0.5% X 20C for 100% SOC - myth?

[sailorboy1]

Originally Posted by sailcrazy

sailorboy1. Can you list the parameters you've set your Victron BM to? We also use T-105s (6 total-arranged into 3 "batteries"-for our house use), and have a Victron BM and Victron Solar Controller. As one not so knowledgeable in all matters LA battery, I'd like to see/compare your settings to what we use. We also have a SmartGage BM (different logic, good to compare), but they almost never agree!

I’ll pm it to you because i’m trainable

[Oceansailor]

I have 8xT105. Have never got much less than 0.7%. And that takes two days!
First day and charge cycle I end up around 1.5%. Let them sit in float over night. Next day I start a new charge cycle and normally get to 0.7%

Today I have been motoring 6 hours and are down to 2%.

Started at about 65% SOC. Alternator did put out +100A for the first 2 hours.

Every time I read “my lead acid are full by noon with solar” I wonder how that is possible?

[motion30]

Originally Posted by Oceansailor

I have 8xT105. Have never got much less than 0.7%. And that takes two days!
First day and charge cycle I end up around 1.5%. Let them sit in float over night. Next day I start a new charge cycle and normally get to 0.7%

Today I have been motoring 6 hours and are down to 2%.

Started at about 65% SOC. Alternator did put out +100A for the first 2 hours.

Every time I read “my lead acid are full by noon with solar” I wonder how that is possible?

Trojen says between 1 and 3 percent. On the 105s. I figure they must know something about these batteries so I will trust their recommendation

[kenbo]

Originally Posted by john61ct

On the contrary, every maker whose true deep-cycling product is worth buying not only publishes their detailed specs, but has technically competent CS staff available to discuss the details with customers.

If they don't you should avoid purchasing their product.

Yes Lifeline may be better than most.

The 0.005C number is common for FLA, but yes a bit stringent for VRLA types where you don't want to overcharge and lose electrolyte.

Going longer results in a higher level 100%, while stopping earlier (higher C rate) will not fight sulfation as well.

For FLA measuring specific gravity with a hydrometer is an alternative to using the endAmps spec.

I'm only familiar with East Penn, US Battery and Trojan. But for all three, none state 0.5% 20C as an end point for absorption. EPM's is stated as delta a/delta t (stop when the current doesnt change after an hour), US Battery is 3% and Trojan is 1-3%.

Look flooded batteries are consumable items, treat them kindly and they'll give good service and good value. But this obsession with 0.5% is bordering on pedantic IMO.

Also the inventor of the original Smart Gauge has a short paper on why specific gravity is not an accurate/reliable measure of SOC. Here it is http://www.smartgauge.co.uk/sg_soc.html

[kenbo]

SB1 in the case you presented I'd say your as charged as your going to get under your current charge parameters. If the charge amps don't fall at all after 2 hours you're running the risk of corroding or shedding the positive plates IMO.

[john61ct]

No one is "obsessed" with any particular spec, not sure where you get that idea.

As stated by many already, the 0.005C does happen to be a recommendation by EPM tech support.

Their main termination standard you and I have already referenced is indeed the one they publish in writing, but there are many ways to get to the same point.

U.S Battery has three separate ones to use in their docs, leaving the choice to the user. The one referencing 0.03C is not the termination point, there is an additional CC "finishing stage" after that as well.

[Oceansailor]

I do not disagree that 0.5 % is obsession. But as Iive on the hook I try to equalize my batteries when on shore power. Before I start that the equalizing charge I want them as fully charged as possible. All batteries are consumable items. You buy, enjoy and when finished buy new again.

[sailorboy1]

Originally Posted by motion30

Trojen says between 1 and 3 percent. On the 105s. I figure they must know something about these batteries so I will trust their recommendation

I did Trojan says 1-3% right at start.

You would think going the manufacturer recommendation route would be the way wouldn't you. But thrown into the mix of the petty barbs and insults aimed at me it appears “experts” chose to accept which parts of manufacturer specs they recommend and repeat.

[kenbo]

Originally Posted by john61ct

No one is "obsessed" with any particular spec, not sure where you get that idea.

As stated by many already, the 0.005C does happen to be a recommendation by EPM tech support.

Their main termination standard you and I have already referenced is indeed the one they publish in writing, but there are many ways to get to the same point.

U.S Battery has three separate ones to use in their docs, leaving the choice to the user. The one referencing 0.03C is not the termination point, there is an additional CC "finishing stage" after that as well.

I'm not going to get into a pas de deux with you. I mentioned obsession since that's your most (read always) stated end point for terminating absorption. But it's not stated anywhere that I can find in the manufacture's literature. I could look up Crown and Rolls but I'm not. What's in your notes from private conversations with tech reps is not in the public domain.

