Freedom Won eTower User manual

Installation Manual
eTower
Lithium Iron Phosphate Battery Modules
Manufactured By Freedom Won (Pty) Ltd
Kimbult Industrial Park, Unit C3 & C4
9 Zeiss Road
Laser Park, Honeydew
2040
South Africa
www.freedomwon.co.za
Technical and Installation Assistance – Contact:
Please contact your Freedom Won Distributor or Reseller Installer for technical and installation
support. A directory of Distributors and Reseller Installers is available at www.freedomwon.co.za.
For advanced support please contact suppo[email protected]o.za.
Update Record:
Revision
Number
Update Summary
Updated By
Date of Issue
0
First Release
Antony English
01 October 2021

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Thank you for choosing eTower for your energy storage needs. Freedom Won is a leading
high-quality brand and we pride ourselves in customer satisfaction and great service. We
hope that you find this manual helpful and complete, but please do reach out to us if you
have any additional requirements or queries.
1. Introduction
This manual is intended to assist an installer with the installation and commissioning of the
eTower lithium iron phosphate (LiFePO4) energy storage modules. This document is not
intended to provide detailed information of the inner workings of eTower that is not
relevant to a person that is performing the installation and final commissioning.
Supplementary information relating to programming of the built-in battery management
system for non-standard inverter interfaces is available to approved integrators directly
from Freedom Won.
This manual does not attempt to cover all the details pertaining to the setup of third-party
equipment in relation to the interface and necessary functionality to work with the eTower.
Freedom Won however is available at the contact details on page one to provide direct
support that specifically relates to the battery interfacing with supported third-party
inverter brands.
2. Product Description
The eTower range presently includes only the e5000 module, which has been designed
specifically for enabling small economical storage solutions that can be upgraded
conveniently and cost effectively over time.
The product includes all accessories required to enable fast and convenient installation.
Although rack mounting is possible, the modules are primarily designed for easy stacking
into a tower through the inclusion of a plastic moulded pedestal that is placed underneath
each module in the tower. Further convenience is offered through the inclusion of the
required communication and power cables along with module connecting busbars.
The eTower is designed primarily for systems that need to start with 5kWh initially with a
view to growing the storage capacity over time in 5kWh increments up to 20kWh.
For designs that require 10kWh or more initially the Freedom LiTE Home and Business range
may be a preferred solution depending on customer preferences and needs.
Freedom Won offers the following ranges in the LiFePO4 technology:
1. Lite 12V
2. eTower
3. Lite Home and Business
4. Lite HV Home and Business
5. Lite Marine
6. Lite Mobility (golf carts, forklifts etc)
7. Lite Commercial (including Lite Commercial 52V, HV, and HV+)

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8. Lite Industrial
This manual covers only the eTower. Please refer to the manuals specific to the other ranges
for help with those models.
The eTower voltage is 52V nominal (to suit so called “48V” systems). This higher nominal
voltage of 52V (compared to 48V nominal batteries) offers superior performance and
efficiency owing to lower DC currents in the battery and in the inverter.
2.1 External Features Summary
An image with numbered labels is provided in Figure 2.1 and described below. Additional
detail is provided in Section 2.2.
Tabulation Descriptions from Figure 2.1:
1. Fixing threads for 19” rack mount brackets if required
2. Carrying handles
3. State of Charge (SoC) capacity indication LED’s
4. Run indication
5. Warning LED
6. Address dip switches
7. RS232 Interface RJ11 plug
8. RS485 dual interface inter module communication bus RJ45plugs
9. Digital Output Dry Contacts (DCT)
10. Reset Button
11. Positive Terminal
12. Negative Terminal
13. Circuit Breaker
14. Inverter RS485 Interface RJ45 plug
15. Inverter CAN Bus Interface RJ45 plug
16. On/Off indication LED
17. Plastic Pedestal
18. CAN Bus Communication Cable
19. DC power cables
20. Earthing Point

