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Detector Coil size VRS. Battery Draw P.I. Detectors


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Sensitivity of the Smaller coil may be such that at the higher levels it maybe swamping out the detector. Not having a Minelab I don't know for sure.

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FRANKC

I really don't understand why you are so concerned with how much current U use, are you not using

rechargable batteries? My battery outlasts me 10 to 1 in a day...

your detecor transmits a signal into the ground and the receiver picks the signal up when you ate over

metal or hot ground when you are not receving a signal there's no sound your receiver is in nutral so to speek

when you are over a weak signal the amp part of the receiver taks little power when you are over a booming target

the amp sucks power big time,I know this for sure because I hooked a amp meter to the battery and read it,the more

you turn the volume up the more power U use..

Therefore you should use an amp with it's own power source......

Happy huntin..

Rodd

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Greetings Rodd, yes thats one thing I've really noticed those overload signals suck that battery quickly.

Another area I am going to experiment with is detector volume control setting when running the amp.

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Frank ( rockhunter1620) I am going to do some experiments with and without the amp, and also using another amp of different manufacturer with my larger coils.

And also some smaller coils.

I believe large overload type trash signals and high volume on both the detector and amp are whats cutting battery charge life.

My ears are super bad and I have never even tried using the detector without an amp but I am going to give it a whirl next time out.

To give you an idea of how bad my ears are I tried using a single earcup type headphone and forget it I can't hear Sh##.

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Yet another reason to build My Epidermis Electro Stimulus Target Identification System!

Not Intiteded for Rainy days!

Animated20Gif20Lightning205.gif1904.gif

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Frank, for my bad hearing I wear PHONAK behind the ear hearing aids and use dual external speakers with My 5000. I used the same setup with My 3500. The $5000 hearing aids are furnished by the VA at no cost to Me. Any Vet with a hearing loss can get them.Plus batterys for life.

I don't miss many targets with this setup.

Harry

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Frank, not sure why you brought this up...but, be sure the batteries are good...some of my l-ions camcorder type batteries have gone bad...but they don't just die they sort of linger, take some charge and seem fine, they even read the correct charge but then....they are dead in a few hours...it can be very difficult to isolate one cause...there can be many small problems that add up to a big one. Problems such as corrosion, loose connections, semi-faulty coils, intermittent detector problems and human perceptions and error...

So, what exactly is your issue...or are you simply curious?

fred

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Fred I'm at a point where I am trying to change a few things around. I've been fairly productive concerning hours spent in the field vrs. quality of finds.

Now I'm sort of trying to streamline my equipment and either retain or improve the production from it.

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Yeah, Frank after using a Minelab Pi for about 15 years, I have almost perfected my set-up...

as to battery draw I think the biggest draw would be an external speaker and double that with a dual speaker system...assuming they are running off the minelab battery...I always carry a spare l-ion as they can go south at any time and with little warning...I donot notice any real difference in battery useage from 11 inch to 18 inch coils...I never use an 8 inch coil...don't have one...I have always used an enhancer on every Minelab Pi I have had...

fred

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Frank I've been using Minelab PI's since the first SD2000 hit the USA.....that was near as I can figure 18

years ago (man where did that time go)....and I've NEVER had a problem with a Minelab battery....some of

mine have been 5 years old and were still out lasting me in the field when I sold the unit....but being a

skeptic I always have another one in the truck for back-up.....it's a know fact that if I go beeping without

a back-up battery mine will go South....

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Fred ... On my GPX5000 ... and previously on my older GPX4500 ... I use a double external speaker that was one of the very first made by Montana for AZO back in my GP3000 days (2003-2005+/-) ... I have never outlasted a battery in my longest of detecting days. I really don't think they draw any more than a high quality set of head phones. And I agree with everyone else a spare battery makes sense even if only to stay charged and ready for duty but never called upon. Made the mistakeof taking only one to Quartzzite last December ... paid the price with a dead and defective battery ... lost a good last day of detecting on that trip.

Mike F

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Mike; I know that if you use the built-in speaker on a vlf the battery will drain much faster...one of these electronic guys could do the math...that being said, I don't notice any difference in battery life between my dual speaker usage and my little sony-behind-the-ear headphones or my rarely used sunrays...and all of these with an amp...

I think the main difference is the battery itself...but, have no proof...

I never had any problem with the stock minelab six pounder...they were/are almost foolproof...

fred

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Fred ... I would agree with all you said ... the L-ion on the GPX5000 is vertually bulletproof as well and last a long time ... more hours than I can detect in a day anyway! I suspect it would take somewhere between 10-14 hours to discharge the stock L-ion on my GPX4500 or 5000 as I have had the detector on a full 8 hours without a lost of service. When I do a battery check late in the day of a long day in the field I am usually down to 7.7v or 7.6v ... it warns at 7.3v and shuts down at 7.2v I believe.

Mike F

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Hi Frank,

I had forgotten about the post that was on another forum pertaining to coil current and battery life, but even though that post is a few years old, the fundamentals still stand.

