12V 3Amp monitor - can I use a 12V 4.5 Amp battery? Help please

[David D]

I don't want to fry my security monitor, but I want to hook up a 12V
4.5A rechargeable battery to it. Since the monitor on the back says
"12V 3amp", would the monitor fry or would it just take what it needs
and be ok with this amperage?

Thanks

 

[Meat Plow]

I don't want to fry my security monitor, but I want to hook up a 12V
4.5A rechargeable battery to it. Since the monitor on the back says
"12V 3amp", would the monitor fry or would it just take what it needs
and be ok with this amperage?

Thanks

It will just use what it needs.

--
#1 Offishul Ruiner of Usenet, March 2007
#1 Usenet Asshole, March 2007
#1 Bartlo Pset, March 13-24 2007
#10 Most hated Usenetizen of all time
Pierre Salinger Memorial Hook, Line & Sinker, June 2004
COOSN-266-06-25794

 

[Ryan Weihl]

I don't want to fry my security monitor, but I want to hook up a 12V
4.5A rechargeable battery to it. Since the monitor on the back says
"12V 3amp", would the monitor fry or would it just take what it needs
and be ok with this amperage?

Thanks

In this case the question should be:
"how long can I use the monitor before I have to recharge the
battery?"

--

 

[Gary Tait]

In this case the question should be:
"how long can I use the monitor before I have to recharge the
battery?"

A little over an hour.Maybe more if you are lucky.

 

[Jumpster Jiver]

I don't want to fry my security monitor, but I want to hook up a 12V
4.5A rechargeable battery to it. Since the monitor on the back says
"12V 3amp", would the monitor fry or would it just take what it needs
and be ok with this amperage?

Thanks

Make sure the polarity (+ and -) are correct and you'll be fine.

 

[Guest]

beware, as the battery discharges, the voltage will drop. as that happens
the monitor will attempt to compensate for the loss of voltage and may (
may) cause internal power regulating components to overheat or fail.

these things require a steady 12v level to attain good design performance
(give or take a volt or two). if you are lucky it will just slowly dimm and
become uselesss, then u know its time to recharge the batt, or it may just
turn itself off due to voltages it will not accept,

it depends on the manufacturer and just how much design thought they have
invested in the monitor

some may be very forgiving, some may give u poor performance as the battery
volts drops.

if it starts to smoke, you know what to expect.

be very attentive during the first time you use the battery setup, smell,
feel and even use a voltage meter DVM to track the voltage value of the
battery power.

 

[[email protected]]

Ï/Ç David D Ýãñáøå:

I don't want to fry my security monitor, but I want to hook up a 12V
4.5A rechargeable battery to it. Since the monitor on the back says
"12V 3amp", would the monitor fry or would it just take what it needs
and be ok with this amperage?

Thanks

I 'm from greece and i don't know so much english. Yes you can use
this battery the problem is in Volts. If you have a batterry with up
of 12V don't try to use it with this monitor because you burn this
monitor. The 4.5 Amperes of battery say how much current you can use
from battery and if you have a monitor with up of 4.5A and conected
with this battery you burn the battery and maybe this can make the
battery to BOOOOOOOOM. You Understand?

 

[David D]

Ï/Ç David D Ýãñáøå:



I 'm from greece and i don't know so much english. Yes you can use
this battery the problem is in Volts. If you have a batterry with up
of 12V don't try to use it with this monitor because you burn this
monitor. The 4.5 Amperes of battery say how much current you can use
from battery and if you have a monitor with up of 4.5A and conected
with this battery you burn the battery and maybe this can make the
battery to BOOOOOOOOM. You Understand?

'thanks for the replies.
Right now, I am interested in getting 12V battery with a 4.5
amperage. The only problem is I am doing it DIY and trying to make it
on the cheap - therefore I am stuck with finding a way to RECHARGE the
battery. Of course without LED lights and levels, I won't know know
if it is charged or not. And yes, I don't want to blow a $100.00
monitor either. My main purpose for this is to create a portable
monitor system. I went to Canadian Tire to find the 12V cordless
drill batteries, but they only pump out 1.5 Amp, so it is getting
harder then I thought...

