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#1 Posted : Friday, January 20, 2017 1:54:37 PM(UTC)

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There has been several people looking for a good rechargeable battery to use for a portable fish detector. There has been a technology around for several years but it was not easy to use them safely without a lot of expense. Lately I have been seeing protected cells at better prices. I have purchased a couple of sets of cells and done some testing and I believe they will work well. I have made a couple of battery holders along the lines of the IKEA holder. The batteries are “Panasonic Protected NCR18650B 3400mAh Li-Ion 18650 Button Top” batteries. I found LIionWholesale has a good price for them. The battery holder pictures weighs 2.6Oz. and a set of 4 batteries weigh 6.27 Oz. Should you use 3 batteries or 4 in series?? All of the detectors will work well with 4 batteries in series. Some low power non color detectors will run almost as long on 3 in series. They will run just a little longer on 4 in series but not 30% longer. The newer color detectors that I tested will run much longer on 4 batteries in series than with 3 in series. 


The mounting clips are from McMASTER-CARR part number 1171A72. Beckson also sells a similar clips in 8 different sizes. I believe the 1 inch size would work best. 
The end caps are one inch “Leg Tips” from Menards. They are displayed in the same area as cane tips. To put the hole in the end use a ALL or ICE PICK to punch a hole and put a washer on both sides of the LEG TIP on a 5/8 6-32 screw. The pipe is a ¾ inch plastic pipe from the electrical department at Menards and it comes in 5 foot lengths. 

protected 3400mAh Battery 

I also purchased one of these CHARGER.

thanks 1 user thanked MagicPaddler for this useful post.
overloaded on 1/21/2017(UTC)
#2 Posted : Saturday, August 17, 2019 11:10:55 AM(UTC)

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I found a protected 18650 battery holder.  This uses the less expensive unprotected flattop 18650 batteries.  I bought one to see if it works and it does.  It will shut off power to your detector when any cell gets lower than 2.4 volts. This will keep you from destroying your batteries by over discharging them.  Once the circuit has blocked the output there are at least 3 ways to get power to your detector again. All three methods involve putting power on the output lead. 

1.  The manufacture recommends putting the unit on a charger for a few seconds.  That works if you have a long extension cord.

2.  After installing charged batteries use a metal object like a knife to short between B+ and P+ pins.  The P+ pin is the one with the red wire attached to it and the B+ is next to it.

3.  Solder a resistor between B+ and P+.  Resistor should be between 20k and 50k ohms.  This will automatically reset the circuit when the load is removed.  Depending on the detector a mome may need the detector to be unplugged for a couple of seconds. 

Protection circuit.



A good choice for a battery.


This needs to be protected from getting wet.  It needs to be in a water tight box with the leads passing through a water tight hole.

Some of these protected holders are sold with a charger.  I do not recommend using this type of charger because there is no balancing circuit. 

There are also similar protected holders that hold 3 18650 batteries.  They will supply longer runtime per ounce of batteries.  The disadvantage of using 3 rather than 4 is that the detector will be running on lower voltage than it is designed to for the last part of the batteries charge life.  If your detector has a low voltage alarm set it to 10 volts and replace the batteries when the alarm goes off. Once the batteries have been replaced the trip circuit will need to be reset by one of the 3 methods above.


Edited by user Saturday, August 17, 2019 11:26:46 AM(UTC)  | Reason: Not specified

#3 Posted : Monday, September 14, 2020 1:44:23 PM(UTC)

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Below is my attempt using 800 mAh AAAs for my Striker 4. I had some schedule-40 PVC laying around the basement and a bunch of appropriately sized hose washers and fender washers rattling around in the toolbox. The wingnuts secure the lugs and compress the hose washers inside the pipe to make a tight seal. Eleven AAAs seemed to be the right number for a day of fishing -- charge the USB brick on the solar panel all day and use it to charge the batteries overnight. Without protection I wonder about the long-term health of my batteries, but I didn't notice any degradation as the week went by and I don't intend to use this more than once a year going forward.

Depth finder stuff

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