I just bought a dirt-cheap wireless lapel microphone with
transmitter and receiver. But, I think there may be a problem with
battery life.

The transmitter is powered by a 9V alkaline battery, and I rigged it
up to test the current draw, which was 38 ma. The receiver is
powered by a single AAA battery, and it draws 52 ma. In both cases,
that's with the power-on LED indicators disconnected to save power.

Back in the day I've used an external battery pack to extend the
life of a digital camera which didn't operate well on rechargeables.
The pack was just a Radio Shack holder for four C cells, plugged
into the AC jack on the camera, to take the place of the usual four
AA's. The C's lasted a long, long time, at not much more cost than
four AA's, but at the cost of "wearing" the battery pack in some
position.

With the wireless mic, there may be times when I want to use it over
an extended period of several hours without having to stop and
change batteries, and without having to wonder if it's gone dead.

In the case of the receiver, I could attach a twin AA holder to the
back, and power it from that, but with the holder wiring modified so
that the batteries are in parallel. That would give me two AA's in
the place of the one AAA, which should significantly extend the
life.

The transmitter is a bit more of a problem. The best I can think of
is to mount two external 9V's on the back, probably with tape, and
wire the connectors together in parallel, possibly also leaving the
internal 9V still connected, which would give me three 9V's in
parallel.

Well, I have a couple questions:

1. Is there a better way to do this?

2. Is connecting the batteries in parallel going to cause any
problems? They will remain connected to each other even when the
power switch is off. Will the batteries do bad things to each other
connected that way for extended periods even when no current is
flowing to the external circuit?

I don't know yet how much voltage drop the devices will tolerate and
still operate. I'm testing that now. The answer might give me
other options.

"George" <gh424NO824SPAM@cox.net> wrote in message
news:6O3mj.10162$q36.1906@newsfe14.lga...
>I just bought a dirt-cheap wireless lapel microphone with
> transmitter and receiver. But, I think there may be a problem with
> battery life.
>
> The transmitter is powered by a 9V alkaline battery, and I rigged it
> up to test the current draw, which was 38 ma. The receiver is
> powered by a single AAA battery, and it draws 52 ma. In both cases,
> that's with the power-on LED indicators disconnected to save power.
>
> Back in the day I've used an external battery pack to extend the
> life of a digital camera which didn't operate well on rechargeables.
> The pack was just a Radio Shack holder for four C cells, plugged
> into the AC jack on the camera, to take the place of the usual four
> AA's. The C's lasted a long, long time, at not much more cost than
> four AA's, but at the cost of "wearing" the battery pack in some
> position.
>
> With the wireless mic, there may be times when I want to use it over
> an extended period of several hours without having to stop and
> change batteries, and without having to wonder if it's gone dead.
>
> In the case of the receiver, I could attach a twin AA holder to the
> back, and power it from that, but with the holder wiring modified so
> that the batteries are in parallel. That would give me two AA's in
> the place of the one AAA, which should significantly extend the
> life.
>
> The transmitter is a bit more of a problem. The best I can think of
> is to mount two external 9V's on the back, probably with tape, and
> wire the connectors together in parallel, possibly also leaving the
> internal 9V still connected, which would give me three 9V's in
> parallel.
>
> Well, I have a couple questions:
>
> 1. Is there a better way to do this?
>
> 2. Is connecting the batteries in parallel going to cause any
> problems? They will remain connected to each other even when the
> power switch is off. Will the batteries do bad things to each other
> connected that way for extended periods even when no current is
> flowing to the external circuit?
>
> I don't know yet how much voltage drop the devices will tolerate and
> still operate. I'm testing that now. The answer might give me
> other options.
>

Usually if you parallel batteries of identical type the internal resistance
is enough to prevent them from "doing bad things to each other".
You could rig up a belt pack to supply the needed voltage at greater
capacity.

Tom

On Jan 24, 9:21=A0am, George <gh424NO824S...@cox.net> wrote:
> I just bought a dirt-cheap wireless lapel microphone with
> transmitter and receiver. =A0But, I think there may be a problem with
> battery life.
>
> The transmitter is powered by a 9V alkaline battery, and I rigged it
> up to test the current draw, which was 38 ma. =A0The receiver is
> powered by a single AAA battery, and it draws 52 ma. =A0In both cases,
> that's with the power-on LED indicators disconnected to save power.
>
> Back in the day I've used an external battery pack to extend the
> life of a digital camera which didn't operate well on rechargeables.
> The pack was just a Radio Shack holder for four C cells, plugged
> into the AC jack on the camera, to take the place of the usual four
> AA's. =A0The C's lasted a long, long time, at not much more cost than
> four AA's, but at the cost of "wearing" the battery pack in some
> position.
>
> With the wireless mic, there may be times when I want to use it over
> an extended period of several hours without having to stop and
> change batteries, and without having to wonder if it's gone dead. =A0
>
> In the case of the receiver, I could attach a twin AA holder to the
> back, and power it from that, but with the holder wiring modified so
> that the batteries are in parallel. =A0That would give me two AA's in
> the place of the one AAA, which should significantly extend the
> life.
>
> The transmitter is a bit more of a problem. =A0The best I can think of
> is to mount two external 9V's on the back, probably with tape, and
> wire the connectors together in parallel, possibly also leaving the
> internal 9V still connected, which would give me three 9V's in
> parallel.
>
> Well, I have a couple questions:
>
> 1. =A0Is there a better way to do this?
>
> 2. =A0Is connecting the batteries in parallel going to cause any
> problems? =A0They will remain connected to each other even when the
> power switch is off. =A0Will the batteries do bad things to each other
> connected that way for extended periods even when no current is
> flowing to the external circuit?
>
> I don't know yet how much voltage drop the devices will tolerate and
> still operate. =A0I'm testing that now. =A0The answer might give me
> other options.

