# Batteries/amps again



## firecat1981 (Nov 27, 2007)

I'm about to go pick up a battery and I'm confused why they all use a different rating system. Years ago when I was shopping they seemed to be rated at 1hr. 
Example: 100 hrs @ 1amp

Now some are rated at 20 amps, or 23, 25.... 
Example: 140 min @ 23 amps

I obviously know what the ratings mean, but how do they compare? How does the math work to convert one way or the other?

IE, is [email protected] equivalent to [email protected]?


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## Brett (Jul 16, 2008)

There's cranking amps and reserve capacity.
Put those terms into Google and enjoy the reading.
I'd be typing for a week to try to explain what has already published.


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## firecat1981 (Nov 27, 2007)

That's not what I'm really asking about. I'm versed in how a battery works. What I need to know is how to convert or compare the capacities. I've searched and all I keep finding are explanations of the terms, but no calculators.


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## Brett (Jul 16, 2008)

I knew you wouldn't like my answer. 

But it is all about what you need the battery to do.
Start an engine or run electronics for extended periods.

There is no straight conversion as battery design fits the purpose.
Choose the battery that will provide the greatest working amperage for the longest time.


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## firecat1981 (Nov 27, 2007)

Your killing me Brett. I need deep cycle, and I'm looking at batteries of the same size and similar design. I just need to know how to calculate the capacity since they are advertised differently. I can do the math as it sounds simple, but as amperage use goes up the time is not linear. I haven't been able to find a way to compare the different ratings.


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## Vertigo (Jun 3, 2012)

Comparison without a physics lab is almost impossible because every battery has a different performance curve. Simple rule: the bigger the better. The biggest and most expensive is possibly more better. The one with the longest warranty is the best.


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## GG34 (May 2, 2014)

I went through the same stuff recently. Here was my simple conclusion There are only a few lead acid battery producers. They just brand them differently. Most of the group size batteries are similar on specs. I got tired of it and just bought one with a reasonable price. It has been great.


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## firecat1981 (Nov 27, 2007)

I found an answer, and I actually get to school Brett for once, lol.

So there is a way to work out the calculations to compare different batteries at different amp draws. It's calculated based on Peukert's Law.

Here's a site that has the different calculators. Question is if it's worth the trouble to dig through it all.
https://planetcalc.com/2283/

I got some things to figure out soon. Going to compare capacities, vs size, vs weight.... wet cell, agm,.... fun times. Cheers.


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## DBStoots (Jul 9, 2011)

I'll be interested to know what you end up buying after all that. Kind of like the joke about the lawyer who had two candidates for a secretary position...which one did he hire? The one with the biggest...


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## Redfisher80 (Jul 17, 2017)

Get AGM’s....I love mine and have put them through hell and back. Have them in my tractor, Polaris ranger, truck, boat....etc. mine are made by Penn Mfg they are one of the major makers noted above. Mount them sideways, upside down, whatever you want. I will say they are an “inbetween option” for those that do not want wet Cell, and those that do not want to spend the $ on gel cells.

Absorbed Glass Matt is a proved design that is safe but again, it’s all about amp hours and what you are using them for.

Personally, go for the smallest allowed by the Mfg for your motor and go as big as you can for trolling and accessories...save on weight.

Redfisher


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## firecat1981 (Nov 27, 2007)

I spent several hours shopping today. I compared specs on a few different batteries, but since they are all made by similar companies they aren't far off from each other. 
For a few minutes I was going to go with AGM, but for the same size class and similar weights they have a much lower amp/hr rating. So I went back to standard wet cell. 

So here is where the different ways to rate batteries comes into play. 

At wally world the group 24 was rated at [email protected], and the group 27 was [email protected] These seem real close right, like why bother with the 27. Well this rating doesn't mean much, as the usage curve isn't linear. 

At sams club they had much better info. After looking up the specs I found the group 24 had a 20hr rating of 65amps, the same sized AGM only had a rating of 55amps, a sizable difference.
Duracell also put the load testing results on the label of the wet cells. For a group 24 you get [email protected] draw. Not bad, but the group 27 was [email protected] draw, or a full hour more run time. Since this will be close to what I might actually use I decided to suck up the extra 8lbs or so and got the group 27.


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## DuckNut (Apr 3, 2009)

Let me tell you first hand Duracell batteries are total crap. I bought 2 and they lasted less time than the ones I was replacing. I was replacing a small deep cell that was 6-7 years old with the bigger marine Duracell and brand new they lasted significantly less time. Took them back and got two new ones. Same issue. Went to Wally World and bought their marine batteries and used two brand new batteries for core charge.

I certainly wish you luck if you buy Duracells.


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## anytide (Jul 30, 2009)

only buy batteries that have free replacement warranties.


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## Brett (Jul 16, 2008)

Ok fc, I waited until now, one last point,
like steel springs, batteries only have so many cycles/recharges in them.
So even though you buy the best amperage rating
it may not have the needed life span/durability.
The amperage draw for extended periods can eat the lead plates.
The plates erode and the lead falls off
weakening the battery or shorting it out.
Get the best warranty for your buck from a retailer who'll back it up.


