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BATTERY
MONITOR BM-1
Compact
NASA
BM-1
Compact
V&A
TIME
%
100%
h
80
60
40
TIME TO DISCHARGE, hours
DESIGNED AND
MANUFACTURED
IN ENGLAND
RoHS
2002/95/EC
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READ THIS FIRST
INTRODUCTION
INSTALLING THE DISPLAY
SAFETY NOTES - IMPORTANT
INSTALLATION OF THE DISPLAY UNIT
NORMAL OPERATION
SWITCHING THE BACKLIGHT
SHOWING THE TIME TO GO
SHOWING THE VOLTAGE AND CURRENT
SETTING UP
SETTING THE BATTERY CAPACITY
SETTING THE ZERO-CURRENT
BATTERY MANAGEMENT BASICS
QUESTIONS AND ANSWERS
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READ THIS FIRST!
Before installing the BM-1 Compact,
CAREFULLY READ THE FOLLOWING INSTRUCTIONS,
ESPECIALLY THE SAFETY NOTES AND WARRANTY CONDITIONS.
INTRODUCTION
The NASA BM-1 Compact is supplied complete with display unit,
current shunt (standard 50mV), and connecting cables. It is
intended for operation on 12V Lead-Acid batteries with capacities
between 5 and 600 Ampere-hours (Ah). Its own current consumption
is less than 1.5mA, which is about 1 Ah per month, less than the selfdischarge rate of most Lead-Acid batteries.
The NASA BM-1 Compact monitors the battery voltage, the current
into and out of the battery, and predicts the time to achieve full charge
(during charging) or the time to full discharge (during discharging).
A visual indication of the state of the battery charge is always available,
and an alarm is used as an alert when the battery voltage falls to a
preset level.
INSTALLING THE DISPLAY
Safety notes - IMPORTANT
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 douse 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
installing any of the BM-1 Compact units, 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.
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INSTALLATION OF THE DISPLAY UNIT
The installation should be performed in the order specified
in the following sections.
Select a convenient position for the display. The area
should be flat and remain dry at all times.
Drill two 2mm holes to accommodate the stainless steel
self-tapping screws supplied. If desired, also drill a 5mm
hole to allow the cable to pass through the panel. Alternatively,
the cable can be folded so as to exit the unit vertically against
the panel face.
Screw the unit to the panel and connect the wires to the
terminal block provided. Connect the shunt cable to the
display unit as shown on Figure 1, above, using the terminal
block supplied. 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
instrument end of the cable.
It is good practice to run the cables vertically downwards from
the unit, even if they later have to rise to connect to the vessel's
supplies. Doing so prevents any water that might get onto the
cables from running back along the cables and into the unit.
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Original
Cables
RED
RED
RED
BLACK
BLACK *
BLACK
WHITE
WHITE
Cables
supplied
Original
cables
WHITE *
YELLOW YELLOW
YELLOW
BATTERY
-
-
+
+
SHUNT
FUSE
* Black & White
MUS T NO T be
joine d a t thi s end.
Cable Supplied
BM-1
Compact
V&A
TIME
Figure 1 - Wiring Installation
5.
4
TO LOADS
AND CHARGERS
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Ensure that all loads and generators are switched off
Disconnect the NEGATIVE terminal from the battery and
connect it to the shunt as shown in Figure 1.
Connect the Black and White wires and Yellow wire
to the shunt as shown on Figure 1.
Connect the short link cable to the shunt and then to the
negative terminal of the battery, as shown on Figure 1.
Ensure it 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 TO AVOID OVER-TIGHTENING THE
CONNECTIONS TO THE SHUNT..
Finally, connect the red wire to the POSITIVE terminal of the
battery to complete the electrical installation. The BM-1 Compact
will now begin assessing the battery state, using its factory
default values. The default values must be set to the values
appropriate to the new installation as discussed in
SETTING UP, below.
Do NOT put the battery on charge immediately.
Apply a load to the battery by switching on lights or instruments
and wait for a few minutes for the BM-1 Compact to “learn”
the battery's characteristics and to show a steady reading
before starting charging.
It is necessary to set the battery capacity to the correct value,
and may be necessary to calibrate the zero current setting,
as described in SETTING UP, below.
