AA Size Batteries....Useful Life for Metal Detectors.

[ToddB66]

Greetings !

I've noticed that small electronic devices that use AA size dcv batteries, such as TV remotes and battery-operated clocks, to mention just a few, often fail to operate when the dcv drops to around 1.32, as checked with my DMM.

Does anyone know the approximate lowest voltage-level for AA's that would make them worth saving for metal detector use ? I would like to "squeeze" out as much of the remaining useful voltage from these batteries before deciding to throw them away.

If you don't know the answer off-hand, then I guess my next step would be to use a set of AA's that check around 1.32 dcv in my Garrett ACE 250. Then when it stops operating, re-check the DC Volt levels again.

I realize the possibility exists that various brands and models of metal detectors that operate on AA size 1.5 dcv batteries have different "minimum-circuit-power" requirements, making it difficult or maybe impossible to answer my question.

Thanks for whatever you can offer.

ToddB66

[Funfinder]

Hi ToddB66,

You can run the Ace 250 with 4 x 1,2v or even with 4,5v solar-accu-pack, no problem, I have tested it.

AA cells of course are practical, especially the new ready2use ones NiMH, but seen from the compact size
and power you better go for Li-ions or Li-polymers.

The 1,5v AA alkaline cells are good for storage and as a reliable backup if the rechargables run out.

btw. most remote controls use AAA cells, the usual smallest size.
Also here you can work often with 1,2v NiMH accus instead of 1,5v.

Many devices have a voltage tolerance and work also if just 60-75% of the usual voltage is applied.

Keep in mind that the less voltage the less depth and e-smog stability you will get.
A detector that works with 4,5volts can't built up strong EM-fields.

However the Ace 250 or Euro-Ace especially with new DD-coil works pretty good for its low price
under non e-smog and non-mineralic conditions!

But real deep and sensitive detectors are chest-mounted and use at least 12 volts!
You can compare it with a light-house that has to shine through fog, with a little candle you won't go much far,
ships won't see it and - metal detectors won't penetrate much mineralized soil with low EM-field energy.

> Does anyone know the approximate lowest voltage-level for AA's that would make them worth saving for metal detector use ?

You have to test it personally how long the 1,2 NM accu or 1,5 battery works, this is different from detector to detector.
The more engery storage they provide the better, so use good quality and keep in mind that nobody cheats more
than if it comes to the true accu capacity values (don't simple trust the values written on the accus!)

The Ace 250 works with a set of rechargables around 20 hours (4,8 volt with just very small sensitivity loss compared to 1,5v batteries). Just keep a set of real long lasting 1,5v alkaline batteries always with you as in need reserve.

Good luck!

[ToddB66]

Funfinder ,

Thanks for taking the time to really answer my question ! Very helpful.

ToddB66

[Silver Dollar]

Well we use a lot of "AA" batteries at work. Fresh ones are around 1.6V and we replace them at 1.2V...

[ToddB66]

Silver Dollar........Thanks ! That gives me a brief and simple answer (1.2V).

ToddB66

[Koala]

It will vary from detector to detector depending on the voltage regulator requirement and any voltage drop of any diode protector

See you have a White's Classic II. I run a homemade Classic. I normally change after 3X 8hours detecting. That's 32 hours total. Only ever run right to the end once and that was due to a faulty batteries. When at the very edge of working you don't get a sharp beep over a target and becomes unstable after the beep in disc mode but in all metal mode it will still works fine. Tried alkaline zinc carbon and carbon all fine.

Did measure the batteries when I got home and was almost exactly 9 volts for the pack so 1.2v which Silver Dollar recommended would give 9.6V so sound good to me.

See you also run a Bandido ll µMax which I believe is good for 20 hours detecting from the Alkaline 9V I believe that the units that have a low battery warning L.E.D that it comes on at 7.35V

Remember to remove the alkalines when not in use as they are prone to leak

[Predrag]

I've noticed that small electronic devices that use AA size dcv batteries, such as TV remotes and battery-operated clocks, to mention just a few, often fail to operate when the dcv drops to around 1.32, as checked with my DMM.

Does anyone know the approximate lowest voltage-level for AA's that would make them worth saving for metal detector use ? I would like to "squeeze" out as much of the remaining useful voltage from these batteries before deciding to throw them away.