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## firecat1981 (Nov 27, 2007)

Brett said:


> Ok fc, I waited until now, one last point,
> like steel springs, batteries only have so many cycles/recharges in them.
> So even though you buy the best amperage rating
> it may not have the needed life span/durability.
> ...


That's all well and good, but isn't that the point of deep cycles in the first place. Technically speaking you can get better amp hours from a starting battery, but the life span would be short because if I'm not mistaken they have less lead. I don't expect a cheap battery to have a long life span, and I'm done paying for expensive ones cause florida heat will cook them before their time reguardless. Most of the warranties are filled with stipulations and limitations, prorated replacements....


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## firecat1981 (Nov 27, 2007)

DuckNut said:


> Let me tell you first hand Duracell batteries are total crap. I bought 2 and they lasted less time than the ones I was replacing. I was replacing a small deep cell that was 6-7 years old with the bigger marine Duracell and brand new they lasted significantly less time. Took them back and got two new ones. Same issue. Went to Wally World and bought their marine batteries and used two brand new batteries for core charge.
> 
> I certainly wish you luck if you buy Duracells.


Duck let me tell you first hand Wally world batteries are crap too. That's what I'm replacing. Let me also tell you that Sams and wally world are the same company, and I'm pretty sure you were just duped into buying the same battery. The Duracell and everstart have the same case, just different labels printed.

If you got 7 years out of a deep cycle consider yourself very lucky. In Florida heat I expect maybe 3-4 years max. My everstart lasted 3. I would buy another everstart, it was the same price point as the duracells, and both wally world and sams have good return policies. A cheap battery is a cheap battery, sometime they are great like my first everstart, sometimes they suck, but it beats paying $300 for an optima to go bad.


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## Brett (Jul 16, 2008)

Quality control isn't all that great from my experiences with both marine and automotive batteries.
I've had brand new batteries that wouldn't accept a charge after only a month of use
and a battery, that came with an abused hull, that was still functioning 4 years later when I sold the boat.
I buy the least expensive with the best warranty that meets the load requirements.
When it dies I get another one. That's as good as it gets.


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## firecat1981 (Nov 27, 2007)

I should add that I may not keep the Duracell. Like I said I wold buy another everstart. One thing not adressed in the specs is weight. I had to use a scale at home. I need to go by walmart, and I'll grab one of their scales to see if there is any real difference cause they also carry group 29's. This is more for curiosity at this point.


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## Jpscott1 (May 2, 2017)

I have had very good success with the Sam's Club Duracell AGM batteries.
Don't be afraid to spend as much or more on the onboard charger as you do on a pair of batteries. I believe the charger has more to do with battery life than the brand of battery.


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## firecat1981 (Nov 27, 2007)

I agree, but I might go without an on board to save weight. At least for now. Since it's garaged using a stand alone charger isn't a big issue now. I may add one later on.


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## Jpscott1 (May 2, 2017)

Firecat- I used a standalone charger for a while- but I got lazy and like to be able to pull the pigtail out on the charger that is already connected to the batteries and plug it up and forget about it until my next trip. I use the ProSeries Battery Onboard chargers from Cabelas. I think it weighs around 6lbs.


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## DuckNut (Apr 3, 2009)

firecat1981 said:


> Duck let me tell you first hand Wally world batteries are crap too. That's what I'm replacing. Let me also tell you that Sams and wally world are the same company, and I'm pretty sure you were just duped into buying the same battery. The Duracell and everstart have the same case, just different labels printed.
> 
> If you got 7 years out of a deep cycle consider yourself very lucky. In Florida heat I expect maybe 3-4 years max. My everstart lasted 3. I would buy another everstart, it was the same price point as the duracells, and both wally world and sams have good return policies. A cheap battery is a cheap battery, sometime they are great like my first everstart, sometimes they suck, but it beats paying $300 for an optima to go bad.


I agree with Brett - quality control seems to be the issue.

I know that I am personally 0 for 4 with Duracell and have had good luck with Wally World brand.

I just wanted to warn you of my first hand personal experience.


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## firecat1981 (Nov 27, 2007)

Quality control is definitely an issue in all batteries. I appreciate the heads up. A few years back everyone here freaked out when I bought an everstart for my gheenoe, telling me they won't last. Luck of the draw I suppose. The first 2 were good, the last one not so much.


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## firecat1981 (Nov 27, 2007)

I'll probably get an onboard charger later on. Especially if we take more trips with the boat, but for now I'll keep it simple. I'll put a pigtail on the batteries so I can quickly hook up the charger.


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## firecat1981 (Nov 27, 2007)

Lol, ok DuckNut, you'll appreciate this one. The Duracell wouldn't charge up right. The charger would get to 65% and stop, even after a few hours. Tried my old charger, same thing.
So since wally world is closer then sams I grabbed an everstart 27. The same thing! This one was better and would go to 74%. 
I've never had this happen before and both batteries are labeled 5/18. I'm going to return both and try one more everstart from a different store. If it work great, if not....


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