Battery Pack Amp Hours

Battery Pack Amp Hours

Post by Matthew and Wendy Plant » Mon, 01 Sep 2003 08:08:18

I am trying to build, or at least cobble together, a battery pack for a
receiver. I will only need one (1) amp of power. The battery will have a one
(1) amp fuse on both the lead in and out of the radio just for safety. What
I have not been able to understand is what amp hours are. I need a twelve
(12) volt battery that will last a while, or at least five hours, and be
rechargeable. I have been looking at UPS battery pack, or even small car
batteries. Any help? Thanks.

Matthew
KC2KEI
Scars are the proof that man can survive his own stupidity.

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Battery Pack Amp Hours

Post by Bill Crocke » Mon, 01 Sep 2003 09:04:11


That is what amp hours is.  A 12v battery rated at 5 amp hours, is capable
of supplying 12 volts, and 5 amps, for 1 hour.  The same battery can supply
12v and 1 amp for 5 hours, or 12v and 3 amps for 1.66 hours, etc.  You could
even use a motorcycle, or car battery if you want.  As long as it's still
12v.  The greater the amp hours, the longer it will power your radio
equipment, between charges.  Make sure the battery is the proper voltage for
your radio!

A note of safety...if you're using a lead-acid battery, such as a
motorcycle, or car battery, make sure it is the sealed type.  Otherwise you
will need to provided good ventilation due to the fumes generated while
charging.  They can be explosive!

Bill Crocker



Quote:> I am trying to build, or at least cobble together, a battery pack for a
> receiver. I will only need one (1) amp of power. The battery will have a
one
> (1) amp fuse on both the lead in and out of the radio just for safety.
What
> I have not been able to understand is what amp hours are. I need a twelve
> (12) volt battery that will last a while, or at least five hours, and be
> rechargeable. I have been looking at UPS battery pack, or even small car
> batteries. Any help? Thanks.

> Matthew
> KC2KEI
> Scars are the proof that man can survive his own stupidity.

> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.514 / Virus Database: 312 - Release Date: 8/28/2003

 
 
 

Battery Pack Amp Hours

Post by The Dawn Soliloq » Mon, 01 Sep 2003 12:30:43

P.S., Amp hours and Milliamp Hours are similar in the following fashion. There
are 1000 milliamps in 1 amp. Even some AA batteries now have 1200 Milliamp
hours. This would be 1.2 Amps for for 1 hour.

I stumbled across the following while researching comments for this posting.
Visit it, it may help. But look below the quoted text for an easier solution.

http://www.powerstream.com/BPD.htm

"Cell capacity is rated in amp-hours or milliamp hours. The symbol for
capacity is C. This is amps times hours. Divide by hours and you get amps,
divide by amps and you get hours. For example a 5 amp hour battery is the same
as a 5000 milliamp-hour battery. If you want to discharge in 10 hours, you can
get a current of 5/10 = 0.5 amps. If you need 100 milliamps current, then you
can run for 5000/100 = 50 hours.

Often a discharge or charge rate is given proportional to C. So a discharge
rate of C/5 means C/(5 hours), or the constant current to fully discharge the
battery in 5 hours.

The calculation of run time versus current is a rough estimate, but is
accurate under the right conditions. The faster you discharge, the lower the
capacity of a battery. This trade-off depends on the battery chemistry and
construction. Usually the capacity of a battery is quoted at a C/20 discharge
rate. So an 12 amp hour battery sealed lead acid battery will actually put out
a steady 0.6 amps for 20 hours. However, if you discharge the same battery at
12 amps, you would expect to run an hour, but you will only last for 22
minutes. Also, if you wan to run at 10 milliamp you will get less than the
expected 1200 days, since self-discharge of the battery will limit your run
time.

Different battery chemistries differ in this respect. Lead acid batteries are
probably the worst at the rapid discharge end of the scale. NiCads and NiMH
are much better."

Or the easiest way is to get a pre-fabricated 12V pack with charger. There
must literally be tons of them available. They usually look like small blocks
with a cigarette lighter jack.

