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Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: June 03, 2017 10:50PM
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 (nickel held flat, parallel to coil) GB off, freq center, gain max. White's 12" DF coil, 18" above ground surface.
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, bar and 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. 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 losses 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

Re: Testing battery voltage comparisons
Posted by: stephenscool
Date: June 04, 2017 09:02AM
I might have to test this out myself. Have you tried it in a mono coil? Just curious where did you get the 16.8v battery? Redman won't ship international

Edit; also which year of the SL was being tested.. I have 1 here that is 2015 and couldn't replicate your results.



Edited 1 time(s). Last edit at 06/04/2017 09:08AM by stephenscool.

Re: Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: June 04, 2017 09:32AM
I'm using the Reidman battery. For the 12.6v I used the RNB L-ion. I did not try this with the mono coil. I have a Miner John 5 x9 Folded Mono...I'll try and get that done today.
My SL is a 2011 model.
Jim

Re: Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: June 04, 2017 03:04PM
OK, I repeated the test with the Miner John 5 x 9 folded mono. 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

Re: Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: July 08, 2017 01:48PM
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. If a person is running the 16.8v pack, I would use the Miner John coil when needing a small coil...though it's not improved by the higher voltage, it seems to handle it better, remaining stable with the GB off or on.
Jim

Re: Testing battery voltage comparisons
Posted by: stephenscool
Date: July 09, 2017 08:22PM
My digger coil 14x8 doesn't function properly with the 16.8v pack. GB on results in depth loss regardless of setting. Didn't try other coils

Re: Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: July 09, 2017 09:40PM
Thanks, Stephen. There's definitely something going on with some coils. Is that coil a mono, or a DD? MY Miner John 5 x 9 doesn't improve with the higher voltage, but doesn't get noisy either. But the 7.5DF sure does get noisy. Now your 8 x 14. But the higher voltage REALLY improves the 12"DF. The trouble with the 7.5DF may have been something external....maybe EMI. Seems like I tried that coil before without any problems. I may do that test again, but out in the sticks where there's no chance of EMI.
Jim



Edited 1 time(s). Last edit at 07/09/2017 09:44PM by Jim in Idaho.

Re: Testing battery voltage comparisons
Posted by: stephenscool
Date: July 10, 2017 07:00AM
Should be a mono coil. Haven't tried it with a tdi pro which has a higher v but I'm pretty sure it would work perfectly

Re: Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: July 10, 2017 07:06AM
If it works fine with the higher voltage TDI's than your SL must be less tolerant of the higher voltage than mine is. Or, the higher voltage is making yours more sensitive, and making it pick up more ground noise.
Jim

Re: Testing battery voltage comparisons
Posted by: stephenscool
Date: July 10, 2017 01:49PM
Any depth difference after 2 or 3 hours runtime? Might be too much time consuming to try

Re: Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: July 10, 2017 05:08PM
Well, the fully discharged 4 cell 16.8v pack is at 12v. It's bad on Li-ion to discharge it below 3v/cell. The good thing about Li-ion, Stephen, is it tends to stay at, or close to, full voltage until about 85% discharged....then it drops fairly quickly to the fully discharged state. So, the increased depth and sensitivity probably lasts for 4 hours, or so. To get the max life out a li-ion battery, it's best to only discharge about 50% before recharging. I plan on building a second 16.8V pack this winter.
Jim

Re: Testing battery voltage comparisons
Posted by: stephenscool
Date: July 10, 2017 08:43PM
i bought a few whites aa battery packs. I will likely tinker in the winter too

Re: Testing battery voltage comparisons
Posted by: Jim in Idaho
Date: July 10, 2017 09:21PM
If I get a project going on it, I'll probably do some pics and instructions.
Jim

Re: Testing battery voltage comparisons
Posted by: stephenscool
Date: July 11, 2017 10:53AM
Great. Looking forward to it

Re: Testing battery voltage comparisons
Posted by: markg
Date: October 08, 2017 06:34AM
Fantastic information on batteries. At one time I considered buying a set of higher voltage batteries but never did.
Thanks again

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