical for the lithium cells, because
from it influence both single charge and life cycle duration
time of the battery pack.
All the cells are charged together because they are con-
nected in series. BMS manages the current that the bat-
tery charger has to send to the cells.
In the beginning of the charge BMS asks always the maxi-
mum current possible, then as soon as one of the cell will
reach 3630 mV, it will reduce the current request.
The BMS can connect every cell to a resistance, so as
soon as one cell reaches the maximum value admitted
(3630 mV), BMS will connect it to its resistance; the result
is that the current coming out from the battery charger is
charging always all the cells, but in the same time the
higher cell will be discharged by its resistance.
As soon as another cell will reach 3630 mV, BMS will con-
nect it to its resistance too; in the end of the charge all the
cells should reach at least a voltage level of approximately
3600 mV and the maximum difference from the highest
and the lowest cell should be 50 mV or less.
The last phase of the charging process is called “balanc-
ing”; during this phase the charger sends intermittent feed
to the pack in order to keep the cells at the same voltage
level.
Maximum current required to the battery charger depends
on the battery pack voltage (48 or 72 Volts) and on the
local network voltage (110 -230 Volt).
For CE marked machines, the maximum current is set at:
25 Amp for 48 Volts battery pack
30 Amp for 72 Volt battery pack
For ANSI marked machines, the maximum current is set
at:
18 Amp for 48 Volts battery pack
13 Amp for 72 Volts battery pack
These values are set in the factory before to ship the
machines.
The difference between CE and ANSI machines is applied
in order to reduce in the ANSI machines the maximum
current required at the network at 15 Amp, that is the max-
imum current available at the standard network plug.
On CE machines the time necessary to charge completely
a battery pack is about 4 hours, however after 2 hours the
level will be already at 80%.
Practically what happen normally is that BMS asks the
maximum current available at the battery charger for two
hours, then at least a cell will reach 3630 mV so BMS will
reduce the charging current.
About the 72 Volt battery pack, the big difference of the
current set from CE to ANSI machines doesn’t means that
on the ANSI the time necessary to charge the battery pack
is 3 times more (30 Amp against 13); in fact if the maxi-
mum current required is lower, probably the cells level will
grow more equable.
The time necessary to reach the balancing phase will be
surely more (4 hours instead of 2), but then the time nec-
essary to balance the cells will be less because they will
be already almost balanced.
Approximately the time necessary to charge a 72 Volts
battery pack on ANSI machine is 6-8 hours.
If during the charging process a cell reaches for some rea-
sons an excessive voltage, the BMS goes in emergency
and it open immediately the internal contactor.
It is possible to work with the machine under charge; in
this condition if the current necessary for the movement is
higher than the max current sent by the battery charger,
the system uses part of the cells power to run the electric
motor.
MEANING OF BMS BOARDS
BMS is composed of a series of boards with the following
functions:
Power board:
Insulation resistance
Other board feed
Control Board:
Management
Software Protection
Prognostic
Communication and Event Logging
Monitoring Boards:
Monitoring
Balancing
Hardware Protection (2nd protection)