[GeoStL] Re: Rechargeable Batteries
- From: "Jon Mertz" <jemertz@xxxxxxxxx>
- To: geocaching@xxxxxxxxxxxxx
- Date: Sat, 14 Jul 2007 19:59:33 -0500
Another note that might come in handy regarding batteries,
Somewhere, I think Consumer Reports some years back, had a comparison of
various types of batteries. There are three categories, and each brand
within a category is very similar.
First you have your traditional Alkaline battery. The voltage graph for
these starts above the 1.5V they're rated at and slowly declines until it
reaches 0.
Second you have Heavy Duty which tend to be cheaper than Alkaline. These
start at about 1.5V and stay close to 1.5V, slowly declining, until they hit
the end of their life and drop voltage rapidly to 0. The graph looks like a
step, compared to the ramp of the Alkalines. This means that for purposes
that require a full (or very near) 1.5V, Heavy Duty is best (i.e. portable
radio), but for applications where a low charge is acceptable, (i.e. smoke
alarm) Alkaline is best.
The final type, as discussed here, is Rechargeable. As I recall the graph
for these was very similar to the Heavy Duty graph, but having been about 15
years ago, putting me in my pre-teens, I didn't have the money for these at
the time and therefore didn't pay much attention to this one.
Note: V= I * R [Voltage (Volts) = Current (Amperes) * Resistance (Ohms)] and
as a battery nears the end of its life, resistance increases, so perhaps it
is current that decreases over time, not voltage. Like I said, I saw these
quite some time ago.) Also because this was so long ago, the rechargeable
only came in one variety - NiCd, or Nickel-Cadmium. These used to have a
pretty severe memory effect, but this has been drastically reduced of late,
by my understanding. You will now find NiMH (Nickel Metal Hydride) and
Li-ion (Lithium Ion; generally not in the AA form factor, typically for
rechargeable device batteries)
Also, as I'm sure that most of you know, keep in mind that rechargeables
quickly lose their charge over time, where Alkalines only lose from 2-25%
per year depending on temperature, among other variables. (Colder is better
for storage, if you're wondering -- just don't freeze them)
Also beware knock-off brands such as Enercell, SQMY, Dinacell and PenesamiG.
These tend to ship defective far more often than name, or even store,
brands. I got some PenesamiGs with some LED flashlights I bought, and some
wouldn't even power the 9 LED lights when they were new. Others were
corroded in the package already, of course I don't know how old these
packages were when I got them.
-Jon
On 7/14/07, Weymouth <wey6567@xxxxxxxxxxxxx> wrote:
-
Be rechargeables have outlasted my alkalines. I also
bought the energizers from Sams/WalMart. The first
time I used them in the GPS they did not last as long
as I thought they would. I had to change my GPS from
Alkaline to Rechargeable.
Jeff
JC_Geo
--- Mike Lusicic <lusicic@xxxxxxxxxxxxx> wrote:
---------------------------------
- The secret to long rechargeable battery life is
the charger itself. Youneed one that is designed for
the type of battery you are using. Notall rechargeable
batteries are the same, and the voltage varies. Thatis
why the rechargeable batteries may not last as long.
They haveslightly lower voltage, so for the same power
output, they have to makeit with more current.
Anyway, all rechargeable batteries have to have some
sort of vent. Itis usually a one way job. That is
because when you charge a battery, itcreates heat.
That creates pressure inside the battery case. Too
muchpressure and the battery will explode. Thus they
have a vent to preventsuch a catastrophic event.
If the battery gets hot and does vent some gas, the
gas that it isventing is actually part of the
electrolyte inside the battery. Youlose too much, and
the battery loses capacity. The most heat isproduced
after the battery is done charging and you keep it on
thecharger. If the charger "knows" what voltage
represents a full charge,it can stop charging the
battery, or only feed it a tiny current tokeep it from
heating up. Dumb chargers, or ones made for
differentbattery types with different fully charged
voltage levels canovercharge and overheat the battery.
That is when you shorten the lifeof the battery.
I hope this helps.
Roger Barnes wrote:
-My experience is that some last a year or two and
some last severalyears. I did not mark my batteries
so I could pair the same twotogether all the time. I
think that helps. The next time I open newones, I
will do that. The ones that last several years have
beenrecharged dozens of times, even the ones that
haven't lasted as longhave been recharged maybe a
dozen time or more. They charge OK, theyjust don't
last very long. Anyway, I think they have been well
worthit. Of course, YMMV.Rogerps - YMMV = Your
Mileage May Very, in case anyone is wondering.
Andrew Senger wrote:Thanks everyone for your
information. I have a couple of
follow-upquestions.Have you ever had the batteries go
"dead" (i.e. won't recharge, orwon't stay charged for
long)? If so, approx how long did that take(in
recharges or months/years)?At Sam's, I bought a
recharge kit with 8 AA batteries and 4 AAAbatteries.
It was the same price as (I believe) a 32-count AA
case.Eric mentioned that he was getting about 3/4 of
the time withrechargeables, so I would need at least 5
recharges to be worth thevalue. Will the 8 batteries
will last 5 times longer than a typicalAA over its
life? If so, is the charge still good after that 5th
use?Thanks again!Andrew
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