motorhome coach batteries

smkettner wrote:
This thread is a bit dated. Is HB still around?

My fault. I necro-posted to respond to a comment I had missed previously.

I don't see any posts from HB since this thread.

MEXICOWANDERER wrote:
The only way to establish if a battery charges "faster" or "slower" than another type of battery is to present both discharged units with a fixed voltage, determine the amperage, and kWh hours consumed until a battery reaches a point in time where fixed voltage reduces to a set number of amperes flowing.

Yeah, that's a warm latitude for RV solar.

OK. I gather you may have not seen enough evidence, either way, to offer qualified comment on my question. I guess I'll have to come to terms with the fact that you may not know everything. Thanks for shattering a "young" man's hero worship. :)

And I get that you would like to see a well thought-out and performed experiment to properly address this.

But that's not really what I'm asking.

A more applicable experiment to test my hypothesis would be to substitute your constant voltage/determined amperage with... "A given, typical RV converter," i.e. Progressive Dynamics, IOTA, etc.

On a budget you could get by with just 2, relatively new and well cared-for batteries; a single AGM and a single, 6-cell hybrid of comparable capacity.

Remove x amp hours from each. Rest 'em and charge 'em 'til the converter quits. Monitor the current throughout. Stop the clock at say 5A.

But we can't even begin this experiment because we, together haven't even made it to step 1 of the scientific method. You're proposing a test without a hypothesis to test.

I'm saying that I've seen more than enough empirical evidence to suggest that there is little to no charge rate advantage to typical RV AGMs over typical and comparable RV flooded batteries using typical RV converters. And I believe a proper, scientific test would prove my hypothesis. Haven't seen ANY evidence to the contrary... as of yet.

Any more thoughts?

Huggybear49 wrote:
i need new coach batteries and wondered what kind i should purchase. at present have 2 12v interstates but very unhappy with their performance thankyou in advance hb ive been told that 6v performs better than 12v. are there any changes to hooking up 6v over 12v? ty hb

Often when batteries fail to perform as expected it is the charging system not the battery.
Might be time to update the converter or better yet get some (200w+) solar.

Otherwise no changes needed to go 12v in parallel to a pair of 6v in series.

This thread is a bit dated. Is HB still around?

"Perform"

"Perform?"

"PERFORM!"

The advantage of thick plates and glass mat separators, is it makes a battery far more survivable to abuse and when treated halfway right, adds a profound number of cycles to the battery lifespan.

Has little to do with CCA, Reserve Capacity or Ampere Hours.

If you robbed the plates out of my Rolls batteries, chopped them and stuffed them in a car jar or even a golf car jar, you would end up with a fine 9 amp hour battery.

The tropic of Cancer line is 770 mile north of Las Peñas.

You might want to re-phrase the statement of You can get 12 volt golf car batteries these days, to...
You can also get six cell batteries for golf cars these days.

One of the main claims to fame for absorbed glass mat technology is a mat saturated with 1.300 density acid feeds pure lead plates. The battery protects itself by having the mat run out of electrolyzing potential before the plates become sulfated as much as a flooded battery. Got it?

Manufacturers try to squeeze all the plates they can get away with into an AGM accumulator to overcome plates that do-not-cycle as deeply as do flooded battery plates.

The only way to establish if a battery charges "faster" or "slower" than another type of battery is to present both discharged units with a fixed voltage, determine the amperage, and kWh hours consumed until a battery reaches a point in time where fixed voltage reduces to a set number of amperes flowing.

So we have two different chemistries at work. Two different operational voltage characteristics. Are we using the identical voltage set point on both? Although the static voltage characteristics of an AGM are higher than the flooded, is the charging voltage correct according to the manufacturer? Do we charge an AGM to the same absorbsion value as the flooded battery? New batteries are easy to test. How do you know when an AGM has lost capacity? A failed AGM may exhibit exactly the same voltage characteristics as a new good AGM but have 30% of the capacity.

Skewing this issue is my age old rant about flooded batteries getting cheated by "smart chargers". Don't laugh AGM owners, you're not in the same boat but you are sure as hell on the same lake. Voltage alone is a ----poor way to determine the capacity of fill for a valve regulated battery. Fill points must be determined by kWh transactions, or trends and tendencies of voltage PLUS amperage values (when filling).

I conduct schools for cruisers who get confounded by their "amp hour meter" and end up with a "bank balance" so far out of kilter their amp hour gauge is worthless until batteries are corrected and kWh are zeroed. 3-amps per 100 amp hours at 14.4 volts is a good compromise with AGM batteries. This will slow the frequency to condition the battery but not eliminate conditioning altogether.

Huggybear49 wrote:
i need new coach batteries and wondered what kind i should purchase. at present have 2 12v interstates but very unhappy with their performance thankyou in advance hb ive been told that 6v performs better than 12v. are there any changes to hooking up 6v over 12v? ty hb

This "Six volts preform better than 12" is a common half-myth.

Sometimes it is true, sometimes it is false, in ever case there is not enough information to make that statement.

I will give you some better numbers

Two group 24 12 volt in parallel 150 amp hours
Two group 27 in parallel About 180
Two GC-2 Six volt in series About 220-230
Two Group 31 12 volt in parallel 250 to 260
Two 8-D 12 volt in parallel, a bit over 500 amp hours.

