Batteries Lead Acid vs AGM

[joema62]

Since we are new to RVing I have questions for which I appreciate all comments. Would like opinions on using AGMs or lead acid for House Batteries bearing in mind that AGM's like to be charged at about 14 vdc while lead acid likes around 13 volts

[pianotuna]

Hi John,

I've taken to "foxing" the Blue Sky 3024 di late in the day by triggering it to equalization mode.

It appears to take the pd40 amp converter about 4 to 5 days before it drops down to 13.2 volts. I don't think that is on a timer.

[full_mosey]

Hi PT;

I have been thinking out your ? about saturation charge.

I see the charging from the battery's point of view.

There are two Voltages; charging and float and, maximum battery temperature. There is a criteria for switching from charging to float. Lets say that when charging acceptance current drops to 1A then float begins.

The job of the charger is to keep under these two voltages according to the temps. Unfortunately some chargers don't pay any attention to battery temps.

When a battery reaches float conditions, it is not fully charged. I look at the float stage of a 3-stage charger as another constant voltage and decreasing current process. That is simply another stage-2 acceptance but with a lower Voltage cap.

When you say 200mA, then that would fit in the stage-3 float range. It would be expected that the current would be less than the 1A transition current from stage-2 due to the lower volts during float. These 200mA could be expected to taper down to the self-discharge rate of the bank. Is this called saturation charge?

I did observe 300mA right after connecting the Turnigy. Within a minute, the Turnigy dropped to 0A. That must be because the bank was already fully charged.

Of course, the SS-10 has no float, but the current does manage to drop to 0 never the less.

[chuckftboy]

I think AGM's are great but choose to use Trojen T105's. I have a progressive 9270 charger and only add a little water once or twice a year. There is never any corrosion. The batteries are now 5 years old and hold a charge just fine so it would be hard for me to justify the AGM's T105's are only 105.00 each locally

[Daveinet]

Gau 8 wrote:

pianotuna wrote:
Hi,

They were originally sold in glass jars. Large 2 volt cells.

Gau 8 wrote:
Is it cool to call a battery a "jar."

I am aware of that fact. As are a lot of folks who call them batteries instead of "jars."

Am I cool if I call a door ajar?

[Gau_8]

pianotuna wrote:
Hi,

They were originally sold in glass jars. Large 2 volt cells.

Gau 8 wrote:
Is it cool to call a battery a "jar."

I am aware of that fact. As are a lot of folks who call them batteries instead of "jars."

[full_mosey]

Mr.Mark wrote:


To me, the price was absolutely not an issue.... putting water in wet cell batteries was wearing me out! Especially the sulfating on the metal parts. Now, with all new AGM's, no water checking, no sulfating, no worries! That's worth the $3,000+/- I paid for 8 batteries (and repainting the metal slide-out trays).

Everybody has their priorities and thresholds.... I'm good.

MM.

You're preaching to the choir with me on the pluses of AGMs. The simpler, use, charge, repeat is worth $11/year extra expense to me as well.

HTH;
John

[Mr_Mark1]

full_mosey wrote:

bluwtr49 wrote:

...
Most of the bad rap flooded cells get is due to dated info.

Some of the AGM batteries, when they are ready to die....they do it right now. One day OK, the next gone. In cases flooded cells will most often exhibit symptoms that allow time for corrective action.

I am not anti wets. I did react to your use of AGM and hype in the same sentence. I see that I was wrong. 😮

Now, lets take a look at the costs over a 10yr period. There are a few AGM folks here that are pushing 10yrs.

Today, the discount stores have 100AH AGMs in both 12V and 6V for $170. A pair would get you 200AH for $340. Are we going to see more parity in prices?

A pair of 6V GCs would be half of that at $85 each, or $170. Add in the $60 watering system to adjust for the maintenance difference gives $230.

Now take the diff and divide by 10yrs, or $110/10 = $11/year cost advantage to the wets.

HTH;
John

To me, the price was absolutely not an issue.... putting water in wet cell batteries was wearing me out! Especially the sulfating on the metal parts. Now, with all new AGM's, no water checking, no sulfating, no worries! That's worth the $3,000+/- I paid for 8 batteries (and repainting the metal slide-out trays).

Everybody has their priorities and thresholds.... I'm good.

MM.

[pianotuna]

Hi Passin,

They require even more specific charging routines than AGM. If they are overcharged bubbles form and that's "the end" for that area on the plates. Not recommended unless you REALLY know what you are doing big time.