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Figure 2.1 Labelled Image of the eTower with four modules stacked together (Labelling
corresponds with the text)
2.2 External Features Detailed Information
Below provides more detailed information pertaining to the external features listed in 2.1
above.
2.2.1 19” Rack Bracket Fixing Points
The eTower modules can be installed into a standard 19” rack. There are three fixing
threads on each side of the module near the front, as indicated, that match the 19” rack
mount brackets available from Freedom Won on request. The primary installation
arrangement is intended to be stacking the modules into a tower using the inter-module
pedestal, but for applications requiring 19” rack mounting the required brackets can be
installed in minutes. Please specify how many of these brackets are required when ordering
eTower.
2.2.2 Carrying handles
Two carrying handles are fitted to the front face of each module to ensure easy and safe
handling and lifting onto the pedestal. Freedom Won recommends two people for stacking
the eTower modules.

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2.2.3 State of Charge Indication
The State of Charge (SoC) of the battery is indicated by six green LED’s as a percentage of the
module’s maximum energy storage value in kWh. These LED’s are numbered one to six where
number one is the LED positioned furthest to the right and number six is the furthest to the left. The
LED indicating the present top SoC range flashes when the battery is receiving charge current. The
SoC level allocation to each LED illumination combination is provided in table 2.2 below.
Table 2.2 State of Charge (SoC) Indicator Capacity Matrix under Discharging/Inactive and Charging
states
Capacity
Status
LED Capacity Indicator
Discharging or Inactive (no current flow)
Charging
●
●
●
●
●
●
●
●
●
●
●
●
LED1
LED2
LED3
LED4
LED5
LED6
LED1
LED2
LED3
LED4
LED5
LED6
0~16.
6%
Light
on
Light
off
Light
off
Light
off
Light
off
Light
off Flash
Light
off
Light
off
Light
off
Light
off
Light
off
16.6~
33.2%
Light
on
Light
on
Light
off
Light
off
Light
off
Light
off
Light
on Flash
Light
off
Light
off
Light
off
Light
off
33.2~
49.8%
Light
on
Light
on
Light
on
Light
off
Light
off
Light
off
Light
on
Light
on Flash
Light
off
Light
off
Light
off
49.8~
66.4%
Light
on
Light
on
Light
on
Light
on
Light
off
Light
off
Light
on
Light
on
Light
on Flash
Light
off
Light
off
66.4~
83.0%
Light
on
Light
on
Light
on
Light
on
Light
on
Light
off
Light
on
Light
on
Light
on
Light
on Flash
Light
off
83.0~
100%
Light
on
Light
on
Light
on
Light
on
Light
on
Light
on
Light
on
Light
on
Light
on
Light
on
Light
on Flash
2.2.4 Run Indication LED
The green “run” LED is illuminated whenever the battery is in a running or ready state, i.e. when the
BMS is on and there are no faults.
2.2.5 Warning LED
The red “Warning” LED illuminates if there is an active alarm or fault. The LED is otherwise
not illuminated. If this LED comes on there is likely a cell over voltage fault if the battery is at
100% SoC at the time. If the battery is at a low SoC the warning will most likely relate to a
low SoC alarm (SoC below 10%) or a low cell voltage alarm, which would normally only occur
below 10% SoC anyway.
2.2.6 Address Dip Switches Block
The block with four binary dip switches must be set to a specific configuration that allocates
the address of the eTower module. Each module must have its own address beginning with

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one and counting consecutively upwards. The module that has the communication cable
connected to the inverter must always be set with address 01. To simplify the setup, set the
top module to address 01 and connect this module’s external communication CAN or RS485
port to the inverter, then increase consecutively through the addresses for each successive
module below the top one. The dip switch numbering and on/off positions are illustrated in
Figure 2.2 and follows a normal binary sequence where the least significant bit is on the far
left.
Figure 2.2 Dip Switch Numbering and On/Off Positions
The dip switch settings for each module according to its address are to be set as shown in
Table 2.2. For a system without the ability to interface between the battery and the
inverter, all dip switches must be left switched off.
Table 2.2 Dip Switch Positions for Address Numbers 1 to 15.
Note that is it important to set these dip switches correctly to ensure proper
communication and system operation!
Although the eTower communication protocol can accommodate up to 15 modules, the
recommended limit is four modules per system because systems that require more than
20kWh are usually better accommodated by the Freedom Won LiTE range of high-
performance batteries.
2.2.7 RS232 Interface RJ11 Plug
This RS232 interface RJ11 plug port is used only for connecting a PC to the battery for
firmware updates, settings updates, real time battery data monitoring, and troubleshooting.
These functions are reserved for Freedom Won technicians or authorised service centres.

