Fisher F2 Batteries: Question

[Ham]

The Fisher F2 requires two 9 volt batteries. The manual for the Fisher F2 states, "only use alkaline batteries". Why can't i use "Lithium" or rechargeable batteries that are 1.5 volts?

[Skippy]

That's a very peculiar thing Fisher have done. Even the front page of the manual says "Use Only Alkaline Batteries", rather than the slogans you might expect. I think they want to discourage you from using junk carbon-zinc ones that say "Lucky Golden Flying Eagle" or similar nonsense. You can use NiMH rechargeables, I would recommend it. I can't see the sense of using Li-Ion rechargeables, they are frugal machines, the extra capacity is not needed, 180mAh NiMH's are fine.

[Ham]

Thank you for your response.

[Funfinder]

Meanwhile you can buy 200mA NiMH or even 250mA rechargeable 9 Volt blocks.
Fast-charging within ca. 5-7 hours with 40 to 60 mA.

Of course those will not last the same long as alkaline 9v blocks but if you have
a second pair for reserve you should have all the time enough energy available.

btw. people also should start to use such NiMH 9V blocks for their pinpointers.
Of course such equipment could be sold directly from the metal-detector shops
so everyone can have it directly.

[Skippy]

I suggested 180mAh capacity as there's no point paying a premium for the 'best' when it's not needed on such a low-power machine. Also, there are plenty of Unknown Brand 280 / 300 mAh capacity batteries on the market, but I'm dubious about their claims. I do own a cheap-brand 250mAh PP3, it's reassuringly heavy, but I've not tested it out.
One other advantage of plastic cased rechargeables is they slide in and out of the battery retaining clips easily. One well-known design flaw of the F2/4/5 is their tendency to 'latch-on' to the lip on the bottom of metal clad batteries. This makes the battery almost impossible to extract, frequently resulting in breaking the retaining lug. I've seen several for sale second-hand with this breakage.

[Funfinder]

If the F2 uses two 9 volt blocks parallel connected (internal voltage 9v and not 18v)
someone should use NiMH accu blocks of the same type and both always exactly identical charged
because otherwise one block could deep-deplete while the detector drains his energy
from the still powerful second 9v accu.

It would be even better to test one time how long the detector works with the accus
and later 1-2 hours before that time the both accus become replaced with the fresh reserve pair.
That way the risk of deep-depleting can be removed.

Of course it depends on the usage time per year if NiMH 9v accus are meaningful at all.
For 10 search-days with this detector per year (because perhaps its not the only available MD)
usual 9V blocks may be the cheaper alternative.

[Skippy]

They are connected in series. Not parallel.

[Funfinder]

OK thx - good to know - in this case even a real powerful 4 x 3,7v Li-Po could be used,
because the voltage 14,4 to 18 should be still within the detectors working range.

I guess a good alkaline 9V block still has 4-5 times more power than a 200mA NiMH accu.
So Li-Po would be a good alternative.

There exists Li-Po packages in all sizes and shapes - perhaps a smaller one
with ca. 1000-1500mA would fit exactly into the battery-hole.

btw. the cheapest solution would be some discounter alkaline 9v battery package.
Made in China or Korea - ultra super heavy duty... !

[Skippy]

The capacity of good alkaline PP3's at modest drains (50, 100mA) is around 500-600 mAh.

[Funfinder]

thx for the info.

from the details here under: specifications
https://en.wikipedia.org/wiki/Nine-volt_battery

Lithium with 1200mA has the double than alkaline
while rechargable Ni-Mh already is up to even 300mA which is a pretty good value.

Personally I use some lipo camcorder 7,4v accu 1500mA changing with a 9v Ni-Mh accu 200mA for my modified Garrett Pro-Pointer.
So I always have a reserve and never need to buy usual 9v block batteries. 5-10 days of working - no problem.

This means that someone also should look for li-po accus 7,4v in the shape of a 9v block battery
for his pinpointer, if he can find any. It should be already as standard available at every electronic shop incl. fast-charger.

btw. you can dismantle old 9v blocks and use its contacts, solder some cable on its ends etc.

And someone can puts his tongue between the two poles of a 9v block to check if its juice is still energetic enough!
Of course I'm shure you know that. We did it already as kids - it was some kind of first interesting contact with electricity.
Meanwhile I felt already a little bit more energy - per instance from shortcuted 220v capacitors... Cool shocking entertainment...
Do not try this or just with one fingertip (No, better leave it be, it creates 0,3mm flash burn marks for some time) ...

But it would be a cool new method to create brandings or special tattoos for the real painfree ones! "Micro-Lightning-Brandings"
Relax on the super high voltage-chair and afterward enjoy your extra fine detailed high-definition branding !!!
It will be the sensation of every party! No color used but instead just crazy and really hot micro flashes!

[Funfinder]

btw. the most easy (for "though" enough persons ) harmless micro-flashes
are creatable with a plasma-ball when you put an alu-cap over it which has
some sharp tip.

This will be the electrode and if the finger comes close to ca. 5-10mm,
a steady stream of extreme low ampere but some 5-10 thousand volts jumps over.

Doing this for a half second is a cool thrill but done longer it starts to micro-burns the skin.

And how to use high-voltage for metal-detecting also still is an unsolved question.
But it might be useful if connected with new and special technology because higher
energy penetrates deeper, even if it may blurres the small and weaker contrasted finds.

btw. did you know that from a populaton of 100 million people just around 6 die every year by lightning stroke?