Folks, Here is a 16V 18650 battery holder for the TDI SL that you can make at home in about an hour.
You will need a set of 4 decent 18650 batteries such as Panasonic NRC18650B (PCB protected 3400mhr) ~AUD$40 and a Whites #802-7150 8 AA battery holder AUD$30.
1) Take your battery holder and with the holder closed and empty slowly & carefully drill thru the embossed Whites symbol on the slide lid using a drill bit 10mm or so, the size is not too critcal. This will remove the little plastic protusion on the underside of the lid which prevents the lid being fully removed.
2) Slide the lid off.
3)All the metal fittings in the case are simply held by friction & if you use a scribe or similar to slightly bend up those little tangs you will easily pull off all fittings with a pair of long nose pliers.
4) Lay your 4 x 18650 batteries as shown in the photo. Take a dremel & cutoff knife and cut out all the reinforcing ribs etc that prevent you laying the batteries neatly in position. Dont cut more than needed.
5) Using the dremel with a cutoff wheel cut a 15mm wide slot thru the case bottom. The slot is centred on the centreline of each pair of batteries. These slots are needed to allow the batteries to sit low enough to slide the cover back on. They also act to hold the batteries laterally once the lid is in place.
Now we need some terminals.
6) For the back end of the battery where we need to join the 2 strings of batteries together just cut a rectangular piece of thin copper strip to fit across the whole back and solder a couple of ~3 x 3mm pieces of copper strip onto the main strip to raise the surface enough to contact the battery terminals.
7) For the front terminals I used the existing Whites +ve & -ve terminals but cut the sides off & bent them to fit and hold the batteries firmly. WARNING. The terminals are made of the most brittle metal I have ever seen. Cold bending is totally out . All bending to be done after heating with a mini gas torch. If you break the Whites terminal a simple U shaped piece of ~3mm wide springy steel or brassy strip wil work just as well.
8) Load the batteries & slide the lid on. If the lid wont go on then check where the batteries are sitting high & cut another mm out of the base slot(s).
9 Once assembled check continuity ie should have 16V at the terminals. Shake the battery around and recheck voltage. If all good you can superglue the back terminal in place. If not then one or more batteries are not touching their terminal. Issue can only be either battery being obstructed by some plastic or insufficient pressure from the front terminal, which acts as the spring. A bit more dremmeling or bending and all will be sorted.
I get 5 hrs runtime from this pack down to 13.8V. Note that you CANNOT rely on the Whites battery light as that is set for 8.5V.
Using a NF Sadie & compared to the Whites NiMH battery pack, depth on a 1 grain 24k ingot goes from 45mm to 60 mm and depth on a 1/2oz 30mm dia 24k coin goes from 220mm to 250mm. Max depth on massive iron goes from 400 to 500mm.
Ok its not a Minelab but its probably the next best thing.
You will need a set of 4 decent 18650 batteries such as Panasonic NRC18650B (PCB protected 3400mhr) ~AUD$40 and a Whites #802-7150 8 AA battery holder AUD$30.
1) Take your battery holder and with the holder closed and empty slowly & carefully drill thru the embossed Whites symbol on the slide lid using a drill bit 10mm or so, the size is not too critcal. This will remove the little plastic protusion on the underside of the lid which prevents the lid being fully removed.
2) Slide the lid off.
3)All the metal fittings in the case are simply held by friction & if you use a scribe or similar to slightly bend up those little tangs you will easily pull off all fittings with a pair of long nose pliers.
4) Lay your 4 x 18650 batteries as shown in the photo. Take a dremel & cutoff knife and cut out all the reinforcing ribs etc that prevent you laying the batteries neatly in position. Dont cut more than needed.
5) Using the dremel with a cutoff wheel cut a 15mm wide slot thru the case bottom. The slot is centred on the centreline of each pair of batteries. These slots are needed to allow the batteries to sit low enough to slide the cover back on. They also act to hold the batteries laterally once the lid is in place.
Now we need some terminals.
6) For the back end of the battery where we need to join the 2 strings of batteries together just cut a rectangular piece of thin copper strip to fit across the whole back and solder a couple of ~3 x 3mm pieces of copper strip onto the main strip to raise the surface enough to contact the battery terminals.
7) For the front terminals I used the existing Whites +ve & -ve terminals but cut the sides off & bent them to fit and hold the batteries firmly. WARNING. The terminals are made of the most brittle metal I have ever seen. Cold bending is totally out . All bending to be done after heating with a mini gas torch. If you break the Whites terminal a simple U shaped piece of ~3mm wide springy steel or brassy strip wil work just as well.
8) Load the batteries & slide the lid on. If the lid wont go on then check where the batteries are sitting high & cut another mm out of the base slot(s).
9 Once assembled check continuity ie should have 16V at the terminals. Shake the battery around and recheck voltage. If all good you can superglue the back terminal in place. If not then one or more batteries are not touching their terminal. Issue can only be either battery being obstructed by some plastic or insufficient pressure from the front terminal, which acts as the spring. A bit more dremmeling or bending and all will be sorted.
I get 5 hrs runtime from this pack down to 13.8V. Note that you CANNOT rely on the Whites battery light as that is set for 8.5V.
Using a NF Sadie & compared to the Whites NiMH battery pack, depth on a 1 grain 24k ingot goes from 45mm to 60 mm and depth on a 1/2oz 30mm dia 24k coin goes from 220mm to 250mm. Max depth on massive iron goes from 400 to 500mm.
Ok its not a Minelab but its probably the next best thing.