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2.2.8 RS485 dual interface inter-module communication bus RJ45
plugs
This RS485 bus is used to link the communications of all parallel connected modules in the
tower so that relevant data can be received by Address Number 01 Module (Module 01),
which is in turn relayed from Module 01 to the inverter over CAN Bus or RS485. There are
two ports on each module so that the communication cables can be “daisy chained” across
all the modules. These cables are standard ethernet cables, and one is included with each
module that is made to the exact right length to jump from one module to the next adjacent
module whether mounted on the pedestals or in a 19” rack.
2.2.9 Digital Output Dry Contacts (DCT)
The Digital Output “Dry” Contacts (DCT) include DO1 (pins 1 and 2) and DO2 (pins 3 and 4),
which are normally closed potential free contacts. DO1 opens when the battery has any
type of fault protection enforced. DO2 opens the battery raises a low State of Charge alarm.
Do not exceed 2A though these contacts. If a higher current is required to drive your
external device use an interposing relay that is controlled by the battery and in turn controls
your external device that requires more than 2A.
2.2.10 Reset Button
Reset Button – When the battery is in a dormant state the reset button can be pressed with
a suitably narrow object to “wake up” the BMS. If the battery is in a fault or alarm state, the
reset button may be pressed to clear the alarm or fault to restore normal operation. The
button must be pressed for about five seconds to initiate a reset – while holding the reset
button down, the SoC indicator LED’s should cycle right to left and then left to right. Once
this initial LED sequence begins you can let go of the button.
2.2.11 Positive Terminal
The positive terminal is equipped with two fastening points supplied with M6x16mm bolts
to accommodate interconnecting busbars and cable lugs. Busbars must be staggered to
alternate between left and right terminals when connecting towers of two or more
modules. See Figure 2.3 showing a four-module eTower. The top module is fitted with two
35mm2cables to accommodate the maximum power capability of the battery stack. One
cable lug is fitted onto the same terminal as the busbar and the other cable lug onto the
second terminal.

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Figure 2.3 Four-Module eTower

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2.2.12 Circuit Breaker
Each eTower module is fitted with a 125A DC rated circuit breaker to provide overcurrent
and short circuit protection as well to switch the battery module onto and off the DC bus.
Once the modules are all connected and it is safe to apply power to the DC bus, switch on all
the module circuit breakers in quick succession starting with the top module set at address
01. The SoC and On and Run LED’s should illuminate. The breaker serves as the means to
disconnect the battery from the DC bus. After switching off the breaker and thus
disconnecting the module from an external voltage source such as the inverter, the BMS will
shut itself down after 24 hours of inactivity. There is no way to force off the BMS and nor
would it ever be necessary.
2.2.13 Inverter RS485 Interface RJ45 Plug
This plug is used to connect the battery external control communications to RS485
compatible inverters (see Freedom Won Inverter Interfacing Guide). The eTower is
packaged with a cable suitable for use with the Voltronic range of inverters such as the
Axpert. For assistance with other inverter types running on RS485 communications please
contact Freedom Won.
Although not needed when using the supplied cable, for information, the pin configuration
of this interface plug is as follows:
RS485 Inverter Interface Plug Pin Configuration
RJ45 Plug Pin Numbers
Corresponding Signal Wires
1, 8
RS485-B
2, 7
RS485-A
3, 4, 5, 6
No Connection
2.2.14 Inverter CAN Bus Interface RJ45 Plug
This interface is used to connect to CAN Bus compatible inverters and system controllers.
There are two cable types with differing pin configurations included in each eTower
package, one to suit Victron, and the other to suit what Freedom Won describes as Type 1
CAN Bus inverters. See the Freedom Won Inverter Interfacing Guide for complete details.
Although not needed when using the supplied cables, for information, the pin configuration
of this interface plug is as follows:
CAN Inverter Interface Plug Pin Configuration
RJ45 Plug Pin Numbers
Corresponding Signal Wires
1, 2, 3, 6, 7
No Connection
4
CANH
5
CANL

