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Old 06-11-2014, 12:41 PM   #11
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Originally Posted by JCamper View Post
Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24
This site should provide you with information you are looking for to make decision.

Frequently Asked Questions (FAQ) - DC Battery Specialists
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Old 06-11-2014, 12:44 PM   #12
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Quote:
Originally Posted by JCamper View Post
Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24
Costco has some good ones under there brand, The best is trojan deep cycle are very popular. I have 2 interstate deep cycle (so called) 27 group but I do not boondock, I'm past that stage. I just do not want to buy a generator or solar system. Just match them......
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Old 06-11-2014, 02:40 PM   #13
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Quote:
Originally Posted by JCamper View Post
Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24

Your yellow top rating are incorrect:

http://d26maze4pb6to3.cloudfront.net...pecs_Sheet.pdf

Yellow tops are not true deep cycle batteries; they are "Marine" type dual purpose batteries and the 20 amp hour (AH rating is defined as the number of hours the battery will last when NEW with a 20 amp continuous draw).

Yellow tops are rated at 75 AH (about par with dual purpose batteries - 60-80 AH).

In fact your Sears battery rating is also not correct:

http://www.sears.com/diehard-marine-...3&blockType=G3

The sears Marine battery is rated at 80AH. This is about how the matter stacks up. AGM type batteries of the same class have less AH than their flooded cousins, but there are advantages that "make up" for the lost capacity (like being maintenance free).

FYI - The Platinum series are starting batteries. That is why the 34M you were looking at is twice as big and yet has only 68AH of storage capacity.

http://www.sears.com/diehard-platinu...7&blockType=G7
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Old 06-11-2014, 02:50 PM   #14
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Quote:
Originally Posted by JCamper View Post
Anyone help explain to me the difference between 20 amp hour rate and the Amp Hour?

Looking at 2 deep cycle 12v batteries...

Battery 1
20 Amp Hour Rate 140Ah
Amp Hour 66Ah
Res Cap 140 Min

Battery 2
20 Amp Hour Rate 68Ah
No Amp Hour listed
Res Cap 135 Min

Whats the difference here?
Comparing the Optima YellowTop Deep Cycle (Battery 1) to the Sears Die Hard Platinum Deep Cycle (Battery2)

I'm not ready to go 6v yet so please don't go down that road. Any other 12v batteries out there that anyone can recommend?

Should mention I only have room for 2 group 24
OK...first...the 20 amp hour rating is what designates a DEEP CYCLE battery. It tells your how many amps of current the battery can support for 20 hours. So a 20 hours rating of 100 amp hours equals 5 amps of current continuous for 20 hours OK?? So MORE amp hours at the 20 hour specification is GOOD GOOD !! If a battery says DEEP CYCLE but does not provide a 20 amp hour rating...you can be sure it is a DUAL PURPOSE BATTERY. STAY AWAY.

NEXT...you need to provide links for the batteries you are looking at. I find NO Group 24 yellow top battery, AND all the yellow top batteries are DUAL PURPOSE. I don't know where those specs come from but they sure as hell ain't yellow top specs for a group 24 DEEP CYCLE. I WOULD believe 65-70 hours at the 20 hour spec from an Optima group 24

Next is the Die Hard Platinum which is a completely different type of battery built by Odyssey for Sears...it is an AGM design but also a TPPL (Thin Plate Pure Lead) which can perform both as an exceptional deep cycle battery AND as a starting battery. Since Sears carries it for cars, they don't really focus on deep cycle use. Unfortunately, I can find NO Sears die hard platinum in size Group 24. Your specs look like those for their group 34. Link to a 24 if you have one but since Odyssey doesn't make one...I'm thinking Sears doesn't have one.

Now...as to recommendations...It looks like you've settled on AGM Group 24 as your choice. Here's the Trojan 24AGM spec sheet:
http://www.trojanbattery.com/pdf/dat...ata_Sheets.pdf
76 amp hours and superior construction to the average.

Also East Penn makes some fine AGM's http://www.dekabatteries.com/assets/...rdeepcycle.pdf
Their brand is DEKA but it may also be found under other store brand names. 79 amp hours. Tri-State Battery Warehouse : 8A24M Deka Intimidator High Performance AGM Battery [8A24M] - $165.00

Either one would be good choices...and they also sell TRUE deep cycle wet cells in group 24 size if you decide to save some bucks.

