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Home > Archive > Alternative Power sources > January 2007 > Charger Size?
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| 2 questions please.
1. Battery Chargers are rated in amps. How do you determine what size
charger you need for a 12V AGM battery?
2. To power my 100W transceiver in case of a blackout, should I use a 75
a/h or (2) 37a/h batteries in parallel? Perhaps someone can explain the pros
& cons of either arrangement. Thank you in advance.
Cordially,
west
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| Neon John 2007-01-08, 9:25 am |
| On Mon, 08 Jan 2007 08:00:15 GMT, "west" <restccq2@verizon.net> wrote:
>2 questions please.
>
>1. Battery Chargers are rated in amps. How do you determine what size
>charger you need for a 12V AGM battery?
By how fast you want to charge it. If you have a 100 amp hour
battery, a 20 amp charger will charge it in about 5 hours. (Actually
a little longer but you get the idea.) Some types of batteries (the
Hawker Genesis, for example) require a certain MINIMUM charge rate for
maximum life. Best to check with the mfr before buying the charger.
>
>2. To power my 100W transceiver in case of a blackout, should I use a 75
>a/h or (2) 37a/h batteries in parallel? Perhaps someone can explain the pros
>& cons of either arrangement. Thank you in advance.
There are several minor considerations. Two 37s might have a lower
impedance (less voltage drop under load) than a single. Or maybe not,
depends on the designs. For me, the overwhelming factor would be
cost. If I could get two 37s for less than one 75 then that's the way
I'd go. Just make sure that the AGMs you choose are rated for deep
cycle. Float service (UPS and emergency lighting) batteries will
withstand but a few deep cycles before failing.
John
---
John De Armond
See my website for my current email address
http://www.neon-john.com
Cleveland, Occupied TN
Don't let your schooling interfere with your education-Mark Twain
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| Chris Hill 2007-01-08, 1:25 pm |
| On Mon, 08 Jan 2007 08:00:15 GMT, "west" <restccq2@verizon.net> wrote:
>2 questions please.
>
>1. Battery Chargers are rated in amps. How do you determine what size
>charger you need for a 12V AGM battery?
For most battery types you look for a charger that can charge at 1/10
of the amp hour rate.
>
>2. To power my 100W transceiver in case of a blackout, should I use a 75
>a/h or (2) 37a/h batteries in parallel? Perhaps someone can explain the pros
>& cons of either arrangement. Thank you in advance.
I wouldn't parallel batteries, one of the two inevitably ends up doing
more work and failing first.
>
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| clare at snyder.on.ca 2007-01-08, 1:25 pm |
| On Mon, 08 Jan 2007 08:00:15 GMT, "west" <restccq2@verizon.net> wrote:
>2 questions please.
>
>1. Battery Chargers are rated in amps. How do you determine what size
>charger you need for a 12V AGM battery?
>
>2. To power my 100W transceiver in case of a blackout, should I use a 75
>a/h or (2) 37a/h batteries in parallel? Perhaps someone can explain the pros
>& cons of either arrangement. Thank you in advance.
>
>Cordially,
>west
>
Genewrally, as a rule, one single larger battery is better than 2
smaller in parallel because of load sharing issues. If one cell on one
battery goes bad, it will drain both batteries. In thas case, having 2
does not give any redundancy - it just doubles the probability you
will have a problem, and makes the problem worse when it occurs.
--
Posted via a free Usenet account from http://www.teranews.com
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| Steve Spence 2007-01-15, 8:25 pm |
| Chris Hill wrote:
> On Mon, 08 Jan 2007 08:00:15 GMT, "west" <restccq2@verizon.net> wrote:
the amp hour rate.
>
>
> I wouldn't parallel batteries, one of the two inevitably ends up doing
> more work and failing first.
Not usually. 3 strings of Trojans will last a decade with proper
maintenance. We run a 125 amp charger on our 1260 ah pack.
--
Steve Spence
Dir., Green Trust
http://www.green-trust.org
| |
| Steve Spence 2007-01-15, 8:25 pm |
| west wrote:
> 2 questions please.
>
> 1. Battery Chargers are rated in amps. How do you determine what size
> charger you need for a 12V AGM battery?
SS> A maximum of 10% of the ah rate. 75 ah of battery would need at
least 4 amps of charging, but not more than 8, unless you have a good 3
stage charger with battery temperature compensation. My charger lets me
dial in the ah rating of the pack, and has a temperature probe.
>
> 2. To power my 100W transceiver in case of a blackout, should I use a 75
> a/h or (2) 37a/h batteries in parallel? Perhaps someone can explain the pros
> & cons of either arrangement. Thank you in advance.
SS> Doesn't matter. Where it gets tricky is series/parallel strings. No
more than 3 is a good rule of thumb, but it's not concrete.
>
> Cordially,
> west
>
>
--
Steve Spence
Dir., Green Trust
http://www.green-trust.org
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