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2.2.15 On/Off indication LED
On/Off indication LED – This LED is illuminated green whenever the battery management
system (BMS) is active.
2.2.16 Plastic Pedestal
The moulded plastic pedestal is a Freedom Won innovation that allows rapid installation on
site by stacking the modules into a tower using the pedestal as an interface between each
module as well as a convenient stand, upon which to place the bottom module. The
pedestal is designed to structurally withstand the weight of up to six modules placed into a
tower, however in most instances a system that requires this many eTower modules would
be better served by the Freedom Won LiTE Home and Business range of high-performance
batteries.
2.2.17 CAN Bus Communication Cable
In this photo the battery is shown with a CAN Bus cable, which is connected to a CAN Bus
compatible inverter system. This cable is part of the included accessories. See 2.2.14.
2.2.18 DC Power Cables
The power cables supplied with the eTower are 35mm2in cross sectional area. Ensure that
sufficient of these cables are used to match the power of the connected inverters or DC
chargers. The positive cable is red, and the negative cable is black.
2.2.19 Earthing Point
For eTower modules installed into a cabinet this earth point may be used to ground all
module casings to the cabinet ground.
3. Detailed Specifications
Table 2.1 provides an overview of important data pertaining to the eTower e5000 modules.
The table provides data specific to the four configurations i.e. a single e5000 module, two
modules stacked together, three modules stacked together, and four modules stacked
together.
Table 2.1 eTower Specification Sheet (next page)

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The maximum current for each model is governed by the rating of the built-in circuit breaker
and the BMS. There is no noticeable cell temperature rise during operation and no active
cooling of the cells is required. The time limit for operation at the maximum current is 5
minutes in a 30-minute cycle. To ensure that the circuit breaker does not trip in normal
operation and to prevent overloading of the BMS power electronics, it is advised that the
design of the system aims to remain at or below the continuous current value under most
scenarios.
The absolute maximum allowable voltage when fully charged is 56V, however a more typical
inverter charge setting range is 55.5V to 55.8V, depending on the inverter voltage tracking
accuracy in preventing a voltage overshoot above 56V. The voltage normally used when
setting up the inverter for the minimum cut off is 48V, however this will not typically be
reached if operating down to 90% Depth of Discharge (DoD). The BMS will command the
compatible connected inverter with CAN Bus or RS485 interface to stop discharging the
battery at 10% SoC (90% DoD), which roughly equates to 49,0V). Under high load the
voltage may drop to 48V whilst still above 10% SoC. A voltage of 48V or even lower can be
observed in systems without a CAN Bus interface or where the standby current draw on the
inverter has caused the battery to be discharged below 10% SoC. The BMS will eventually
cut off the battery from the DC bus at around 46V to protect the cells from undervoltage.
The dimensions given are for the principal outlines of the aluminium housing and exclude
items that protrude such as the lifting handles and DC terminals.
The eTower modules are primarily designed to stand on the floor on the supplied pedestal
but if space is a problem, they can also be placed on end against a wall with the front panel
facing upwards.

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4. Packaging, Transport, Handling and Mounting
4.1.1 Packaging
The eTower modules are packaged with protective foam and placed inside a cardboard box.
The box is easily handled by two people.
The eTower is available from Freedom Won in singles or per crate, with a crate containing
12 eTower e5000 modules. For storage or transport, the boxes may be stacked four high.
The crates may be stacked two high.
The eTower boxes and crates must be kept dry.
4.1.2 Transport
Although the eTower incorporates the safe LiFePO4 lithium cell design, it is unfortunately
classified along with all lithium batteries as dangerous goods Class 9 Miscellaneous and UN
3480. When shipped by sea the package must be labelled as such using the correct label (Fig
3.1). The eTower box has this label printed on it already, so this is only required if shipped
inside another crate or packaging. The packaging design must also comply with the
dangerous goods regulations, so should always be transported in its original packaging.
For sea freight and road freight the transporter will require the Safety Data Sheet for the
product, which is available from your distributor or from Freedom Won.
Figure 3.1 eTower Dangerous Goods Label for Sea Freight