Passin Thru wrote:
Gel cells are good. They take vibration well.

[Passin_Thru]

Gel cells are good. They take vibration well.

[full_mosey]

bluwtr49 wrote:

...
Most of the bad rap flooded cells get is due to dated info.

Some of the AGM batteries, when they are ready to die....they do it right now. One day OK, the next gone. In cases flooded cells will most often exhibit symptoms that allow time for corrective action.

I am not anti wets. I did react to your use of AGM and hype in the same sentence. I see that I was wrong. 😮

Now, lets take a look at the costs over a 10yr period. There are a few AGM folks here that are pushing 10yrs.

Today, the discount stores have 100AH AGMs in both 12V and 6V for $170. A pair would get you 200AH for $340. Are we going to see more parity in prices?

A pair of 6V GCs would be half of that at $85 each, or $170. Add in the $60 watering system to adjust for the maintenance difference gives $230.

Now take the diff and divide by 10yrs, or $110/10 = $11/year cost advantage to the wets.

HTH;
John

[full_mosey]

pianotuna wrote:
Hi John,

I was aware of the lifeline recommendations--but not of the Optima. Thanks for adding to the knowledge base.

Do you happen to know how AGM chemistry batteries react to saturation charging? (i.e 200 milliamps per cell for 14 to 16 hours)

The Optima rapid charge rate is no doubt related to a racing situation where the pit stop must be as short as possible. They don't say how many cycles you can do this.

Don't know anything re saturation. I have never run across that term regarding how to maintain my AGMs.

I did observe a 0A charge rate this past week from the MS SS-10 solar controller over three days. HiTech says it is because the Turnigy cannot see anything under 10mA. My bank is resting between trips and is fully charged by any reasonable definition.

The only draws must be from overnight from the SS-10 and the Turnigy. The SS-10 manual says 8 to 10Ma self consumption. Including the Turnigy, the SS-10 would draw ~0.100mA overnight. The Turnigy displayed 0.430Ah this morning after three days. That is 0.143/day of charging. If the 0.100mA draw is correct, that leaves 0.043Ah/10hr-night of self discharge for the Optimas. Certainly the Turnigy is accumulating the early morning top-up. It is possible that the SS-10 is charging at its 10mA self consumption rate all day as well. Small numbers any way you slice them.

I guess what I am saying is I have not observed any long term charging Amps at the 0.200mA level. All I see is 0A sometime before 8AM.

Would I want a saturation charge?

HTH;
John

[Daveinet]

I'm trying my first AGM in the coach. My hope is that the slower discharge rate will help the battery tolerate periods of non-use better. My motorcycle AGM seemed to last much longer than a standard battery, so I'm hoping for the same result with the one in the coach.

[bluwtr49]

full_mosey wrote:

bluwtr49 wrote:

I just install a battery watering system that eliminates opening the caps and also recombined the gasses. End result, no mess, no corrosion, and adding water is a 1 minute operation.

Those recombining caps are standard with AGM, plus there are valves that keep the water in there so you never need to worry about exposing the plates to air. I guess that is just hype, right?

How much does a watering system cost? Why is a watering system important enough for the extra expense? Doesn't the extra expense bring the wet cost closer to the AGM cost? Do you pull the caps and check the SG? How often?

Thinking I don't need to do any of that is a 1 minute operation for me too!

HTH;
John

Watering system is ~120.00 for 4 batteries and I never pull the caps. Checking the SG is pretty unnecessary unless you suspect one battery is going bad. To check the water level, you attach the pump, give it a squeeze or two and water will either go into the cells or not depending on the level. This is a one time thing and will be moved to the next set of batteries. Think of it like buying an air chuck with a pressure gauge for you tires.

My 10 yo interstates never needed any water and I pulled the caps to checked the SG because I wasn't getting the proper discharge time....yep, I had a couple of cells below spec.

Most of the bad rap flooded cells get is due to dated info. On the other hand if you have a MH using a less than optimal charger...like many converters, you can have some maintenance/longevity issues but than these are not great candidates for AGM either.

Some of the AGM batteries, when they are ready to die....they do it right now. One day OK, the next gone. In cases flooded cells will most often exhibit symptoms that allow time for corrective action.

[pianotuna]

Hi John,

I was aware of the lifeline recommendations--but not of the Optima. Thanks for adding to the knowledge base.

Do you happen to know how AGM chemistry batteries react to saturation charging? (i.e 200 milliamps per cell for 14 to 16 hours)