Don't mixed used and new batteries when paralleling. Use all new
identical batteries (same size and brand). No problemo.
I took apart a 9 volt battery once. It has six individual cells,
wired in series. It's kind of cute, they look just like the A type
batteries but much smaller. Cute, but inefficient. The nine volters
cost far more per unit energy than a single cell "battery" (misnomer,
a single cell is not a battery of cells). I calculated it and you get
way more bang for the buck (calculted per joule) with single cells.
You were contemplating weighing yourself down with more nine volt
batteries in parallel, but you would do better in my opinion to put
six single cells in series, AAA or whatever you want. Clip it on your
belt and run some 20 or 22 gauge wire to the mic. Get a 9 volt
connector clip to connect to the mic.

George wrote:
> I just bought a dirt-cheap wireless lapel microphone with
> transmitter and receiver. But, I think there may be a problem with
> battery life.
>
> The transmitter is powered by a 9V alkaline battery, and I rigged it
> up to test the current draw, which was 38 ma. The receiver is
> powered by a single AAA battery, and it draws 52 ma. In both cases,
> that's with the power-on LED indicators disconnected to save power.
>
> Back in the day I've used an external battery pack to extend the
> life of a digital camera which didn't operate well on rechargeables.
> The pack was just a Radio Shack holder for four C cells, plugged
> into the AC jack on the camera, to take the place of the usual four
> AA's. The C's lasted a long, long time, at not much more cost than
> four AA's, but at the cost of "wearing" the battery pack in some
> position.
>
> With the wireless mic, there may be times when I want to use it over
> an extended period of several hours without having to stop and
> change batteries, and without having to wonder if it's gone dead.
>
> In the case of the receiver, I could attach a twin AA holder to the
> back, and power it from that, but with the holder wiring modified so
> that the batteries are in parallel. That would give me two AA's in
> the place of the one AAA, which should significantly extend the
> life.
>
> The transmitter is a bit more of a problem. The best I can think of
> is to mount two external 9V's on the back, probably with tape, and
> wire the connectors together in parallel, possibly also leaving the
> internal 9V still connected, which would give me three 9V's in
> parallel.
>
> Well, I have a couple questions:
>
> 1. Is there a better way to do this?
>
> 2. Is connecting the batteries in parallel going to cause any
> problems? They will remain connected to each other even when the
> power switch is off. Will the batteries do bad things to each other
> connected that way for extended periods even when no current is
> flowing to the external circuit?
>
> I don't know yet how much voltage drop the devices will tolerate and
> still operate. I'm testing that now. The answer might give me
> other options.
>

You might want to try a 9V lithium battery.
http://www.batterymart.com/p-ultralife- ... ttery.html

Ed

On Jan 24, 5:21 pm, George <gh424NO824S...@cox.net> wrote:
> I just bought a dirt-cheap wireless lapel microphone with
> transmitter and receiver. But, I think there may be a problem with
> battery life.
>
> The transmitter is powered by a 9V alkaline battery, and I rigged it
> up to test the current draw, which was 38 ma. The receiver is
> powered by a single AAA battery, and it draws 52 ma. In both cases,
> that's with the power-on LED indicators disconnected to save power.
>
> Back in the day I've used an external battery pack to extend the
> life of a digital camera which didn't operate well on rechargeables.
> The pack was just a Radio Shack holder for four C cells, plugged
> into the AC jack on the camera, to take the place of the usual four
> AA's. The C's lasted a long, long time, at not much more cost than
> four AA's, but at the cost of "wearing" the battery pack in some
> position.
>
> With the wireless mic, there may be times when I want to use it over
> an extended period of several hours without having to stop and
> change batteries, and without having to wonder if it's gone dead.
>
> In the case of the receiver, I could attach a twin AA holder to the
> back, and power it from that, but with the holder wiring modified so
> that the batteries are in parallel. That would give me two AA's in
> the place of the one AAA, which should significantly extend the
> life.
>
> The transmitter is a bit more of a problem. The best I can think of
> is to mount two external 9V's on the back, probably with tape, and
> wire the connectors together in parallel, possibly also leaving the
> internal 9V still connected, which would give me three 9V's in
> parallel.
>
> Well, I have a couple questions:
>
> 1. Is there a better way to do this?
>
> 2. Is connecting the batteries in parallel going to cause any
> problems? They will remain connected to each other even when the
> power switch is off. Will the batteries do bad things to each other
> connected that way for extended periods even when no current is
> flowing to the external circuit?
>
> I don't know yet how much voltage drop the devices will tolerate and
> still operate. I'm testing that now. The answer might give me
> other options.

