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Old 08-10-2009, 11:58   #61
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"A fully charged and rested 12v battery should read between 12.6v - 12.8v at 100% charge on a good handheld multimeter, period. "
Again, that makes the assumption that you've got some magic way to know the battery really is a) good and b) fully charged. And then you still have a 20% difference between 12.6 and 12.8 volts, which is significant.
Without calibration? All you know is how that battery compares to the last one, or the next one, or how charged it was some other day. You still don't KNOW the real battery state. With calibration, you KNOW it, and many other things become possible. Like, pursuing that last 20% of capacity.
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Old 08-10-2009, 13:34   #62
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... If you put most batteries on their small side, one post will be further up from the "floor" than when it's positioned "right side up" and so that position on it's side is the better one in that respect too.
A group 31 battery, for instance, is typically about >13” L x <7"W x >9“ H, so it’s terminals will have maximum elevation when right side up.

Side mount battery terminals (at least the 1/4" bolt type used in cars) are the devil's spawn.
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Old 08-10-2009, 14:22   #63
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not to mention...

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I think we all realize that AGM costs more per amp/hour. Until you factor in the cost of the first shirt, jacket, or pants with an acid burn from the wet cell. Or the extra 20% of engine or genset run time to recharge a wet cell. Or things like that.
...the superior life expectancy of AGM batteries. I expect mine to last more than twice as long as the flooded batteries they replaced. Once you figure this into the equation, cost per amp hour is less.
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Old 08-10-2009, 14:25   #64
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My Lifeline AGM 8D's died after about 4 years of constant use. We stay at anchor for 6m out of the year in the Caribbean and the batteries get a big workout. Four years doesn't seem alot of time for $3000 worth of batteries.
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Old 08-10-2009, 15:26   #65
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AGM's have a superior life expectancy to FLAs under one condition: if you're the type to ignore "maintenance free" FLAs, then they'll probably last longer for you. But it's well known that they usually don't have the charging cycles that well-constructed, well-maintained FLA like Rolls do.

But sometimes that's not the number one criteria...
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Old 08-10-2009, 18:03   #66
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NotSure,

If you really think your batteries inside your boxes will not become submerged , you need to re-think that. The boxes are not watertight and will fill up in a flash.

Someone, maybe you, also thinks that putting a battery with the posts facing up makes a difference because the posts will be above water. That one really needs rethinking also. If you put most batteries on their small side, one post will be further up from the &quot;floor&quot; than when it's positioned &quot;right side up&quot; and so that position on it's side is the better one in that respect too. Not that it matters much when the water comes up high enough because the bilge pumps don't cope. If the bilge pumps cope, the position doesn't matter anyway.

Positioning AGM's on their side is a big positive when you want to stack them up, something that isn't possible with vented/flooded batteries.

And then there's many batteries that are meant to be on their side, or with the terminals on the side, like the big Sonnenschein 2V gel cells or the deep cycle Odysseys.

cheers,
Nick.
They sure won't get 'submerged' in a minor flood that would put your batteries and entire electrical system out of commission, that's for sure. Nobody claimed that boxing them up prevented them from getting submerged, just that when water enters the compartment where the batteries are, having them sealed in battery boxes gives the bilge pumps time to clear the water.....while your batteries (on their sides to boot) are sucking on seawater.

The object isn't that they are 'watertight', only water-protected.
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Old 08-10-2009, 18:07   #67
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Originally Posted by hellosailor View Post
&quot;A fully charged and rested 12v battery should read between 12.6v - 12.8v at 100% charge on a good handheld multimeter, period. &quot;
Again, that makes the assumption that you've got some magic way to know the battery really is a) good and b) fully charged. And then you still have a 20% difference between 12.6 and 12.8 volts, which is significant.
Without calibration? All you know is how that battery compares to the last one, or the next one, or how charged it was some other day. You still don't KNOW the real battery state. With calibration, you KNOW it, and many other things become possible. Like, pursuing that last 20% of capacity.
What? It's not 'magic'. Either your battery is or it isn't fully charged. If it reads 12.7v on a decent multimeter, its fully charged. If it reads 12.5v then it isn't fully charged, regardless of the reason.

