Using AAA batteries in my Garrett Carrot (Pro-Pointer AT)

mh9162013

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I will upload a blog post about this build and its history very soon (you can see the URL in the "Contact Info" section of my profile). But in the meantime, below are pictures of the build and should mostly speak for themselves.

In case you're wondering:

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.
 

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I admire the ingenuity, but they do make rechargeable 9v batteries! I use vibration and audio and still find that regular 9v batteries last long enough that I'm not worried about buying them. I also don't want to worry about whether the backup 9v in my pouch has lost its charge.

My grocery store has a clearance shelf and they regularly put marked down batteries in it. A few times I've scored handfuls of Energizer Lithium 9v and Duracell Quantum batteries. Those things last forever.

By the way, what's the significance of the white versus green cap in the last two photos?
 
I admire the ingenuity, but they do make rechargeable 9v batteries! I use vibration and audio and still find that regular 9v batteries last long enough that I'm not worried about buying them. I also don't want to worry about whether the backup 9v in my pouch has lost its charge.

My grocery store has a clearance shelf and they regularly put marked down batteries in it. A few times I've scored handfuls of Energizer Lithium 9v and Duracell Quantum batteries. Those things last forever.

By the way, what's the significance of the white versus green cap in the last two photos?

I know they make rechargeable 9V batteries, but there are two problems with those.

First, it's indirectly condoning the lazy engineering and/or overly conservative attitude of electrical engineers.

Second, I still have to carry around a 9V battery when I almost exclusively use AA and AAA batteries for almost all my other electronic devices (I have C and D adapters). I appreciate standardization.

As for the last photo, that's just a silly picture showing the Garrett Carrot as an actual "carrot." I wanted the battery endcap extension to be green, but couldn't find one. But when I do, I'll install it.
 
As for the last photo, that's just a silly picture showing the Garrett Carrot as an actual "carrot." I wanted the battery endcap extension to be green, but couldn't find one. But when I do, I'll install it.

Ahhh....the green and orange carrot! Clever. Garrett should embrace the carrot name and make green battery compartment lids.
 
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Clever tinker work! I am surprised that the unit would operate at all, let alone acceptably with a 1.2V battery.

It uses a booster circuit that takes 2.5 to 9V of input and outputs 9.0-9.1V. The adapter uses 3 AAA batteries in series, so the booster is getting 3.6V* and turning it into 9V.

As for these AAA cells, they're FAR superior to the cells located inside a 9V battery in terms of internal resistance and current draw capability.

* In reality, it's getting close to 4V for most of the batteries' runtime.
 
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Pretty cool setup. Personally not something I would do for this particularly but I can see where it could be useful for other applications and it's a nice example of what can be done. Always fun to tinker around in your spare time just to see what you can do if you set your mind to it. Thanks for posting it.
 
Pretty cool setup. Personally not something I would do for this particularly but I can see where it could be useful for other applications and it's a nice example of what can be done. Always fun to tinker around in your spare time just to see what you can do if you set your mind to it. Thanks for posting it.

You're welcome and thank you for the kind words.

Metal detecting is just my excuse to tinker with electronics and batteries.

And you're right, this isn't something most people will want to do, even if they could buy a turnkey product, where all they had to do was replace the endcap with one that's provided and install the AAA batteries.

Another factor to consider is that few, if any, hobby-level metal detectors use AAA batteries. At best, machines will use AA batteries. However, for my next metal detector, I plan on using AAA batteries with it (a la AT Pro, Vanquish or F75 with AAA to AA adapters). Based on my rough number crunching, I'll get about 1/3 the run time with a AAA cell that I'd get with a AA cell. As most detectors get 20-30 hours on AA NiMH cells, that should easily last one full day of hunting. Of course, I'll have spares with me, too. Another advantage will be the reduced weight. AAA cells + adapters still weigh less than AA cells alone.
 
Great hack! I detest 9v batteries , and would love it if Garret had just made the Pro Pointer rechargeable or capable of accepting 3 AA cells from the get go.
 
Great hack! I detest 9v batteries , and would love it if Garret had just made the Pro Pointer rechargeable or capable of accepting 3 AA cells from the get go.

Thanks!

Using 3 AAA cells probably wouldn't be the best option for a manufacturer. But 2 AA cells (a la the F-Pulse or TRX) is a great option.

I'd be happy with rechargeable batteries too, but only if they could be easily replace by the customer.
 
It uses a booster circuit that takes 2.5 to 9V of input and outputs 9.0-9.1V. The adapter uses 3 AAA batteries in series, so the booster is getting 3.6V* and turning it into 9V.

As for these AAA cells, they're FAR superior to the cells located inside a 9V battery in terms of internal resistance and current draw capability.

* In reality, it's getting close to 4V for most of the batteries' runtime.

Are you saying the carrot has a booster circuit, or youve incorporated one into your design?
 
Are you saying the carrot has a booster circuit, or youve incorporated one into your design?

I incorporated one; it's located in the copper "top" of the adapter. The Garrett Carrot is designed to work off of a 9V power source, not a 3.6V power source.
 
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