Why don't you run the reciever from a mains power supply?
A single D cell would be better than paralleling two AA's.

For the tx there are lithium PP3 batterys with more than
twice the capacity of a typical alkaline PP3. A few suppliers
have PP3's they specifically recommend for long life in
radio mikes.

Personally I prefer rechargable batterys. Since I have a suitable
charger (and take precautions just in case they do catch fire
while on charge) I'd use three 18650 cells and a couples of
diodes to drop the voltage a bit as 11V from a full charge
might be a bit high, a little polyfuse in case the wires get
shorted and insulate the whole thing in heatshrink.
That would not be much more bulky than a single extra external PP3.
2200mAH 18650 cells would in theory give 58 hours at 38mA drain.
18650 cells are used in most laptop battery packs, cheap and
high capacity but you have to charge then properly and not short
circuit them so I'm allways slightly hesitant to recommend them
for projects.

Bob

On Thu, 24 Jan 2008 11:21:06 -0600, George <gh424NO824SPAM@cox.net>
wrote:

>I just bought a dirt-cheap wireless lapel microphone with
>transmitter and receiver. But, I think there may be a problem with
>battery life.
>
>The transmitter is powered by a 9V alkaline battery, and I rigged it
>up to test the current draw, which was 38 ma. The receiver is
>powered by a single AAA battery, and it draws 52 ma. In both cases,
>that's with the power-on LED indicators disconnected to save power.
>
>Back in the day I've used an external battery pack to extend the
>life of a digital camera which didn't operate well on rechargeables.
>The pack was just a Radio Shack holder for four C cells, plugged
>into the AC jack on the camera, to take the place of the usual four
>AA's. The C's lasted a long, long time, at not much more cost than
>four AA's, but at the cost of "wearing" the battery pack in some
>position.
>
>With the wireless mic, there may be times when I want to use it over
>an extended period of several hours without having to stop and
>change batteries, and without having to wonder if it's gone dead.
>
>In the case of the receiver, I could attach a twin AA holder to the
>back, and power it from that, but with the holder wiring modified so
>that the batteries are in parallel. That would give me two AA's in
>the place of the one AAA, which should significantly extend the
>life.
>
>The transmitter is a bit more of a problem. The best I can think of
>is to mount two external 9V's on the back, probably with tape, and
>wire the connectors together in parallel, possibly also leaving the
>internal 9V still connected, which would give me three 9V's in
>parallel.
>
>Well, I have a couple questions:
>
>1. Is there a better way to do this?
>
>2. Is connecting the batteries in parallel going to cause any
>problems? They will remain connected to each other even when the
>power switch is off. Will the batteries do bad things to each other
>connected that way for extended periods even when no current is
>flowing to the external circuit?
>
>I don't know yet how much voltage drop the devices will tolerate and
>still operate. I'm testing that now. The answer might give me
>other options.

Connecting batteries in parallel isn't a good idea, if you do it make
sure they are with the same date code and both new and replaced as a
pair.

If you are going to strap batteries on the outside . . . go to radio
shack and get a holder for 6 AA batteries with a 9V snap on the case
and use that. That would increase the capacity by about 3.5X

A 9V battery should last a good while in the transmitter.

The alkaline 9 V should have a capacity of about 700 milliamp hours
and at 38 ma that's 18 hours . . .

A single AAA has a capacity of about 1.25 amp hours or should last
around 24 hours . . .

Maybe the switches are being left on?
--

George says...

> I just bought a dirt-cheap wireless lapel microphone
> with transmitter and receiver. But, I think there may
> be a problem with battery life.

-snip-

> Well, I have a couple questions:

> 1. Is there a better way to do this?

> 2. Is connecting the batteries in parallel going to
> cause any problems? They will remain connected to each
> other even when the power switch is off. Will the
> batteries do bad things to each other connected that way
> for extended periods even when no current is flowing to
> the external circuit?

> I don't know yet how much voltage drop the devices will
> tolerate and still operate. I'm testing that now. The
> answer might give me other options.

Thanks very much for all the suggestions. I had to
interrupt my battery-life test, but at 15 hours both the
transmitter and receiver were still working. With the power
on, the 9V was at 5.47V and the AAA was at 1.20V.

What I was trying to find was the voltage at which the
circuits stop working, since of course that could have a
substantial impact on how long the batteries will last. And
so far the numbers are better than I expected.

I'll finish the test, but I think if I need better life than
provided by alkaline batteries, I think using lithiums is
the best option rather than adding on external packs.

In article <de2e686d-8259-4b41-8dc0-6e838f375361@d4g2000prg.googlegroups.com>,
gearhead <nospam@billburg.com> wrote:
>I took apart a 9 volt battery once. It has six individual cells,
>wired in series. It's kind of cute, they look just like the A type
>batteries but much smaller.

Yup, those are AAAA cells --- as far as I know, they're only ever
found inside 9V batteries...

--
Wim Lewis <wiml@hhhh.org>, Seattle, WA, USA. PGP keyID 27F772C1