You don't need to 'calibrate' a good multimeter, or a battery. It is what it is, and if it isn't, it ain't. Jesus H. Christ.
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Old 08-10-2009, 19:25   #68
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Originally Posted by Not Sure View Post
What? It's not 'magic'. Either your battery is or it isn't fully charged. If it reads 12.7v on a decent multimeter, its fully charged. If it reads 12.5v then it isn't fully charged, regardless of the reason.

You don't need to 'calibrate' a good multimeter, or a battery. It is what it is, and if it isn't, it ain't. Jesus H. Christ.
Reading voltage is only valid when any residual surface charge has been drained from the batteries - typically by waiting 24 hours or so after charging, or by draining a fully charged battery at the rate of a few amps for few minutes. Otherwise you'll get a false, high reading.

hellosailor is right about using a calibrated DMM - most are rated at +/- 0.5%. If your DMM says it's reading a voltage of 12.5V, that 3 digit display is really saying the voltage is somewhere between 12.45 and 12.55V. Add/subtract 0.5% and the true voltage could be anywhere from 12.38V to 12.61V. At 75°F, that's a range from about 50% to 90% SoC. Not good enough in my book. Change the temperature the reading's taken at and the SoC changes - more inaccuracy.

That's barely a ballpark measurement. More like in the vicinity of the parking lot...

Jesus H. Christ has nothing to do with it. His boat didn't have a battery bank.
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Old 08-10-2009, 19:34   #69
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Unfortunately, AGM's are not all that they are cracked up to be, and neither are Gel cells, which is why dollar for dollar the regular flooded wet cell battery is still the best deal in town.
If you are "Not Sure" you may want to include the following when evaluating Flooded vs Gel vs AGM Lead Acid batteries:
- Standing voltage?
- Self discharge rate?
- Charge acceptance rate?
- Charge times?
- Charge efficiency factor?
- Peukert's exponent?
- Charging system?
- Typical power usage?
- Battery bank size?
- Battery environmental temperature?
Not saying which battery is better, but if there was any indication that one was giving proper consideration to what clearly makes a difference before making/giving their carte blanche statement/opinion, then their opinion may be worth considering.
A proper spreadsheet comparison considering the above might give some credence.

Extemp.
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Old 18-10-2009, 12:01   #70
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Apparently, if I'm anal I'll be using spreadsheets and new math to calculate that a 1/2% error range on a multimeter translates to '50% -90% SoC'. LOL! I swear, the autism rate in society in general seems to have affected evey aspect of life to the point that even simple concepts become complex when dissected down to the nth atom.

It's a battery, people. It's reasonably simple. You slap a decent multimeter on after a sufficient rest period, and you take a reading (using common sense, again, and taking the reading during a reasonably ambient temperature range). The reading is usually accurate within a 1/2% or so error margin. It ain't rocket science.
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Old 18-10-2009, 14:30   #71
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Not Sure seems to be real sure when it comes to being aggressive and anal towards members that have a different opinion of his own highly inflated opinions.

Seriously man, why do you even belong to a group (this forum) that you so are obiviously at odds with. The majority of your posts make me want to just block you out...
You might be right in some respects but no one likes to hear it, at least I don't, the way you put it.
Take a chill pill.
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Old 18-10-2009, 14:53   #72
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this chap is making a case for standard lead acid batteries instead of the more expensive gel types.. sounds convincing
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Old 18-10-2009, 16:07   #73
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Lets talk about the real world. It depends on a number of factors which type of battery is best for a certain application. If you have a small to medium battery bank (to 400 amps) and a small alterator and charger then a flooded battery is your best bet. If you onlyuse the top 40% and keep it charged a budget battery like the Trojan 105 should last 5 years and ischeap to replace.