ML detectors are very finicky about what coil will work on them, so as a general rule, the inductance and resistance remain the same regardless of coil size. As mentioned in the other post, there can be some variation between the DD's and the Mono type coils but this can occur because on a DD, the receive winding is the winding that plays an important part as to whether the coil will work or not. In the case of a DD, one can vary the inductance a little more and still get the detector to work ok. This was pointed out by Robby H. on the post on the other forum. However, even as he stated, the change is very little.

One other interesting post on that other forum indicated the ML average current draw to be about 0.8 amps with variations of up to about 0.1amp. So, in very simple terms, the current draw is over 3/4 amp and usually less than 1 amp per hour.

Now, with all that gobbly-gook out of the way, the basic rules still apply and that means because coils have basically the same resistance and inductance regardless of their shape and size, the results will be the same current useage.

We have a tendency to try to think in common sense terms and not so much in technical terms, especially if the technical training is not there. This is what makes us human and always trying to find an answer to a problem needing technical training to better understand.

As a perfect example, if you run a battery down froma full charge does it weigh less? Think about it, something changed, right?

Well, that is off the subject a little, but when you read all the different posts on this thread, there are some good answers relating to battery life to keep in mind. One good one has to do with external amplifiers. If that amplifier has its own battery then the detector battery useage is or should be minimal.

As mentioned before, some typical battery currents of a ML PI were in the .80 amp range. Now, if a person uses a 7800 ma battery which is the same as saying it is a 7.8A battery, will the battery last almost 10 hours? The simple answer is no and that is based upon the fact that most batteries are rated based upon an ideal current draw. Change the amount of current used and the battery life can diminish quite dramatically. Actual battery life at heavy current drains can reduce to half time or so and in doing so, the internal battery resistance can become a problem resulting in detector stability. So, in simple terms, a 7800ma battery may only last 4 to 5 hours continual use and still be be in good or at least usual shape.

Just so you know, the typical current output of a Li Ion 18650 cell is about 2600 ma or 2.6A at 3.6V. So, for a 7.2V battery we have two cells in series. Now,, if you want a 7800 ma battery rated at 7.2V, there will be three battery stacks in parallel (where a stack consists of two cells in series). thus, there will be 6 batteries that could fail.

What makes things worse is the ease of buying lower priced batteries with claims of having the same battery life as a quality made battery. A cheap chinese knockoff, as a general rule will not last as long or work as well as a quality made battery from a different source.

All of this is compounded by the fact that when a battery pack fails, it usually is because of one weak battery giving up. Since the batteries are usually in series, then one weak one renders the entire pack useless that is made up of only one series stack. In the case of multiple batteries in parallel, one dead battery drops the effectiveness signficantly, thus one will experience a shorter run time.

Finally, if battery life is something one is trying to increase, then when you stop detecting, turn the machine off, even if it only for a few minutes at a time. You would be surprised at how much battery drain can happen if this simple rule isn't followed.

JasonG pointed out something to keep in mind and that is, the edge of a large coil allows a person to detect small gold quite well. No, you won't get dramatic depth but a few inches is better than trying to detect that same nugget by using the center of the coil. Try it and you will see what I mean.

Now, knowing the edge of the coil can be the detection zone for very small nuggets, can anyone now better understand how one can dig a deep hole before finding the nugget? The bottom line is the nugget isn't where we think it is.

Now, for those of you who still want to check for themselves on this coil size and battery current, I strongly recommend you use non contact test equipment. In this case, a simple clamp on ammeter that uses an inductive pickup works quite well and is reasonably accurate. Here is a link to what I mean.

http://www.ebay.com/...=item1e6641e475

There are lots of clamp on meters but most do not read DC current, so be careful when buying one if that is your purpose in buying one. Personally, I like the DC current clamp on because I can even read the battery current draw of a vehicle without taking a battery lead off.

Just clamp the jaws around one of the leads coming from the battery and read the current. This is about the safest test one can do and should be accurate enough for what you are wanting to know regardless if you are checking a detector or your car.

On the detector, use an old lead acid battery hookup for the easiest access to a battery lead and clamp around one of the battery leads and you should get an idea of the current drawn. Change coils and you should see little to no difference.

Reg

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Reg ... Believe it or not that clears up a few questions I have from time to time. Thank you for the non-technical version!

Mike F

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Thank you for tuning in on this Reg.

Hapy Huntn

Frank,

I have all the wizbang electronic test equipment. If I remember right, your battery was external. Are the leads available to get a clamp around. I can measure DC current with a good quality clamp on. We we hunt together again, remind me to throw it in the go bag and we can test actual current on your unit, if you would like.

Jim

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Thank you Jim, we do need to get together again in a more productive environment to hunt for sure.

As far as the test equipment goes it won't be necessary. I have my ways thru many years of DIY handyman/craftsman or of being able to ascertain problems and remedies and I have everything under control.

I am just doing a bit of "BALANCING" on my equipment setups to test things as I go along to find the exact combination that satisfies me with its performance.

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