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  1. #1
    IdahoJim's Avatar
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    Testing battery voltage comparisons on the TDI SL

    I had some requests for testing to see if the higher battery voltage of the 4-cell L-ion added much depth to the TDI SL. To do the tests I placed the coil on a flat surface with the rod vertical. I taped a marked stick to the rod. For a target, I used a 1984 nickel. To do the test, I moved the nickel vertically toward the coil. GB off, freq center, gain max. White's 12" DF coil, 18" above ground surface. Nickel held flat, parallel to coil.

    16.8v L-ion 12.6v L-ion 10.7v nicad
    16.5" 14.5" 13.75"
    1 grain gold bar, same test, same settings.
    2.0" 2.0" 2.0"

    Nickel test GB on, but set at 0.
    17" 15" 14"

    1 grain gold bar GB on, but set at 0
    3.0" 2.5" 2.25"

    Raising the GB to max added about 1/2" to all figures for both the gold bar and the nickel

    Ground balance back to "off". Sweeping the nickel from side to side, finding the correct sweep speed by target volume....best depth at slow speed sweep.
    14" 12.25" 11.25"

    I didn't bother with the sweep test with the gold bar.

    Results:
    It's obvious the battery voltage has a direct impact on both depth, and sensitivity to small nuggets, assuming the Gb is on. All the test methods were suggested by Reg Sniff, other than the testing of the GB on and off comparisons. One thing I learned from the testing was in finding a weak signal, moving the coil up and down may enhance the target signal, if the target is metal.
    Assuming his health issues don't prevent it, Reg is going to do some experimentation on the SL to try and figure out why sweeping the nickel loses so much depth compared to moving the nickel vertically toward the coil. If we're fortunate, Reg will also test his ideas on improving the range of sweep speeds that work well. Right now, for max sensitivity, the best sweep speed is slow.

    Hat's off to John, down under (Auminsweeper) for his suggestion in a PM to me that the SL is the most sensitive with GB "on", which is contrary to most detectors. Turn that GB on, even if you set it at zero, for max sensitivity. if you can run it full on, better yet!
    Jim
    Last edited by IdahoJim; 06-03-2017 at 08:00 PM.

  2. #2
    deolslyfox's Avatar
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    Thanks for sharing !!
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  3. #3
    rchalker's Avatar
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    Thanks for the information.
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  4. #4
    IdahoJim's Avatar
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    Somebody requested that I repeat the tests using aMOno coil. I have a Miner john 5 x 9 Folded Mono, so used that.
    Far different results. Sweep speed is much less critical. It would only detect the nickel at 11". Changing batteries might have made a 1/4" of difference. same with turning GB on and off..... much less difference in detection distance. But, with the 16.8v battery, the White's DF 12" coil is 1" better on the gold bar. Even with the 12.6v battery, the DF still had 1/2" better performance on the gold bar.
    On the sweep speed..the MJ was much less critical, and the optimal speed is faster.
    There was MUCH less difference in distance with the different battery voltages, too. The max difference was about 3/8".
    Turning GB on and off, and cranking it to max made very little difference.
    The MJ coil was noisier with the GB maxed out.

    All this makes me think the mono coil is reaching it's max current with the standard voltage, so extra voltage doesn't accomplish much.
    I would never have guessed that there could be so much difference simply by changing coil types.
    Jim

  5. #5
    deolslyfox's Avatar
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    This is how we all learn Jim. Thanks !!
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  6. #6
    IdahoJim's Avatar
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    I tested the 7.5DF coil today. Absolutely no benefit to the higher voltage. In fact, with the GB on, the coil was pretty noisy. It's obvious it's maxed out in the SL at 12v. With a 16.8v battery pack, the 12"DF is more sensitive to small gold, by a considerable margin, than either the 7.5DF, or the MJ 5 x 9, at least in an air test. The 12DF is also deeper on the nickel than either of the other two. Again, by a considerable margin. The downside to the 12" is it's 12"!. Lots of places require a small coil, just for access. I would like to try a 14" with the higher voltage pack, though I'm starting to think the 12" gives you the most "bang for the buck" with the higher voltage in the TDI SL.
    Jim

