Low Voltage Disconnect for 0 to 5 Volt Range

Posted on February 26, 2020 by neil

We build and sell a wide range of low voltage disconnects for use with 12V and (less frequently) 24V battery systems to protect batteries from being overly discharged and therefore damaged.

Pictured above is a device for a slightly different application, but which is based around our REUK Programmable Low Voltage Disconnect with OLED Display.

This Arduino powered device is designed to interrupt a signal line (using an on board relay) when an input voltage is measured to be below a user set value expected to be in the range 0 to 5V. Since the input voltage could be too low to power the microcontroller and display etc, the board is powered by an external 12V supply with a common ground connection to the voltage to be measured.

The user can set the low voltage threshold below which the signal line will be cut (by the relay being de-energised), and then a higher voltage threshold above which the signal line connection will be restored (by the relay being re-energised). Timers are built in to this device so that 10 seconds of consistent low or high voltage is required for a change of state of the relay to occur so any brief input voltage spikes and dips, or interference do not have an effect.

If you need any kind of low voltage disconnect or automatic voltage monitoring device, please email neil@reuk.co.uk with details of your specific requirements.

2x12V 24V Battery Bank Low Voltage Disconnect

Posted on June 28, 2018 by neil

Pictured above is a low voltage disconnect (LVD) we recently made for use with a 24V battery bank comprising two 12V batteries. These two batteries do not equalise well (i.e. they do not hold the exact same charge or show the same voltage), and so this low voltage disconnect has to look at both batteries independently and take actions based upon the measurements of the weakest battery.

This device is based around our OLED display 12V LVD with some major modifications. The batteries are connected in series to make a 24V bank. The device measures the voltage of the whole battery bank and also measures the voltage of the first 12V battery. The second 12V battery voltage is then calculated by subtracting the first 12V battery voltage from the 24V battery bank voltage.

The OLED display on the low voltage disconnect shows the two battery voltages which make up the bank, the status of the LVD, and the voltage threshold (user programmable) at which the status of the LVD will next change (turn off the output if it is on, turn it on if it is off) depending on the charge level of the two batteries in the bank.

If the voltage of either battery in the battery bank falls below the low voltage threshold set by the user, the output will be turned off cutting the power to any devices being powered by the battery bank. When both of the batteries in the bank then reach a voltage in excess of the high voltage threshold set by the user, the output is restored reconnecting power to the devices powered by the battery bank.

If you need any kind of low voltage disconnect, please take a look at our range of LVD products, and email neil@reuk.co.uk if you have any special requirements.

24V Battery Charging Control Circuit

Posted on September 22, 2017 by neil

Pictured below is a 24V battery charging circuit which we recently made based around our more standard low voltage disconnects.

Rather than a low voltage disconnect, this is a low voltage connect with the output used to control a relay which in turn connects a battery charger to the 24V battery bank. For this particular unit, the charger will be a hydraulic turbine generator, but everything would work the same if a plug-in battery charger was being used.

When the voltage from battery bank is measured to be below a user set value continuously for 10 seconds, the output turns on which starts battery charging. Charging continues until the battery bank is measured to be above a second (higher) user set value continuously for 10 seconds.

If you need any kind of low voltage disconnect/connect or anything to monitor an charge 12V or 24V batteries, email neil@reuk.co.uk with details of your requirements.

12V Low Voltage Disconnect with Display and SD Card Datalogger

Posted on June 26, 2017 by neil

Pictured above is a low voltage disconnect device which we recently made for a client. It offers all of the battery monitoring, protecting, and datalogging functions and features of our REUK Programmable Low Voltage Disconnect with Display and Datalogger, but with the added benefit of an on board microSD card to store the measured battery voltage once per minute.

The voltage data is written to a simple text file on the SD card. When the battery is connected to the low voltage disconnect and powers it, POWER CONNECTED is written to the log file. Then each subsequent minute, the battery voltage is written to the file preceded by the number of minutes since the power was last connected. For example the line 6,13.98 indicates that 6 minutes after the power was connected, the battery voltage was measured to be 13.98V.

While the pre-existing basic datalogging of the LVD is useful for constantly displaying the minimum, maximum, and average measured voltages, every now and then it is good to have the option to copy the data from the SD card to a PC for more detailed analysis and plotting etc.

If you need any kind of datalogger, please email neil@reuk.co.uk with details of your requirements.

Low Voltage Disconnect for Glacial Movement Research GPS in Greenland

Posted on May 15, 2017 by neil

Pictured below is a special low voltage disconnect (LVD) device which we have been supplying for a few years for use by academic researchers in glaciology.

Solar charged batteries are being used to power GPS dataloggers on glaciers in Greenland. These GPS devices accurately record the movement of glaciers, and this (velocity) data can be used in a wide range of polar and climate change research.

The specific set up for which these LVD devices were designed has a 48 Watt PV solar panel charging a 60-100Ah 12V battery via a Sunguard solar charge controller.