 

[DaveM]

Ï/Ç David D Ýãñáøå:



I 'm from greece and i don't know so much english. Yes you can use
this battery the problem is in Volts. If you have a batterry with up
of 12V don't try to use it with this monitor because you burn this
monitor. The 4.5 Amperes of battery say how much current you can use
from battery and if you have a monitor with up of 4.5A and conected
with this battery you burn the battery and maybe this can make the
battery to BOOOOOOOOM. You Understand?

'thanks for the replies.
Right now, I am interested in getting 12V battery with a 4.5
amperage. The only problem is I am doing it DIY and trying to make it
on the cheap - therefore I am stuck with finding a way to RECHARGE the
battery. Of course without LED lights and levels, I won't know know
if it is charged or not. And yes, I don't want to blow a $100.00
monitor either. My main purpose for this is to create a portable
monitor system. I went to Canadian Tire to find the 12V cordless
drill batteries, but they only pump out 1.5 Amp, so it is getting
harder then I thought...


Well, now we're getting to the root of the problem. The answers that other
posters have given are correct, for the most part. The issue now is.. how long
do you need to operate the monitor on battery? The ampere-hour (AH) rating of a
battery is useful in determining how long the battery can supply power. The
load current is a major factor in determining this time. The chemistry of the
battery is also a major factor in this calculation.

A fairly good tutorial on batteries, AH ratings, Loads and recharging is at
http://homepages.which.net/~paul.hills/Batteries/BatteriesBody.html. I suggest
that you read that with great attention and you will get a better understanding
of your situation.

For your portable application, I suggest that you look primarily at sealed
lead-acid (SLA) batteries to start. Newer chemistries such as Lithium-Ion and
others typically used in laptop computers have a higher energy/weight ratio, but
are significantly more expensive.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer to the end, the faster it goes.

 

[David D]

Yes, you are right. I am going to a local electronic store - bringing
the monitor with me - to see what they say. It would be nice to use
the monitor for 3-4 hours at a time, longer would be a bonus. I will
also ask about SLA batteries, thanks for that.

 

[Homer J Simpson]

I went to Canadian Tire to find the 12V cordless
drill batteries

There's problem one. Don't go to Canadian Slime.

 

[David D]

Ha, I do like their return policy though.

Ok, I found a battery - $24.00 - 12V 4.5amp so therefore I am going
to only get 1.5 hours out of the monitor, right? Ok, I also picked up
a female sleeve for a 12V lighter - but it is called "VDC 12V", is
that the same?
I guess I am going to have to spend more money to get a larger battery
with more Amps, right?

 

[DaveM]

Ha, I do like their return policy though.

Ok, I found a battery - $24.00 - 12V 4.5amp so therefore I am going
to only get 1.5 hours out of the monitor, right? Ok, I also picked up
a female sleeve for a 12V lighter - but it is called "VDC 12V", is
that the same?
I guess I am going to have to spend more money to get a larger battery
with more Amps, right?

Yep... that's what I'd suggest as a starter. You still need to do the math and
figure just how long you need to operate the monitor from battery. It's the
single most important piece of information you need to have. Next, use the
charts on that web site that I posted for you to calculate the approximate run
time for a given AH rating.
Generally speaking, the higher the AH rating, the longer your monitor will run.
Charging the battery is another question altogether. If you don't feel
comfortable constructing your own charger (and from your previous questions, I
gather that you don't), I suggest that you look for a charger that has normal
charging with automatic switchover to float charging. Use Google.. search for
SLA battery charger.
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Life is like a roll of toilet paper; the closer to the end, the faster it goes.

 

[[email protected]]

Yes, you are right. I am going to a local electronic store - bringing
the monitor with me - to see what they say. It would be nice to use
the monitor for 3-4 hours at a time, longer would be a bonus. I will
also ask about SLA batteries, thanks for that.

There seem to be some misunderstandings here.

Firstly there is no such a thing as a 4.5A battery, what you have is a
4.5Ah battery. This tells nothing about what current it will supply,
but rather its capacity.