  7. #7
    deolslyfox's Avatar
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    Thanks Jim !!
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  8. #8
    rchalker's Avatar
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    Interesting test results.
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  9. #9
    IdahoJim's Avatar
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    One thing that is becoming apparent is that there are limits to how hard you can drive a coil. At some point, the coil is saturated and that's that...more voltage doesn't accomplish anything, and may, in fact, be a bad thing. A mono coil my become so saturated that it doesn't quiet down enough, when listening, to hear a faint target. That may be what happened when the coil became noisy when the GB was turned on. The Miner John 5 x 9 didn't improve, nor did it get noisy. That may be because with it's folded design, it actually has the windings of a larger coil...the portion that is twisted and folded back into the center. So, it's about maxed out at somewhere between 12 and 16.8v, but not over-saturated, so as to become noisy. When both the 7.5DF and the MJ are operated at 12.6v, there's little difference between them, in my experience. One of the guys in the UK, I think, mentioned his aftermarket coil also became noisy when he tried to run it at higher voltages, too. I forget who it was. As I recall, that also was a smaller coil.`
    Jim
    Last edited by IdahoJim; 07-08-2017 at 01:48 PM.

  10. #10
    I wish Whites would make one of those battery packs for the SL, I have been saying it for a couple of years now because I would rather use Whites Branded/Approved Products, The New Coils that are made in Australia are the only Coils that I know of that takes the TDI's to the next level, Although the TDI's can run Coils made for another Brand These new Coils are made soley for the TDI Range of Detectors and they have more horsepower when it comes to dealing with that Red Aussie Dirt, Like I said before it is a shame that Whites has ceased making the TDI Pro because with these new Coils you can see the difference in sensitivity and depth, Given the Battery power the SL can hang with the TDI Pro, So it would be a good idea if Whites endorsed or agreed the use of those Coils because they could keep the TDI SL going for a few more years.

    To make the SL more suitable for prospecting It Must have the Higher power battery packs and those Coils because without them it becomes more of a Relic machine and as such people are buying older Tech machines of another brand, The MXT is a classic example of this because there are over 40 coil on the market and there is nothing you can't do with the MXT apart from take it swimming.

    Food for thought, aye.

    John.

  11. #11
    IdahoJim's Avatar
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    The other coil that had noise problems with the higher voltage was an 8 x 14. This was reported by the user on a different forum. He quit using the higher voltage pack, as he was concerned it was messing up his TDI SL. I'm wondering if the noise problem is simply a significant increase in sensitivity, which requires reducing the gain to quiet things down. it dawned on me that I've used the 7.5DF with the higher voltage pack without problems. Why it got noisy during the recent test could have been an external issue not related to voltage. If I can remember to do it, I may run that test again, and in a more remote location to be sure EMI isn't the noise source. The noise got much worse when the GB was turned on.
    Jim

  12. #12
    Quote Originally Posted by IdahoJim View Post
    The other coil that had noise problems with the higher voltage was an 8 x 14. This was reported by the user on a different forum. He quit using the higher voltage pack, as he was concerned it was messing up his TDI SL. I'm wondering if the noise problem is simply a significant increase in sensitivity, which requires reducing the gain to quiet things down. it dawned on me that I've used the 7.5DF with the higher voltage pack without problems. Why it got noisy during the recent test could have been an external issue not related to voltage. If I can remember to do it, I may run that test again, and in a more remote location to be sure EMI isn't the noise source. The noise got much worse when the GB was turned on.
    Jim
    Yes Jim you are right because even with the Gain set to 10 by boosting the Voltage you are in effect turning it up to 11 or 12 so with such a Coil and that Voltage you can afford to turn it down a notch and live the quiet life, lol.

    But most prospector like to run their machines right on the edge but that does not always pan out right, Sometimes too much power is not always a good thing, But I would be running it somewhere between a 3rd of the way where it starts to get noisy and the maximum setting So it can deal with the ground but also pick up those fine targets.