In high polar regions, in the summer, the sun is in the sky 24 hours day, but in the winter is is below the horizon 24 hours per day. Therefore, during the winter months the battery cannot be charged. For the battery to still be usable in the spring it must retain some charge, so the GPS has to be disconnected before it overly discharges the battery.

The GPS modules have their own built in low voltage disconnect circuitry, but a step-up voltage regulator is fitted between the 12V battery and the GPS modules (which need 15+V to operate), so the GPS sees a steady consistent good voltage right up until the 12V battery is virtually dead.

In our standard low voltage disconnects, the output is turned off when the battery voltage falls and remains below a user set low voltage for 10 seconds. The output turns back on when the battery voltage reaches and remains above a user set cancellation voltage for 10 seconds.

For a solar powered system and often very limited daylight hours, this can see the output being turned on and off multiple times per day. This is not a problem for an LVD used with lighting for example, but the GPS modules used for this project create a new datalog file each time the power to the module is connected, and there is a 512 file limit. If over the course of the many months that the GPS module remains on the glacier unattended, the power to it is cut and restored more than 512 times, data will be lost which is not acceptable.

In order to prevent this problem, our low voltage disconnect engages as usual after 10 seconds of low voltage being measured ensuring that power to the GPS is rapidly cut if the voltage is low, but then the voltage has to remain consistently over the cancellation voltage for one hour before the power to the GPS module is restored. Doing this ensures that the GPS is only powered up when the battery is known to hold enough charge to make it worthwhile taking up one of the 512 available file spaces.

If you need any kind of special low voltage disconnect or voltage monitoring device, email neil@reuk.co.uk with details of your requirements.

Multi Level Low Voltage Disconnect with Display

Posted on May 5, 2017 by neil

Pictured below is a special multi level low voltage disconnect controller which we recently made. As with our other low voltage disconnect products, this device is designed to automatically disconnect loads from a battery when the battery voltage drops below a user set threshold. The loads are then reconnected when the battery voltage has risen above a second higher threshold.

What makes this low voltage disconnect special is that it can be programmed with three independent pairs of voltage thresholds, and control three sets of loads. If you have a selection of devices powered from your 12V battery, some will be more important than others, and some will use more power than others. Having multiple LVD voltage thresholds allows you to choose which devices should have their power cut first as the battery charge level goes down. Cutting the power to high consumption low importance devices leaves more charge available to keep the more critical devices going for as long as possible.

If the battery was powering a large amount of lights for example, one light could be connected to the lowest voltage threshold output to stay on as an emergency light, while the rest of the lights could be turned off at a higher threshold. On a boat, the fridge and navigation system would be connected to the lowest threshold output, while the television and most lighting could be connected to a higher threshold.

The standard display shows the voltage measured on the battery, as well as the status of the three outputs corresponding to the Bot (Bottom), Mid (Middle), and Top ranges. In the image above, at a battery voltage of 12.32V, the Top range is off while the other two remain on.

At a lower voltage (10.55V shown above), all three outputs are off.

…and then with the battery voltage fully restored (13.53V while being charged), all three outputs are on.

By pressing the View Thresholds button, the user set voltage ranges are shown on the display.

Above for example the bottom range has the low voltage disconnect at 11.0V and the cancellation voltage (at which the output will be turned on again) at 12.2V.

Programming the six voltage thresholds is done using the two on board buttons. These thresholds are stored in non-volatile (long term) memory and are therefore not lost when/if it is disconnected from the battery.

When the battery voltage is measured to have moved above or below a threshold which will result in an output status changing, the back light of the display flashes on and off. The voltage has to remain constantly on the new side of the threshold for 10 seconds before the output status will actually change so that any spikes and dips in measured voltage do not result in devices being turned on or off unnecessarily.

Six Level Low Voltage Disconnect

Pictured below is a similar device we made in July 2018 with six user programmable low voltage disconnects and six outputs to be connected to external relays.

This particular device was made to be used with a 12v immersion comprising 6 individual 100 watt elements which had been controlled by 6 individual programmable relays to dump off excess battery charge and gain hot water.

The display for this version shows the status of each of the outputs.

And the different thresholds programmed can still be viewed two at a time on the display.

Programming this device is done in the same way as the original three output version using the up and down buttons on the device to change and set each of the 12 thresholds.

Nine Level Low Voltage Disconnect

A further development of this is the below pictured 9 level low voltage disconnect from August 2018 with nine independently programmable on board relays to switch various loads.

Twelve Level Low Voltage Disconnect

Pictured below is a unique device with twelve independently programmable low and high voltage thresholds.

This device has its twelve outputs (relays) split into two banks of six for use with two hot water tanks and twelve heating elements. When the temperature of the first tank reaches a user programmed high value, the second bank of elements is used to heat up the second tank of water. As with the nine level LVD shown earlier, this device has a display and it shows the battery voltage, tank 1 temperature, and the status of tank 1 or tank 2’s heating elements (depending on which tank is to be heated).