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NORMAL OPERATION
The BM-1 Compact offers two normal modes of operation:
Time to go.
Volts and Amps;
The battery charge state is always displayed on the scale on the right
of the display. If the battery voltage falls below the preset alarm level
representing dangerous discharge, the alarm bell symbol is flashed.
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SWITCHING THE BACKLIGHT
Pressing either key switches the backlight on for approximately
two minutes, after which it switches off to reduce the battery discharge.
SHOWING THE TIME TO GO.
BM-1
Compact
V&A
TIME
%
100%
h
80
60
40
TIME TO DISCHARGE, hours
Figure 2 - Percentage & Time to Go
Figure 2 shows the display when the TIME key is pressed.
The remaining battery capacity in digits as a percentage
and analogue “thermometer” displays, and the up-to-date estimate
of how long it will take to charge or discharge the battery fully, are
shown. If the current changes, the estimate of the time updates
continuously, reflecting the best estimate of time to be fully charged
or fully discharged. Times in excess of 199 hours are shown as 199 hr.
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SHOWING THE VOLTAGE AND CURRENT
BM-1
Compact
V&A
TIME
100%
A
80
60
40
DISCHARGE
V
Figure 3 - Voltage and Current
Figure 3 shows the display when the V&A key is pressed. The
present battery voltage and battery current, as well as the
estimate of the state of the battery's charge are shown.
The maximum current measurement is 102 Amps.
If the BM-1 Compact is left for long periods registering little or
no charge or discharge current, the estimate of capacity may
become unreliable. It is important to switch some load onto the
battery for a few minutes so a reliable estimate can be calculated,
and its value settles, before starting charging.
SETTING UP
Setting up can be done after applying power to the unit while one
of the keys is pressed. This procedure prevents inadvertent changes
being made by an unfamiliar user. Applying power is usually most
easily achieved by removing the fuse for a few seconds, and then
re-inserting it. When the setting is finished, removing the power
again returns the unit to normal operation when power is re-applied
with no key pressed.
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SETTING THE BATTERY CAPACITY
Turn off the unit.
With the V&A key pressed, re-apply the power.
Release the key. CAP is briefly displayed to show that the capacity
is to be changed.
The TIME key increases the setting, and the V&A key reduces it.
Keyboard repeat allows quick changes if the keys are kept pressed.
The maximum capacity is 600 A-hr, and the minimum is 5 A-hr.
When the correct value has been set, turn off the power to the unit
to save the setting.
Turn the power back on for normal operation.
SETTING THE ZERO-CURRENT
If no current is flowing into or out of the battery, and yet a small
residual current is shown on the display, the reading can be
adjusted to zero.
Ensure that no current is flowing into or out of the battery.
Turn off the unit.
With the TIME key pressed, re-apply the power.
Release the key. SET A is briefly displayed to show that the
zero current is to be changed. The TIME key increases the
setting, and the V&A key reduces it
Adjust the setting until the value is shown as zero discharge.
(Note: several presses of the key are needed to change the
setting by 0.1).
When the correct value has been set, turn off the power to
the unit to save the setting.
Turn the power back on for normal operation.
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BATTERY MANAGEMENT BASICS
After Voltage and Current, the most useful measurement available
from a battery condition monitor is the state 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 Ah, then
the 20-hour rate for that battery is 5 Amps (because 100/20 = 5).
Likewise, a 40 Ah 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 100Ah
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 BM-1 Compact makes due allowance for these effects
when estimating the battery's state of charge and the expected time
to discharge the battery fully.
When the battery is being charged, the voltage is no longer a reliable
estimate of the state of charge, and so the BM-1 Compact 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.
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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 BM-1 Compact has an alarm which flashes the bell symbol
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 BM-1 Compact
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.
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Why is the screen of my BM-1 Compact blank?
Check the wiring is correct and securely terminated.
Check the fuse, and check that the battery is not completely flat.
Why does my BM-1 Compact show that the number of hours
remaining is high or low when a constant discharge
current is flowing?.
The actual battery capacity is different from the value you have
entered in Engineering. The reasons for this difference have
been discussed above. Adjust the battery capacity in
Engineering to match the battery.
