NASA Marine BM-1 Compact User manual

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

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
2
2
2
2
2
5
6
6
7
7
8
8
9
11
1

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 self-
discharge 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.
2

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.
1.
2.
3.
4.
3

Original
Cables
RED RED
RED
BLACK BLACK *
BLACK
WHITE
WHITE
Cables
supplied
Original
cables
WHITE *
YELLOW YELLOW
YELLOW
BATTERY
-
-
+
+
SHUNT
FUSE
* Black & White
MUST NOT be
joined at this end.
Cable Supplied
BM-1
Compact
V&A
TIME
Figure 1 - Wiring Installation
5.
4
TO LOADS
AND CHARGERS

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.
6.
7.
8.
9.
10.
11.
12.
13.
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.
5

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.
6

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.
7

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.
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
6.
7.
8

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.
9