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TDI Battery Pack Conversion


Dave Rosy

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Got my SPP back from Centreville Electronics NW. Todd replaced U3 IC and a 100uf SMD Capacitor.

It is definitely back up and working well for very little expense. 

My only small gripe is that it is not as sensitive to smaller targets .5 gram and under as it was before those parts fried. It air tests to less distance with coin sized targets than it did before also by about an inch using the MJD 9X5 folded Mono and Detect 8" Mono. Both are detecting a .5 gram gold coin at 6" and will barely hit a .25 gram nugget. The .5 gram gold coin was air testing out to 7" and the .25 gram nugget was testing out to 2" before the parts fried.

Also, I am seeing no difference in depth or sensitivity with the 14.8 volt 4 lithium battery pack and the 12.6 volt 3 lithium battery pack and the 12.6 volt NiMH 9 battery pack......... 

I will keep testing and maybe get to hunt with it tomorrow a little. 

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Jeff, what voltage are you charging the 4-cell pack to? It should be making a noticeable difference.

Jim

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4 minutes ago, Jim in Idaho said:

Jeff, what voltage are you charging the 4-cell pack to? It should be making a noticeable difference.

Jim

Hi Jim

I am being super careful and only charging to 3.7v per battery so 14.8v.

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I got some time today to test the repaired SPP.

I went ahead and charged the lithium pack to 16 volts, got a 9 AA NiMH rechargeable battery tray charged to 12.6 volts, some targets..... US quarter, US nickel, 0.5 gram gold coin, 1.2 gram specie and .25 gram flat nugget and headed out to the testing area I usually go to that has next to no audible EMI.

I had the Miner Johns 9X5 folded Mono and the Detech 8" Mono.

I found the 16 volt tray got about an inch more air test distance than the 12.6v tray. Results with the 16v tray were = the .5 gram gold coin (7"), US nickel (11"), US quarter (11.5") while .25 gram flat nugget was barely detectable at 1" and the 1.2 gram specie was detectable to 2" using the Detech 8" Mono.  The Miner Johns 9X5" folded Mono was about 1/2 inch shorter distance than the Detech 8" on all the coins, hit the specie at about 1" and could not detect the .25 gram flat nugget unless it was touching the coil.

So the 16v tray was marginally better than the 12.6v tray. However, the 16v tray got a lot warmer to almost hot at the +/- terminal end of the tray where the tray is closest to the PCB. The 12.6v tray got slightly warm but definitely not hot.........

I also had the Ukrainian orange, three lithium battery 12.6v tray with me. I tried all four batteries in that tray to see if I might have a bad cell among the four. That tray did not get hot, only slightly warm. Maybe I made a lousy 4 lithium tray or something else is going on.

thanks for reading.

Jeff

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I ended up selling my MJ 5x9., Jeff. I just didn't think it was very good. I much prefer the DF 71/2, or 8 x 6 Sadie. I do like the MJ 8 x 12, however. Sorry to hear your detector gets hot with the 16v battery. it does make a difference.

Jim

 

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On 10/10/2022 at 8:09 PM, Jim in Idaho said:

I ended up selling my MJ 5x9., Jeff. I just didn't think it was very good. I much prefer the DF 71/2, or 8 x 6 Sadie. I do like the MJ 8 x 12, however. Sorry to hear your detector gets hot with the 16v battery. it does make a difference.

Jim

 

I've never owned a 7.5 DF so I have no idea how it performs. I love the Sadie coil. Personally I had the exact opposite experience with the MJD 8X12 versus the MJD 5X9. I really like the 5X9 that came with my SPP.

So, I got to do a lot more testing today. I think the entire overheating and maybe fried U3 and 100uf cap were caused by the Detect 8" coil. On power up I get all kinds of weird, loud tones for almost 3 seconds and all three of my battery trays heat up quite a bit. With the MJD 5X9 I get the normal quick startup tone that I am used to with TDI Sls and all of my battery trays from 12 volt to 16 volt just get warm not hot.

Does that make any sense?

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Yup, does to me. Maybe that one coil has lower resistance than the SL circuit requires. That would allow more current to flow, raising the heat. That's good for you. It means you can charge your pack to 16v and enjoy the benefits, using the other coils. Good deal!

 I've found the Sadie, and 7 1/2DF to be very near equals. Actually slightly prefer the DF, but wouldn't feel handicapped with nothing but the Sadie in tight quarters.

Jim

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  • 3 months later...

hello to all, I'm new to the site, I saw that on the tdi pro you could increase the voltage up to 21 volts and on the surfmaster how much can you increase the voltage, it's a box of 8 batteries for 12 volt. what is the difference in power between the surfmaster and the tdi pro oz and why, is it not the same components, thank you for your answer

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5 hours ago, JPS said:

hello to all, I'm new to the site, I saw that on the tdi pro you could increase the voltage up to 21 volts and on the surfmaster how much can you increase the voltage, it's a box of 8 batteries for 12 volt. what is the difference in power between the surfmaster and the tdi pro oz and why, is it not the same components, thank you for your answer

JPS……I replied (again) to your PM.

I did extensive testing and field use with my TDI BeachHunter…..there’s plenty archived for you to read about this subject. Essentially, I achieved between 10% and 15% depth increase moving from the 12v pack to 14.6v. Not much of a real gain. The heat increase on the PCB was unbelievable….I opened the case to check things out and one part of the board left a small red mark when I put my finger on it for just a second or two…..that’s hot. Amps to the coil has a far bigger result than voltage when it comes to coil “depth”. A capacitor may be able to handle the extra voltage but I can assure you that not all parts on the PCB will enjoy the extra heat. Maybe you can add a heat sink? Stick with the stock battery and let Mother Nature take off the extra 10% to 15% of sand.

An example of volts v Amps is my GP3500 which I use at the beach. Now it’s only running on a measly 6v battery but it’s drawing about 0.75A from that battery…..that’s where the power is.

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thank you tony, but as I saw that many people increased their white's up to 18 or even 21 volts I inquire, I don't know anything about the pi. 16 volt i think is a good deal🙂

 

hello to all, I'm new to the site, I saw that on the tdi pro you could increase the voltage up to 21 volts and on the surfmaster how much can you increase the voltage, it's a box of 8 batteries for 12 volt. what is the difference in power between the surfmaster and the tdi pro oz and why, is it not the same components, thank you for your answer 

 

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