Go Power GP-BMK-50 User manual

BATTERY MONITOR
GP-BMK-50
User Manual
© 2018 Go Power!®
Worldwide Technical Support and Product Information gpelectric.com
Go Power! Headquarters
201-710 Redbrick St, Victoria, BC Canada V8T 5J3
MAN_GP-BMK-50_RevE

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1. CONTENTS
2. GETTING STARTED ............................................................................................................... 5
2.1 BATTERY CAPACITY ............................................................................................. 5
2.2 AUXILIARY INPUT (GP-BMK-50)........................................................................... 5
2.3 IMPORTANT COMBINED BUTTON FUNCTIONS ................................................. 6
3. NORMAL OPERATING MODE ............................................................................................... 7
3.1 READ OUT OVERVIEW ......................................................................................... 7
3.2 SYNCHRONIZING THE GP-BMK-50 ..................................................................... 8
3.3 COMMON PROBLEMS .......................................................................................... 9
4. FEATURES AND FUNCTIONALITY ..................................................................................... 10
4.1 WHY SHOULD I MONITOR MY BATTERY? ........................................................ 10
4.2 HOW DOES THE GP-BMK-50 WORK? ............................................................... 10
4.2.1 BATTERY CAPACITY AND RATE OF DISCHARGE .............................. 10
4.2.2 CHARGE EFFICIENCY (CEF).................................................................11
4.3 BATTERY STATE-OF-CHANGE DISPLAY OPTIONS...........................................11
4.4 HISTORY DATA .....................................................................................................11
4.5 USE OF ALTERNATIVE SHUNTS ........................................................................ 12
4.6 AUTOMATIC DETECTION OF NOMINAL SYSTEM VOLTAGE............................12
4.7 ALARM, BUZZER AND RELAY ............................................................................ 13
4.8 INTERFACE OPTIONS......................................................................................... 14
4.8.1 PC SOFTWARE...................................................................................... 14
4.8.2 LARGE DISPLAY AND REMOTE MONITORING................................... 14
4.8.3 CUSTOM INTEGRATION (PROGRAMMING REQUIRED).................... 14
4.9 ADDITIONAL FUNCTIONALITY OF THE GP-BMK-50......................................... 14
4.9.1 AUXILIARY BATTERY MONITORING .................................................... 15
4.9.2 BATTERY TEMPERATURE MONITORING............................................ 15
4.9.3 MIDPOINT VOLTAGE MONITORING..................................................... 15
5. FULL SET-UP DETAILS........................................................................................................ 16
5.1 USING THE MENUS............................................................................................. 16
5.2 FUNCTIONS OVERVIEW..................................................................................... 17
5.2.1 BATTERY SETTINGS............................................................................. 17
5.2.2 RELAY SETTINGS.................................................................................. 19
5.2.3 ALARM·BUZZER SETTINGS ................................................................. 22
5.2.4 DISPLAY SETTINGS .............................................................................. 24
5.2.5 MISCELLANEOUS ................................................................................. 25
5.3 HISTORY DATA .................................................................................................... 26
6. MORE ABOUT PEUKERT’S FORMULA & MIDPOINT MONITORING ............................... 28
6.1 PEUKERT’S FORMULA: BATTERY CAPACITY AND DISCHARGE RATE ......... 29
6.2 MIDPOINT VOLTAGE MONITORING................................................................... 29
6.2.1 HOW THE % MIDPOINT DEVIATION IS CALCULATED ....................... 30
6.2.2 SETTING THE ALARM LEVEL ............................................................... 30
6.2.3 ALARM·DELAY ....................................................................................... 30
6.2.4 WHAT TO DO IN CASE OF AN ALARM DURING CHARGING.............. 31
6.2.5 WHAT TO DO IN CASE OF AN ALARM DURING DISCHARGING........ 31
7. LITHIUM IRON PHOSPHATE BATTERIES (LiFeP04)......................................................... 32
8. DISPLAY................................................................................................................................ 33
9. TECHNICAL DATA................................................................................................................ 35

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Safety Precautions
WARNING!
Personal Injury
Working in the vicinity of a lead acid battery is dangerous. Batteries can generate explosive
gases during operation. Never smoke or allow a spark or ame in the vicinity of a battery.
Provide su󰀩cient ventilation around the battery.
Wear eye and clothing protection. Avoid touching eyes while working near batteries. Wash
your hands when done.
If battery acid contacts skin or clothing, wash them immediately with soap and water. If acid
enters an eye, immediately ood the eye with running cold water for at least 15 minutes and
get medical attention immediately.
Be careful when using metal tools in the vicinity of batteries. Dropping a metal tool onto a
battery might cause a short circuit and possibly an explosion.
Ensure that children, pets, and other animals are kept away from the inverter, solar arrays,
battery bank, and utility grid components.
Remove personal metal items such as rings, bracelets, necklaces, and watches when working
with a battery. A battery can produce a short circuit current high enough to melt objects such
as rings, causing severe burns.

