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Author Topic: AH Vs RC ratings  (Read 2944 times)

wkndfun

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AH Vs RC ratings
« on: February 23, 2009, 06:20:14 PM »
Napa has group 27 rv batteries rated at RC 182min, How does this relate to AH? I can fit 4 of they under my step. If I understand it right 182mins x 25 amps / 60mins= 75.83 so are they 75 AH batteries?

Item#: BAT8270

Attributes:
Months Warranty:30 Months
# of Volts:12 v
Wet or Dry:Wet
Application:RV
BCI Group #:27DC
Post Type:Top Mount
C.A.at 32 Degrees F.:675 CA
Load Test Amps:275 Amp
Reserve Capacity:182 Minutes
Length:12"
Width:6 13/16"
Height:9 1/2"
Weight:54 lbs
« Last Edit: February 23, 2009, 06:33:53 PM by wkndfun »
Glenn and Tamie
Richmond VA.
1999 Winnebago Adventurer 34V diesel

Ned

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Re: installing 3 12v batteries
« Reply #1 on: February 23, 2009, 06:25:48 PM »
If these are for your house system, and they don't specifically say deep cycle, they are not the right batteries.  The fact that they specify reserve capacity and not AH indicates that these are starting batteries, not deep cycle.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

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Just Lou

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Re: installing 3 12v batteries
« Reply #2 on: February 23, 2009, 06:31:08 PM »
The specs found on the web say (dual purpose) medium duty deep cycle marine/RV battery.  Not the best for the job.
'97 Bounder 34V (F53 w/tag), '99 Honda Accord EX

wkndfun

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Re: AH Vs RC ratings
« Reply #3 on: February 23, 2009, 06:36:08 PM »
changed the topic title. is my math right?
Glenn and Tamie
Richmond VA.
1999 Winnebago Adventurer 34V diesel

Ned

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Re: AH Vs RC ratings
« Reply #4 on: February 23, 2009, 06:36:39 PM »
Dual purpose means they don't do either job very well :)
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Want to know what we're doing? http://blog.usabyrv.us

Ron

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Re: AH Vs RC ratings
« Reply #5 on: February 23, 2009, 06:42:05 PM »
Not really a good deep cycle battery.  Also if they are made by Exide I wouldn't recommend them even if they were a true deep cycle battery.
Ron & Sam-home is where we park it. Currently located   HERE

wkndfun

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Re: AH Vs RC ratings
« Reply #6 on: February 23, 2009, 06:46:55 PM »
The Tojan group 27 has the same RC rating of 175 and is a 105AH battery. The Napa is a deep cycle rv not a dual unit, I think.
Glenn and Tamie
Richmond VA.
1999 Winnebago Adventurer 34V diesel

wkndfun

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Re: AH Vs RC ratings
« Reply #7 on: February 23, 2009, 07:11:42 PM »
found Trojan batteries in my area at Batteries Plus 225AH 6V units, their house brand has 250AH. about $95.00 each.
Glenn and Tamie
Richmond VA.
1999 Winnebago Adventurer 34V diesel

Gary RV Roamer

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Re: AH Vs RC ratings
« Reply #8 on: February 23, 2009, 07:14:53 PM »
Your math is ok as far as it goes but it does not take into account the differences in how the AH and RC tests are performed.  RC is measured at a constant 25A discharge rate, which is a fairly heavy load and similar to what you might expect with an inverter running a tv and satellite receiver plus a few background Dc loads (lights and such) or about 300 watts.  AH, on the other hand, is measured at a much lower discharge rate, typically around 5A. It is defined as the the number of AH provided over a 20 hour time period, so an AH of 100 means it delivered 5A for 20 hours. 120 AH means 6A xr 20 hours, and so on.

The difference in the measurement technique is important because a battery can deliver many more AH at a low discharge rate than a high one, often substantially more. So a battery with an RV of 182 is probably closer to 90-100 AH than 75. For example, a Trojan 27TM deep cycle has an RC of 160 and a AH rating of 105, while a Trojan 27AGM has an RC of 175 but an AH of 100.

Also, I disagree that an RC rating indicates a starting battery. RC was invented in an attempt to standardize battery capacity ratings so that apples to apples comparisons could be made.  Since each battery is discharged at a different amp rate in the AH measurement, it is not really an exact comparison. Some manufacturers adopted the RC measurement and others stayed with AH. Some of the very best battery brands give both, e.g.Trojan and Lifeline.

None of this answers the question "is it a good battery?"  You can compare it to other NAPA batteries and learn something about their relative capacities, but if you want a really top quality deep cycle, I would shop at a different store. Trojan and Lifeline are some of the very best. Interstates 6v golf cart batteries (U220, U2600) are also very good, but that does not mean their entire line of batteries are good. Trojan's MinnKota trolling motor batteries are also quite good deep cycles and sometimes found in Walmarts or KMarts at attractive prices.
Gary
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Gary Brinck
2004 American Tradition
2007 GMC Acadia
Homebase: Ocala National Forest, FL

wkndfun

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Re: AH Vs RC ratings
« Reply #9 on: February 23, 2009, 07:23:32 PM »
Gary, Thanks. I can get Trojan T105 6V units and I believe that I can fit 4 of them in my step area. At 225 AH each thats 450AH total, right? Their house brand is 250ah.  With 447min RC each!! Is the this the best way to go?

Also I have lot at all the diagrams to hook them up. The only ? I have is can I use the battery terminal as my connection block, or do I need to have both positive cable coming off the battery first and then connected together? If that makes sense...

Man I getting confused...In series the AH do not double but in Parallel they do. So with 4 6V units 225AH = 450 total. If I use 4 12v units at 115AH thats 460. So if I'm right then way at 6v units better then 12v units?
« Last Edit: February 23, 2009, 08:29:14 PM by wkndfun »
Glenn and Tamie
Richmond VA.
1999 Winnebago Adventurer 34V diesel