NiMH Batteries

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The BH Sharp Shooter II uses two 9v batteries and the manual states that you should only use alkaline batteries.

Since rechargable NiMH batteries are usually recommended for high current drain situations; shouldn't I be able to use them without an issue in this metal detector?
It is certainly a high drain application, this thing eats batteries and demands a fairly high voltage. So the alkalines start to roll off and the detector won't work. Whereas NiMHs have a relatively flat voltage curve.

Thoughts? Experiences?


Thanks,
Tim

 

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[RobRieman]

They will work fine and should perform exactly as you stated. Stay relatively flat and then die hard.

 

[hvacker]

The company probably doesn't want warranty problems with lead acid batteries.
A battery labeled "heavy duty" is lead acid from my understanding. I guess the label helps a sub standard battery.

 

[DDancer]

NiMh batteries have a slightly lower voltage but are a good substitute for alkaline over all. The manufacture most likely recommends them because of the better performance at higher voltage that the alkaline provides. Its a trade off between the two types. Your correct in that the voltage curve over the time batteries drain is flatter with NiMh than alkaline and I feel its better to use NiMh for performance purposes than the slight degradation that the voltage difference implies. Never notice it myself and besides its cheaper and greener to go rechargeable.

 

[eddiecurrent]

I'd call a MD a "low drain" device. 2 9v batts lasting for over 20hrs. is not much power draw, the circuit can't put out over 100mw anyway, so it doesn't emit a strong EMF, it's a low power radio signal. The NIMH will work till they reach the end of their charge then decay all of a sudden, An alkaline will give warning of it's coming death. Alkalines also last longer sitting unused, rechargeables drain slightly even when sitting idle.

I prefer to use alkaline, to me they're more convenient. 9volts are less susceptible to leaking than other types like AA's ime.
Alkalines are also less likely to leak than carbon zinc, like heavy duty types.
BTW ddancer your avatar reminds me of a pelican I walked up on on the beach once. It was dead and shriveled, and when I looked close I saw how it died. It had eaten a puffer fish, which inflated halfway down it's throat. " Never ever give up!" or the last gesture of defiance!

 

[DDancer]

Yeah its a rather Darwinian statement eddiecurrent but in all its forms a good motivator to just keep on trying in the face of adversity.
As to alkaline charges verse's Nimh I'm referring to the voltage curve over time as these batteries are depleted. Nimh are more stable till depletion than alkaline and in relation to the original question overall operation for a detector is more satisfactory with higher and more stable voltage potentials. The best time in alkaline is generally till about 50 percent depletion then voltage falls and stability degrades. Nimh are good for about 70 percent before dropping off and degrading performance. Manufactures suggestions are geared toward the best performance not performance over time.

 

[Jackalope]

Any quality detector will have a voltage regulator to maintain stability, so unless the voltage falls below the min required, it shouldn't matter which type of battery you use.

 

[eddiecurrent]

OTOH, the regulator may clamp the voltage @ 5v in a detector that uses 4 AA's. 4 alkalines will yield a little over 6v when brand new, more for lithiums. Nimh rechargeables will put out 4.8v. In a detector that runs on 9v batteries, an alkaline puts out 9v but a nimh puts out 8.4. When the nimh AA's are on their last leg, they can go down to 4V, now the detector may be designed to keep operating at 4.5v but I doubt anything under that. Certainly the regulator isn't going to be able to raise the voltage, unless it's of a special type.

 

[donj]

Just for an example of a high drain device, LED flashlight.

 

[eddiecurrent]

An led flashlight is actually a low-drain device...other examples of low-drain include devices such as LED headlamps, toys, remote control devices, clocks and radios.

Examples of high-drain devices are gps's and digital cameras.
BTW how does your Nokta Fors perform, do you like it? Word is it goes deep.

 

[1942 merc]

I was looking at these batteries for my AT pro . They are the highest MAH at 2900 I could find .

4 x AA 2900 mAh Accupower NiMH Rechargeable Batteries

And this 9v for my garrett pointer

2 x 9 Volt 300 mAh AccuPower NiMH Rechargeable Batteries

Anyone else use these ?

 

[Target Terror]

The BH Sharp Shooter II uses two 9v batteries and the manual states that you should only use alkaline batteries.

Since rechargable NiMH batteries are usually recommended for high current drain situations; shouldn't I be able to use them without an issue in this metal detector?
It is certainly a high drain application, this thing eats batteries and demands a fairly high voltage. So the alkalines start to roll off and the detector won't work. Whereas NiMHs have a relatively flat voltage curve.

Thoughts? Experiences?


Thanks,
Tim

I know this is older but it's my domain so i'll add.

It is likely these devices are suggesting alkaline because the voltages are higher than most replacement renewable chemistries. An alkaline AA is nominally 1.5v. A NiMh AA is 1.2v. As stated by another user these devices have built in regulation at a much lower voltage so the worry of a dropout there is minimal. However, if they employ battery level meters, they are calibrated against the voltage curves of Alkaline. Use of the lower voltage cells with different discharge curves will throw the battery meters off. That's probably just an annoyance. Unless the detector is designed to turn OFF in a low battery state. This could lead to much lower run times than you hope for despite the batteries having plenty left in them. You'll have to figure out if that applies to your detector and at what voltage that occurs. I typically use a variable bench supply to determine dropout voltages on devices.

