Rechargeable Batteries
Pan
1) What's better, NiCd or NiMh. Or are they meant for
different kind of usage.
2) Batteries have stuff like 1000 mAh, 2000 mAh etc
written on them - i would assume that this is the amount of
charge they hold - i.e. how long they would last on a single
charge for a particular kind of use. For comparison, does
anyone know who much charge that a regular non-rechargeable
Duracell hold - so that I can figure out what mAh rechargeables
I would need?
3) What is the highest mAh available in the market?
4) Are there good & bad brands for the rechareable batteries &
the chargers?
5) Let's say I buy a charger & 2000 mAh batteries & tommorow
I decide to get 2500 mAh battereries, would I have to buy a new
charger or can the same old one charge the 2500 mAh batteries
also.
6) I would mainly be requiring AAA but can the same charger charge
both AA & AAA cells?
Logan Shaw
> Can some give some info on rechargeable batteries?
> 1) What's better, NiCd or NiMh. Or are they meant for
> different kind of usage.
NiMH tends to last longer and have less memory effect. But it also
costs more. Is it worth it? Depends on whether cost is important.
Personally, I like NiMH a lot because I like not having to worry
about the memory effect and just charging them whenever convenient.
> 2) Batteries have stuff like 1000 mAh, 2000 mAh etc
> written on them - i would assume that this is the amount of
> charge they hold - i.e. how long they would last on a single
> charge for a particular kind of use. For comparison, does
> anyone know who much charge that a regular non-rechargeable
> Duracell hold - so that I can figure out what mAh rechargeables
> I would need?
mAh means milliamp-hours. Milliamps are a measure of electrical
current, and of course hours are a measure of time. So theoretically
a 2000 mAh battery could sustain a 100 milliamp current for 20 hours
or a 1000 milliamp current for 2 hours.
However, there isn't, as far as I know, any kind of standardized
measuring procedure to actually come up with the number. You can
get a different amount of energy out of a battery depending on
whether you discharge it quickly or slowly, and there are a bunch
of other variations that could go into the measurement (like that
how much energy you get out depends also on the voltage the batteries
are delivering and not just the current), so basically the number
is not extremely meaningful. You can't say for sure that a 2100
mAh battery from one manufacturer is going to last longer in your
particular device than a 1900 mAh battery from another manufacturer.
Also, comparing mAh ratings between different types of batteries
is more meaningless, because a device will generally keep working
until the voltage is too low (or the internal resistant of the
battery is too high), and the voltage drop over time is different
with different types of batteries. So it really depends on the
device a lot.
> 3) What is the highest mAh available in the market?
Well, that would depend on the size of battery. A D-cell battery is
physically a lot bigger, so it can get a much higher mAh rating than
a AAA-cell.
Anyway, you probably don't want the highest available. Designing
batteries is, from what I understand, a compromise. The ones with
the very longest lives (how much energy you get out of a single
charge) are probably not the ones that you can use the most times
(most charge cycles) before they stop holding a charge and wear out.
And the ones with high mAh ratings tend to cost more, and there's
definitely a law of diminishing returns where it'd be better to
buy 3 sets of batteries that last a little less time than 2 sets
that last only slightly longer.
> 4) Are there good & bad brands for the rechareable batteries &
> the chargers?
Yes. From what I can tell MAHA is a pretty good brand in general,
although there are probably other good brands too.
> 5) Let's say I buy a charger & 2000 mAh batteries & tommorow
> I decide to get 2500 mAh battereries, would I have to buy a new
> charger or can the same old one charge the 2500 mAh batteries
> also.
You can charge just about anything with just about anything. The
difference is whether you're shortening the life of the battery
by overcharging or something else along those lines.
Most decent chargers these days have a computerized charging circuit
where they monitor the voltage of the cells being charged and watch
for a pattern, then stop the charging at "just" the right moment,
so with that kind of charger, you can put in almost any battery
(of the right type -- NiMH or NiCd, or whatever it says in the
instructions) and it will "just work".
I would go for a smart charger because I feel like if you use a
lot of batteries, it'll probably pay for itself eventually. I
personally like the idea of a charger that has a separate circuit
for every individual battery so that each battery is charged just
the right amount. But maybe that just makes me feel good.
> 6) I would mainly be requiring AAA but can the same charger charge
> both AA & AAA cells?
I'm pretty sure that most chargers which charge one charge the other
as well, but there are some special-purpose chargers that don't.
- Logan
Pan
"Logan Shaw" <lshaw-...@austin.rr.com> wrote in message
news:4726c3f1$0$32473$4c36...@roadrunner.com...
