Help with a battery pack design

[Ryan]

Ok so I have a wireless device the plugs into the wall with no option to
make it completely wireless (darn..guess I have to do it).

What I know is that the power supply outputs is DC 5V/2.5A, switching
type. Also the tech specs say "Power Communication 4.5W (900mA x 5v)"
which I don't know what they mean by power communication.

I'm thinking of going to Radio Shack and getting some AAA, AA packs and
testing the output and then just putting some diodes on until I get the
desired output.

Can anyone help and elevate some of the guess work with some tips for
me? Should I be working for an output of 5v/2.5a from the battery pack?

Thanks for any information.
Ryan

 

[Ken Taylor]

Ok so I have a wireless device the plugs into the wall with no option to
make it completely wireless (darn..guess I have to do it).

What I know is that the power supply outputs is DC 5V/2.5A, switching
type. Also the tech specs say "Power Communication 4.5W (900mA x 5v)"
which I don't know what they mean by power communication.

I'm thinking of going to Radio Shack and getting some AAA, AA packs and
testing the output and then just putting some diodes on until I get the
desired output.

Can anyone help and elevate some of the guess work with some tips for me?
Should I be working for an output of 5v/2.5a from the battery pack?

Thanks for any information.
Ryan

Does your plug-pack supply 5V DC @ 2.5A, and your wireless device require 5V
(DC?) @ 900mA ?

If so then you can use this plug-pack for this device.

Ken

 

[Dan Hollands]

4 Batteries in series will probably make it work but the batteries will not
last long enough to be useful.

I think the label may say power consumption not communication.

--

Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
[email protected]
www.QuickScoreRace.com

 

[Ryan]

Does your plug-pack supply 5V DC @ 2.5A, and your wireless device require 5V
(DC?) @ 900mA ?

I don't have a plug-pack. I have the power supply for the device which
states Output 5V @ 2.5A. But I also look at the tech specs online which
stated "Power Communication 4.5W (900mA x 5v)" which I have know clue
what they mean by this?

Do it mean the device can operate at 5v @ 900mA? Can I test this any way?

 

[Ryan]

4 Batteries in series will probably make it work but the batteries will not
last long enough to be useful.

4 AA? How long would they last? And how can I calculate how long so I
can type in differet numbers for different batteries?

I think the label may say power consumption not communication.

Thats what I though as well but its not. It might be a typo in the doc
though.

http://rnelnet.com/pg84-manual_130.pdf

 

[Luhan Monat]

I don't have a plug-pack. I have the power supply for the device which
states Output 5V @ 2.5A. But I also look at the tech specs online which
stated "Power Communication 4.5W (900mA x 5v)" which I have know clue
what they mean by this?

Do it mean the device can operate at 5v @ 900mA? Can I test this any way?

You need to supply 5V at 900ma to power the device. A set of 4 2400mah
NiMH will give you 4.8volts for less than 3 hours.

 

[Ryan]

You need to supply 5V at 900ma to power the device. A set of 4 2400mah
NiMH will give you 4.8volts for less than 3 hours.

So if I go with something like 6v @ 2900mah with a 5v zener diode would
I be ok?

 

[Ken Taylor]

So if I go with something like 6v @ 2900mah with a 5v zener diode would I
be ok?

No, just use the power supply you have for the device. It has plenty of
capacity for the task.

Ken

 

[Ken Taylor]

4 AA? How long would they last? And how can I calculate how long so I can
type in differet numbers for different batteries?


Thats what I though as well but its not. It might be a typo in the doc
though.

http://rnelnet.com/pg84-manual_130.pdf

Yeah, that's spell-check for you. It's a typo - it should be 'consumption'.
Like I said, use the supply you have, it's fine.

Ken

 

[Ryan]

No, just use the power supply you have for the device. It has plenty of
capacity for the task.

Ken

The problem is I don't have a battery pack. I only have the power
supply that plugs into the wall. I'm looking to make one from parts. I
just don't know enough of the engineering to do it correctly the first
time. (Trying not to destroy my device)

Thanks for the replys.
Ryan

 

[Ken Taylor]

The problem is I don't have a battery pack. I only have the power supply
that plugs into the wall. I'm looking to make one from parts. I just
don't know enough of the engineering to do it correctly the first time.
(Trying not to destroy my device)

Thanks for the replys.
Ryan

Sorry, I lost track of what you were asking. Get four Lithium or other
hi-capacity rechargeables and use them. You'll probably find that four will
do the trick (4.8V versus 5V required) or if needs be get a fifth and use
that as well, and a diode (say, 1N4001 or virtually any other power diode)
and put that in series.

Sorry about the side-tracks. That sorta day. :-(

Ken

 

[Ken Taylor]

Sorry, I lost track of what you were asking. Get four Lithium or other
hi-capacity rechargeables and use them. You'll probably find that four
will do the trick (4.8V versus 5V required) or if needs be get a fifth and
use that as well, and a diode (say, 1N4001 or virtually any other power
diode) and put that in series.

Sorry about the side-tracks. That sorta day. :-(

Ken

What the......

Not Lithium, NiMH. Sheesh! Or the newer Alkaline rechargeables, for that
matter. There's some pretty beefy types out there (1800mAh or more).

Cheers.

Ken

 

[Pooh Bear]

I don't have a plug-pack. I have the power supply for the device which
states Output 5V @ 2.5A.

It's probably a convenient inexpensive 'off the shelf' unit that made sense to
package with the device.

It can cost *more* to make a 'special' with a lower rating !

But I also look at the tech specs online which stated "Power Communication 4.5W
(900mA x 5v)" which I have know clue what they mean by this?

