Contains BM-1 User manual

DESIGNED AND
MANUFACTURED
IN ENGLAND
RoHS
2002/95/EC
Battery Monitor
BM-1BM-1
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Bluetooth

This device Contains Transmitter Module FCC ID: T9JRN4020
This device complies with Part 15 of the FCC Rules. Operation is subject to the
following two conditions:
(1) this device may not cause harmful interference, and (2) this device must accept
any interference received, including interference that may cause
undesired operation
This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful interference in a residential installation.
This equipment generates, uses and can radiate radio frequency energy, and if not
installed and used in accordance with the instructions, may cause harmful
interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does cause
harmful interference to radio or television reception, which can be determined by
turning the equipment off and on, the user is encouraged to try to correct the
interference by one or more of the following measures:
Reorient or relocate the receiving antenna.
Increase the separation between the equipment and receiver.
Connect the equipment into an outlet on a circuit different from that to which the
receiver is connected.
Consult the dealer or an experienced radio/TV technician for help.
The RN4020 module has been tested to R&TTE Directive 1999/5/EC Essential
Requirements for Health and Safety (Article (3.1(a)), Electromagnetic Compatibility
(EMC) (Article 3.1(b)), and Radio (Article 3.2) and are summarized in Table 3-1:
European Compliance Testing.
A Notified Body Opinion has also been issued. All test reports are available on the
RN4020 product web page at http://www.microchip.com.

Page 1
INTRODUCTION
The NASA BM1(BT) Bluetooth battery monitor is supplied complete
with a 100 Amp 50mV shunt and all necessary cables to connect to
the main service battery. It is intended to monitor a 12 volt lead-acid
battery, or bank of batteries, with a total capacity between 5 and 600
Ampere-hours (Ahr). The current consumption of the device is
typically 2 mA which represents a tiny discharge of less than 1.5 Ahr
per month.
The unit monitors the main battery voltage, the current flowing into or
out of the battery and calculates the best approximation of the state
of charge and the time to charge or discharge. An alarm alerts the
user if the charge gets dangerously low when load shedding or
charging becomes necessary. A second input measures the voltage
on the starter battery. As that battery is not normally under load its
open circuit voltage gives a good indication of its condition.
The information is transmitted using Low Energy Bluetooth (Bluetooth
4) and can be viewed on any compatible device with a suitable App.
An Android App can be freely downloaded from the Nasa Marine
website while a third party more sophisticated Apple App, with
additional features, can be found on the apple App store.
IMPORTANT SAFETY NOTICE
Lead-acid batteries can emit hydrogen when in operation. Hydrogen
and air forms a potentially explosive mixture. Accordingly, ensure that
the area around the batteries is well-ventilated and extinguish all
naked flames and prevent sparks.
Short-circuiting a battery with a metal tool or piece of jewellery can
cause catastrophic currents to flow. Before undertaking any work on
the electrical system remove all jewellery (such as rings or metal
necklaces). Ensure that no metal tool can cause a short circuit.
If you are not sufficiently skilled to undertake any part of this
installation safely, you must seek the assistance of a suitably qualified
person.

Page 2
INSTALLATION OF THE BM1(BT) MONITOR
1. Connect the shunt cable to the monitor as shown on Figure 1.
Be careful to connect the wires exactly as shown, noting that the black
and white wires are joined at the shunt connection, and are connected
separately at the monitor end of the cable.
2. Mount the unit on a convenient bulkhead using the mounting
flanges. Ensure the position you choose remains dry and free from
contaminants at all times. It is good practice to run the cables
vertically downwards from the unit, even if they later have to rise to
connect to the battery. Doing so prevents any water that might get
onto the cables from running back along the cables and into the unit.
3. Ensure that all loads are switched off
4. Disconnect all the wires from the negative terminal of the
battery and connect to the shunt as shown on Figure 1. Ensure the
shunt is positioned where it cannot come into electrical contact with
other parts and ensure it will remain dry and free from contaminants.
Also note that the shunt can get warm when heavy currents flow, so
ensure it is secured in a position where its heat cannot affect other
parts. Take care not to over tighten the connections to the shunt.
5. Connect the Black and White wires and Yellow wire to the
shunt as shown on Figure 1.

