TDI Battery Pack Conversion

[Steve Herschbach]

On 2/1/2022 at 12:07 PM, Dave Rosy said:

Well, that's a bit (more than a bit) of a bummer... "Does Not Ship To Canada"... Frustrating.

https://www.reship.com

[Jeff McClendon]

I also ordered the orange battery pack from Kiev Ukraine about 3 weeks ago. It arrived today. Outstanding product and a great way to get 12.6 volts of power from three 18650 lithiums.

I made the 9 AA battery holder recommended by Auminesweeper since I had an extra battery tray and several single battery holders. Since I like to use rechargeable NiMH batteries which are 1.2 to 1.4 volts that gives me another way to get 12 volts into my SPP.

A word of extreme caution. I also made a 4 Lithium battery pack out of another Whites battery tray. I only charged the Lithiums to 3.7 volts so I had exactly 14.8 volts going into my SPP that I got from Snakejim. I had been hunting for about half an hour but it was a really hot day. I heard a really loud rise and fall in the threshold tone and something popped. Turned it off and back on. All I had was a steady threshold tone. It was like there wasn't even a coil on the detector since the SPP could not detect any targets. When I got home I tested the charge level and volts of the battery pack=14 volts exactly.

So, my nice SPP has been sent to the Oregon repair facility. Hopefully it can be fixed. 

If it is repairable.......no more 14+volts. I will keep the voltage at 12.6 maximum from now on.

[chiil]

Oh dang.  Sorry to hear that.  Isn't the SPP based on the SLI?  I recall Geotech stating the SLI could handle up to 20V, and possibly 25V.  I wonder if something else popped.

[V3i/MXT Pro]

Sorry to hear about your SPP Jeff. I ran my TDI SL for many hours with the 16.8v Li-ion setup, on hot Summer beaches, without any issues. My guess would be something unrelated let go inside your machine… I hope it’s repaired and back in your hands soon!

[Jeff McClendon]

I seem to remember somebody with a whole lot more knowledge of the TdI SL than I will ever have....(Carl or Reg) once mentioning that part of the audio circuitry was only rated for roughly 12 volts......maybe I misunderstood.

[chiil]

Link to the information.  According to Carl... "There are a couple of 16V caps in the audio stage but they are on a regulator that maintains 11.2V regardless of battery. I did that so audio volume remains the same if you use a bigger battery."

[V3i/MXT Pro]

I remember reading that from Carl, thanks for sharing again. I was getting similar depth on my TDI SL (with the 16.8v battery) as my TDI Pro. The main difference was the TDI SL had a much smoother threshold and was a lot lighter in weight. I ran many hours with that pack fully charged to 16.8v and never had a problem.

[Jeff McClendon]

Thanks Chiil for reposting that information.

Makes me feel a little better……….?

[Geotech]

Jeff, it's likely that something in the transmitter popped, maybe the TX FET overheated. Components should be able to handle up to a 20V battery but there is a chance that a high battery voltage will cause the TX to run hot. Unlike the TDI, the FET on the SL does not have a heat sink, rather it uses the PCB as a heat sink. I'm surprised that 14V caused a problem. Let me know what you find out from Todd.