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8 minutes ago, Mark Gillespie said:

It might be of interest, the voltage of a freshly charged battery pack is only 11.5 v that is lower than using new AA batteries in the optional battery pack by quite a bit.

Are you referring to the the White's NiMH pack?  I have an R&B Li-ion pack which I just measured at 12.35 V.  (I think when fully charged it is closer to 12.5 V.)

One thing to keep in mind regarding all batteries (rechargeable and single-use) is that the stated voltage is a nominal value, and the initial (fully charged) value usually lasts only a short time.  There is a plateau (approximately constant) value which occurs for most of the battery's life which is typically a fair amount below the initial full charge.  Most of the time (marketing trickery?) the plateau voltage is below the advertised/stated voltage.

Most modern electronics (including most metal detectors) use voltage regulation circuitry which converts the supplied voltage to a fixed value, regardless of the actual supply voltage, within limits.  The White's TDI/SL is apparently a rare exception to this practice.

 

 

 

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I did a whole series of tests, on the TDI SL, and 16.8v battery. at the request of Reg S. He had particular rules about how the tests would be performed. In a nutshell, the results were a definite improvement in both depth, and sensitivity to small items. But the improvement only came with the larger coil. The smaller coils tested included the MJ 5 x 9,  and the 7,5"DF. Neither showed much improvement over the 12v battery. Reg and I discussed this, and did not come to a conclusion on the reasons. My thought was that the smaller coils are saturated at 12v, and the extra voltage doesn't allow any more current into the generated magnetic field. On the 12"DF, however the improvement was about 20% as I recall. With the 12"DF, my SL can see a 1 grain nugget at 3" in an air test. It can also see a nickel at 16.5". Best depth was with the target moving vertically toward the coil. That was one of Reg's rules for the testing. I had posted all the test results, but don't remember where. This was about 3 years ago.

Jim

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10 hours ago, Jim in Idaho said:

I did a whole series of tests, on the TDI SL, and 16.8v battery. at the request of Reg S. He had particular rules about how the tests would be performed. In a nutshell, the results were a definite improvement in both depth, and sensitivity to small items. But the improvement only came with the larger coil. The smaller coils tested included the MJ 5 x 9,  and the 7,5"DF. Neither showed much improvement over the 12v battery. Reg and I discussed this, and did not come to a conclusion on the reasons. My thought was that the smaller coils are saturated at 12v, and the extra voltage doesn't allow any more current into the generated magnetic field. On the 12"DF, however the improvement was about 20% as I recall. With the 12"DF, my SL can see a 1 grain nugget at 3" in an air test. It can also see a nickel at 16.5". Best depth was with the target moving vertically toward the coil. That was one of Reg's rules for the testing. I had posted all the test results, but don't remember where. This was about 3 years ago.

Jim

Very interesting post.  Thanks for the extra insights as to your testing.  The statement "Best depth was with the target moving vertically toward the coil. That was one of Reg's rules for the testing" is exactly the same technique I used.   I can't explain why I did my test that way instead of sweeping the coin across the coil horizontally.  There is a very noticeable different voltage if I use a fresh set of alkaline batteries.  Good to see you noticed a improvements of about 20% while using the large coil. 

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Mark, I think the entire results were posted on the White's forum on Findmall, and I may have posted them on the White's factory forum, too. I'll do some looking around. I did some other testing, too. I may have all that in my PC, too. haven't looked at it  for a while.

 I did some looking and found this in my files, on the 7.5DF:

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"

Jim

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More on this subject.....I'm just going to attach the files, as I find them

Jim

TDI SL Tests.doc

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Very interesting information.  Thanks.😀

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Jim, there's a lot of useful information in your test document.  It's opened up a lot of thoughts for me and my machines.  Thanks for taking the time.

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My pleasure, Mark. It's nice to be able to make a contribution to the forum. I've looked at, and enjoyed your videos, too, and appreciate your efforts to educate us on the TDI SL.

Jim

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I wrote that " How Too" using different batteries and a couple of things I noticed about both the TDI Pro and the TDI SL and that was feeding the SL Over 12v made signals a slightly harder response,

2 In Air Tests It was hard to tell the difference between the two,

3 For some reason my SL saw things deeper in Air Tests with the GB On, which I decided was a good thing if a person was operating it in bad ground

4 The smoothing effect shown it that beach video with the TDI Pro with the GB OFF my SL would do it with the GB ON,

5 The Battery Pack I made was good and gave me over 12v when using 9 X Duracell AA's gave me 14.49v and using Energizer Lithium gave me 16.4 because they have a much higher surface charge, But using 8 of the Energizer Lithium would give me 14.64v and a run time of over 20 hours,

6 Using the factory NiMh 2200mah battery pack would run the SL for around 4h 20mins, Using my 9 cell pack with NiMh AA's would run the SL for just over 5 and a half hours,

 

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On 4/19/2019 at 6:58 PM, GB_Amateur said:

Are you referring to the the White's NiMH pack?  I have an R&B Li-ion pack which I just measured at 12.35 V.  (I think when fully charged it is closer to 12.5 V.)

One thing to keep in mind regarding all batteries (rechargeable and single-use) is that the stated voltage is a nominal value, and the initial (fully charged) value usually lasts only a short time.  There is a plateau (approximately constant) value which occurs for most of the battery's life which is typically a fair amount below the initial full charge.  Most of the time (marketing trickery?) the plateau voltage is below the advertised/stated voltage.

Most modern electronics (including most metal detectors) use voltage regulation circuitry which converts the supplied voltage to a fixed value, regardless of the actual supply voltage, within limits.  The White's TDI/SL is apparently a rare exception to this practice.

 

 

 

The PI detectors use a voltage regulator on the Receiver, but the transmit circuitry is current driven, so a higher battery voltage means a stronger pulse into the ground. My personal theory on why this mostly pertains to the larger coils is that the smaller coils are "maxed out", or saturated, at the regular 12v nominal, so don't benefit much from the higher voltage.

Jim

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