Page 3
Original
cables
Figure 1 - Domestic battery only
Cables
supplied
NEGATIVE
TO ALL LOADS
AND GENERATORS
POSITIVE
TO ALL LOADS
AND GENERATORS
No other connection
should be made to
this post
6. Connect the short link cable to the shunt and then to the
negative terminal of the battery. This should be the only connection to
the negative battery terminal.
7. If the starter battery voltage is to be monitored then connect
the orange wire (not supplied) to the positive terminal of the starter
battery as shown in Figure 2. A 1 amp fuse close to the starter battery
will afford protection if a fault occurs.

Page 4
Figure 2 – Domestic and starter batteries
8. Finally connect the red wire to the positive battery terminal.
The red “DATA” LED will now start to flash showing that data being
sent to the bluetooth transmitter.
9. Do NOT put the battery on charge immediately.
10. Apply a load to the battery by switching on lights or
instruments and wait for a few minutes for the monitor to "learn" the
batteries characteristics.

Page 5
INITIALISING AND USING THE BM1(BT) MONITOR
The bluetooth transmitter will now be advertising its presence so
select the Android app on your phone or tablet and press the "scan for
device" icon. After a few seconds the scan will stop and all low energy
bluetooth devices in range will be listed. The default name for the
battery monitor is "BoatName".
Click on the "BoatName" icon to connect with the monitor and display
the main battery's rated capacity, the voltage, the current flowing into
the load, the state of charge and the time to go. The green
"CONNECT" led on the monitor will illuminate to indicate that
connection has been established. Pressing the "starter battery" icon
will display the starter battery voltage for a few seconds before
returning to the service battery characteristics. Press the "settings"
icon to edit the stored information. First select "Amp hour capacity"
and enter the total capacity of your service battery.
(Example: If you have two 110 Ahr batteries wired in parallel then you
would enter 220 Ahr.) The entered capacity must be in the range 5 to
600 Ahr. Now click on "BoatName" and enter the name you want as
your device name. This must be 8 characters long. (Upper and lower
case letters, numbers and spaces can be used). Then select the
typical temperature of the battery.
Finally, when you press the "submit" key the data is made available to
the BM1(BT) monitor. However the monitor will not accept the new
data without confirmation. The red LED on the monitor will flash for 15
seconds. To accept the data you must press the "LOAD DATA" key on
the monitor while the LED is flashing. (This process ensures that a
third party cannot alter data in your battery monitor.)
After accepting new data the bluetooth connection will be terminated.
Now, close the app and wait one minute, when you next open the app
it will open with the new name and the parameters you have selected.
The monitor is intended to be permanently connected to the battery
but, if you should need to turn it off for any reason, then, when re-
starting, it is important that the monitor sees a load of a few amps until
the state of charge settles before putting the battery on charge.

