AGM Batteries

[GordMay]

Originally Posted by Albro359

Still the equalisation deal with AGMs is not totally clear...some say yes, some say no...
So we still don't know !
Alan

Seems fairly obvious, to me.
Consult the manufacturer of your specific AGM batteries.
✓ Concorde Lifline - yes, equalize
✗ East Penn - no, don't equalize

[Captain Bill]

I believe the lifelines have a catalyst that recombines the H2 and O2 internally. Perhaps other brands don't have that feature. The Lifeline web site definitely recommends equalization. I would not do it with any that don't recommend it. Interestingly my primary AC based charger will not go into equalization mode while set for AGMs. My solar controller however is not as "smart" and will do the job for me. All of the voltages on the solar controller have to be set manually according to a chart rather than having presets.

[s/v Jedi]

Jedi ships log: steer clear of Concorde Lifeline AGM's because AGM's by design should never be equalized so there's something fishy with them.

cheers,
Nick.

[billyehh]

AGM Batteries should not be equalized if they are treated properly. If charged at the proper voltage and not discharged nore than 40% they can last more than 10 years and I have heard that 15 years is not all that uncommon. However, if they are mistreated they will sulphate like a standard battery. At this point they must be equalized. Unfortnately this will do damage to the battery, but is still better than letting it continue to sulphate.

[Albro359]

I think I'll just try to keep 'em charged up and forget about equalisation...

I've had AGMs for 3 years now and I'm impressed with their performance.

[Solitude]

Sealed gel works for me.

[anathema]

Actually an AGM should have little to no leakage even if broken or punctured because the glass mats inside them are only 95% soaked with acid.

Its like taking a sponge, soaking it with water, then squeezing a (very little) bit out. You may get the occasional drip, but they will be few and far between if you even see any, and the sponge will still feel very wet obviously.

Great battery tech overall!

EDIT: Sorry I see this was mentioned 2 posts up, but I stand by my endorsement

[s/v Jedi]

When you submerge an AGM battery in sea water, the only problem you get is that the battery will discharge itself into the low electrical resistance of the water. Don't think that the water will short the battery. Copper conducts electricity more than 10 million times as good as sea water (see Electrical conductivity - Wikipedia, the free encyclopedia).

I think nothing much will happen. Even if the path through the water is as low as 120 Ohms, you only get 1A discharge from a 12V system or 2A from a 24V system. If the resistance gets as low as 12 Ohms, you get 10A for 12V / 20A for 24V. All that is just not enough to create enough gas for explosive/poisonous concentrations to worry about.

I once flooded my Trojan L16's with fresh water and was highly surprised that the water did not get through the vent-holes in the caps into the batteries.

cheers,
Nick.

[Not Sure]

Originally Posted by s/v Jedi

When you submerge an AGM battery in sea water, the only problem you get is that the battery will discharge itself into the low electrical resistance of the water. Don't think that the water will short the battery. Copper conducts electricity more than 10 million times as good as sea water (see Electrical conductivity - Wikipedia, the free encyclopedia).

I think nothing much will happen. Even if the path through the water is as low as 120 Ohms, you only get 1A discharge from a 12V system or 2A from a 24V system. If the resistance gets as low as 12 Ohms, you get 10A for 12V / 20A for 24V. All that is just not enough to create enough gas for explosive/poisonous concentrations to worry about.

I once flooded my Trojan L16's with fresh water and was highly surprised that the water did not get through the vent-holes in the caps into the batteries.

cheers,
Nick.

Assuming of course that an errant screwdriver or any other piece of conductor material isn't washed nearby. No, it appears that you've just traded one problem for another, particularly since your old battery terminals, which were upright, were sticking up further out of the water than your new setup is, and therefore were better protected.

Regardless, you seemed to have convinced yourself of the 'safety' of your current setup, so what do I care.

[GordMay]

Originally Posted by s/v Jedi

When you submerge an AGM battery in sea water, the only problem you get is that the battery will discharge itself into the low electrical resistance of the water. Don't think that the water will short the battery. Copper conducts electricity more than 10 million times as good as sea water (see Electrical conductivity - Wikipedia, the free encyclopedia).

I think nothing much will happen. Even if the path through the water is as low as 120 Ohms, you only get 1A discharge from a 12V system...

However, if the path is as low as 0.04 Ohms*, you might expect get a discharge of about 3,000 Amps.

Distilled Water has a resistance of about 1,000,000 Ohms per meter; whereas Sea Water has a resistance of bout 0.1 Ohms per meter.

However, Conductivity is measured in MS/cm2 which is Micro-Siemans* per Square Centimeter. Resistivety is measured in Meg-Ohm/cm2 which is Million Ohms per Square Centimeter. These terms were adopted because Ohms of resistance per foot of distance was too easily understood.

A Siemen is a mho. It is called Siemen to make it harder to remember than mho.
Mho is Ohm spelled backwards, a clear clue to its meaning which is 1/ohms or reciprocal Ohms. Since Ohms is resistance, mhos is conduction.
Mhos had too many people understanding what was going on, so it was renamed Siemen to make it sound really technical, keeping most people from understanding it easily. A deci-Siemen is one tenth of a Siemen or 0.1 mho, and a a micro-Siemen is 1 millionth of a Siemen.