But wait there is more...

There are basically 3 classes of batteries.
Starting
Marine/Deep cycle

DEEP CYCLE

You will notice the blank line

DEEP CYCLE can be safely taken down to around half full without doing major harm, and if you accidentally take them down lower on rare occasions,.. They may still recover.

Starting batteries like to be better fed.. Marine/Deep cycle are closer to starting than they are Golf Car (GC) batteries.

But you can also get 12 volt Golf Car batteries now days.

MEXICOWANDERER wrote:
I am also biased against placing my rig in the sun for PV use and needing to run the generator to keep the rig habitable.

Ha!

Me too!

But I imagine most of our members don't reside within close proximity to The Tropic of Cancer either.

Southern Oregon summers can crest 100F. I definitely look for shade when dry camping... which is about all we do. If I went the solar route, it would have to be a portable system of some kind.

I'd love to have some PV, but fortunately my old rig has virtually zero parasitic draw. My 3-27s and LEDs can get me a week if I push 'em a bit. And that's with music all day and a couple hours of TV at night. 'Course... I don't cook microwave popcorn every day like ol' BFL13 does. ;)

As to your suggested experiment... yeah... I'll get right on that. :)

My point was not in regard to lifespan, though, Mex. It was only geared toward the myth that AGMs will charge faster than their flooded cousins by a typical RV converter. I have never seen any evidence of that in all the years that I've been on this site. But I've seen plenty of evidence to the contrary.

Do you have an opinion on this point, specifically?

For most people brand doesn't matter. When most complain about poor battery life it is usually a case of poor maintenance. Most batteries die of abuse and neglect, not old age.

Tell us how you plan to use these batteries.

Yes, there is a difference between hooking up 12v and 6v batteries.

Computing battery charging characteristics and then matching them to a charger is not cut and dried. Some batteries have an "initial" higher charge acceptance then that higher acceptance rate "advantage" vanishes as the battery fills. Overall "fill time" may be reduced, but batteries are not a foot race.

Batteries are cranky. Good intentions but in reality, abuse, will have a battery commit suicide or clean your clock so fast, it'd make a person's head spin.

Here is an exercise:

Two 100 mp hour batteries. Both are heavily (identical kWh) discharged cycled.

Establish a timed limited recharging profile for both flooded and absorbed glass mat construction. Let's use a two hour figure. Furnish values for the record.

Pursue the test for say 300 cycles.

In what state of HEALTH would the batteries end up in?

How does a person establish the state of health of both types of battery?

Does YOUR (no one else's) charger have the ability to meet or exceed all of the above criteria? Leave the battery in the best NUMERICALLY PROVEN state of health?

Note: I am biased toward wilderness camping versus running from electrical receptacle to electrical receptacle. I am also biased against placing my rig in the sun for PV use and needing to run the generator to keep the rig habitable.

full_mosey wrote:
Hi KendallP;

I see you are back with your anti-AGM dis-information campaign.

Always a fun read that belongs in the fiction section.

Settled science?; that's a good chuckle.

HTH;
John

Heh heh heh. You still livin' in your fantasy world, mose?

We don't need another long thread for this. Just ask Mexicowanderer or another engineer like Bigfootford. Bigfoot was a Lifeline guy. Still might be. He and I had this conversation way back when. He had to concede.

The following is a canned response of mine on this. It begins with one example of a test that Bigfootford and Reddog1 performed. That's about as high a charge rate as you will ever see in RVing; A single 100 Ah Lifeline charged by a 55A IOTA and then a 60A PD.

So you call 2 1/2 hours with a better than C/2 charger to get from 40-90% fast?

Okie doke.

BFL13 regularly achieves that... at a slower charge rate... on his Golf Cart batteries.


My canned response... with evidence...

(Note: The "wo/Boost on the PD is a typo. The PD was in "Boost.")


I have yet to see any test results on an AGM that when charged at any fast rate with a typical converter at say 14.4V or so... doesn't begin to force the current to taper long before 90% SOC.

Here's one that is being charged at about C/2. The IOTA dropped out of boost at 15 minutes or so, but notice that the current still began to taper at just 10 minutes in. These are typical RV converters. This is how a Lifeline reacts to them in real life. Even at C/2 it took over 2 hours to go from 40% to 90%. The IOTA 2 1/2 hours.

(Below the Lifeline chart is BFL13's infamous "ugly graph" that shows it took 129 minutes to do a 50-90 on a pair of 6V GC2s at only C/3. And as we all know (or should know)... with typical RV converters... the 40-50% portion of the charge is definitely the easy part... AGM or flooded. It only added about 10 minutes to the Lifeline's charge. So the speed winner here is actually the GC2s. At best it's a draw... even at a slower charge rate for the GC2s.)

(And at the bottom of the page is Fisherguy's graph. 2 hours or maybe 2:15 to do a 47-90 at C/3 using another typical converter.)





BFL13's Ugly Graph

Hi KendallP;

I see you are back with your anti-AGM dis-information campaign.

Always a fun read that belongs in the fiction section.

Settled science?; that's a good chuckle.

HTH;
John