If you need any kind of low voltage disconnect, battery monitor, and/or datalogging device, email neil@reuk.co.uk with details of your requirements.

Battery mAh Capactity Tester

Posted on July 16, 2016 by neil

Pictured above is a device we made recently to help estimate the capacity of 12V and 24V batteries. It is based loosely around our 12V Low Voltage Disconnect with Display, but with some major changes and functionality additions.

The customer for this device has a Farnell Electronic load which is capable of discharging batteries at up to 1.5kW (e.g. 12V @ 125A). He wanted to be able to use this to discharge batteries under test, to time accurately the discharge duration, and to automatically turn off the electronic load when the battery voltage falls below a user set level (for example 9.5V for a 12V battery).

This electronic load can be controlled externally by terminals on the back of the unit (Load Enable/Disable). If 5 VDC is connected across those terminals, the electronic load is enabled (turned on), otherwise it is disabled (turned off).

We therefore designed a device which the user can set with their choice of low voltage threshold. Then, when they press the Start Button, a regulated 5V is put across the terminals on the back of the electronic load which starts discharging the battery under test. At the same time, a stopwatch (created in software on the Arduino Pro Mini around which this controller is built) starts to display the number of days, hours, minutes, and seconds that have elapsed since the battery discharge began.

When the battery voltage is measured to have fallen below the low voltage threshold, the stopwatch stops, and the 5V signal to the electronic load is disconnected preventing the battery being discharged any further and potentially being permanently damaged.

The time on the stopwatch is saved in memory on our device and is displayed on the LCD until the user presses the reset button. It is saved in this way just in case after a multi-hour/day test has been completed, someone accidentally disconnects the battery from the timing device before noting the displayed timing results.

Pictured below is an alternative version of the same thing, designed for use with 12V batteries, and provided with an OLED display on board.

This device works the same as the unit detailed above, but it has a smaller footprint, draws slightly less current from the battery itself, and it has a 1 Amp rated output to the electronic load @ 12VDC.

Pictured above is the display in standard operation showing the battery voltage at present, the low voltage threshold level (below which the electronic load will be switched off), and the running time so far.

Below shows the display when the device is in programming mode when the low voltage threshold can be set to a suitable value by the user.

If you need any kind of voltage measuring device, low voltage disconnect, and/or timer, please email neil@reuk.co.uk with details of your exact requirements.

12V Low Voltage Disconnect with Warning Buzzer

Posted on June 17, 2015 by neil

Pictured below is a 12V low voltage disconnect circuit with a low battery warning buzzer.

We sell a wide range of low voltage disconnect circuits in the REUK Shop as well as producing many bespoke LVDs on request. This particular circuit is based around our standard user programmable mini 12V low voltage disconnect, but enhanced to have a buzzer which sounds for one minute when the low voltage disconnect is triggered by 10 continuous seconds of low voltage measured on the battery. This warns the user that they need to take measures to recharge the battery.

There is also a switch on the circuit board so that the buzzer function can be turned off when not desired/required.

If you need any kind of low voltage disconnect, please email neil@reuk.co.uk with details of your requirements.

24V Low Voltage Disconnect with SD Card Datalogger

Posted on May 13, 2015 by neil

Pictured below is a low voltage disconnect device we recently made for use with a 24V battery system. In addition to the user-programmable low voltage disconnect functionality and LCD display of our standard Programmable 12V LVD with Display, this modified 24V device also includes a full datalogger, storing measured battery voltages at regular intervals to a micro-SD card for later analysis.

This particular unit is destined to be used by a company specialising in the maintenance of the UK’s transport infrastructure; with the low voltage disconnect used to protect batteries from being overly depleted, and the datalogger used to track the rise and fall of battery voltage over time.

If you need any kind of low voltage disconnect and/or datalogging solution, please email neil@reuk.co.uk with details of your requirements.

Low Voltage Disconnect used as Charge Controller

Posted on January 31, 2015 by neil

Pictured below is our 12V Programmable Low Voltage Disconnect with Display as sold in the REUK Shop. The product is designed to prevent batteries from being overly discharged and damaged by automatically turning the load devices on or off depending on the measured battery voltage.

We recently made a few modifications to this design of this LVD for a customer to enable this device to be used as a charge controller; turning it into a high voltage disconnect.

There is a battery bank and a generator which is used to charge it. We replaced the standard 12V output on the low voltage disconnect board with a relay so that it could switch the generator on and off automatically. We then changed the code on the Arduino microcontroller so that the relay would open (turning off the generator) if the battery bank voltage exceeded a user set value, and would then close the relay again (turning on the generator) when the battery voltage fell below a second user set value. By doing this the batteries are well cared for – never being overcharged, and never becoming overly depleted.

If you require a low voltage disconnect or a modification made to one of our LVD products such as this charge controller, please email neil@reuk.co.uk with details of your requirements.

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