Hope this helps!
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Old 06-11-2014, 02:57 PM   #15
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Originally Posted by Herk7769 View Post
and the 20 amp hour (AH rating is defined as the number of hours the battery will last when NEW with a 20 amp continuous draw).
Herk...think you misquoted the 20 amp rating vs. the 20amphour rating.
The latter is what we are concerned with in COMPARING deep cycles.
It represents the STEADY CURRENT AMPS that can be used before a battery is fully depleted at 20 hours of use.
So a group 24 ...78 amp hour battery can supply 78/20 or a little less than 4 amps of current steadily for 20 hours.
A 255 amp hour battery (8D!) can supply 255/20 or 12.5 amps steadily for 20 hours. You can run 3 times the stuff for 20 hours.
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Old 06-11-2014, 03:11 PM   #16
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You are much more knowledgeable about this than me.

The way I understood it is that AH are a product of the amps demanded and the hours it can deliver at that amperage.

So the 20 AH rate is the number of hours it can deliver a continuous 20 amps.

20 amps times 5 hours = 100 AH. OR 5 amps for 20 hours = 100 AH.

Is this "potatoes/potatoes" or am I missing something?

I believed the "generally accepted" (by battery manufacturers) amperage to rate capacity is the 20 amp demand. RC in minutes is rated at 25 amp demand for starting batteries.

What am I doing wrong?
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Old 06-11-2014, 03:13 PM   #17
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Originally Posted by camaraderie View Post
Herk...think you misquoted the 20 amp rating vs. the 20amphour rating.
The latter is what we are concerned with in COMPARING deep cycles.
It represents the STEADY CURRENT AMPS that can be used before a battery is fully depleted at 20 hours of use.
So a group 24 ...78 amp hour battery can supply 78/20 or a little less than 4 amps of current steadily for 20 hours.
A 255 amp hour battery (8D!) can supply 255/20 or 12.5 amps steadily for 20 hours. You can run 3 times the stuff for 20 hours.
I am having difficulty squaring this with the graph in my post that came from a textbook on solar/wind energy battery systems.
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Old 06-11-2014, 04:09 PM   #18
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OK, I think you are right and I was incorrect. (or we were saying the same thing differently).

The graph shows a 20 HOUR rated 100 AH battery. It is 100% of rating at 5 amps. The capacity to deliver plummets as amperage required increases above 5 amps.

It make more sense to me know, thank you.

So using the graph, a single 100 AH battery delivering 20 amps has an effective capacity of 62 AH (from the graph); so will that 20 amp load continuous would kill the battery in 3.1 hours (62/20) or in 62% of 20 hours (12.4 hours)?
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Old 06-11-2014, 04:28 PM   #19
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LOL...actually I was getting set to PASTE that graph in to help explain it!! It quite nicely reinforces what I said. So lets review what I said the 20 hour measurement actually measures: The maximum total amount of STEADY current that the battery can produce for 20 hours before going flat. Notice NO mention of 20 amps of current.

OK now lets look at your graph which is a 20 hour rated group 31 battery rated at 100 amp hours.


Now look at the left side where it says AH capacity and see what VERTICAL line is crossed ... read down that line and find the continuous amp draw required to get 100 amp hours in 20 hours. It is 5.
So 5 amps current run for 20 hours gives us a capacity of 100amp hours at the 20 hour rating.
Now just for fun...lets look across at the result from drawing 20 amps...and you can see you would get just 63 amphours total capacity before the battery was flat. So you can also figure out that 20 amps of current only allowed the battery to LAST a little over 3 hours at 20 amps per hour.

The 20 amp hour rating method is of little value in and of itself since we don't run steady state loads in real life. But it does give a meaningful comparison about the current loads a battery will support for 20 hours before going flat. You cannot compare ANY other amp load rating with the 20 hour rating as you can see from your battery curve...batt's can last longer with lower loads..and a lot shorter with higher loads.

Whenever you see a battery amp hour rating at the 20 hour spec...simply divide by 20 to see the maximum continuous amps you can run for 20 hours staight when new.

BTW...your pdf attachment verifies this with their analysis of a 70 amp hour battery...quoting:

"For example, an average automotive battery might have a capacity of about 70 amp-hours, specified at a current of 3.5 amps. This means that the amount of time this battery could continuously supply a current of 3.5 amps to a load would be 20 hours (70 amp-hours / 3.5 amps)."
So 20 hours = 70 AMP HOURS/3.5 amps.
Transposing we get 20 hours x 3.5 amps = 70 amp hours.

Notice no mention of 20 amps in the purple either.

Hope that makes it more clear...

EDIT...was typing this as you wrote you last reply...you figured it out without me but maybe this post will help others.
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Old 06-11-2014, 04:38 PM   #20
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BTW...the difference in real life in amp hours delivered in total is based on the various current draws you use at different times in your coach and where they fall on that curve. Dr. Peukert figured that out and Peukerts LAW is built into both the Trimetric and Victron battery monitors we've been talking about recently...so they actually compensate for actual use patterns to tell you what % you have left AND how long the batts will last at CURRENT current use! Pretty cool that they do that!
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