    John.

  13. #13
    IdahoJim's Avatar
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    Thanks, John...I'm definitely going to try that next time I'm out. Right now, I just got done mowing 2,000 sq ft of lawn, and I'm beat...LOL Got the fan blowing on me, and a cool drink in hand.
    Jim

  14. #14
    Quote Originally Posted by IdahoJim View Post
    Thanks, John...I'm definitely going to try that next time I'm out. Right now, I just got done mowing 2,000 sq ft of lawn, and I'm beat...LOL Got the fan blowing on me, and a cool drink in hand.
    Jim
    Forget the Mower and buy a Goat, lol They are much cheaper to Run and they get great gas Mileage too, lol. You can still have the beer while you watch the Goat do all the hard work,

    Another thing about turning it down a touch is that you have a few extra horsepower in reserve where the ground is not so noisy which has to be a Bonus I reckon,

    John.

  15. #15
    IdahoJim's Avatar
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    Yup...having a reserve is always good. I don't need a goat to mow the lawn...I need to teach it mechanics. I spent the day replacing the upper and lower control arm bushings on the driver's side of the Dodge. Passenger side tomorrow, if I don't get it done today, too. At 68, I'm getting a little old for this stuff...LOL...and my aching body is reminding me of that...Ha!
    jim

  16. #16
    rchalker's Avatar
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    Well Jim, just don't over do it. Take your time and get it done though. Nowadays, I draft my son for stuff like that.
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  17. #17
    IdahoJim's Avatar
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    What gets me, Rodney, isn't the work so much as that getting up and down from under the truck. I've been rebuilding the Dodge a little at a time since late last summer. Mostly done now. Now I'm down to the suspension. I'm going to quit after the control arm bushings...for now. Probably put in new rear leaf spring bushings during the winter. I installed a new power steering pump last fall, and even though the it was a top brand, it started leaking. The dealer gave me a new one, but I still have to do the work. Another 4 hour job this week. But then I should be good to go for awhile....back to prospecting...LOL
    Jim

  18. #18
    IdahoJim's Avatar
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    OK, Guys. On the battery tests I did on the 7.5DF, I screwed up. I forgot to turn the pasture pump off. There's a buried 220v line that goes over to the ditch bank, and that was giving me some nasty EMI during the test. I redid the test this morning, and here's the result. It's obvious that with the smaller coils, there isn't much, if any, difference because of the battery voltage. But, note the difference on the nickel with the GB on and off. That is a significant difference and has shown up through all the tests, regardless of coil, though the Miner John 5 x 9 Folded Mono showed the least difference. Considerable difference on both of the DF coils.

    Battery Voltage tests Whites TDI SL 7.5"DF coil
    Freq: centered: Pulse Delay: 10: Gain: Max

    !6.2V

    Nickel 1 grain Gold Bar
    GB OFF: 10.75" 2.75"
    GB ON Switch in "all"
    Min. 12.75" 2.75"
    Max. 13.25" 3.00"

    GB On Switch set in "low"
    N/C N/C


    12.3v Nickel 1 grain Gold Bar
    GB OFF 11.0" 2.75"
    GB ON
    Min. 12.75" 2.75"
    Max. 13.0" 2.75"
    Last edited by IdahoJim; 07-24-2017 at 09:21 AM.

  19. #19
    deolslyfox's Avatar
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    Thanks for the update Jim !!
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  20. #20

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    Quote Originally Posted by IdahoJim View Post
    Yup...having a reserve is always good. I don't need a goat to mow the lawn...I need to teach it mechanics. I spent the day replacing the upper and lower control arm bushings on the driver's side of the Dodge. Passenger side tomorrow, if I don't get it done today, too. At 68, I'm getting a little old for this stuff...LOL...and my aching body is reminding me of that...Ha!
    jim
    Well theres the problem, only thing dodge ever did right was put a cummins in it! sooooo sad I had to get rid of my 12 valve, one day i'll wad one into a proper truck.