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4.1.3 Handling
The individual eTower modules require no special handling considerations since the weight
is such that two people can easily carry it in the box. The 12 module crates require a pallet
trolley to move and a forklift for loading and offloading.
The installation of the eTower is easily performed manually by two people.
4.1.4 Mounting
The first eTower module can be placed on the floor or a stand or shelf on its supplied
pedestal, with units stacked on top of it, each sitting on their own pedestal, see Figure 2.3
for an example of a system stacked with four modules. The eTower must be placed on a firm
level surface to ensure that the tower remains stable. The pedestal is designed to
comfortably withstand the weight of six eTower modules. Stacking more in a tower is not
recommended as the tower may become unstable.
Installation into 19” racks is made possible by ordering the angle brackets required from
Freedom Won. The eTower is exactly five standard rack units high (5U). Two brackets are
required per module.
If floor mounting on the pedestal is not suitable for a given application the eTower may also
be installed with the terminals facing upwards, preferably not directly on the floor, but on a
stand or shelf or wall mount bracket. Wall mount brackets are available from Freedom Won
on request, which must be ordered along with the 19” rack mount brackets, because they
are incorporated into the wall mounting system.
Ensure that the eTower is mounted at least 0.5m away from any heat source, and away
from direct sunlight in a dry cool area free of moisture.
5. Environmental Requirements
No specific venting is required since the eTower emits no hazardous gases, however air
circulation may be required to ensure room temperature is maintained at reasonable levels,
preferably below 30˚C (see eTower warranty for information regarding upper temperature
limits for hot environments).
Room heating may be required in cold climates to keep the room above 0˚C, since charging
of the eTower is not permitted below 0˚C. Ambient environments that regularly exceed 35˚C
should employ room cooling if practicable to ensure optimal eTower service life.
Temporary storage or transport of the battery is permitted in the range -20˚C to 45˚C,
however extended storage longer than 60 days should be between 0˚C and 30˚C.
The eTower IP rating is IP20.

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6. Connecting the Freedom Lite
6.1 Power Cables
The eTower is simple to connect and the required accessories are all included in the box.
The supplied tower interconnecting busbars must be connected as illustrated in Figure 2.3,
making sure to put the red on the positive and the black on the negative – observe the +
and – signs near the terminals. The supplied 35mm2cables to connect to the inverter must
be connected to the top eTower module, one cable per pole is required for inverters up to
10kVA, and two per pole for inverters up to 20kVA. The lugs for the eTower end of the DC
cables are already fitted and the terminal bolts are long enough to accommodate both a
busbar and a lug on the same terminal when required. Torque all terminal bolts to 12N.m.
Caution: Prior to connecting any of the positive and negative cables and busbars to the
inverter and eTower modules, be sure to check that the main battery circuit breaker is
switched off on all eTower modules and that the inverter is also switched off. This will
ensure that there are no short circuits between the loose ends of the cables and prevent
the risk of metal tools causing a short circuit.
The DC cable cross sectional area is based on an acceptable voltage drop with the inverter
being mounted on the wall adjacent to the eTower with a maximum cable run of 5m (note
however that the standard cable length is 1,8m, longer cables are available on request or
can be made up by the installer).
Cable runs longer than 5m should be assessed and larger cables. Double Insulation welding
cable is recommended.
The cables may be routed through trunking and connected into the inverter on the positive
and negative terminals respectively. The inverter terminals on most inverters can then be
used for linking up the charge controller(s) to the DC Bus. On Installations where there are
too many inverters and/or charge controllers to connect to the DC bus using the inverter
terminals as a junction point a DC connector box is required.
6.2 Control Cables – Overview
For controlling external devices, you will need to connect the CAN Bus cable or RS485 cable
depending on the inverter, which allows the Battery Management System inside the eTower
to control and interface with these devices. The cables used are CAT5e or CAT6 Ethernet
cables with RJ45 plugs.
Cables are included in the eTower box for most inverter options. See 2.2.13 and 2.2.14 for
details on cable pin configurations should you need to make your own cables. Figure 5.1
provides the pin numbering of the RJ45 connector.

