Captain Kirk
New member
The other day I was out hunting, detected a target and laid down the detector to dig the target. Immediately upon laying the detector down it gave the low pitched warble and shut down. I was confused because I knew that I had many more hours left on the battery pack. After retrieving the target I picked up the detector and turned it back on. It came up as usual and the battery indicator was at the 50% mark. That was as expected. But, why did the unit shut down? I hunted for a few more hours and went home.
The battery being used was the auxiliary battery pack in which I had 8 of the 2300mAH cells. Yesterday I recharged the cells and reinstalled them in the holder. As I usually do, I measured the voltage of the battery to make sure that the cells were fully charged (and to make sure that none of the cells were installed backwards). I was surprised to see that the voltage read zero, not low but zero. The first step was the bang the meter on the table (to wake it up!!) and then rechecked the voltage. Still zero. Now I am really puzzled.
I decided to remove the cells to do an investigation. The cells were too hot to hold in my hand. First thought was that something is shorting out the battery. I called Dick Shultz at Minelab to see if they had had any problems with shorting out of the auxiliary battery. He stated that this had not been a problem. He told me that the battery was only warranted for a year and that I could buy a new one for $15.00, but they did not sell directly to the public and I would have to get a new one from the distributor. I called J & J detectors (a plug for my good friend Jeral Smith). I could come in an pick up a new battery case tomorrow.
My engineering background got the best of me and I had to know what was causing the short. I found that you can pop open the top cover of the battery case. This is what I found. The battery holder uses the two cone shaped spiral springs (one at each end of the case) to apply pressure to the negative terminal of the cell. There are two spring tabs (one at each end of the case) that applies pressure to the positive terminal of the cell. The spiral spring at the output terminal end of the case has been very poorly installed and was soldered in way off center in such a manner that the positive terminal spring was positioned in between the bottom two leaves of the spiral spring. Whenever the cells were installed on the side that connects to the positive terminal of the battery, then the positive terminal spring would short to the negative terminal spiral spring. Viola, a shorted battery. It is interesting that it was after almost two years of operation before the problem manifested itself.
I also noted that there is what looks like a capacitor between the positive terminal of the battery and the positive terminal of the last cell. This turns out not to be a capacitor, but rather a fuse. After closer examination I concluded that the solder joint of the fuse to the battery positive terminal was very poorly done. In fact, it appeared that there was no solder on the fuse wire. I used a small screw driver to put pressure on the fuse lead. Sure enough it was only being held in place by pressure with NO SOLDER ON IT (There was no solder on the lead of the fuse or the terminal. Someone just forgot to solder the lead in place.).
CONCLUSIONS:
#1 Whoever is making the auxiliary battery pack for Minelab needs some lessons in quality control. Two problems in one battery case.
#2 It could well be that the poor solder connection of the battery fuse is the cause of so many reports of the Explorer II shutting down during operation.
The battery being used was the auxiliary battery pack in which I had 8 of the 2300mAH cells. Yesterday I recharged the cells and reinstalled them in the holder. As I usually do, I measured the voltage of the battery to make sure that the cells were fully charged (and to make sure that none of the cells were installed backwards). I was surprised to see that the voltage read zero, not low but zero. The first step was the bang the meter on the table (to wake it up!!) and then rechecked the voltage. Still zero. Now I am really puzzled.
I decided to remove the cells to do an investigation. The cells were too hot to hold in my hand. First thought was that something is shorting out the battery. I called Dick Shultz at Minelab to see if they had had any problems with shorting out of the auxiliary battery. He stated that this had not been a problem. He told me that the battery was only warranted for a year and that I could buy a new one for $15.00, but they did not sell directly to the public and I would have to get a new one from the distributor. I called J & J detectors (a plug for my good friend Jeral Smith). I could come in an pick up a new battery case tomorrow.
My engineering background got the best of me and I had to know what was causing the short. I found that you can pop open the top cover of the battery case. This is what I found. The battery holder uses the two cone shaped spiral springs (one at each end of the case) to apply pressure to the negative terminal of the cell. There are two spring tabs (one at each end of the case) that applies pressure to the positive terminal of the cell. The spiral spring at the output terminal end of the case has been very poorly installed and was soldered in way off center in such a manner that the positive terminal spring was positioned in between the bottom two leaves of the spiral spring. Whenever the cells were installed on the side that connects to the positive terminal of the battery, then the positive terminal spring would short to the negative terminal spiral spring. Viola, a shorted battery. It is interesting that it was after almost two years of operation before the problem manifested itself.
I also noted that there is what looks like a capacitor between the positive terminal of the battery and the positive terminal of the last cell. This turns out not to be a capacitor, but rather a fuse. After closer examination I concluded that the solder joint of the fuse to the battery positive terminal was very poorly done. In fact, it appeared that there was no solder on the fuse wire. I used a small screw driver to put pressure on the fuse lead. Sure enough it was only being held in place by pressure with NO SOLDER ON IT (There was no solder on the lead of the fuse or the terminal. Someone just forgot to solder the lead in place.).
CONCLUSIONS:
#1 Whoever is making the auxiliary battery pack for Minelab needs some lessons in quality control. Two problems in one battery case.
#2 It could well be that the poor solder connection of the battery fuse is the cause of so many reports of the Explorer II shutting down during operation.