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This manual assumes that the GP-BMK-50 is being installed for the rst time, or that factory settings have been
restored.
The GP-BMK-50 factory settings are suitable or all battery chemistries.
The GP-BMK-50 will automatically detect the nominal voltage of the battery system immediately after completion of
the set-up wizard (for details and limitations of automatic nominal voltage detection, see section 3.8). Therefore, the
only settings which need to be made are the battery capacity and the functionality of the auxiliary input.
Please install the GP-BMK-50 in accordance with the Quick Start Guide. After inserting the fuse in the positive
supply cable to the main battery, the GP-BMK-50 will automatically start the set-up wizard.
PLEASE NOTE:
a) In case of Li-ion batteries, several settings may have to be changed. Please refer to section 6. The set-up
wizard below must be completed before other settings can be made.
b) When using a shunt other than the one supplied with the GP-BMK-50, please refer to section 3.6. The set-up
wizard below must be completed before other settings can be made.
USING THE SET-UP WIZARD
2.1 SETTING BATTERY CAPACITY
a) After inserting the fuse, the display will show scrolling text.
If this text is not shown, press SETUP and SELECT simultaneously for a 3 second period to restore the factory
settings or go to section 4 for the full set-up details (setting 64, Lock set-up must be OFF to restore factory settings.
See section 4.2.5).
b) Press any button to stop scrolling and the factory default value Ah (total amp hours of battery bank) will appear
in the edit mode; the rst digit will blink.
Enter the desired value with the + and - buttons.
c) Press SETUP or + or - to proceed to auxiliary input setting.
2.2 USING AN AUXILIARY INPUT
a) The display will show (second battery) scrolling.
b) Press SELECT to stop scrolling and the LCD will show:
Use the + or - key to select the required function of the auxiliary input
for monitoring the starter battery voltage.
for monitoring the mid-point voltage of a battery bank.
for using the optional temperature sensor.
Press SELECT to conrm. Conrmation is indicated with a short beep.
c) Press SETUP or + or - to end the set-up wizard and switch to normal operating mode.
The GP-BMK-50 is now ready for use.
When powered up for the rst time, the GP-BMK-50 will display 100% state of change.
2. GETTING STARTED

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GETTING STARTED
When in normal mode, the back-light of the GP-BMK-50 switches o󰀨 after no key has been pressed for 60 seconds.
Press any key to restore the back-light. Go Power disclaims liability for any direct, indirect or incidental damages
caused by, or in case of, installation not performed following the instructions and cautions in this manual. Go Power
will refuse requests for exchanges or returns, resulting from the purchase and installation of items which do not
comply with local codes. To avoid such concerns Go Power recommends installation by a professional electrician,
RV or marine, or solar technician. Examples that are shown within this manual are for illustrative purposes only.
2.3 IMPORTANT COMBINED BUTTON FUNCTIONS
a) Restore factory settings
Press and hold SETUP and SELECT simultaneously for 3 seconds.
b) Manual synchronization
Press and hold the up and down buttons simultaneously for 3 seconds.
c) Silence audible alarm
An alarm is acknowledged when any button is pressed, however, the alarm icon is displayed as long as the alarm
condition remains.
GET REAL-TIME DATA DISPLAYED ON A SMART PHONE
With the GP-BTD (Go Power! Battery Monitor Dongle), real-time data and alarms can be
displayed on Apple and Android smart phones, tables and other devices.
You will need to download the free Go Power! ConnectTM app from Google Play or the Apple Store.