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Fig 5.1 Pin Configuration for standard RJ45 plug
6.3 CAN Bus Control – Detailed Description
CAN is a widely used communication protocol in systems with many devices that must
report their status or send commands to other devices on the same network. The eTower
BMS can transmit messages and commands in CAN protocol to provide information to, but
more importantly to control, external devices. CAN allows great versatility and provides a
simple installation because there are only two wires required in this form of
communication, namely CAN High and CAN Low. In order for an inverter or charge
controller to be controlled by CAN it must first of all be equipped with a CAN interface as
well as a suitable method of connecting the CAN wires. Further to this the eTower BMS
must be programmed with a CAN messaging profile that is developed for the inverter or
charge controller being used. This profile must be specifically developed for each inverter
model or model range. To date Freedom Won has developed CAN profiles for a wide range
of inverters – see the Freedom Won Inverter Interfacing Guide for more information.
Freedom Won welcomes any requests to produce BMS CAN profiles for other inverters that
are CAN equipped for BMS interface.
The CAN interface can provide the following functionality to compatible devices:
i. Charge Current Limit of all Lite’s connected
ii. Discharge Current Limit of all Lite’s connected
iii. Actual State of Charge (minimum of all lights connected)
iv. Actual Battery Temperature (highest of all lights connected)
v. Actual Voltage
vi. Actual Current (total of all Lite’s connected)
vii. Maximum real time charge voltage setpoint
viii. Battery Name
ix. Highest Cell Voltage of all Lite’s connected
x. Lowest Cell Voltage of all Lite’s connected.
xi. Firmware Version
xii. Ah capacity of all batteries connected

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The CAN 2.0 Part A and Part B standard uses the SAE J1939 standard in the eTower. It is
necessary to install a 120 Ohm resistor on each extreme end of the CAN cable (splices or
branch connections do not require a resistor). Most devices operating on CAN have two
plugs to connect an incoming cable in and then outgoing cable on the CAN Bus. The first and
the last device in the chain must have a termination resistor plugged into the spare (second)
plug. These resistor plugs are available from Freedom Won (if you are using Victron then
you can use the Victron supplied resistors). SMA and Victron operate on this basis for
example. The eTower however is designed to always be one of the end-of-line devices, and
hence has only one CAN port, and has a built-in termination resistor.
Ingeteam for example has a separate CAN terminal block for bare wires to be inserted from
the BMS and these units have an internal resistor fitted into the device.
The third-party device manuals must be referenced for all details regarding connecting the
CAN interface.
Most inverter brands use 500kbps BAUD rate and so does the eTower. Systems requiring
250kbps are not compatible with the eTower. Consider using a Freedom LiTE battery
programmed to operate at 250kbps if this BAUD rate must be used.
6.4 Parallel Configurations
It is permissible to connect multiple eTower e5000 modules in parallel. It may however be
more cost effective to purchase one Freedom LiTE model of the applicable size than
connecting multiple eTower units in parallel. The eTower is more intended as a solution
where 5kWh is adequate for the starting point of the system but where future expansion is
planned in multiple phases.
One eTower must be programmed as the Master by setting it to Address 01 (see 2.2.6),
while the rest of the eTower modules connected to the DC bus are programmed as Slaves by
default when they have addresses of 02 or higher. A total of 15 eTower modules can be
connected in parallel, however for this capacity level there are better solutions from the
Freedom LiTE Business and Commercial ranges.
Each eTower module communicates with the master module through an independent
RS485 bus by “daisy chaining” the modules together using standard Ethernet cables with
and RJ45 plugs. Note that these cables are included in the eTower box.
New units can be placed in parallel with old units up to about 5 years or 1 500 cycles, after
which it is preferable to trade in for a new unit(s) should a capacity upgrade be required.
7. Programming the eTower
The eTower firmware and parameter programming is performed only by Freedom Won or
authorised distributors and instruction of such is outside the scope of this manual.

