Powering DC TV off of D batteries...

S

SA Dev

Guest
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the 18AH
life, I was assuming the batteries could power the TV for about 4 hours. Do
I just need to add one or two more cells into the series to up the voltage a
bit to account for the voltage loss?

Thanks,

SA Dev
 
Hello SA Dev,

Please don't simply add two cells as this may fry the TV when for example the
brightness is turned down and the voltage might exceed what it can stand.

I suggest to check the load curves for the chosen D cells at the manufacturer
web site. Most have very detailed data available. Probably the internal
resistance of D cells is too high. I don't think D cells are meant to deliver 4
amps. Could even be dangerous with some types but the mfg can tell you that.

Regards, Joerg
http://www.analogconsultants.com
 
SA Dev <nospam38925@forme.com> wrote:
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the 18AH
Click to expand...
I'd guess that it probably will, if you use premium quality D cells, or NiCd/
NiMH ones.

Lead-acid is probably the way to go.
 
Subject: Re: Powering DC TV off of D batteries...
From: Ian Stirling root@mauve.demon.co.uk
Date: 4/25/2004 4:52 PM Central Standard Time
Message-id: <MqWic.36501$Y%6.4873181@wards.force9.net

SA Dev <nospam38925@forme.com> wrote:
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I
noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the
18AH

I'd guess that it probably will, if you use premium quality D cells, or NiCd/
NiMH ones.

Lead-acid is probably the way to go.
Click to expand...
Lead-acid *is* the way to go, because of current capability, and the ability to
be recharged. However, if you insist on using off-the-shelf, disposable
batteries to power your TV, you might have some luck with two 6V lantern
batteries in series (like Ray-O-Vac 928 or 945). You can't depend on "D"
batteries for more than an amp, and the contact resistance of 8 in series is
going to bog you down even further.

Good luck
Chris
 
The batteries you are using are not capable of delivering the current
required to run the TV
Increase the current capacity, not the voltage.

Vlad


On Sun, 25 Apr 2004 21:52:44 GMT, Ian Stirling
<root@mauve.demon.co.uk> wrote:

SA Dev <nospam38925@forme.com> wrote:
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the 18AH

I'd guess that it probably will, if you use premium quality D cells, or NiCd/
NiMH ones.

Lead-acid is probably the way to go.
Click to expand...
 
"SA Dev" <nospam38925@forme.com> wrote in message
news:408c29bb@news.tulsaconnect.com...
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I
noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the
18AH
life, I was assuming the batteries could power the TV for about 4
hours...........................
Click to expand...

I can't believe that an Energizer D cell is rated at 18 AH. I hope you
didn't multiply the number by 8 for 8 in series. Many D cells are C cells +
fluff. A few are AA + fluff.

Tam
 
Hi,

IIRC alkaline "D" cells have a capacity of around 4 AmpHours not 18
AmpHours. Four amps is just too much current for these batteries. Perhaps,
10 true NiCad "D" cells in series would work for a short time say 30 - 40
minutes of run time. But, as others suggested, I'd go with a lead-acid gel
cell battery with a 10 or more AmpHour capacity. It's also probably the
cheapest solution.

Big John


"SA Dev" <nospam38925@forme.com> wrote in message
news:408c29bb@news.tulsaconnect.com...
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I
noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the
18AH
life, I was assuming the batteries could power the TV for about 4 hours.
Do
I just need to add one or two more cells into the series to up the voltage
a
bit to account for the voltage loss?

Thanks,

SA Dev
Click to expand...
 
Hi,

Lead-acid *is* the way to go, because of current capability, and the
ability to
be recharged. However, if you insist on using off-the-shelf, disposable
batteries to power your TV, you might have some luck with two 6V lantern
batteries in series (like Ray-O-Vac 928 or 945). You can't depend on "D"
batteries for more than an amp, and the contact resistance of 8 in series
is
going to bog you down even further.
Click to expand...
That is what I was afraid of! Oh well, I guess I'll use my car jump start
backup battery instead of D cells.

Thanks for the help!

