Re: Alkaline batteries in parallel?
- From: default <default@xxxxxxxxxxxxx>
- Date: Fri, 25 Jan 2008 16:16:59 -0500
On Thu, 24 Jan 2008 11:21:06 -0600, George <gh424NO824SPAM@xxxxxxx>
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?
--
.
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