Also if you are hard on your batteries the Trojan 105 is cheap to replace when you destroy them.

However, If you have more sophisticated charging system, large solar panels with a smart controler such as an Outback or Blue Sky or a heavy duty alternator then AGM's can take a much higher charging current in the bulk phase and be topped up quicker then flooded cells. The advantage is especially on the hook is your battery bank is more likely to be closer to being fully charged. This helps prevent sulfation and leads to longer battery life. It is important especially with AGM's since they should not be equallized except as a last measure. Equalizing will cause gassing and since they are sealed, fluids cannot be replaced. Some manufactures say not even then should you eqalize.

My experience with AGM's has been extremely positive. The 600 amp bank is almost 9 years old. The previous owner used two 120 amp alternators for primary charging (catamaran 2 engines). I have added over 500 watts of solar panels with a 3 stage controller. Last season in the eastern caribbean I only used the engines for charging when I was anchored for more than a week. I am adding a freezer this season, so we will see how that works.

If you are tied to the dock most of the time with a good smart charger, then again the cost of AGM's is probably not worthit, but on the hook a well thought out and maintained system is worth the money and saves extra engine hours.
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Old 19-10-2009, 08:37   #74
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All good points.
One more to consider. At sears, they now sell the PM1 and PM2 marine battery.
It is a Oddesey battery in disguise for considerably less cash.
At 100 ah for a TPPL battery with over 1100 CCA, at 75 lbs or so. It can take more charge than most people can give, has a 3 year warrrenty, is a sealed agm battery...
so that is how I went. I have no numbers to give yet, but will give a report on them next year after some usage.
I would not ever go with a flooded type battery again. Not even for starting.
Bob
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Old 19-10-2009, 18:02   #75
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Lets talk about the real world. It depends on a number of factors which type of battery is best for a certain application. If you have a small to medium battery bank (to 400 amps) and a small alterator and charger then a flooded battery is your best bet. If you onlyuse the top 40% and keep it charged a budget battery like the Trojan 105 should last 5 years and ischeap to replace.

Also if you are hard on your batteries the Trojan 105 is cheap to replace when you destroy them.

However, If you have more sophisticated charging system, large solar panels with a smart controler such as an Outback or Blue Sky or a heavy duty alternator then AGM's can take a much higher charging current in the bulk phase and be topped up quicker then flooded cells. The advantage is especially on the hook is your battery bank is more likely to be closer to being fully charged. This helps prevent sulfation and leads to longer battery life. It is important especially with AGM's since they should not be equallized except as a last measure. Equalizing will cause gassing and since they are sealed, fluids cannot be replaced. Some manufactures say not even then should you eqalize.

My experience with AGM's has been extremely positive. The 600 amp bank is almost 9 years old. The previous owner used two 120 amp alternators for primary charging (catamaran 2 engines). I have added over 500 watts of solar panels with a 3 stage controller. Last season in the eastern caribbean I only used the engines for charging when I was anchored for more than a week. I am adding a freezer this season, so we will see how that works.

If you are tied to the dock most of the time with a good smart charger, then again the cost of AGM's is probably not worthit, but on the hook a well thought out and maintained system is worth the money and saves extra engine hours.
Um, how can I put this nicely....that is not exactly correct. When you fast charge a battery (higher charging current) you create more gassing and higher temps, which is exactly what you're supposed to avoid with AGM's (and Gels).

The only actual benefit of AGM's is that they are supposedly 'spillproof', and they can't be refilled, which translates to .....they are popular with people who have little to no interest in messing with batteries, bottom line. The only benefit of Gel cells is that they can be put on standby for years with little to no maintenance, such as backup for a grid-tie solar powered home. Don't for a minute confuse either with being 'better' than the regular deep cell lead acid 'wet' cells. Other than for specific installations, they aren't. Sorry.
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