SA Dev
 
Whoops, I spoke too soon. I saw some D cell rated at 15 AH, which is close
enough to 18. However, if I interpret their data correctly, it is for a load
of 100 Ohms which would be an initial current of 15 ma. Also, they consider
the end point as 0.9 V, which might not fly.

Tam
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:mbCdnbmZTd6W1RHdRVn-sw@comcast.com...
"SA Dev" <nospam38925@forme.com> wrote in message
news:408c29bb@news.tulsaconnect.com...
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I
noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers,
the
picture doesn't fill the screen and the voltage across the batteries
drops
to 7V when the TV is on. The voltage across the sealed type battery
only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the
18AH
life, I was assuming the batteries could power the TV for about 4
hours...........................

I can't believe that an Energizer D cell is rated at 18 AH. I hope you
didn't multiply the number by 8 for 8 in series. Many D cells are C cells
+
fluff. A few are AA + fluff.

Tam
Click to expand...
 
Hi,

IIRC alkaline "D" cells have a capacity of around 4 AmpHours not 18
AmpHours. Four amps is just too much current for these batteries.
Perhaps,
10 true NiCad "D" cells in series would work for a short time say 30 - 40
minutes of run time. But, as others suggested, I'd go with a lead-acid
gel
cell battery with a 10 or more AmpHour capacity. It's also probably the
cheapest solution.
Click to expand...
Thanks to everyone for their posts--I appreciate it!! I'm going to go with
a SLA type battery...

SA Dev
 
On a sunny day (Sun, 25 Apr 2004 16:12:24 -0500) it happened "SA Dev"
<nospam38925@forme.com> wrote in <408c29bb@news.tulsaconnect.com>:

Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the 18AH
life, I was assuming the batteries could power the TV for about 4 hours. Do
I just need to add one or two more cells into the series to up the voltage a
bit to account for the voltage loss?

Thanks,

SA Dev
Perhaps you could use 10 NicCads, high power type, or NiMh, and a charger.
Click to expand...
these things are relatively cheap, especially recharging - versus - replacing
every few hours.
These rechargables have MUCH lower internal resistance then normal batteries.
Or you could consider a small sealed lead battery.
JP
 
You might have overlooked 1 thing, Im not sure.
If the batteries are NiCad or NiMH (rechargeables), they only deliver 1.2V
per cell not 1.5V

In this case (and this case only) adding 2 cells would be precisely the
right thing to do (1.2V*10 = 2V)

also, how do you figure that you have 18AH. When batteries are connected in
series, their voltage increases, but their amperage stays the same. When
they are connected in parralel, the voltage stays the same, but he amperage
increases.

RoD

"SA Dev" <nospam38925@forme.com> wrote in message
news:408c29bb@news.tulsaconnect.com...
Hi,

I have a 9" TV that runs on DC power and it takes about 4A @ 12V. I
noticed
that when I run it off of a car starter which contains a sealed type 12V
battery that it works great, but when I run it off of 8 D Energizers, the
picture doesn't fill the screen and the voltage across the batteries drops
to 7V when the TV is on. The voltage across the sealed type battery only
drops 0.5V or so. Can a 12V 4A device be run on D batteries? With the
18AH
life, I was assuming the batteries could power the TV for about 4 hours.
Do
I just need to add one or two more cells into the series to up the voltage
a
bit to account for the voltage loss?

Thanks,

SA Dev
Click to expand...
 
Hi RoD,

You might have overlooked 1 thing, Im not sure.
If the batteries are NiCad or NiMH (rechargeables), they only deliver 1.2V
per cell not 1.5V
In this case (and this case only) adding 2 cells would be precisely the
right thing to do (1.2V*10 = 2V)
also, how do you figure that you have 18AH. When batteries are connected
in
series, their voltage increases, but their amperage stays the same. When
they are connected in parralel, the voltage stays the same, but he
amperage
increases.
Click to expand...
I was using Energizer Alkalines, but I didn't realize that they aren't
capable of delivering more than about 1A very reliably according to some
others that posted. You can get the battery specs from
http://data.energizer.com/ by clicking datasheets, consumer/oem.

Have a great day,

SA Dev
 
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