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White's TDI SL 4x18650 Battery Tray Made Simple


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I was looking for battery tray design for my Tdi SL which would allow 4 x 18650 batteries. As luck would have it on the local Prospecting Australia website  XLOOX posted a simple mod for a Whites factory battery tray. I don't know how to post links so the full description is to be found in the Prospecting Australia site. IMG_1286_edited.jpg.903a2d9c62b1e567617c6427d9343955.jpgSimple cut out the guts of the tray, leaving the original battery connectors with mods on one end and a copper connector on the other.  I can fit Panasonic NCR18650B cells, without nipples but with protection. They just fit snuggly. The only issue is closing the lid, you need to cut a channel under the batteries into the base of the tray to allow for this. I'll cover this with a thin carbon fibre sheet and look at using a thinner sheet for the cover also. I will also add something to secure the batteries in position. Just waiting for the postman to deliver my carbon fibre sheet before finishing my own version of XLOOX's design. What I like most is that this is simple and cheap. Must confess I am aware of many different designs, since there have been no reports of smoking Tdi Sl machines I have finally decided to give it a go.

All the best, Karelian

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Don't need to cut a channel, Karelian. Just replace the factory cover with something thin...like a section of vinyl notebook cover. When I made mine, which is almost exactly like yours, I used a section of plastic milk jug for the cover.

Jim

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Just having completed the project, I decided to do a quick check to see if the increase in voltage is worth out time, simple air test would lean towards a yes vote. Should mention that this design requires the use of the flat Panasonic cells without any protection circuit. So I use a smart charger that will not over charge cells and I'll check to see how long the 4 x 18650 pack lasts before it requires fresh cells. Yes this design allows me to carry fresh cells and swap out when required in the field.  I managed to retain the original White's battery holder cover. No smoke or issues were present when using the 4 cell pack, seems to handle the extra voltage without issue.

I did a quick air test comparing the Orange 3 x 18650 pack with the modified 4 x 18650 pack. Finally compared the results with a Tdi Pro using the same coil.

Tdi SL with gain a max, conductivity in all, pulse delay at 10, frequency in the middle. Using Super Pulse 220 coil.

12.38 volt gave 6cm on 1 grain ingot, 24cm on 0.5 gram gold coin, 32cm on gold Half Sovereign, 27 cm on US Quarter.

16.48 volt gave 8cm on 1 grain ingot, 26cm on 0.5 gram gold coin, 35 cm on gold Half Sovereign, 30 cm on US Quarter.

Tdi Pro     gave 8cm on 1 grain ingot, 27cm on 0.5 gram gold coin, 36 cm on gold Half Sovereign, 33 cm on Us Quarter.

Must mention Tdi Pro had gain set a 5 whilst the SL was on MAX...

All the best, Karelian

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I ran the pack for 4 hours to check the drain in voltage over that time. Personal habits mean I'll rarely go over 4 hours without a break so that is my personal time limit. I was using 4 x 18650 3400 mah Panasonic NCR18650B cells. The Tdi SL had an threshold hum using the speaker, to maximise power use and the coil was a 10 x 6 mono by Miner John. A cool day, fresh and pleasant. The pack was warm but not hot during testing.

9.00    am start. 16.4 volts.

10.00 am            15.5 volts.

11.00 am            14.9 volts.

11.30 am            14.6 volts.

Noon                   14.4 volts.

12.30pm            14.15 volts.

1.00 pm             13.9 volts.

Faster drop in the beginning and slowing down as the cells discharge further..  I'll swap out for fresh cells after three hours to maximise depth. The design allows for it and I have spare cells so three hours will be my limit. Still way above the starting voltage for the three cell battery tray and other options.. 

All the best, Karelian

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Yes, the nominal voltage is 14.8. That's where you get the flattest discharge curve. The voltage drops to that fairly quickly, and then you get 3 hours or so at that voltage. Anywhere under 4 hours you should be good.

Jim

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Completed product, the carbon fibre arrived so some cosmetic changes only. No danger of using this by accident in my MXT or XL Pro.

A nice project and I am satisfied with the outcome. Karelian

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Nice work, Karelian! You're going to love that added voltage.

Jim

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Karelian, are you using the stock Miner Johns coil?

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AllenJ, the air test was conducted with the White's Super Pulse 220 coil. The coil that came with the Tdi SL Special Edition has so far not seen much use. I also used an external speaker, Nokia MD-11 which works almost as well as good headphones. I like the Miner John coils for their weight and  performance, but I'm spoiled for choice. Because the Tdi SL has seen mostly beach use I have used the Super Pulse 220 and the Jimmy Sierra 14 x 8 mono that was made for him by Miner John. I don't use the folded mono coils on the beach. Because of the Coiltek Tdi 6' mono and Sadie I rarely use the smaller Miner John folded mono coils. I do like some of his larger coils for their blend of performance and super light weight. That 14 x 8 is good on all sized targets encountered on the beach and is as close to a 'bigfoot' coil I can get. It covers a lot of ground quickly.  Karelian

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That 8 x 12 MJ coil that comes with the SE is a very good coil from the tests I've done.

Jim

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