Diagnostic Charger Support



Frequently Asked Questions


What is a Diagnostic Charger?
Midtronics pioneered the development of the Diagnostic Charger, creating the category by mating the benefits and functions of a professional battery charger with a battery analyzer. The result is a product line that provides battery analysis and highly controlled, customized charging specific to an individual battery's unique requirements. Midtronics makes several models of diagnostic chargers, including the GR-8 andGR-1 120 that use the proven conductance technology and battery analysis algorithms available in Midtronics handheld battery testers. Most Midtronics diagnostic chargers perform an initial load-test of the battery, measure various parameters of charge acceptance, and include conductance measurements for a full analysis of the battery’s condition. After the initial analysis, if warranted, the charger automatically begins the charging process. During this process, a Midtronics diagnostic charger will repeatedly test the battery to provide the appropriate charge energy and maximize efficiency and minimize charge time. If the charger identifies a problem during the cycle it stops the charge session and alerts the user, providing additional safety to the process. As the market leader in diagnostic charging, Midtronics continually enhances the algorithms test parameters and technology used in this rapidly growing product category.

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How long can I leave my charger connected to my battery?
There is no single answer to this question. The type of charger you are using and how it is designed determines this. Refer to the instructions provided with the charger. It is generally safe to use a fully automatic charger on any healthy battery is that is simply discharged. The automatic feature means the charge current will eventually taper with a predetermined voltage limit and then cycle on and off once the battery has reached a full charge. Manual chargers should be removed as soon as the battery has reached a full charge. Manual chargers will not cycle off or shut down by themselves, so you must be more cautious with their use. It is recommended that you continually monitor the battery’s state of charge by using a hydrometer and/or a voltmeter when using any manual battery charger. It is common practice to use a small “brick” charger which typically has a regulated voltage output and a very low current rating to keep a battery in storage at full charge. Make sure the charger is rated for extended charging or a storage applications. Several vendors make 12-volt chargers rated at 2 amps or less that are specifically designed for long term, slow trickle-charging or maintenance applications. Consult the charger manufacturer’s specifications to be sure. CAUTION: Never leave a battery unattended when connected to a manual charger or a charger that is not voltage limited. Manual chargers can elevate charge voltages to a level where significant gassing may occur, which is dangerous. This is hydrogen gas and it can be explosive at very low concentration levels of only 4% per volume of air.


How long can I use the Engine Start/Cranking Assist on my manual charger?
No more than 5 seconds per start attempt. The engine start/cranking assist feature in any charger is intended for short duration power burst (typically 3 to 5 seconds) to assist in starting an otherwise healthy vehicle. This time limit rating is a UL standard based on the amperage output of the charger at 7.2 volts (fully loaded) for 5 seconds. In the Engine Start position the charger output could be as high as 250 amps, which quickly raises the temperature the charger’s circuitry to a high level. Allow the charger to cool for at least 5 minutes after trying to boost-start the engine. The rest period protects the circuitry by allowing heat in the charger to dissipate If you have time, use a diagnostic charger or test the battery to determined how long to use a manual charger to insure that the battery is fully charged before starting the vehicle.

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How do I charge batteries connected hooked up in parallel/series?
In parallel, the charger’s voltage setting must match the voltage of each individual battery. If you have two 6-volt batteries connected in parallel, the total voltage is only 6 volts. If those same two 6-volt batteries are connected in series, the total voltage is 2 volts. In series you add the voltages. Battery basics say that you parallel for “Power” and you series for “Strength” or higher electrical potential. For example, if four 12-volt, 50-amp/hr batteries are connected in parallel, they would provided a total of 200 amp/hrs of rated power. If this configuration is fully discharged, you will need to recharge at least 200 amp/hrs of energy at the 12-volt level to recover these batteries. That means a 10-amp charge rate for 20 hours will equal 200 amp/hrs of energy returned to the batteries. If you take the same configuration and make it series parallel at 24-volt potential, the capacity drops to 100 amp/hrs, but at the higher 24-volt potential. Determine the total voltage of the system that you want to charge. Once you know the appropriate voltage, select the correct voltage setting on the charger. Parallel charging: When charging a system of batteries in parallel, it always a good idea to connect one output lead to the first battery, (for example, negative lead to negative post), then connect the other output lead to the last battery in the parallel system (positive lead to positive post). The procedure helps the batteries get an equal amount of charge. Series charging: When charging a system of batteries in series

This is a review of the most frequently asked questions regarding Midtronics battery chargers based on the call volume in the Technical Support/Customer Service Department. This should assist you in the majority of questions your customers ask.

If you encounter an application, question, or situation that falls outside this FAQ guide, please feel free to call Midtronics Technical Support. This FAQ guide will be updated as our call log indicates a need. Our hours of operation are Monday through Friday; 7:00 am to 5:00 pm CST. Thank you.


If you are still having trouble with your diagnostic charger please call Customer Service between 7AM and 5PM CST at 1-800-776-1995 (USA).

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Diagnostic Charger Support

Frequently Asked Questions

What is a Diagnostic Charger?

What general battery charging safety precautions should I take?

How long can I leave my charger connected to my battery?

How long can I use the Engine Start/Cranking Assist on my manual charger?

How do I charge batteries connected hooked up in parallel/series?