Here's one that I found. http://www.batterybusters.com/PowerPac12.htm

Or here!

http://www.kooleraire.com/12%20Volt%20Power%20Pack.htm

Hell, for that matter, a 12Volt pack with recharger for a modern hand drill
should work.

http://www.contractorstools.com/dewaltbatteries.html
http://sale-depot.net/tools-hardware/item/B00004Y2MK/

But looking at the hand Drill specs, I don't think that the amp hours (2) are
great enough. Refer to the links for the Power Packs.

Regards.



>That is what amp hours is.  A 12v battery rated at 5 amp hours, is capable
>of supplying 12 volts, and 5 amps, for 1 hour.  The same battery can supply
>12v and 1 amp for 5 hours, or 12v and 3 amps for 1.66 hours, etc.  You could
>even use a motorcycle, or car battery if you want.  As long as it's still
>12v.  The greater the amp hours, the longer it will power your radio
>equipment, between charges.  Make sure the battery is the proper voltage for
>your radio!

Never say never.
Nothing is absolute.
 
 
 

Battery Pack Amp Hours

Post by The Dawn Soliloq » Mon, 01 Sep 2003 12:31:42

P.S., Amp hours and Milliamp Hours are similar in the following fashion. There
are 1000 milliamps in 1 amp. Even some AA batteries now have 1200 Milliamp
hours. This would be 1.2 Amps for for 1 hour.

I stumbled across the following while researching comments for this posting.
Visit it, it may help. But look below the quoted text for an easier solution.

http://www.powerstream.com/BPD.htm

"Cell capacity is rated in amp-hours or milliamp hours. The symbol for
capacity is C. This is amps times hours. Divide by hours and you get amps,
divide by amps and you get hours. For example a 5 amp hour battery is the same
as a 5000 milliamp-hour battery. If you want to discharge in 10 hours, you can
get a current of 5/10 = 0.5 amps. If you need 100 milliamps current, then you
can run for 5000/100 = 50 hours.

Often a discharge or charge rate is given proportional to C. So a discharge
rate of C/5 means C/(5 hours), or the constant current to fully discharge the
battery in 5 hours.

The calculation of run time versus current is a rough estimate, but is
accurate under the right conditions. The faster you discharge, the lower the
capacity of a battery. This trade-off depends on the battery chemistry and
construction. Usually the capacity of a battery is quoted at a C/20 discharge
rate. So an 12 amp hour battery sealed lead acid battery will actually put out
a steady 0.6 amps for 20 hours. However, if you discharge the same battery at
12 amps, you would expect to run an hour, but you will only last for 22
minutes. Also, if you wan to run at 10 milliamp you will get less than the
expected 1200 days, since self-discharge of the battery will limit your run
time.

Different battery chemistries differ in this respect. Lead acid batteries are
probably the worst at the rapid discharge end of the scale. NiCads and NiMH
are much better."

Or the easiest way is to get a pre-fabricated 12V pack with charger. There
must literally be tons of them available. They usually look like small blocks
with a cigarette lighter jack.

Here's one that I found. http://www.batterybusters.com/PowerPac12.htm

Or here!

http://www.kooleraire.com/12%20Volt%20Power%20Pack.htm

Hell, for that matter, a 12Volt pack with recharger for a modern hand drill
should work.

http://www.contractorstools.com/dewaltbatteries.html
http://sale-depot.net/tools-hardware/item/B00004Y2MK/

But looking at the hand Drill specs, I don't think that the amp hours (2) are
great enough. Refer to the links for the Power Packs.

Regards.



>I am trying to build, or at least cobble together, a battery pack for a
>receiver. I will only need one (1) amp of power. The battery will have a one
>(1) amp fuse on both the lead in and out of the radio just for safety. What
>I have not been able to understand is what amp hours are. I need a twelve
>(12) volt battery that will last a while, or at least five hours, and be
>rechargeable. I have been looking at UPS battery pack, or even small car
>batteries. Any help? Thanks.

>Matthew
>KC2KEI
>Scars are the proof that man can survive his own stupidity.

Never say never.
Nothing is absolute.