Made a GPX battery pack

soky72

Jr. Member
Jan 30, 2011
32
34
Southern Kentucky
Here's a battery pack I made for my GPX. I used 18650 rechargeable batteries which is probably the most common kind used for built in battery packs like for laptops and flash lights. I used the plug off some old computer speakers that plug into a 4.2 low latency bluetooth transmitter (the white round disk). The power leads were then soldered to a Fatshark Battery Box used for powering Fatshark Drone goggles. You can use any 18650 battery holder but I liked the fatshark battery box because it has the battery indicator on the side. It's important when building an alternative battery sources to use good quality batteries and charger. The batteries are Panasonic rated at 3400 mAh. You can find batteries with higher ratings but it will be junk as 3400 is about the current max output for good 18650s. The longest I've gotten to hunt is 2 hours and I showed half charge so I feel confident I can go 3 to 3.5 before putting two more in and I have 8. The setup is extremely light and I have several bluetooth options including Sony and Minelab earphones but prefer ear buds as the sound is crisper and it's cooler in summer.


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mascard1

Sr. Member
Oct 28, 2008
393
33
SACRAMENTO CALIFORNIA
Detector(s) used
Ctx 3030...E-TRAC...EXPLORER SE...EXCALIBER II...TEJON...ELDORADO..LOBO ST...F75LTD...F70...CZ3D...XLT...T2...MXT Pro.. 1861 HALF DOLLAR
How do you charge them?...I see how now...Thanks!!
 

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soky72

Jr. Member
Jan 30, 2011
32
34
Southern Kentucky
I use a Zanflare LCD display universal charger. It's a nifty little charger that can also be used in your car. Cost me about 30 bucks but I can use my AA batteries on it as well as the 18650's.
 

jebinpa

Newbie
Aug 22, 2019
1
0
Bechtelsville, Pa.
Primary Interest:
All Treasure Hunting
Hi soky, saw this from you on another site. I thought it's a great idea! Just wondering where the red and black wires connect to from the Fat Shark. Thanks
 

garikfox

Jr. Member
May 30, 2019
54
52
Queen Creek, AZ
Detector(s) used
EQ800, GM1000, GPX5000
Primary Interest:
Metal Detecting
For the power cord did you start off with the coiltek short 5pin ?
 

InAustralia.Jones

Jr. Member
Mar 16, 2016
90
143
Detector(s) used
MineLab - GP3000, GPX4500, GPX5000
Primary Interest:
All Treasure Hunting
When does your compact kit hit the market? eBay store?
 

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soky72

Jr. Member
Jan 30, 2011
32
34
Southern Kentucky
I just cut the red and black wires off from the box. I did use a shortened cord, can't remember if it was handmade or coiltech. It came with my detector. I have bought the materials to make my own but haven't gotten around to making them up. A good RC or electronics guy could solder one of these setups together in 15 minutes.
 

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soky72

Jr. Member
Jan 30, 2011
32
34
Southern Kentucky
Well looking at my pics the cord says coiltech so I guess it is. I got another one that looks homemade. It will get this conversion as well. I haven't had them out since last winter as I don't hunt much during the summer.
 

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bklein

Full Member
Feb 15, 2012
165
83
Primary Interest:
All Treasure Hunting
I just tried one of these on my GP Extreme. The GP Extreme has an input cutout voltage of about 7.9V. Crappy batteries power the detector ok but new good ones charge up to 8.4V and the detector doesn't even come on. So I got a buck converter off Amazon and adjusted it for 6.87Vout. I stuck this inside the Barrie Johnson Nuggettfinder MKII I'm using. This worked fine for most of the 1.5hr battery life - but towards the end if the coil got near my scoop and overloaded the detector, the detector would go into a low frequency oscillation that I could only stop by shutting down everything. I took the battery and Nuggettfinder and tried inputting an audio signal to duplicate the problem but it didn't fail. So maybe the detector is going into a real nasty state and I'm wondering if the input fets are at risk...
I'm going to run two 26650 cells for more duration, add a 2S protection circuit, and try a buck boost converter next. I'll try the bluetooth transmitter too. Did you connect it direct to the two audio pins on the 4 pin connector?
 

bklein

Full Member
Feb 15, 2012
165
83
Primary Interest:
All Treasure Hunting
The buck boost converter works great - no issues. Probably 2.5 hours on two 18650 EBL cells.
 

OBN

Gold Member
Dec 30, 2008
6,527
7,004
Maryland Waters
🏆 Honorable Mentions:
1
Detector(s) used
"Excalibur"..
"AQ" Impulse
Primary Interest:
Other
I'm going to run two 26650 cells for more duration, add a 2S protection circuit, and try a buck boost converter next.
I love the EBL 26650's 5000mAh, cheaper then the 18650's which has jumped in price the last 6 months.
 

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