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DMM-1-B 12 Volt DC Battery Monitoring System / 2 Banks - INCLUDES 135 amp Shunts and Wiring kit
In-line monitoring of your boat's 12V energy system!
If you want symplicity of Volts and Amps only, and low cost, than the Microlog is the choice - Practical Sailor 4/15/04

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Feature Benefits
  • Very accurate 2-battery bank voltage measurements
  • System charge current measurement
  • Separate discharge/consumption current measurement with dual 135 AMP shunts! This is a feature unique to the Microlog! In other words, you can measure your output Amps at the same time as your input Amps independently!
    "A very attractive feature" - Practical Sailor
  • Low and high voltage monitoring with alarm protects againts deep discharge & overcharge
  • Red backlit display
  • Simple operation with one MODE button for all functions
  • Polycarbonate facing
  • Marine grade corrosion resistant glass / PCB circuit
  • Surface mount with sealed trimers makes installation location less of a challenge
  • Stainless steel hardware
  • Easy to install and operate
  • Very low current draw (2 mA with monitor on)
  • Two year limited warranty
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Your batteries are an expensive investment and you want to keep them in their optimum state of performance at all times. Their effective life is directly related to the level of care and maintenance they will receive.

The Microlog Battery Monitoring System is designed to measure the status of batteries and efficiently manage the energy flow in the charging and distribution systems. Our system include a precision digital instrument, much more accurate than the standard analog battery monitoring equipment found in most boats, which only give approximate values. Afterall, the most important range in voltage is between 11.5 - 12.8 volts. That's pretty difficult to read on an analog panel meter. Precision digital monitoring delivers the necessary data to manage electrical resources more efficiently. In challenging circumstances, such as at sea, this information may be crucial in making important decisions.

Precision Voltage Monitoring:
The Microlog Battery Monitoring System is designed to monitor the level of charge for 2 batteries or battery banks in measuring the Total Battery Cells Voltages with great precision. The voltage monitoring will tell you the state and condition of your batteries, charging equipment and also when it's time to charge and stop charging.

Separate Charge and Discharge Current Monitoring:
The Microlog System will also monitor the intensity (Amperes) of incoming current from charging equipment such as alternators, wind generators or solar panels and, at the same time, measure the separate discharging or outgoing current, consumed by electrical appliances or equipment powered by the battery system. This is a unique feature. You can now measure output regardless of weather the alternator is on. Charging current are represented with a “+” sign and discharging current with a “–” sign. For example, a typical onboard 12 Volt system includes two batteries: one battery (battery bank or house bank) is usually assigned to feed electrical appliances (fridge, lighting etc..), the second battery is dedicated to start the engine (See typical installation in the circuit diagram. Some boats can have two house banks and two engine batteries. Total charging or discharging current to be measured, is passed through the “Shunts” independently.

Low and High Voltage Level Alarms:
Batteries can sustain permanent damage if drained below 11.5 volts too often or for long periods or if they are overcharged, so we included an integrated alarm, which will trigger a warning signal if the voltages fall below 11.8 volts or surpass 15.1 volts on both monitored banks.

As good as it gets:
The Microlog System is carefully made with the finest components and materials in order to optimize its reliability and performance, such as: Use of Surface-Mount Technology (SMT), Anti-Corrosion Treatment, Sealed Adjustments Trimmers, Lexan® Facing and Stainless Steel Hardware for harsh marine environment. The system also use a very low current draw.

The Microlog System is covered with a 2 year limited warranty and include Fuses-Holders and Fuses for short circuit prevention.

Plug and Play:
The system is easy to install and operate; no programing or resets of any kind; simple one mode button for all functions.

How it works:
The Microlog Battery Monitor is designed to monitor the voltage status of up to two batteries or battery banks. It measures the current flow of charging devices and separate equipment current consumption for precise DC system monitoring and management.

Integrated Alarm
An integrated alarm system is included, sending a warning signal, should the voltage of any battery fall under 11.8 volts or exceed 15.1 volts, while charging.

Measuring Voltage:
Measuring Specific gravity of the battery electrolyte (acid+water) in each cell of a lead-acid battery with caps will tell the level of charge but it can be messy and is not an easy task.Voltage indication is also a prime way to learn the status of charge of your batteries. This voltage also corresponds to the level of specific gravity related to any given level of charge.

A Lead-Acid Battery voltage level of 11.7 Volts at rest (no load or charging device), indicates a completely discharged battery, while a voltage level of 12.60 Volts (12.95 Volts/Gelcell),without any charging device connected, indicate a full charged battery (at room temperature). Any battery that discharges often below 11.6 volts (50%, under load) will eventually shorten its service life. The voltage table shown below will vary with type and capacity of your batteries.

The different Battery Charging Stages:
Basic battery charging stages can be monitored with your Microlog.
  1. The BULK stage of charging is the first stage and the AMP level will be equal to the maximum output delivered by your charging equipment or between 25-40% of your Amp-Hour battery capacity (also limited by the maximum output of the charging equipment). A typical Alternator will deliver 38-60 Amps (gradually decreasing) to a 150 Amp-Hour (AH) battery. You will get 75% of your battery charge with this stage. The voltage will be higher than the preceding Typical Battery voltage chart.

  2. The second stage called Absorption stage will provide the remaining 25% of charge to the battery (ies) where they will be considered fully charged with a remaining current of 2-4% of the AH battery capacity (3-6 Amps, with a 150 Amp-Hour (AH) battery, on the DMM-1 charge mode) with a voltage of 14.4 Volts (14.2 for gels). This stage is slower as the current is lower and some people will stop charging stage before the 2-4% of the AH battery capacity point has been reached.

  3. The Float Phase stage will maintain the battery charge after the full charge point has been reached.

  4. The Equalization stage is optional on some battery chargers and allows you to de-sulphatize your batteries with a higher voltage. The alternator, or other charging devices, will raise the battery (ies) voltage to 14.4 Volts. This voltage information combined with the level of current supplied will tell you when you have
The typical status of charge of your batteries is shown in the following table:

Battery Voltage at rest
(no load or charging device)
% of charge
Lead-acid Battery Voltage
(under load,no charging device)
Specific Gravity
12.60 V
12.95 V
12.80 V
12.60 V
12.42 V
12.65 V
12.60 V
12.06 V
12.18 V
12.35 V
12.30 V
11.58 V
12.00 V
12.00 V
12.00 V
11.04 V
11.70 V
11.80 V
10.50 V
Typical Battery Voltage vs % of charge chart at 77°F (25°C )
(according to a major battery manufacturer)

Voltage measurement range: 8.0 -17.0 volts
Resolution (volts): 0. 01 volts
Measurement precision: ± 0.03 volts (20ºC)
Low voltage level alarm trigger: 11.8 volts± 0.1
High voltage level alarm trigger: 15.1 volts± 0.1
* Current measurement range: 0-135 amps.
* Resolution (amperes): 0.1 amps.
* Measurement precision: 0.2 amps. (20ºC)
* Operating current requirements: 2.0mA (off) - 18.0mA (on)
Backlight current requirements: 9.0mA @ 12.5 volts
Operating temperature range: 0ºC to 40ºC
Storage temperature range: -30º to+60ºC
4.3” L. x 3.3” W. x 0.9” D.


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