With the cost of batteries on the rise, constant replacement of a detector's batteries with fresh ones can become expensive. Just how important are new batteries? Do new batteries help in obtaining greater depth? How often should we change them? Are alkalines a better investment than standard type? Are ni-cads a better choice? Is using one size of battery better than another? What are the real differences between batteries? Do more batteries make an instrument more powerful?
These are some of the questions that plague many of the treasure hunters concerning the energy sources of our metal detectors. Hopefully, by the time this two-part article is over, many of the above questions haunting serious treasure hunters will be answered.
A CAUTION FROM THE AUTHOR
Some of the answers to the above questions are not that simple. Battery technology is constantly changing - making comparisons difficult. Also, modern metal detector technology is constantly being improved with the development of new and better electronic components requiring less energy. Together, these two realms of improvements make comparisons very difficult. So, before we start evaluating the differences and benefits of the different power sources, we must remember that there are no general answers that span each and every detector.
DO NEW BATTERIES MAKE A DETECTOR MORE POWERFUL?
Over the years, articles have been written that implied a fresh set of batteries will increase the power capabilities, thus enhance the depth capabilities of a detector. Is this true? Strange as it may seem, the general answer is no.
But, in the most liberal sense, there may be some very slight credibility to this statement. Changing batteries can, and quite often seems to, give an increase in sensitivity. However, this increase is not the result of a more powerful signal transmitted by the search coil, but the result of small changes in the detector's audio circuitry making the signal appear louder.
In most of the newer motion detectors, the audio portion of a detector is one of the few sections of a metal detector's electronic circuitry directly affected by differences in voltage between new batteries and partially exhausted ones. The circuits that supply the transmitted signal to the search coil and other critical analyzing circuits obtain their power from the battery only after this voltage has been processed.
For a metal detector to be extremely sensitive to small signal changes, the energy supplied by the power source is critical. It has to have the ability of maintaining a constant voltage output at all times. Batteries by themselves cannot do this, and some batteries are worse than others in this respect.
To assure a quality voltage source to the electronic components, manufacturers use various types of special electronic circuitry, including some called voltage regulators. A voltage regulator has the ability to regulate or hold its output at a constant level under the most severe conditions. Normally, a regulator will keep its output voltage constant as long as the battery voltage is greater than the regulator output.
Batteries begin to deteriorate the minute they are put into use. As they weaken, their voltage output drops, and at some point this voltage is insufficient to meet the requirements needed by the regulating circuitry. It is at this point that the battery voltage becomes critical and has an effect on the detector's operations.
Until this minimum battery voltage is reached, most of the electronic circuitry within the detector does not even see the difference in the battery output. In other words, in most cases, changing batteries prematurely really has insignificant advantages as far as depth is concerned.
WHAT ABOUT THE NUMBER OF BATTERIES USED?
Are the number or type of batteries used by a metal detector an indication of the voltage, power, or depth capabilities of an instrument? The answer to this question is also no. A metal detector's sensitivity or depth capabilities should not be evaluated upon the number or types of batteries used. The depth capabilities are the result of carefully engineering all aspects of a detector, including the coil.
Also, the number and type of batteries do not necessarily reflect what the real voltage is being used by the circuitry. Due to modern technology, it is possible to use the power from batteries and generate higher and/or different voltages. Therefore, the number or types of batteries do not reflect the actual voltage used by the majority of the electronic circuitry of a metal detector.
As a general rule, the selection of various batteries by the manufacturers is done to meet certain requirements concerning weight, space, and/or overall power needs of the electronic circuitry. The selection has nothing to do with the depth capabilities of the instrument. In some cases, the size and type of batteries used are due to the evolution of that particular model.
The misconception that new batteries increase the depth capabilities has lead to people thinking that increasing the number or types of batteries can further increase the depth of their detector. Such experimentation can lead to disaster. Even if tampering with the type or number of batteries used in a detector doesn't display any negative effects, any increases in depth capabilities would be insignificant.