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8. Switching on the eTower
The Lite is fitted with an “ON/OFF” breaker. When this breaker is switched on the DC
terminals of the eTower may immediately become live if the BMS is active. If the BMS is not
active and the eTower detects an external voltage source the BMS will come alive, observed
by the illumination of LED’s on the front panel.
Note: On some inverters there is a large inrush current when switching on the DC supply. It
is important in these instances to pre-charge the DC bus. With Victron this can be achieved
by switching on the PV to the MPPT’s to allow them to apply voltage to the DC bus before
closing the battery breaker. If this option is not available, you can switch on the AC input
power to the Victron inverter as this allows the inverter to place voltage on the DC bus (it
may be necessary to unplug the Ve.Bus cable from the GX device to allow the inverter to
energise). If you are using inverters that cannot do this, you will need to use a pre charge
resistor.
To switch off the DC output from the eTower switch off the breaker. To switch off the power
to the BMS, press the reset button for 3 seconds and release. If this is not done the BMS will
shut down automatically after 24 hours anyway.
9. Settings Required for Setting up Inverters and Charge
Controllers
The maximum and continuous discharge currents for the eTower in configurations of one to
four are provided in Table 2.1. The charge current limit should be observed for the current
limit settings of the inverter(s). The average recommended charge current is one third of
the continuous rating of the battery. This will usually ensure that the combination of the
mains charger and the Solar Charge Controller (SCC) does not exceed the maximum
continuous charge current, although this must be specifically checked.
The voltage settings for the eTower when operating in a system where the BMS can control
the external devices as explained above are as follows:
•Minimum (cut off) – 47V (the Lite should never reach this low voltage but is it good
to have this set as a redundancy protection measure.
•Low Battery Voltage Warning (if applicable, often used to revert to grid power in
increased self-consumption applications because it approximates 30% SoC) – 51V
•Max Charge Voltage – 55,8V (Bulk, Absorption and Float are all set to this value)
If the BMS is not able to control the external devices with remote enable functions, then
the voltages must be set at slightly conservative values. This is to reduce the likelihood that
an outlying cell will reach its voltage limit ahead of the pack, which the external devices
would not be aware of because they can only monitor the total pack voltage. Using a lower
pack voltage to monitor and control charging and a higher voltage for discharge cut off will
allow a greater spread in cell voltage values without any of them reaching their limits.

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The BMS inside the Freedom Lite will deal with an excessive spread of cell voltages by
balancing them out using the cell tap wires attached to each cell and its internal circuitry. If
a cell voltage does reach its limit the BMS will be forced to intervene by internally
disconnecting the cells from the terminals. The breaker will remain ON. Once the problem is
cleared the eTower module may reconnect.
Frequent occurrences of this situation is not desirable so the voltages should be set to the
following to reduce this occurrence to abnormal circumstances:
•Minimum (cut off) – 49V
•Low Battery Voltage Warning (if applicable) – 51V
•Max Charge Voltage – 55.5V
A voltage can also be set according to user requirements on the inverter depending on how
much battery power may be used before grid power will take over from the battery (if it is
available). It should be determined based on how much battery SoC is desired at all times as
a minimum to ensure adequate capacity to handle a grid outage or load shedding. The daily
cycling depth is also a consideration for the user in terms of battery service life.
The recommended voltage for forcing the inverter back to grid power in a self-consumption
setup without communication is:
•52,0V for approximately 60% DoD
•51,0V for approximately 70% DoD
In non-CAN/R485 systems fitted with DC solar charge controllers (SCC) the AC charger
should stop charging at 53.5V to allow the remainder of the charge to be performed by the
SCC.
The SCC voltage set point would be set to 55,8V if BMS control is functional and 55,5V
without BMS control. Note that it may be necessary to use a slightly lower voltage initially if
the cells have not had sufficient balancing time – if the battery trips prior to reaching 55,5V
it is because one cell has reached its maximum too early. Try starting with 54,5V and then
after several days of balancing increasing it to 55,5V.
Note: For applications where voltages are measured during high current discharge it might
be necessary to adjust slightly the values given above to cater for cell internal resistance.
Note: For systems with an interface between the battery and the rest of the system it is
advisable to use SoC for controlling charge and discharge algorithms as this is the only
accurate method – using voltage as described above is only an approximation.