Someone help me !!!

[s/v Jedi]

Originally Posted by GordMay

However, if the path is as low as 0.04 Ohms*, you might expect get a discharge of about 3,000 Amps.

Distilled Water has a resistance of about 1,000,000 Ohms per meter; whereas Sea Water has a resistance of bout 0.1 Ohms per meter.

However, Conductivity is measured in MS/cm2 which is Micro-Siemans* per Square Centimeter. Resistivety is measured in Meg-Ohm/cm2 which is Million Ohms per Square Centimeter. These terms were adopted because Ohms of resistance per foot of distance was too easily understood.
[...]
Someone help me !!!

Oh Gord, I got you now ;-)

First, it's a Siemens, not Siemen nor Siemans. Yes, this is the German scientist and related to the Siemens brand of electric/electronic products.

Next, MS/cm2 would be MegaSiemens per square centimeter, not Micro-Siemens. that's a 10^12 difference. uS(micro) -> mS(milli) -> S -> kS (kilo)-> MS(mega) -> GS(Giga).

According to the wiki, avg. seawater is 4.8 S.m^-1. If we take the two battery poles to be 25 cm apart, the conductivity in S becomes 4.8 / 0.25^-1 = 1.2S. If we convert that to resistance, we get 1/1.2 = 0.83 Ohm. At 12V battery we get 12/0.83 = 14A

So, no sensational explosions, sorry...

ciao!
Nick.

[GordMay]

Originally Posted by s/v Jedi

Oh Gord, I got you now ...
... According to the wiki, avg. seawater is 4.8 S.m^-1. If we take the two battery poles to be 25 cm apart, the conductivity in S becomes 4.8 / 0.25^-1 = 1.2S. If we convert that to resistance, we get 1/1.2 = 0.83 Ohm. At 12V battery we get 12/0.83 = 14A ...

It shouldn't be difficult to "get" this math-challenged dolt, who doesn’t really get this seawater conductivity stuff.

Could you direct me to the Wikki?

How do we convert a linear measurement (electrodes 25cm apart) to a volumetric measurement (cubic/cm or m)?

According to the chart on page 9, the specific conductivity of “average”* (±S = 35, or 3.5% salt ?) seawater is 0.0532 Ohms per centimetre (? 18.7969 mhos/cm ?).
➥ http://www.ocean.washington.edu/cour...otes/CHPT3.pdf

[s/v Jedi]

Originally Posted by GordMay

It shouldn't be difficult to "get" this math-challenged dolt, who doesn’t really get this seawater conductivity stuff.

Well, I'm not a math wizard either compared to some study-friends but we did take 6 different math classes and I managed just above average. I amazed myself that I even managed Discrete Math because when I first looked at that, it went beyond my imagination (prove that 1 equals 1 etc.)

Could you direct me to the Wikki?

I found my conductivity number here: Electrical conductivity - Wikipedia, the free encyclopedia

and the Siemens unit (uS, MS etc.) here: http://en.wikipedia.org/wiki/Siemens_(unit)

How do we convert a linear measurement (electrodes 25cm apart) to a volumetric measurement (cubic/cm or m)?

You don't. Conductivity of a liquid is, by definition, between two electrodes. A bigger volume only matters when absolute volume is very low. It does matter for maximum current carrying capability (not start boiling away with more volume and same current).

According to the chart on page 9, the specific conductivity of “average”* (±S = 35, or 3.5% salt ?) seawater is 0.0532 Ohms per centimetre (? 18.7969 mhos/cm ?).

I use the notation "^-1" where you put your "?" It is "to the power of -1".
The notation of ohm^-1 or cm^-1 means you take the reciprocal value of that number (Multiplicative inverse - Wikipedia, the free encyclopedia). The easy way of doing that is to divide one by that number.

The value/formula I came up with:

1/R = 4.8 x 1/D where R=resistance in Ohm and D=distance in meters
gives R = 1 / (4.8 x 1/D) equals 1 / (4.8 x 1/0.25) equals 1 / (4.8 x 4) equals 1/19.2 equals 0.052 Ohm. At 12V this is 230A

Earlier in the thread I did 4.8 / 4 while I noted S.m^-1 (and that "." is multiplication) which was stupid and because my mind works in "resistance" instead of conductivity which is the opposite ;-)

And the one you found:

1/R = 0.0532 x 1/(D/100)
gives R = 1 / (0.0532 x 1/(D/100)) equals 1 / (0.0532 x 1/(0.25/100)) equals 1 / (0.0532 x 1/0.0025) equals 1 / (0.0532 x 400) equals 1/21.28 equals 0.047 Ohm gives 255A at 12V

I should have converted to 1/R = 5.32 x 1/D but that's too easy ;-)

All we need now is someone to take a multimeter to the sea and measure resistance with the probes 25 cm apart in the water. I can't do that here because it's rainy season and the upper level of the water is brackish so much higher resistance.

So, even if resistance is that low, all we end up with is an empty battery.

cheers,
Nick.

[Albro359]

Seems to me there is no difference in flooding danger between liquid LA battery and SLA batteries...its the terminals that are the issue...

What kind of battery box is going to protect the terminals of ANY battery from flooding ?

I'd really like to know !

Cheers

Alan

[Albro359]

sorry...wrong thread !