COMMON BATTERIES USED
The three most common sizes of batteries used by metal detectors today are the 9-volt transistor, 1-1/2 volt AA, and the 1-1/2 volt C cell. Each of these batteries have their advantages and disadvantages.
The different size 1-1/2 volt batteries (AAA, AA, C cell and D cell) all produce the same voltage - 1-1/2 volts. They differ in their current capabilities or, to a metal detector operator, the operating time. Obviously, the larger batteries will operate longer before running down.
In other words, manufacturers that have elected to use "C" cell batteries have done so because of the increased operating time over smaller 1-1/2 volt batteries such as AA or AAA types. The disadvantage of the larger batteries is the increased weight and the necessary room for housing.
Can a person add up the number of batteries in a metal detector and determine the voltage used? The answer is no. It's true that, in most cases, using the little AA size batteries, the number can be added. But there are other metal detector designs where the batteries are in parallel. For example, some detectors use two, 9-volt transistor batteries that are connected together so that the output voltage is still 9 volts. This paralleling of the batteries is done to provide extra current for a longer operating time rather than for more voltage. Connecting batteries in series [end to end] increases the output voltage, while paralleling them [connecting the batteries' positive terminals together and negative terminals together] can increase the available current.
The detector's battery situation can be confusing because of the different possibilities of use. For example, some detectors use a separate battery to power the audio portion of the circuitry. Because the audio portion of the detector can drain batteries the fastest, it is possible to replace the particular audio battery only and reduce overall battery expenses. A more common and recommended approach is to rotate the batteries periodically to assure even discharge. The best place to find such information is in a detector's manual.
In emergency situations, can battery types be substituted? For example, can a 9-volt transistor battery be substituted for a six pack of AA's (which is also equal to 9 volts). In most cases the answer is yes, but operating time will be limited. In a few cases, a 9-volt battery may not have the necessary current capability to operate satisfactorily for any sufficient time. Again, a person should check the particular detector's owner's manual.
What about substituting a 9-volt transistor battery for other size AA packs such as a four pack or an 8 pack? The general answer is DON'T. Remember to never change voltages. Using two, 9-volt transistor batteries to replace two 4 packs of AA's could change the applied voltage from the original 12 volts (the voltage of the two 4 packs) to 18 volts (the voltage of the two 8-volt batteries).
One point to remember about the different battery packs such as the 4 or 8 pack of AA's is - all these batteries are connected in series. If any one of them fail, the effectiveness of the total pack is greatly diminished. In other words, this pack is as strong as its weakest link.
Generally, if all the batteries were changed at one time and one fails some time later, the possibilities are great that the rest are marginal and probably should be replaced also.
An exception to the general replacement of all batteries when one fails is in the case of ni-cads. Due to their ability to be recharged, these batteries can last for years. Unfortunately, some fail earlier than others. In such cases, the defective one can be replaced by itself.
The use of different sizes and types of batteries by the different manufacturers can seem perplexing and confusing to a serious treasure hunter. Just remember the depth capabilities of an instrument has no correlation to the number, size, or type of batteries used. Also, remember that by increasing the number of batteries, this does not increase the power output of the detector.
Any slight increase in sensitivity that appears to occur as a result of changing batteries is usually due to a very slight increase in efficiency of the audio portion of the detector and not the transmitted power. On motion detectors having a silent search feature, these increases will normally show up in the all metal mode only.
The bottom line is, many batteries are replaced unnecessarily or prematurely. In my years of testing, I have found little advantage in changing batteries early. I have not experienced any significant difference in depth capabilities as batteries age, especially when using the discrimination mode.
A wise treasure hunter will carry spare batteries when out treasure hunting. Even new batteries fail prematurely, so, by having a spare set on hand, a treasure hunter can change them when they fail rather than arbitrarily changing them because they "might be bad."
The only time I have changed batteries early, I have done so to avoid the possibility of a battery failure when I know I am going to be a long distance from the spares for an extended period of time.
In part two of this series, we will cover the differences in battery types themselves. Hopefully, we will find answers to questions like:
1) What are the advantages of alkaline type batteries over a standard battery?
2) Are ni-cad batteries a good investment?