[Dsanduril]

Originally Posted by john61ct

On the contrary, every maker whose true deep-cycling product is worth buying not only publishes their detailed specs, but has technically competent CS staff available to discuss the details with customers.
...
The 0.005C number is common for FLA, but yes a bit stringent for VRLA types where you don't want to overcharge and lose electrolyte.
...

Originally Posted by john61ct

As stated by many already, the 0.005C does happen to be a recommendation by EPM tech support.

Yes, all the decent battery manufacturers post reasonably complete information, and not a single one says to charge FLA to 0.005C or C20/200 or 0.5% C20. Links to Trojan (previously), Rolls, EPM all say some number > 1% of C20 or (EPM) no change in acceptance current.

The OP specifically asked for a technical reference from one of those decent battery manufacturers that says 0.005C and yet the only references provided for that value have been anecdotal "I heard it from a tech support guy."

Still interested to see it in writing from one of the reputable manufacturers (the one's whose batteries are worth buying).

[Mike Banks]

Once your batteries reach full charge (it was easier with flooded cells, one simply used a hydrometer) any excess current at 14 volts is simply turning your electrolyte into a more concentrated form and releasing hydrogen and oxygen gas, never a good combination, although some sealed batteries use catalytic recombination of these gasses.

I work on the voltage delivered by the batteries premise, after charging has ceased for about half an hour or so and battery has cooled a bit. If the no-load voltage is not optimum for your type of battery--charge it some more. If no difference after a couple of hours and your no-load battery voltage is still below par, maybe some replacement is required or your measurements are crap. Try another meter--

[sailorboy1]

I wonder how many people really follow ALL of their battery manufacturers specs. I definitely don’t on my T105s.

- absorption voltage varies 14.6 - 14.82, so Ive used 14.6 and 14.8 (this makes a lot of gas) but it all depends on which literature you believe because Trojan isn't being consistent

- charging % of C20 they say max is 13%, if i use the battery charger i put in 16+%, if i turn on the engine at same time i put in 25%

- time at absorption 4 hours max, been lots of threads and posts here saying to basically just disregard this

- equalize charge 16.2, well i can only do that if everything works out with the sun in the afternoon so dont think it has ever been done

I also learned than that 1-3% of C20 for finish charge amps really varies with which absorption voltage. 2% at 14.6 becomes 3% at 14.8, even if you had been at than 2% for 3 hours. This of course is expected that more voltage mans higher current. But it works out that you can be “finished” if using 14.6 but not at 14.8.

Oh well

[ramblinrod]

Originally Posted by sailorboy1

I've read it here lots of time and accepted it and even repeated it.

Batteries aren't really 100% charged till they will only accept 0.5% of the 20C capacity at absorption voltage, measured as amps.

Who can provide a link to a battery manufacturer or similar that says this?

Trojan says 1-3%. Victron in my battery monitor directions say 4%. Battery University says 3-5%.

My batteries (T105s) have been at 14.8V for 2 hours accepting 2.2% steady. Am I charged? Trojan also says to not do more than 4 hours at absorption, if I'm still at 2% at end of that should I keep charging at absorption voltage?

I'm only using my batteries as an example, the real questions is - Who can provide a true technical reference that says 0.5% of the 20C AH capacity as as an amperage for 100% state of charge?

The real issue is, what happens when you have a load that is higher than the absorption cut-off current? Is absorption voltage held on the batteries indefinitely. (Read your charger manual, and if not clear, contact the manufacturer.)

[john61ct]

Well some are not worth paying attention to, so no need to be slavish or anxious about them all.

Higher end of the voltage range is healthier, especially for FLA.

Letting CV/Absorb go **way** too long could be a problem for sealed, while FLA just keep them watered.

No such thing as too much current with all lead except maybe GEL, AGM and FLA are basically self-regulating.

Equalizing is best done on shore power.

Obviously there may be bits that just aren't practical.

Do the best you can, no stress.

So many owners just don't care if they have to replace at 3-4 years rather than 6-8, perfectly valid POV.

[a64pilot]

I believe the only time you really need to use end amps is with an AGM or Gel battery, and that’s because of course you can’t check specific gravity of the acid.
I would assume for batteries that you can check specific gravity, that method maybe out to be primary, with end amps as a back up as who checks SG of every battery at every charge?

Or said another way if your SG is correct and your at 3%, fine, but if it’s a little low, keep charging until either end amps stop dropping or SG is correct.
If end amps stop dropping and SG is low, then maybe an equalization ought to be done.
However I don’t see how anyone can equalize on Solar, most of the world has a hard time getting to full charge on Solar, much less holding equalization voltage for hours after the full charge.