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3. NORMAL OPERATING MODE
3.1 READ-OUT OVERVIEW
In normal operating mode, the GP-BMK-50 displays an overview of important parameters.
The + and - selection buttons give access to various read-outs.
BATTERY VOLTAGE:
AUXILIARY BATTERY VOLTAGE:
When the auxiliary input is set to START.
CURRENT:
The actual current owing out of the battery (negative
sign) or into the battery (positive sign).
POWER:
The power drawn from the battery (negative sign) or
owing into the battery (positive sign).
CONSUMED AMP-HOURS:
The amount of Ah consumed from the battery
Example:
If a current of 12A is drawn from a fully charged battery for a period of 3 hours, this readout will show -36.0Ah.
(-12 x 3 = -36)
STATE OF CHANGE:
A fully charged battery will be indicated by a value of 100.0%. A
fully discharged battery will be indicated by a value of 0.0%.
TIME TO GO:
An estimation of how long the battery can support the present load
until it needs recharging.
The time-to-go displayed is the time to reach the discharge oor. See 4.2.2, setting number 16.
BATTERY TEMPERATURE:
When the auxiliary input is set to TEMP.
The value can be displayed in degrees Celsius or degrees
Fahrenheit. See section 4.2.5

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NORMAL OPERATING MODE
BATTERY BANK TOP SECTION VOLTAGE:
When the auxiliary input set to MID. Compare with the bottom
section voltage to check battery balancing. For more about battery
midpoint monitoring, see section 5.2.
BATTERY BANK BOTTOM SECTION VOLTAGE:
When the auxiliary input is set to MID. Compare with the top section
voltage to check battery balancing.
BATTERY BANK MID-POINT DEVIATION VOLTAGE:
When the auxiliary input is set to MID. Deviation in Volts of the
mid-point voltage.
3.2 SYNCHRONIZING THE GP-BMK-50
For a reliable readout, the state of charge as displayed by the battery monitor has to be synchronized regularly with
the true state of charge of the battery. This is accomplished by fully charging the battery.
In case of a 12V battery, the GP-BMK resets to ‘fully charged’ when the following ‘charged parameters’ are met: the
voltage exceeds 13.2V and simultaneously the (tail-) charge current is less than 4.0% of the total battery capacity
(e.g. 8A for a 200Ah battery) during 4 minutes.
The GP-BMK can also be synchronized (i.e. set to ‘battery fully charged’) manually if required. This can be achieved
in normal operating mode by holding the + and – buttons simultaneously for 3 seconds, or in setup mode by using
the SYNC option (see section 4.2.1, setting number 10).
If the GP-BMK does not synchronize automatically, the charged voltage, tail current, and/or charged time may need
adjustment.
When the voltage supply to the BMK has been interrupted, the battery monitor must be resynchronized before it
can operate correctly.
3.3 COMMON PROBLEMS
NO SIGNS OF LIFE ON THE DISPLAY
Probably the GP-BMK-50 is not properly wired. The UTP cable should be properly inserted at both ends, the shunts
must be connected to the minus pole of the battery and the positive supply cable should be connected to the plus
pole of the battery with the fuse inserted.
The temperature sensor (when used) must be connected to the positive pole of the battery bank (one of the two
wires for the sensor doubles as the power supply wire).
CHARGE AND DISCHARGE CURRENT ARE INVERTED
Charge current should be shown as a positive value. For example: +1.45A.
Discharge current should be shown as a negative value. For example: -1.45A.
If charge and discharge current are inverted, the power cables on the shunt must be swapped: see the quick
installation guide.