You will note that most 9v rechargables finely print 8.4v on the battery. So no exceptions on the 9v replacement renewables either; Lower nominal voltage. However, there are rechargable 9v batteries out there that meet (and exceed) the 9v alkaline. Powerex is one brand the paintballers love to use. You can typically pick up a pair of those and a fast charger for 99 bucks on Amazon. But it's been years since i've purchased them so that figure may not be very accurate any more. You'll have to shop around. I have used them in the past and they are solid little batteries.

In regards to drain. All of these chemistries are capable of sustaining voltage throughout their rated capacity span. There is nowhere near a discharge demand by your detector to bring C ratings into question here. Hope that has added something of value here.

EDIT: For clarification, not all powerex batteries are 9.6v. There are several models. You want ones that say 'true 9.6v' on them, such as this one: http://www.amazon.com/Powerex-MH-96V230-230mAh-Rechargeable-Battery/dp/B00LT0LS92?ie=UTF8&keywords=powerex%209v&qid=1459814695&ref_=sr_1_2&sr=8-2

 

[TheHunterGT]

I have been using the EBL brand 9v's...600mah....Li-Ion.

Use(d) them in a Fisher Gold Bug....BH SharpShooter2.....BH Land Ranger Pro....BH Lone Star Pro.....BH Gold Digger...BH Junior....Garrett Scorpion (took 3 of them)....Garrett Pro-Pointer and Pro-Pointer AT.

Never an issue other than one I dropped and the housing cracked so I tossed it out to be safe. Always last me a full day of hunting...charge them overnight when I get home.

 

[Target Terror]

I have been using the EBL brand 9v's...600mah....Li-Ion.

Use(d) them in a Fisher Gold Bug....BH SharpShooter2.....BH Land Ranger Pro....BH Lone Star Pro.....BH Gold Digger...BH Junior....Garrett Scorpion (took 3 of them)....Garrett Pro-Pointer and Pro-Pointer AT.

Never an issue other than one I dropped and the housing cracked so I tossed it out to be safe. Always last me a full day of hunting...charge them overnight when I get home.

They'll work in most things just fine but i've found low battery warnings all too soon on detectors. No Li-xx 9v will ever be 9v. They're two 3.7v cells in series which at peak charge voltage will rest at 8.4v. Perhaps you're not getting the warnings because you charge them nightly. Have you ever metered the resting voltage on them after a day of detecting?

 

[TheHunterGT]

The EBL's are 8.3 to 8.4v at charge...no doubt about that. I use First Texas detectors...which allow you to run pretty low. Obviously other brands will have different power draws and cut-offs....but I cannot comment on that other than the Garrett Scorpion I owned. The battery change was ridiculous on that machine so I basically let them die before replacing.

I do know on the Fisher Gold Bug the EBL's should not illuminate all 3 bars according to the manual...but they do.

According to the Gold Bug manual.....(expect 15 - 20 hours from alkaline)

3 segments = more than 8.4 volts
2 segments = more than 7.5 volts
1 segment = more than 6.8 volts
1 segment flashing = less than 6.8 volts

After the first segment begins flashing...expect the detector to turn off within 10 minutes.

The EBL freshly charged is 8.4v tops...but it will keep all 3 segments lit for a good 4-6 hours before the first bar blanks. From there (according to manual) I should still be at more than 7.5 volts. I checked after about a 6-7 hour hunt where the machine was not turned off at all. Down to 2 bars for a good hour or so...meter read 7.3 exactly. So either the manual is off...or the LCD reading is off. I rarely let it go to one bar and have never seen it blink. Always home by then and back on the charger. I will assume a 12 hour run time TOPS before it blinks and shuts down. Perhaps I will let it happen one day just for testing sakes.

Just for conversation and information for anybody wondering.....the Land Ranger Pro has a tad different specs.

According to the Land Ranger Pro manual....(20-25 hours from alkaline)

3 segments = more than 8.1 volts
2 segments = 7.1 to 8.0 volts
1 segment = 6.5 to 7.0 volts
0 segments = 6.2 to 6.4 volts
Outline flashing = 6.1 or less

I have tested that as well and can say it is dead perfect according to my meter. I have actually ran this machine pretty low down to 1 segment. Never down to zero segments. At 1 segment I was 6.8 volts. Charged it after that. I would say it took me roughly 10-12 hours to get to one segment in 2X 6 hours trips. So perhaps 15 hour tops on the Land Ranger Pro? Just a guess....

I never tested the SharpShooter 2 on hours or the meter unfortunately. I do know that one 9v drains faster than the other on the SS2. Tested that once. One was 8.0+ still and the other was low to like 6.1 or so after a day of detecting. Found that odd...so I tested my sons Bounty Hunter Gold Digger and my daughters BH Junior after a day of detecting. Both use 2X 9V as well.....both did the same. Drain one first...then the other. Found that odd.

Was is the word on that Target Terror?

 

[Target Terror]

I do know that one 9v drains faster than the other on the SS2. Tested that once. One was 8.0+ still and the other was low to like 6.1 or so after a day of detecting. Found that odd...so I tested my sons Bounty Hunter Gold Digger and my daughters BH Junior after a day of detecting. Both use 2X 9V as well.....both did the same. Drain one first...then the other. Found that odd.

Was is the word on that Target Terror?

If it's using one battery for function and the other for audio (Like the Whites line that use x2 9v), that would explain the imbalance. They do this to keep the voltage supply to the circuitry stable through audio demands. So they separate the supply lines between two voltage sources. They're not actually in parallel. That's speculation until someone tears one down to confirm it but I can confirm that on a Whites Prism V. You might find removing one or the other 9v that the detector still turns on but lacks audio.

Also, it would appear your detectors take sub 9v rechargables into account by calibration. That's reassuring to hear.