  21. #21
    IdahoJim's Avatar
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    Actually, this truck has been the best rig I've ever owned. Drove it almost 300,000 miles, a lot of it in very rough country. In the last year I put another $9,500 in it, but it now runs great, and I trust it to bring me home. Should last the remainder of my driving years.
    Jim

  22. #22

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    Thanks for posting this.

    I have a Dual Field. I like to dig really dig stuff, like heavy gold. I think I am at my limit at around 16 inches, with a faint signal on "honker" gold and silver rings.

    My question is this: I currently use rechargeable batteries. And, when the speaker volume gets low, I recharge them. But, what I don't know is whether a lower charge on the batteries also translates to less depth?? If so, I will probably quit using rechargeables, and go to regular batteries. What do you think? Are lower charged batteries affecting my depth?

    The other thing that I am trying to figure out is whether there is a way to get up to four more inches of depth on the same sized objects, on the Dual Field?? Would some sort of stronger batteries do the trick? Is there a way to buy a more powerful battery pack? It looks to me like you are getting three more inches on the nickel, with the 16.8 volt battery pack. Is that correct? If so, that is a whopping three inches, which is a big deal when digging rings. Is there a way that I can run higher power batteries to get a few more inches of depth, on my Dual Field? I currently own three Dual Fields. One is a back up. And, one is a back up to the back up. I would be willing to spend money modifying one or two of my Dual Fields, and then keeping the third one for a backup. Is that feasible? If I could get three more inches on the detector, for the same sized objects, I would not want any other detector. What do you think?

    Also, I am very serious about detecting. I am close to going in to this full time.

  23. #23
    IdahoJim's Avatar
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    I'm not familiar with the DF. I don't know what voltage the factory battery pack is. I do know you can pack more power into less space using Li-ion. The 16.8v pack I'm using in the TDI SL is a 4 cell pack. I can't use a 5 cell pack without damaging my detector. The capacitors in the power supply are rated at 16v. Basically, when fully charged I'm exceeding the rated voltage, but there's some safety factor in the rating, and that enables the power supply to tolerate the higher voltage. So, before you decide to use a higher voltage, you have to know a few things about your detector. What's the standard voltage? What type of battery does it come with from the factory? What's the physical size of the pack? What tolerance is there for increasing the voltage? On pulse induction units, the transmitter is usually not run from a regulated supply, so any voltage increase, up to a point, increases the power going into the ground. The extra voltage has no effect on the receiver circuit, as that circuit is fed by a regulated power supply...increasing the voltage does nothing.
    Jim

  24. #24

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    Quote Originally Posted by IdahoJim View Post
    I'm not familiar with the DF. I don't know what voltage the factory battery pack is. I do know you can pack more power into less space using Li-ion. The 16.8v pack I'm using in the TDI SL is a 4 cell pack. I can't use a 5 cell pack without damaging my detector. The capacitors in the power supply are rated at 16v. Basically, when fully charged I'm exceeding the rated voltage, but there's some safety factor in the rating, and that enables the power supply to tolerate the higher voltage. So, before you decide to use a higher voltage, you have to know a few things about your detector. What's the standard voltage? What type of battery does it come with from the factory? What's the physical size of the pack? What tolerance is there for increasing the voltage? On pulse induction units, the transmitter is usually not run from a regulated supply, so any voltage increase, up to a point, increases the power going into the ground. The extra voltage has no effect on the receiver circuit, as that circuit is fed by a regulated power supply...increasing the voltage does nothing.
    Jim
    Sorry, in a previous post, I wrongly assumed that DF stood for "Dual Field". I mis-read the entire post, as a consequence.

  25. #25
    IdahoJim's Avatar
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    Quote Originally Posted by BenjaminE View Post
    Sorry, in a previous post, I wrongly assumed that DF stood for "Dual Field". I mis-read the entire post, as a consequence.
    No reason to be sorry. Do a little research on your model on the 'net. There's probably all the info you need to make a decision on a higher voltage battery pack for it.
    jim

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