> mAh means milliamp-hours. Milliamps are a measure of electrical
> current, and of course hours are a measure of time. So theoretically
> a 2000 mAh battery could sustain a 100 milliamp current for 20 hours
> or a 1000 milliamp current for 2 hours.
Thank you for your reply.
So if I want a AAA which would last as long or more than a regular duracell
AAA what mAh rated rated rechargeable should I buy?
Jeff
> Pan wrote:
>
>> Can some give some info on rechargeable batteries?
>> 1) What's better, NiCd or NiMh. Or are they meant for
>> different kind of usage.
>
>
> NiMH tends to last longer and have less memory effect. But it also
> costs more. Is it worth it? Depends on whether cost is important.
> Personally, I like NiMH a lot because I like not having to worry
> about the memory effect and just charging them whenever convenient.
Logan has done an excellent job of answering this, I'll just add a
few points. Most of what I'll add is about NiMh.
Apparently for high drain devices like power tools NiCd are superior.
Otherwise NiMh are terrific, particularly in digital cameras. A NiMh
battery will run a camera many times longer than a set of a alkalines
before it needs recharging.
They do have a few quirks though. If your NiMh batteries have been
sitting around they may take several charges before they come up to full
capacity. Once at capacity they have a nice long slow decline of
capacity. Number of charges possible is higher than NiCds. I have seen a
NiMh fail while charging though.
>
>> 2) Batteries have stuff like 1000 mAh, 2000 mAh etc
>> written on them - i would assume that this is the amount of
>> charge they hold - i.e. how long they would last on a single
>> charge for a particular kind of use. For comparison, does
>> anyone know who much charge that a regular non-rechargeable
>> Duracell hold - so that I can figure out what mAh rechargeables
>> I would need?
It's hard to compare becaue you have to consider discharge rates. As
mentioned above I find that NiMh batteries last much longer than
alkalines although they have similar AHr, I *think* a AA alkaline is
around 1500mAHr. Go for the bigger number, particulary within a
manufacturers line. Usual caveats about buying from dollar stores (like
Big Lots) apply.
If you want something in a low drain, long life device like a remote or
firealarm, alkalines should be your choice.
NiMh tend to come at a max size of AA, I've seen covers that turn AA's
into D's. About 2700mAhr was the biggest I saw last time I went shopping.
>
>> 4) Are there good & bad brands for the rechareable batteries &
>> the chargers?
>
>
> Yes. From what I can tell MAHA is a pretty good brand in general,
> although there are probably other good brands too.
>
>> 5) Let's say I buy a charger & 2000 mAh batteries & tommorow
>> I decide to get 2500 mAh battereries, would I have to buy a new
>> charger or can the same old one charge the 2500 mAh batteries
>> also.
>
>
> You can charge just about anything with just about anything. The
> difference is whether you're shortening the life of the battery
> by overcharging or something else along those lines.
The one caveat here is fast charge NiMh. You can't charge regular
batteries in a fast charge NiMh charger. But the slow chargers dominate
the market anyways. The fast chargers and batteries are clearly marked.
Most of the regular chargers come with a wall wart, you may wish to
look for one with a little more ooomph for a little faster charge as
NiMh can take hours to come up.
>
> Most decent chargers these days have a computerized charging circuit
> where they monitor the voltage of the cells being charged and watch
> for a pattern, then stop the charging at "just" the right moment,
> so with that kind of charger, you can put in almost any battery
> (of the right type -- NiMH or NiCd, or whatever it says in the
> instructions) and it will "just work".
>
> I would go for a smart charger because I feel like if you use a
> lot of batteries, it'll probably pay for itself eventually. I
> personally like the idea of a charger that has a separate circuit
> for every individual battery so that each battery is charged just
> the right amount. But maybe that just makes me feel good.
>
>> 6) I would mainly be requiring AAA but can the same charger charge
>> both AA & AAA cells?
Yes.
Jeff
Bill Rider
> Can some give some info on rechargeable batteries?
> 1) What's better, NiCd or NiMh. Or are they meant for
> different kind of usage.
In 1981, my first set of NiCads lasted only a year. Ten years ago I
bought 8 NiMH that are still in daily use. I thought they were better.
I was wrong. The big secret is fast charging. Slow charging allows
crystals to grow, and they cause internal shorts. Soon your battery
won't hold a charge long. Then it won't charge at all.
Two drawbacks to NiCads are that a given size probably won't hold as
much charge as NiMH and the cadmium is toxic. Advantages are that a
fast charger can charge NiCad more reliably than NiMH, NiCad will hold a
charge more weeks, and NiCad will last more cycles.