My battery is made up of a bank of several batteries.
Is that a problem?
Not as long as the combination produces a nominal 12 volts,
and all the current drawn from the bank passes through the shunt.
Can the BM-1 Compact monitor my engine starting battery as
well as my service battery?
No, it cannot. The service battery is in continuous use, and so
needs continuous monitoring. The starter battery, however, is
subject only to periodic heavy loads followed by float charging,
and so does not need to be monitored.
I have another voltmeter on my vehicle which shows a different
value to the BM-1 Compact indication.
The BM-1 Compact very accurately measures the voltage
directly across the battery terminals. Other voltmeters may
read differently owing to volt drops in the wiring.
Why does my BM-1 Compact show a higher capacity
immediately after charging than it does after a few minutes'
discharging?
This is an unavoidable feature of battery chemistry, which
varies from battery to battery, and the charging regime used.
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Q
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Q
A
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A
Q
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Q
A
QUESTIONS AND ANSWERS
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Do I need to disconnect my BM-1 Compact when I leave the
vehicle for long periods?
No. The BM-1 Compact is designed to be permanently
connected to the battery. It is independently fused, and draws
only 1.5mA from the battery. At such a low current, it would
take several years to discharge a typical fully-charged
service battery.
Why does my battery seem to have less capacity than it says
on its label?
The value on the manufacturer's label is seldom the value
achieved in service, because of the deterioration of the cells'
plates and many other factors. If it seems to have much lower
than its expected capacity, it may need replacement, or you may
feel that changing the nominal capacity from the Engineering
mode will suffice to let you know well enough the percentage
charge remaining.
When on heavy load, the time to run is lower than I expect.
Is this correct?
YES. When heavily loaded, a lead-acid battery delivers less
energy than expected owing to electrolyte exhaustion and
stagnation. When the battery is delivering heavy currents the
BM-1 Compact uses Peukert's equation to allow for these
effects and so show a better estimate for the time to run.
I have a 500W appliance. How do I know what current it
will draw?
Divide the power rating by the nominal supply voltage to find
the current. So, for example, your 500W appliance will draw
500W/12V Amps from a nominal 12V battery: i.e. about 42Amps
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Declaration of Conformity
NASA Marine Ltd declare this product is in compliance with the essential requirements of
R&TTE directive 1995/5/EC.
The original Declaration of Conformity certificate can be requested at info@nasamarine.com
THIS PRODUCT IS INTENDED FOR USE ONLY ON NON SOLAS VESSELS
IMPORTANT READ THIS BEFORE
UNPACKING INSTRUMENT
LIMITED WARRANTY
Prior to unpacking this instrument read and fully understand the installation instructions.
Only proceed with the installation if you are competent to do so. Nasa Marine Ltd. will
not accept any responsibility for injury or damage caused by, during or as a result of
the installation of this product. Any piece of equipment can fail due to a number of
causes. Do not install this equipment if it is the only source of information and its failure
could result in injury or death. Instead return the instrument to your retailer for full credit.
Remember this equipment is an aid to navigation and not a substitute for proper
seamanship. This instrument is used at your own risk, use it prudently and check its
operation from time to time against other data. Inspect the installation from time to time
and seek advice if any part thereof is not fully seaworthy.
Nasa Marine Ltd. warrants this instrument to be substantially free of defects in both
materials and workmanship for a period of one year from the date of purchase.
Nasa Marine Ltd. will at its discretion repair or replace any components which fail in
normal use within the warranty period. Such repairs or replacements will be made at
no charge to the customer for parts and labour. The customer is however responsible
for transport costs. This warranty excludes failures resulting from abuse, misuse,
accident or unauthorised modifications or repairs. In no event shall Nasa Marine Ltd.
be liable for incidental, special, indirect or consequential damages, whether resulting
from the use, misuse, the inability to correctly use the instrument or from defects in
the instrument. If any of the above terms are unacceptable to you then return the
instrument unopened and unused to your retailer for full credit.
Name
Address
Dealer Name
Address
Date of Purchase
Proof of purchase may be required for warranty claims.
Nasa Marine Ltd.
Boulton Road, Stevenage, Herts SG1 4QG England
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