The dirty-little-secret about FLA Batteries

[davidbrady]

Foks,

There's a characteristic of all battery technologies quantified in the Peukert Constant which says that the shorter the time that you discharge a battery the less the 'effective' AH capacity of the battery.

Brand new batteries display this behavior but it only gets worse with the age of the battery and it's especially bad with Flooded Lead Acid (FLA) batteries. This is the dirty little secret about FLA's that no one talks about and this is where AGM's routinely outperform FLA's in the real world.

Here's a chart showing the effective capacity of a battery with different Peukert Constants:



Lifeline AGM's have a constant of 1.12; your typical FLA is in the range of 1.3 to 1.5. For instance, say your powering you 600W hair dryer, that's about a 50 amp draw from your 12V system. Looking at the chart, the AGM is performing at 78 AH while the best equally rated flooded/wet battery is only performing at a 38 AH capacity.

IOW's start your coach and you've dramatically cut down the available AH capacity of your battery. Start your coach with an FLA (flooded/wet) battery and you've effectively halved the capacity that you would have if you were running AGM's.

Folks, the battery company's published ampere-hour rating isn't the full story. You can't do simple math and truly compare AGM capacities with FLA (flooded wet lead acid) battery capacities.

So we know that:
1) the true (Peukert Constant) corrected real world AH capacity of AGM's outshines that of even the best equally rated wet battery,

2) in the bulk charge stage Lifeline's can be charged at 5C! That means a 100AH battery can accept a bulk inrush current of 500A. This is an impossibility with a wet battery and dramatically reduces AGM charge times, and

3) AGM's are happy with charge voltage up to even 15V. Many of us WB and LXi owners have been charging banks of AGM's with our 50DN alternators for years with little discernible ill effects.

AGM's are simply more robust and higher performing than Flooded Lead Acid batteries.

[Darrell Snell]

(04-30-2013 13:05)davidmbrady Wrote:  Foks,

There's a characteristic of all battery technologies quantified in the Peukert Constant which says that the shorter the time that you discharge a battery the less the 'effective' AH capacity of the battery.

Brand new batteries display this behavior but it only gets worse with the age of the battery and it's especially bad with Flooded Lead Acid (FLA) batteries. This is the dirty little secret about FLA's that no one talks about and this is where AGM's routinely outperform FLA's in the real world.

Here's a chart showing the effective capacity of a battery with different Peukert Constants:


Hey David
Any recommendation for lxi chassis batteries?
Darrell
Lifeline AGM's have a constant of 1.12; your typical FLA is in the range of 1.3 to 1.5. For instance, say your powering you 600W hair dryer, that's about a 50 amp draw from your 12V system. Looking at the chart, the AGM is performing at 78 AH while the best equally rated flooded/wet battery is only performing at a 38 AH capacity.

IOW's start your coach and you've dramatically cut down the available AH capacity of your battery. Start your coach with an FLA (flooded/wet) battery and you've effectively halved the capacity that you would have if you were running AGM's.

Folks, the battery company's published ampere-hour rating isn't the full story. You can't do simple math and truly compare AGM capacities with FLA (flooded wet lead acid) battery capacities.

So we know that:
1) the true (Peukert Constant) corrected real world AH capacity of AGM's outshines that of even the best equally rated wet battery,

2) in the bulk charge stage Lifeline's can be charged at 5C! That means a 100AH battery can accept a bulk inrush current of 500A. This is an impossibility with a wet battery and dramatically reduces AGM charge times, and

3) AGM's are happy with charge voltage up to even 15V. Many of us WB and LXi owners have been charging banks of AGM's with our 50DN alternators for years with little discernible ill effects.

AGM's are simply more robust and higher performing than Flooded Lead Acid batteries.

[Bob Johannesen]

Does anyone have Lifelines that have actually lasted more than 6 years?

.

[davidbrady]

Hi Bob,

Seven years on my last set and I didn't really have to replace them. I had one that was weak and we were planning a cross country trip so I replaced them more for a preventative maintenance measure. From what I've seen on the forums over the years, getting 7.5 plus years from Lifelines is fairly common.

[cmillsap]

The best thing about AGMs is you don't have to replenish the water in 36 cells in 6 house batteries every few weeks including several more cells in the chassis batteries. The PO had just replaced all of the batteries in my bus. Alas, they are all flooded cell. Now the Irish in me wouldn't allow me to change them all to AGMs but I must confess I did consider it. Soooo, I did the next best thing I knew which was to install an AquaPro watering system and live with the new flooded cell batteries for a few years.

Already, I have seen how easily they lose their charge. Given the parasitic drain when the coach sits without being plugged in to 120V like at the repair shop where it currently is. I finally convinced them to keep it plugged in to save the life of the flooded cell batteries.

Yes, I know there are other ways to stop or limit the drain on the battery bank like switching off the main battery disconnect or the 12V switches. The only problem when doing that is knowing how much they are slowly discharging with little or no load on them. Besides, I feel better keeping them float charged.

[pgchin]

(06-10-2013 21:22)Darrell Snell Wrote:  Any recommendation for lxi chassis batteries?
Darrell

Buy the Interstate, no maintenance, group 31 batteries 31-mhd, no water service required, no more cleaning the terminals annually, and if you shop around, you'll get a good price from a local jobber. 3 years and counting, good buys. List 178, retail, 146, but you can get them cheaper if you know the jobber.

[Darrell Snell]

Thanks all
Good advice
Darrell

[davidbrady]

(06-10-2013 21:22)Darrell Snell Wrote:  Hey David
Any recommendation for lxi chassis batteries?
Darrell

Hey Darrell,

I run Napa 7235's. The price I last paid on 12/2012 was $149.00. I believe they're made by Exide. I routinely get 5 years out of them.

Part Number: BAT 7235

Attributes:
Battery BCI # : BCI #31P
Battery Cold Cranking Amps @ 0 Degrees F : 1,125
Battery Cranking Amps @ 32 Degrees F : 1,260
Battery Height : 9 1/2"
Battery Length : 13"
Battery Posts Type : Top Post
Battery Reserve Capacity (Minutes) : 195
Battery Voltage : 12 Volt
Battery Width : 6 3/4"
Wet or Dry : Wet
Battery Weight : 61 lbs

[Wanderer]

(06-10-2013 21:48)Bob Johannesen Wrote:  Does anyone have Lifelines that have actually lasted more than 6 years?

.

Yes. I am on the end of my 9th year on my M450. If you take care of them with a float charge of 13.5 VDC and keep them clean, they will last.

The most important thing is to never let them go below 12.1 VDC. When you deep cycle them they will lose cycle life.

[truk4u]

Remember to keep me in mind boy's when it's time to replace those Lifelines, you'll like the Guru price.

Two months ago I provided batteries for one of the Prevost guys that had date codes of 10 yrs. Now that's service from Lifelines!