Tejon and rechargeables

[NWMP]

Sorry to drop this one on you guys, but I can't seem to get a straight answer anywhere. Will the Tesoro Tejon function, and function properly, with good quality high mAh NIMH batteries? Thanks.

[EpsilonMinus]

Sorry to drop this one on you guys, but I can't seem to get a straight answer anywhere. Will the Tesoro Tejon function, and function properly, with good quality high mAh NIMH batteries? Thanks.

I can't answer this directly regarding the specifications of that exact detector, but many manufactures (and many detectorists as well) will discourage this, even if it is 'safe' because rechargeables have a l lower voltage. For example, regular alkaline are 1.5 volts, but rechargeables tend to be in the 1.2 range. This may not seem like a big deal, but when you multiply the loss of 0.3 volts times 4-8 batteries, it adds up, or rather 'subtracts down', heh. I hope this helps, but I'm sure you'll get better comments in more detail on this pretty soon. If not, google is your friend!

[Carl-NC]

Most manufacturers, including Tesoro, design their detectors to run just as well on NiMH & NiCAD rechargeables as alkalines. In fact, if you look at the discharge curve for NiMH vs alkaline, you will see that NiMH maintains a higher voltage over the long run:



Complete article here:

http://www.geotech1.com/pages/misc/info/batteries.pdf

[DGDancer]

It should work fine with NiMh batteries. If you haven't read the article that Carl provided on the link in his post.
What you'll want to look for in NiMh batteries are ones with a high mAh, milliamp hour, rating. They come
in 1500mAh and 2800mAh flavors. More is better. Energizer and Duracell make some good ones but Energizer
is more available in the higher ratings. Dont worry about the 12Vdc rating of the power pack as that does not
affect the effective voltage used by the machien.

Thats the short ansewer~ read on if you would like to know a little more about batteries in general
The Tech end :

What I'm speaking about is a bit of conjecture based on my own experiences building and working with
battery pack power supplies and thier associated power regulation. I'll try to keep it simple~~

The primary difference between an Alkaline and a NiMh *or any rechargeable* is that when they get ready to
die~ fall below the effective voltage needed to operate the device~ NiMh's drop off suddenly. Alkalines
do not. The curve's in the chart posted demonstrate this nicely. There is a benifit for this with NiMh~ you will know
quickly when you need to change batteries where as with Alkalines you'll get a long period of less than
optimal operation and will be guessing if your device is wonkers or the batt's are flat.
Alkalines also have a bouncy voltage~ what I mean is that they can self regenerate a little bit~ and
as they die will mess with the regulator giving it fits of good operation and bad. The self regeneration
only occurs when the batteries are unloaded, turned off, for a period of time. Regulating circuits
dont like this.
NiMh batteries work at a more stable effective voltage over time than do Alkalines and this is a key to
device operation~ power regulation likes stablity. They do not self regenerate however they will self discharge
over time. The article says this and my experience has proven it true many times.
Keep a good scheduel on recharging and you'll be golden.

Dont worry about the voltage that a AA pack supplies with Akalines. Yes it takes 8 AA's and being series
linked to provide an output of 12Vdc. 1.5Vdc X 8 = 12Vdc~ as the article states the effective voltage
of Alkaline batteries under load is really only 1.2Vdc per bat making the effective voltage only 9.6Vdc *approximate*.
I've found this to be true by my own experience.
NiMh batteries start off at about 1.3 to 1.5Vdc unloaded and drop to about 1.2Vdc loaded so there is no
difference in effective voltage when compaired to Alkalines.
The device is most likely internally regulated at 9Vdc. This is a standard regulation. Why do I say that~
regulation is the key to stable operation of any device and it comes in fixed flavors, 1.5, 3, 6, 9, 10.5 and 12 are
typical. Voltage's supplied to the regulator will be anywere from approx 1 to 3 volts higher *under load* than the
rating of the regulator to provide the appropriate working voltage the regulator circuit needs.

A thought:

Why not use a 9 volt battery instead? It has to do with the current rating of the batteries and thier effective voltage
over time as well as the preference of the engineering and costs. As said a regulator wants a voltage about 1 to 3 volts
higher than its rating. To high a voltage and you risk damaging the regulator by working it to hard. 9 volts
typically operate at about 9.2Vdc but they are a shallow battery. Shallow means they just dont have much
of a current capacity~ usually only about 595mAh. Alkaline AA's individually have about 2800mAh making them
a deeper battery in terms of current capacity. The deeper the current capacity the longer your effective voltage
will remain above the cut off of the regulating circuit. To make an equivalent 9 volt battery with a deep capacity
you have to connect them in parallel to maintain your regulator input voltage. Because the 9 volt battery
operates very close to the cut off of a 9 volt regulator it becomes wastefull to use a battery like this as there
will still be useful life in the batteries even though the regulator will not accept it due to low effective voltage.

As current capacity is used up the voltage drops off.
That being said 9 volts will effectivly die for effective voltage to a regulator long before a series of AA's will.
9 volts are more complicated and expensive to connect in parallel to create the same effective current capacity that a
set of 8 AA's in series will provide. Also AA's are cheaper and easier to find than 9 volts~ things like this
are considerations if you ever want to build your own power supplies.

Well I'll get off my rant Thanks if you read this.... might aught to make a new topic on batteries here
in tech talk. A thought.

[jimmyjiver]

Hi, I'm going to be running mine off rechargeable batteries this spring. I really don't foresee a problem... If you are worried about rechargable batteries that have a nominal output voltage of 1.2 volts they do make rechargable batteries with an output of 1.5 volts..... JJ