Made a GPX battery pack

[soky72]

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]

How do you charge them?...I see how now...Thanks!!

 

[soky72]

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]

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]

For the power cord did you start off with the coiltek short 5pin ?

 

[InAustralia.Jones]

When does your compact kit hit the market? eBay store?

 

[soky72]

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.

 

[soky72]

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.

 

[garikfox]

Right on, that's cool

 

[bklein]

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]

The buck boost converter works great - no issues. Probably 2.5 hours on two 18650 EBL cells.

 

[OBN]

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.