Page 6
The zero current has been set in the factory and should not require
subsequent adjustment. However if a small residual current is
detected which cannot be attributed to a clock, sensor or standby
LED etc. the zero set can be adjusted. Turn sightly clockwise for a
small residual discharge current or anti-clockwise for a residual
charge current. The control has a limited range of just a few hundred
mA.
BATTERY MANAGEMENT BASICS
After Voltage and Current, the most useful measurement available
from a battery condition monitor is the sate of charge of the battery.
However, estimation of the state of charge of lead-acid batteries is
never exact. The problem of making accurate estimates results from
the characteristics of the cells, the electrolyte, and the history of
currents drawn from (discharge) and supplied to (charge) the battery.
The basis for the best capacity estimates is that the starting condition
is known. The only well-established "known" state of a battery is when
it is fully charged after a long period of trickle or float charging,
usually on a shore or regulated alternator-driven charging system.
Discharging a fully charged new battery at a current 1/20 of the
manufacturer's stated capacity will discharge it fully in 20 hours. This
current is known as the "20-hour rate".
So, for example, if a battery has a stated capacity of 100 Ahr, then the
20- hour rate for that battery is 5 Amps (because 100/20 = 5).
Likewise, a 40 Ahr battery would have a 20-hour rate of 2 Amps
(because 40/20 = 2). If higher currents than the 20-hour rate are
drawn from the battery, the available capacity is reduced. For
example, if it is steadily discharged at 10 times the 20-hour rate (50
Amps from a 100 Ahr battery), the available capacity falls to about half
of the stated capacity. The battery will be flat after about 1 hour
instead of the expected 2 hours. (However, if the battery
is left to recover with the heavy load removed, most of its remaining
capacity will return after perhaps 20 hours' resting or at a discharge
rate close to the 20-hour rate.) The BM1 makes due allowance for
these effects when estimating the battery's state of charge and the
expected time to discharge the battery fully.

Page 7
When the battery is being charged, the voltage is no longer a reliable
estimate of the state of charge, and so the BM1 integrates the
Ampere hours added to the last known capacity to estimate the
battery's state of charge on a continuous basis. Allowance for charge
efficiency (not all charging current results in useful charge in the
battery) is also computed. Available battery capacity is significantly
reduced at temperatures significantly below 20C. The value quoted
by the manufacturers is valid at 20C. However, at 0C the capacity may
be only 90%, and at -20C may be only 70% of the 20C value. A small
increase in capacity is achieved at battery temperatures above 20C,
rising to about 105% of the nominal value at 40C. The effects of cell
deterioration on the available capacity are significant. If the battery is
charged for long periods, gassing takes place. The gases are
Hydrogen and Oxygen, derived from the water in the battery acid.
Loss of this water needs to be made up by topping up the cells if
possible, or by avoiding lengthy overcharges in sealed cells. Other
irretrievable effects include sulphation (encouraged by leaving the
battery flat for long periods), and deterioration of the cells' plates. If
the battery voltage falls below 10.7 Volts (for a nominally 12 Volt
battery), and charging is not started, sulphation of the plates can
begin.
The BM1 has an alarm when the voltage falls below 10.7 Volts. If the
alarm is triggered, it is important to reduce the current being drawn
immediately, and if possible place the battery on charge, to avoid
permanent damage to the cells. If the alarm is ignored, the total
number of charge/discharge cycles which the battery will survive
before it loses a substantial fraction of its nominal capacity may be
substantially reduced.
All of these (and other effects) reduce the available charge after fully
charging the battery. If the effects are ignored, the BM1 will incorrectly
estimate that more capacity is available at any state of discharge than
is actually the case. If so, it is wise to alter the nominal capacity stored
in the unit to match the reality of the battery's condition.

Page 8
Q Why is the red LED not flashing?
A Check that the wiring is correct. Check the fuse. Check that there
is 12 volt at the red and black terminals of the monitor.
Q The discharge current reads correctly but the charge current
reads low or zero.
A You have probably still got a heavy cable between the engine
block and the battery negative terminal so the charge current is
bypassing the shunt. Refer to the wiring diagram.
Q Why does my BM1 show that the number of hours remaining is
high or low when a constant discharge current is flowing?.
A The actual battery capacity is different from the value you have
entered in Engineering. Adjust the battery capacity in Engineering to
match the battery.
Q My battery is made up of a bank of several batteries. Is that a
problem?
A Not as long as the combination produces a nominal 12 volts, and
all the current drawn from the bank passes through the shunt.
Q Can the BM1 monitor my engine starting battery as well as my
service battery?
A Yes it can monitor the engine start battery voltage. The open
current voltage of the starter battery can be used to estimate its state
of charge
Q I have another voltmeter on my boat which shows a different
value to the BM1 indication.
A The BM1 very accurately measures the voltage directly across the
battery terminals. Other voltmeters may read differently owing to volt
drops in the boat's wiring.
A