Garrett Carrot Without A 9v Battery (continued)

[mh9162013 119]

I just finished the next iteration of my 9V to AAA battery adapter for my Pro-Pointer AT (Carrot). You can read about it in my blog post that will be uploaded soon (see my profile for the link, if you're that curious), but most of the "juice" is in the pictures.

In case you're wondering (or you don't recall my prior blog posts about this building process😞

1. Yes, waterproof integrity is maintained.
2. Yes, the performance when using this adapter is identical to using a regular 9V battery.
3. Yes, this can still use a regular 9V battery.
4. Yes, runtime is less than with a regular 9V battery, but should be enough to get you at least a full day (8+ hours) of run time. I estimate this will get you about 1/3 of whatever an alkaline 9V battery will get you.
5. Yes, this can run on other types of AAA cells, including NiCd, NiMH, lithium (primary; think Energizer Ultimate Lithiums) and alkaline.
6. I did this modification because I like tinkering and because I really hate 9V batteries.

Background info of prior builds: 

 

 

[PimentoUK 430]

It might be an idea to add a link to the original thread on this topic, so folks can remind themselves of prior discussions.

Cylindrical lithium cells are available in AAA size, thought they usually refer to them as '10440' size ( 10 x 44mm), and they are very similar in length to PP3 9V batteries. Two of them would make a decent PP3 substitute, the capacity of them seems to be about 350mAh, adequate, though not excellent. But they would at least be removeable individually for charging, so there would not be any constraints caused by having them made up as a two-cell assembly.
Whilst thinking about making my '2 x foil-pouch cell' PP3 substitute, this AAA idea seemed workable.

[mh9162013 119]

10 minutes ago, PimentoUK said:

It might be an idea to add a link to the original thread on this topic, so folks can remind themselves of prior discussions.

Cylindrical lithium cells are available in AAA size, thought they usually refer to them as '10440' size ( 10 x 44mm), and they are very similar in length to PP3 9V batteries. Two of them would make a decent PP3 substitute, the capacity of them seems to be about 350mAh, adequate, though not excellent. But they would at least be removeable individually for charging, so there would not be any constraints caused by having them made up as a two-cell assembly.
Whilst thinking about making my '2 x foil-pouch cell' PP3 substitute, this AAA idea seemed workable.

I'm trying to stick with cells I already have. I have more than a hundred of LSD AA and AAA cells (mostly Eneloop) for all my devices (flashlights, controllers, homemade battery banks, radios, etc.), so I try to stick with my standardization of choice.

[PimentoUK 430]

When running on a standard PP3, you are presumably adding a rubber/plastic etc insert into the extended cap ?

On the subject of modifying pinpointer end-caps : I think that's one of the design flaws of the original Garrett propointer, which seems to have been repeatedly copied by everyone, the big names and Chinese clone makers. Unscrewing the thing if you've got wet, muddy or cold hands is terrible, the smooth slighly undulating pattern is hopeless. What's needed is an aggressive, finer-pitched grip. Something similar to the teeth of a gear wheel, or the square splines of toothed drive belt pulleys. I actually rummaged through my 'engineers junk box' years ago, to see if there was anything suitable I could fit on there with some lathe work. I never did do anything ... and it still frustrates me today.

[mh9162013 119]

16 minutes ago, PimentoUK said:

When running on a standard PP3, you are presumably adding a rubber/plastic etc insert into the extended cap ?

If I had to do that, yes, I'd use some sort of insert/spacer.

As for the end-cap being slick, I hear you. The endcap on the Pro-Find 35 was a little bit better, but it was still a bit of a hassle.

I noticed that adding some silicone grease (which is a necessary part of maintenance) to the o-ring can help a little bit with the difficult endcap removal.

[PimentoUK 430]

I also thought a 'fin' bonded onto the flat back of the cap would work. I've definitely seen that type of device used on torches ( US: flashlights), the long 3 x D-cell sort. A single central flat rib, that can be gripped between thumb and index finger.
I have plenty of scrap plastic... that T - profile is something that could be found in commercial equipment enclosures, like computer printers , I'm going to have to rummage tomorrow.

[mh9162013 119]

How would you bond the "T" to the endcap? Is there a solvent that would work? I think, given the forces needed to twist off the endcap, a solvent would be needed, not just an adhesive or glue. Or maybe some kind of mechanical way of attaching it.

Another idea is to attach a thick, round disc to the endcap. I'm thinking this disc can be 6 to 10 mm thick. Then in the middle you can cut/etch a line so you can use a coin to twist off the endcap, kind of like what the F-Pulse has.

I dunno how durable this would be. You'd need a very durable material if you wanted to keep the round disc as thin as possible. However, I doubt a hard enough material would be able to be solvent-welded to the OEM endcap.

[PimentoUK 430]

Bonding plastics is always a bit tricky, especially if the type of plastic is unknown. It should be possible to find out what the Garrett is made of, and most of the scrap bits will have some recycling labelling. But from experience, computer printers etc can use all sorts, ABS, ABS + polycarbonate blend, Polystyrene. So I would probably go for thixotropic cyanoacrylate. However, a few tiny self-tapping screws through the lot wouldn't be a bad idea, except they would rust, so a bit of paint would be needed.

[mh9162013 119]

11 minutes ago, PimentoUK said:

However, a few tiny self-tapping screws through the lot wouldn't be a bad idea, except they would rust, so a bit of paint would be needed.

Rusting shouldn't be a problem as long as you use stainless steel.The problem is that if they penetrate the OEM endcap from the top, that could potentially lead to water intrusion. Also, if they stick past the endcap too far, they might interfere with the 9V battery inside.

Screwing into the sides of the endcap might work, though. You have far more plastic to work with.