2nd, you wont get 1.5hrs from a 4.5Ah battery on 3A, for 2 reasons:
a) Ah capacities are only correct for 20 hour discharge. High
discharge rates will reduce capacity considerably.
b) If you discharge a lead acid battery until flat it wont last long.
You need to stay above 20% charge at least.

For 4 hours of run time, if we momentarily ignore the 2 above issues:
4x3 = 12Ah
Add 50% (guessed) for a short run time -> 18Ah
Add 25% to permit discharge down to 20%: 22.5Ah

So really you want a 25Ah or more battery to do what you want.

There is one last issue. Is the monitor 12 real volts or 12 battery
volts? What are known as 12v batteries arent really 12v. This is fine
if the monitor is designed to run off car supplies, but if it needs a
12v regulated supply it might be unfine - or it might be ok. Would be
wisest to check first.


NT

 

[David D]

There seem to be some misunderstandings here.

You are probably right, I don;t have the battery in front of me to
check.

Firstly there is no such a thing as a 4.5A battery, what you have is a
4.5Ah battery. This tells nothing about what current it will supply,
but rather its capacity.

2nd, you wont get 1.5hrs from a 4.5Ah battery on 3A, for 2 reasons:
a) Ah capacities are only correct for 20 hour discharge. High
discharge rates will reduce capacity considerably.
b) If you discharge a lead acid battery until flat it wont last long.
You need to stay above 20% charge at least.

For 4 hours of run time, if we momentarily ignore the 2 above issues:
4x3 = 12Ah
Add 50% (guessed) for a short run time -> 18Ah
Add 25% to permit discharge down to 20%: 22.5Ah

So really you want a 25Ah or more battery to do what you want.

that is probably a good start.

There is one last issue. Is the monitor 12 real volts or 12 battery
volts? What are known as 12v batteries arent really 12v. This is fine
if the monitor is designed to run off car supplies, but if it needs a
12v regulated supply it might be unfine - or it might be ok. Would be
wisest to check first.

NT

How do I check? The monitor did not come with instructions and the
specs I am detailing are from the back of the monitor, so I cannot
really tell the voltage it needs. IS there a way to check this
reliably?

Thank you for the interest.

 

[Ryan Weihl]

Ha, I do like their return policy though.

Ok, I found a battery - $24.00 - 12V 4.5amp so therefore I am going
to only get 1.5 hours out of the monitor, right? Ok, I also picked up
a female sleeve for a 12V lighter - but it is called "VDC 12V", is
that the same?
I guess I am going to have to spend more money to get a larger battery
with more Amps, right?

I wish you people would get your terminology right.
Nowhere do I see anybody talking about Ah (amphours/Battery capacity)
A battery does not produce Amps, what you mean the battery
produces 12V(DC) at 4.5Ah for 1 hour (amp hours). Thats 12V for 4.5
hours at 1Amp load. If the monitor needs 1.5A, the you take the 4.5 Ah
from the battery and divide this by 1.5A load from the monitor and it
will tell you how long the monitor will run.
rw

--

 

[[email protected]]

How do I check? The monitor did not come with instructions and the
specs I am detailing are from the back of the monitor, so I cannot
really tell the voltage it needs. IS there a way to check this
reliably?

Thank you for the interest.

Simple way is to determine what it expects to run off, large wall
wart, stabilised psu or battery. One giveaway would be a dotted equals
sign, meaning rectified ac, which would mean it expects to see
unregulated supply, hence a battery would be fine.

____
.....
(works in non-proportional font)

However there's no guarantee that there will be anything on it to tell
you one way or the other.


NT

 

[[email protected]]

I wish you people would get your terminology right.
Nowhere do I see anybody talking about Ah (amphours/Battery capacity)
A battery does not produce Amps, what you mean the battery
produces 12V(DC) at 4.5Ah for 1 hour (amp hours). Thats 12V for 4.5
hours at 1Amp load. If the monitor needs 1.5A, the you take the 4.5 Ah
from the battery and divide this by 1.5A load from the monitor and it
will tell you how long the monitor will run.
rw

No, this is a common mistake. My post explains why.


NT