That sounds like the actual power consumption.

It doesn't matter if the power supply is capable of delivering a bit more.

Do it mean the device can operate at 5v @ 900mA? Can I test this any way?

That's what it sounds like to me.

Graham

 

[Pooh Bear]

So if I go with something like 6v @ 2900mah with a 5v zener diode would
I be ok?

NOOOOOOOOOOOO !

I think you need to do electricity 101 first !

Graham

 

[Pooh Bear]

4 AA? How long would they last? And how can I calculate how long so I
can type in differet numbers for different batteries?


Thats what I though as well but its not. It might be a typo in the doc
though.

http://rnelnet.com/pg84-manual_130.pdf

Chinese English I suspect ! I've seen far worse. ;-)

Graham

 

[Ryan]

Ryan wrote:




NOOOOOOOOOOOO !

I think you need to do electricity 101 first !

Graham

I agree, but I'm trying to learn as I go. I got 4 NmH AAs to work
with, no I just need to get battery life to last longer. I guess the
question I'm asking what does the 5.1v zener diode do? Does the diode
only allow the 5.1v to pass through? And if so how much tolerance would
it have, 6v ok 20v bad.

5v @ 10000mah would be ok, right, it would just mean the battery power
would last longer?

Thanks for the patients and help.

Ryan

 

[Pooh Bear]

I agree, but I'm trying to learn as I go. I got 4 NmH AAs to work

4 NiMhs or indeed 4 Nicads will give around 4.8 ~ 4.9 V terminal voltage (
close enought to 5 V ) when fully charged - which is clearly enough to make
your device operate. Trouble is - when discharging - the voltage will
gradually drop.

This may or may not - depending on the design of your device - prove to be
problematic or not.

with, no I just need to get battery life to last longer. I guess the
question I'm asking what does the 5.1v zener diode do?

If you put a zener in parallel with the batteries - it'll simply exhaust them
faster. It'll take current ( charge ) that that could be usefully used by the
device.

Does the diode only allow the 5.1v to pass through? And if so how much
tolerance would it have, 6v ok 20v bad.

There's no chance of 20V so why are you worrying ?

5v @ 10000mah would be ok, right, it would just mean the battery power
would last longer?

The more mAh you have - the longer your battery pack will last. As long as you
don't put any zeners in there !

Pls report back !

Graham

 

[Roger Johansson]

4 AA? How long would they last? And how can I calculate how long so
I can type in differet numbers for different batteries?

All batteries have a capacity in mAh (milliAmphours). This is marked on
the battery and you can read it in the specifications for a certain
battery.

A big battery like you will need can have a capacity of 4000 mAh. Which
means it can deliver 4000 mAmps for 1 hour, or 1 Amp for 4 hours. Or 2
Amps for 8 hours. You need 2.5 Amps so it will run for 6 hours, or so.

You need recharchable batteries, of the biggest sort you can afford, 4
of them in series will probably work.


If your device really needs carefully regulated 5Volt DC you may need
to use a few more batteries and build a 5Volt 2.5 Amp regulator.

If this battery needs to work 24/7 you may want to consider a 12Volt
car battery, and a 5Volt regulator, because you need really big
batteries if this is going to run without being recharched for days and
weeks.

2.5Amps is a lot of current to take out continously.

A typical car battery can have 70Ah capacity. That is 70 Amps for 1
hour, or 1 Amp for 70 hours. 2 Amps for 35 hours. 2.5 Amps for...?

 

[ehsjr]

So if I go with something like 6v @ 2900mah with a 5v zener diode would
I be ok?

No. A zener is the wrong choice for you, unless you have
one that is rated at over 5 watts at 5 volts. Don't know
where you'll find a zener like that. You would not get a
huge increase in run time, even if you could get the 2900
mah cells and a proper zener. With a 6 volts supply, and
a zener shunt regulator, you have to waste about a watt
of power.

The solution Luhan proposed - 4.8 volts using NiMh cells
rated at 2400 mAh - would work, and wastes no power. You
might be able to use a 6 volt battery with a 1N540x diode
in series to drop the voltage to about 5.4 (wasting a bit
over 1/2 watt). Or you could use a battery with a high
efficiency (up to 95% efficient) DC-DC converter. But, if
you need more run time than Luhan's solution, your battery
capacity *must* be increased, no matter what configuration
you use.

So - how much run time do you need?

Ed

 

[Ryan]

Pooh Bear wrote:

4 NiMhs or indeed 4 Nicads will give around 4.8 ~ 4.9 V terminal voltage (
close enought to 5 V ) when fully charged - which is clearly enough to make
your device operate. Trouble is - when discharging - the voltage will
gradually drop.

This may or may not - depending on the design of your device - prove to be
problematic or not.

So, I used 4 NiMhs that tested at 5.1v fully charged. The device ran
for about 25min, I added a simple toggle switch so I could kill the use
of the batteries. I turn the device on and off a couple of time to
change settings. I'm recharging now to do a constant run to get a
better time. When I took them out they tested at 4.6v. So indeed you
are right when the voltage drop it wasn't able to run the device.

If you put a zener in parallel with the batteries - it'll simply exhaust them
faster. It'll take current ( charge ) that that could be usefully used by the
device.




There's no chance of 20V so why are you worrying ?

My question was more geared to learn the function of a diode. So I get
now that it takes (wastes) current but if I passed 20v to a 5.1v diode
would to still function or would it burn?

The more mAh you have - the longer your battery pack will last. As long as you
don't put any zeners in there !

So this brings up the question what can I do to make the life last
longer now. Different batteries but I don't know of any that run a 5v
that provide more mAh, thus the need to bring the voltage down.