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Tdi Pro 18v + Battery Pack. 5 X 18650 With Dedicated Charger.

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First test using the higher voltage battery matched with Miner John 14 x 8 mono. No issues with smoke or fire, everything works well so far. Lousy EMI today, lots of people working from home etc, Picked up 12 wifi connections on my ipad... Lots of EMI. Might retest super early in the morning. I could not get gain up very high, max was 6 with the modified Pro today and even then it was playing up. Super stable and smooth at a gain of 3... so I pushed it to 6.

Ground balance was off, conductivity was in ALL and pulse delay was 10.

 A one grain ingot came in at 10cm, or a 1 cm increase over the stock battery.

The half gram gold coin was 37cm or a 2 cm increase over the stock battery.

The half Sovereign gold coin was 46cm for a 1 cm increase of the stock battery.

The conditions today warrant a retest at a later date. When circumstances allow I'll take the machine down to the beach and perhaps even the goldfields. Not possible now.

So no issues with the battery pack itself, machine behaved well. Very small gain in performance over standard battery pack, but there is an increase. I can see myself using two of these higher voltage packs in an eight hour day, to maintain the peak performance and not run down the packs too much.

I removed the heat shrink and will reapply later with lessons learnt from my first attempt. Parts list etc more to come later.




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Good job, Karelian! Kinda wish I could find a cheap original version and do the same.


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I've spent time using the Tdi Pro machines and have noticed that they vary a lot in their performance. One day you can push gain all the way with no issues, other days three or four is as high as you can go if smooth operation is the goal.

Contrast the Tdi Sl, almost always it will let you push the gain to max with rare exceptions. Push it and it is still smooth and stable. This is particularly true in urban areas where EMI is always present to some degree.

In my view the Pro machines are deeper most of the time, even in bad EMI but the SL sure is one smooth operator..

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Do you believe you would see a similar performance increase with ground balance on?  I have an original TDI but I always have ground balance on when I am out detecting.

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Yes the extra voltage will provide a small increase in performance over the standard battery regardless of other variables, including ground balance. So the same machine with ground balance on operating at the same location will see a small increase with the higher voltage battery. The combinations of a modified Tdi Pro and the higher output battery will combined increase depth by only a small margin. For example: the standard Pro with standard battery will detect 1 grain at 9 cm, modified pro with standard battery gets 10 cm, modified Pro with high voltage battery 11 cm. Baby steps all the way. So no dramatic increases, the main benefits being smoother threshold and the peace of mind that the machine is operating at its peak performance..

When circumstance change I will take the modified Pro with higher voltage battery prospecting and beach detecting  putting them to the full test, same goes for the White's GMX. Air tests are a poor substitute for real operational use in the field.

tdi shadow dusk.jpg

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  • 5 months later...

Sorry for the delay, it's been a distracting year or so. Will complete testing the Tdi Pro modified with the upgraded  battery, as soon as it stops raining... in the goldfields with targets in the ground. I'll include the parts list etc.

The modified pro with that 18 x 6 mono coil has performed very well on the beach, punches deep and covers lots of ground.   The modified unit is going soon but I'm keeping the standard machine. Apparently 'she who must be obeyed' just noticed there are two Tdi Pro machines and is on the warpath..  I just need to give it a final run on the goldfields.  Some testing and opinions to follow shortly. Rain permitting..

All the best. Karelian


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Just finished my second attempt at the heat shrink wrap. This time I used a hair dryer, perfect for this material. Stay away from flame lighters etc. Just wanted it simple and tidy. Perfect fit no issues.

Kept the battery in the machine for over a month, naughty but I wanted to check for parasitic drain. None found.  Next job was to run the machine until the battery was run down and then recharge. Then repeat a few times.. Again so far no issues found. Setup seems to work well.

The heat shrink wrap was new to me, once I worked out that a hair dryer is best I was comfortable with the material and should only improve my technique.  Important since I will be refurbishing older factory packs with new cells in the near future. Again giving the Tdi Pro a boost and longer service life. The issue of older battery packs is now much less of an issue for me since the idea of refurbishing them seems less of a challenge. We learn as we go along.

Once I've fully tested the 5 x 18650 battery pack I'll consider making a second one since I've got enough spare parts and cells for the project. Two upgraded battery packs will provide the Tdi Pro modified unit with enough power for a full days detecting.  So far so good, next step is to give her a good run out in the goldfields.

All the best.







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And here’s me going back to a stock battery......well not quite....it’s a 3 x 18650 setup @ 11.1v. In another thread, I mentioned the super hotspot on my TDIBH board when running the 14.4v battery which got me worried. Being sealed up, there's probably less opportunity for the heat to dissipate. Even when opened, the hotspot was severe.....couldn’t touch it for more than a second or so without burning a finger. 
My depth results were a maximum increase of 2” over the stock battery. In fact, my current 11.1v Lithium setup sits in the middle (depth wise) between the stock battery and my retired 14.4v battery so I’m more than okay with just the 1” drop.



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Now that White's is gone, pays to nurse the machines. I keep the SL machines well under 16 volts, just peace of mind.

My standard Tdi Pro had standard battery packs that are 16.8 volts hot off the charger, no problems there. The modified Tdi Pro is the machine that gets the hotter  5 x 18650 battery pack, in for a penny in for a pound.. Hot off the charger it has 21.5 volts if I let it. I use a timer and try and keep it at 20 volts max or just a bit under.

Just started a discharge experiment, battery was in the machine for a month after being charged to 20 volts.

Starting voltage was 19.53 and I'll check it every hour after that to see how much run time if provides. I am looking to go down to roughly 3.2 volts per cell or 16 volts for the pack.  So maximum charge of 20 volts and maximum discharge to 16 volts. We have to draw our lines somewhere. That leave run times. I'll have the answer to that shortly.

Ok so after one hour or run time starting at 19.53 volts it is down to 18.47 volts.  . no outward signs of heat issues. Removed battery and checked the machine for warm spots etc. Have used this setup on the beach for many hours and the Tdi Pro seems to work without any issues at the higher voltages. Long term wear or strain on components is another issue, so far so good.


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Results of the battery endurance test. No surprises here, I've used the battery enough to know that a full charge will see you to 4 hours. From 21.5 volts to 16 volts is 4 hours. Today I used the speaker and started at a lower voltage, just over three hours and twenty minutes runtime. The PCB will cut the power at 16 volts so you cannot overly discharge the cells. No warning the machine just turns OFF. That is a good thing.

Started at 19.53 volts, an hour later 18.47 volts. An hour later 17.74 volts , an hour later 16.76 volts and twenty minutes later it cut out at 15.97 volts. Three hours and twenty minutes, use a set of headphones and you will get extra runtime.

Ok maybe I need three battery packs for a full days detecting...? All for now, all the best.

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