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THE GP-BMK-50 DOES NOT SYNCHRONIZE AUTOMATICALLY
One possibility is that the battery never reaches the fully charged state. The other possibility is that the charged
voltage setting should be lowered and/or the tail current setting should be increased. See section 4.2.1.
THE GP-BMK-50 SYNCHRONIZES TOO EARLY
In solar systems or other applications with uctuating charge currents the charged voltage should be set only slightly
below the absorption charge voltage (for example: 14.1V in case of 14.4V absorption voltage). This will prevent the
GP-BMK-50 from switching prematurely to 100% state of charge.
SYNC AND BATTERY ICON ARE BLINKING
This means the battery is not synchronized. Charge the batteries and the GP-BMK-50 should sync automatically.
If that doesn’t work, review the sync settings, Or if you know the battery is fully charged but don’t want to wait until
the GP-BMK-50 synchronizes, press and hold the UP and DOWN button simultaneously until you hear a beep. See
section 4.2.1.
4.1 WHY SHOULD I MONITOR MY BATTERY?
Batteries are used in a wide variety of applications, mostly to store energy for later use. But how much energy is
stored in the battery? No one can tell just by looking at it.
The service life of batteries depends on many factors. Battery life may be shortened by under-charging, over-charging,
excessively deep discharges, excessive charge or discharge current and high ambient temperature. By monitoring
the battery with an advanced battery monitor, important feedback is given to the user so that remedial measures
can be taken when necessary. Doing this will extend battery liferesulting in the GP-BMK-50 quickly paying for itself.
4.2 HOW DOES THE GP-BMK-50 WORK?
The main function of the GP-BMK-50 is to follow and indicate the state of change of a battery, in particular to prevent
unexpected total discharge.
The GP-BMK-50 continuously measures the current ow in and out of the battery. Integration of this current over
time (which, if the current is a xed amount of Amps, boils down to multiplying current and time) gives the net amount
of Ah added or removed.
Example: discharge current of 10A during 2 hours will take 10 x 2 = 20Ah from the battery.
However, there are external components that negatively a󰀨ect a battery capacities, such as rate of discharge, charge
e󰀩ciency, and temperature.
4.2.1 BATTERY CAPACITY AND THE RATE OF DISCHARGE
The capacity of a battery is rated in ampere-hours (Ah). For example, a lead acid battery that can deliver a current
of 5A during 20 hours is rated at C20 = 100Ah (5 x 20 = 100).
When the same 100Ah battery is discharged completely in two hours, it may only give C2 = 56AH (because the
higher rate of discharge).
The GP-BMK-50 takes this phenomenon into account with Peukert’s formula. (See section 5.1).
4. FEATURES AND FUNCTIONALITY

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4.2.2 CHARGE EFFICIENCY (CEF)
The charge e󰀩ciency of a lead acid battery is almost 100% as long as no gas generation takes place. Gassing
means that part of the charge current is not transformed into chemical energy, which is stored in the plates of the
battery, but is used to decompose water into oxygen and hydrogen gas (highly explosive!). The Amp-hours stored
in the plates can be retrieved during the next discharge, whereas the Amp-hours used to decompose water are
lost. Gassing can easily be observed in ooded batteries. Please note that the oxygen only end of charge phase of
sealed (VRLA) gel and AGM batteries also results in a reduced charge e󰀩ciency.
A charge e󰀩ciency of 95% means that 10Ah must be transferred to the battery to get 9.5Ah actually stored in the
battery. The charge e󰀩ciency of a battery depends on battery type, age and usage.
The GP-BMK-50 takes this phenomenon into account with the charge e󰀩ciency factor. (See section 4.2.2, setting
number 06.
4.3 BATTERY STATE OF CHANGE DISPLAY OPTIONS
The GP-BMK-50 can display both the Amp-hours removed (consumed Amphours readout, compensated for charge
e󰀩ciency only) and the actual state of charge in percent (state of charge readout, compensated for charge e󰀩ciency
and Peukert e󰀩ciency). Reading the state of charge is the best way to monitor the battery.
The GP-BMK-50 also estimates how long the battery can support the present load, the time to go readout. This
is the actual time left until the battery is discharged to the discharge oor. The factory setting is 50% (See 4.2.2,
setting number 16).
If the loads are uctuating heavily, it is best not to rely on this reading too much since it is a momentary readout
and must be used as a guideline only. We always encourage the use of the state of change readout for accurate
battery monitoring.
4.4 HISTORY DATA
The GP-BMK-50 stores events which can be used at a later date to evaluate usage patterns and battery health.
Select the history data menu by pressing ENTER when in normal mode (See section 4.3).
4.5 USE OF ALTERNATIVE SHUNTS
The GP-BMK-50 is supplied with a 500A/50mV shunt. For most applications, this should be suitable, however, the
GP-BMK-50 can be congured to work with a wide range of di󰀨erent shunts. Shunts of up to 9999A and/or 75mV
can be used.
When using a shunt other than the one supplied with the GP-BMK-50, please proceed as follows:
Unscrew the PCB from the supplied shunt.
Mount the PCB on the new shunt, ensuring that there is good electrical contact between the PCB and the shunt.
Connect the shunt and GP-BMK-50 as shown in the quick installation guide.
Follow the set-up wizard (Section 1.1 and 1.2).