Be aware ToddB66, that simple battery voltage measuring without powering something will give you false information. Unloaded voltage is often higher than the loaded voltage. To test voltage with a DMM, stick the battery in the device, turn it on, and then test the voltage.

"Squeezing" batteries have more meaning in devices tolerant to low voltage, in clocks (down to 1.0V) or remote controls (down to 0.8V). Alkaline voltage plummets after 0.8V, so an alkaline that hits 0.8V is completely used up.

Second life of batteries in MD is not so good policy. You could stay "dry" in a middle of work.

Here is the nice place with a lot information: http://michaelbluejay.com/batteries/tips.html

Predrag

[Carl-NC]

Todd,

1.32v has barely used the capacity of the battery. Even 1.2v leaves a lot behind. Some rechargeables start out at 1.2, so circuits should be designed to run on the lower voltage.

Predrag is right, unloaded a battery will read higher than loaded, and batteries also have a bounce-back effect so if you let them sit a short while their (open circuit) voltage increases. When measuring a battery put a ~10mA load on it. Maybe 100 ohms on a cell.

See my now-somewhat-dated article on batteries. It has typical discharge curves for various battery types. Look up "battery discharge curve" on the 'Net for more accurate data. Generally, an alkaline cell is approaching worthless at 0.9-1.0 V, with a fairly soft knee. Other types have a much more abrupt death.

None of this takes into account how a circuit operates on low batteries. I think the Ace uses 4-AA, but I don't know how it behaves on 4V. You'll just have to try it.

- Carl

[Funfinder]

Todd, thx for your friendly answer

You can test it or ask before that the 1,5v devices work with rechargeables a 1.2v or not.
This means that those devices are able to run from 1,5v to 1,0v per cell.
The Ace 250 does, it is able to work from 6v to 4v, as long as the batteries provide enough current aka (milli)Ampere.


Usually today almost every AA battery devices are able to work with rechargables, too.

If you have such a new detector that works with 4 AA rechargeable cells the fine thing is - you also can
use the modern Li-Ion USB-Accu-Packs. They contain alot mA, mine with 2 cells has 5200mA, output 4,5v.

Those power-packs can be used to recharge navi's, smart-phones or eveything with USB like mp3 players - out in the wilderness etc.
But you also can use them as great rechargeable power source for metal-detectors,
because they last much longer than the usual NiMH accus.

You even can built such a power-pack into the detecors-housing and leave the USB-jack accessable from the outside.
Some also contain inbuilt LED-lamps.
If you use packs with just 2 Li-po cells inside they are very lightweight by providing alot power.

http://thewirecutter.com/reviews/bes...y-pack-travel/
http://gizmodo.com/5926985/the-best-portable-power-pack

[ToddB66]

AA Size Batteries....Useful Life for Metal Detectors.

It will vary from detector to detector depending on the voltage regulator requirement and any voltage drop of any diode protector

See you have a White's Classic II. I run a homemade Classic. I normally change after 3X 8hours detecting. That's 32 hours total. Only ever run right to the end once and that was due to a faulty batteries. When at the very edge of working you don't get a sharp beep over a target and becomes unstable after the beep in disc mode but in all metal mode it will still works fine. Tried alkaline zinc carbon and carbon all fine.

Did measure the batteries when I got home and was almost exactly 9 volts for the pack so 1.2v which Silver Dollar recommended would give 9.6V so sound good to me.

See you also run a Bandido ll µMax which I believe is good for 20 hours detecting from the Alkaline 9V I believe that the units that have a low battery warning L.E.D that it comes on at 7.35V

Remember to remove the alkalines when not in use as they are prone to leak

Koala,

Thanks for your reply and the information.

Did you mean to say 3x8 = 24 hours, or 4x8 = 32 hours ?

ToddB66

[ToddB66]

AA Size Batteries.... Useful Life for Metal Detectors.

Predrag,

Thanks much for the information and the link which I saved to my Favorites list. That's a great link, with lots of information on batteries !

ToddB66

[ToddB66]

AA Size Batteries.... Useful Life for Metal Detectors.

Carl,

Terrific reply ! Thanks so much for the information in your post and the linked document All About Batteries ,by yourself...I read it all and saved to my Favorites list and Documents folder for future reference.

I have great respect for your extensive knowledge in the field of electronics and willingness to share it.


ToddB66

[ToddB66]

Funfinder,

Thanks for all the information in your reply-post #9 and the links !

I saved it all !

ToddB66