> 2) Batteries have stuff like 1000 mAh, 2000 mAh etc
> written on them - i would assume that this is the amount of
> charge they hold - i.e. how long they would last on a single
> charge for a particular kind of use. For comparison, does
> anyone know who much charge that a regular non-rechargeable
> Duracell hold - so that I can figure out what mAh rechargeables
> I would need?
It depends on how much power you draw. An alkaline cell has more energy
than a rechargeable, but you can't get all the energy out because
internal resistance increases as the battery drains. An alkaline won't
supply as much energy to a 5-amp load as to a 1-amp load. If you let
the alkaline rest, resistance will drop and you can get some more energy
out of it. So it's complicated.
> 3) What is the highest mAh available in the market?
I don't pay attention to that. It's easier to keep charged cells handy.
I'm afraid the ones with the highest capacity may have layers too
thin to last long.
> 4) Are there good & bad brands for the rechareable batteries &
> the chargers?
I'd look for a charger that has a light for each cell. I think most
have a light for each pair of cells. I don't like that. When you have
a light for each cell, the microprocessor knows when that cell is charged.
> 5) Let's say I buy a charger & 2000 mAh batteries & tommorow
> I decide to get 2500 mAh battereries, would I have to buy a new
> charger or can the same old one charge the 2500 mAh batteries
> also.
No problem. There may be a problem between NiCad and NiMH. I have a
charger that will charge four NiMH on four circuits in 20 minutes or so.
It warns against charging NiCad. I have a slower fast charger that
will work for either.
> 6) I would mainly be requiring AAA but can the same charger charge
> both AA & AAA cells?
>
>
AA is supposed to be the ideal size for NiCad or NiMH. For remotes I
stick to alkaline AAA because alkalines hold their charge a lot longer.
I got an MP3 player that uses 1 AAA. I wish it used AA. Instead of
fooling with AAA rechargeables, I'll buy a new player. I got an LED
flashlight that uses 3 AAAs. I'll use it as little as possible. Maybe
I ought to look into the feasibility of AAA rechargeables.
skar...@gmail.com
I think you should seriously consider hybrid rechargeable batteries.
One added advantage with these batteries is that, once charged, they
hold the charge for a long time (better shelf life).
Regular rechargeable batteries slowly lose their charge (even when not
used) and have no juice in them when you really need them.
Wal-Mart used to sell them (I don't recall the brand) for much cheaper
than online price. Use the keywords "hybrid" and "rechargeable" on
Amazon to find those batteries.
I bought 8 of those batteries at Wal-Mart last year for use in my S2-
IS camera and I am extremely happy with them. I used to have plain old
NiMH rechargeables before and had bad experience (no energy when I
needed them).
John Weiss
>
> So if I want a AAA which would last as long or more than a regular duracell
> AAA what mAh rated rated rechargeable should I buy?
Buy the highest rating you can find, without paying an exorbitant price premium.
m...@privacy.net
>stick to alkaline AAA because alkalines hold their charge a lot longer.
Does anyone make rechargeable Lithium Ion AA cells and
charger?
Anthony Matonak
No. Lithium batteries have a cell voltage around 3.3V so they
can't be used to replace single AA cells. They can be used to
replace two AA cells though and this is common in digital
cameras. You can use either a single lithium battery or two
AAs.
Anthony
Jeff
In addition Lithium Ion batteries need to be used in devices that are
tailored for them. If they are discharged too far, they can not be
recharged.
Jeff
>
> Anthony
Don K
news:4726c3f1$0$32473$4c36...@roadrunner.com...
> You can charge just about anything with just about anything. The
> difference is whether you're shortening the life of the battery
> by overcharging or something else along those lines.
>
> Most decent chargers these days have a computerized charging circuit
> where they monitor the voltage of the cells being charged and watch
> for a pattern, then stop the charging at "just" the right moment,
> so with that kind of charger, you can put in almost any battery
> (of the right type -- NiMH or NiCd, or whatever it says in the
> instructions) and it will "just work".
Duracell says monitoring temperature change is better than monitoring
voltage. They recommend charging at a high rate until the rate of temperature
change increases, then cutting the current to one-tenth for a half-hour, then
trickle-charging at 1/300th current to maintain charge indefinitely.
http://www.duracell.com/oem/Pdf/others/TECHBULL.pdf
Don
Bill Rider
He also makes chargers for medical equipment, public-safety equipment,
and the military. He's against trickle charging nickel batteries. He
says it causes deterioration through the buildup of crystals.
He says to remove them as soon as they are charged and, if they've been
on the shelf, you could top them up before use. However, he recommends
trickle charging a new battery 24 hours.
His chargers monitor voltage, temperature, and time.