Mex's Flash?

[BFL13]

Does "Flash charging" mean we (some of us anyway) are wrong to hate it when the PowerMax or Iota converters drop their voltages so soon for the absorption stage?

In another thread Mex says, "A flash formula is to achieve absorbsion limit (I prefer 14.8) as fast as possible then maintain it there until all battery cells start to bubble lightly, then back off to an intermediate voltage, perhaps 14.0 volts. The bubbling will subside at the lower voltage, but when it resumes, drop the charge rate to float."

I think Mex is saying he likes to have no constant amps stage at all, but have such a high charging rate (charging amps wrt size of bank in AH, that the voltage spikes to the top immediately and amps taper while voltage remains constant at the high point for a time after that

(This thread linked below is about something else, but I need to refer to the graphs in its OP and this is the easiest way to show them with my computer lack of skill.)

So that would look like the later recharges in the second and third graphs here I think, where the bank has shrunk in AH, making the charging rate higher, and so the constant amps stage is lost.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/24849190.cfm

But then he says to wait during the absorption stage till bubbles start and then drop the voltage. BUT that means when you reach "gassing voltage", which I thought was when you first reach that (14.x volts) which in Mex's case would be right away not later.

Or are we getting into the tiny bubbles counting again? I don't think taking the caps off is practical or desirable for normal recharging, but ???

I don't know if Mex's flash profile would get you high enough in SOC before the bubbles make you lower the voltage. I would want to keep the voltage at its high point until at 90% SOC anyway (doing 50-90s)

You wouldn't do a generator recharge above 90% SOC, so that seems to suggest Mex lowers the voltage sooner. But that would reduce the amps acceptance rate, and slow down the recharge, but Mex says the flash method is the fastest.

So, Mex, what is it that I am missing ? Thanks

[MEXICOWANDERER]

Where I camp down here, there is far far less light than this. When I parked a bus in the sun at Xcalak I had a 24/7 generator and THREE roof airs going to keep interior temps in the 80's and humidity in the sixties. Maybe it's different up there, running a generator marathon style down here is a loser. Fuel, access to fuel, fuel cost make it ridiculous. Slow charging a battery bank is like barbecuing a steak one briquette at a time.

I had neighbor's kids make a palm frond and bamboo cocoon for the bus. For the shade. Solar works when it can work. Where it can work.

[KJINTF]

No flashlight aka torch needed
Why would anyone ever stay in a place like that
Might as well go to a trailer park and pay home owners dues

[MEXICOWANDERER]

Anyone got a flashlight? I need to find my solar panels!

[pianotuna]

If you have 150 watts of solar per 100 amp-hours of battery, a great controller, and decent solar conditions shore power is not much of an issue. It may have a long pay back at 12 cents per kwh.

Perhaps when LI becomes main stream and inexpensive we can all leave generators at home.

[MEXICOWANDERER]

I had my attention pulled 16-different ways yesterday and failed to answer a perfectly valid question...

"What about generated heat?"

How many calories does it take to raise battery components by say a Delta T of 30 degrees? The difference between air temp and electrolyte temp...

Less emissions than what it takes to charge a battery by the V/max method. By the time the battery is even thinking of getting too warm the charge is over with. The intermediate level of 14.0 allows the electrolyte to cool down.

Batteries that DO raise temperature excessively HAVE SOMETHING WRONG WITH THEM. They are either bad or sulfated.

And hysteresis absolutely does enter the picture. V/max charging accentuates this variance. But a fast dip after the protocol finishes and rests will confirm the validity of the process. The process is an algorithm.

Algorithm - Wikipedia, the free encyclopedia


https://en.wikipedia.org/wiki/Algorithm
Wikipedia
Jump to Informal definition - In mathematics and computer science, an algorithm ( i/?æl??r?ð?m/ AL-g?-ri-dh?m) is a self-contained step-by-step set of operations to be performed. Algorithms exist that perform calculation, data processing, and automated reasoning.

If you're camped where fuel is NOT an issue, price is of no object, neighbors are generator noise tolerant, then charging at V/max may be completely idiotic reasoning.

Nothing will EVER replace the ease and compliance of Power Pedestal battery management. But then why not wander across the city and rent a penthouse suite with room service and a wet bar? To each their own...

[BFL13]

Reviewing the last 50-90 I did camping in October, I don't see where I can apply the Flash procedure anyway. Here is a quick look (without an ugly graph)

Bank of four 6s, temp 9C/48F, estimated Bank size at the time approx. 400AH. Charging amps going in 155a set at 15v (=14.8 at that temp) Bank down 192AH at start = 52% SOC

Time, amps, battV, AH replaced according to Trimetric ( including using its heat factor) Note- only one decimal place V makes it choppy.

0900, 155, 14.0, -
0915, 141, 14.2, -
0930, 117, 14.3/4, 77
0945, 99, 14.4,-
1000, 69, 14.4, 117
1033, 42, 14.5, -
1100, 27, 14.6, 159 (if 159 is 40% then 100% is 398AH) so in ballpark for estimated bank size.

Ok, so the thing is, battery voltage only got up to near 14.7 when charger voltage was 15, at the end of the two hours at about 90% SOC.

So when would I have seen the bubbles and lowered the charger voltage?

I would have to trust my home testing results as my "marker" for whether I got a 50-90 done or not instead of the Tri if I wanted to treat the batts better without so much gassing. (On the Tri it would look like I didn't get as many AH in during the 2 hours)

As it is I don't know how much bubbling I was getting in that recharge, so it might not be so bad anyway. Have to check for bubbles next time.

[NinerBikes]

BFL13 wrote:
Sounds good, but I expect "SG lag" to ruin that plan. Worth a try at home for a test run though.

http://www.engineersedge.com/battery/specific_gravity_battery.htm

True, but even with the lag, you will get a timer setting, and SG reading (even with lag) and an idea of when to modify and drop your voltage.

The key is to know when the bubbling is getting too vigorous, the voltage at the battery terminals either climbing too fast, or how much time V at the battery terminal has been at 14.8V, that it's time to go to absorption voltage. Call it trends and tendencies. You don't have to get it perfect, close is good enough, before the temp of the battery electrolyte gets too hot. All these observation signs are correlated, there's multiple ways to skin a cat, or look at one observation or reading vs another, to know when to cut the generator or drop the voltage from 14.8V, and that bulk charging stage is over, next step, absorption charging voltage is now needed.

None of us mere mortals with batteries will ever get to the level of observations or perfection as MW does when it comes to balancing all the variables of costs of fuel, oil, motor time, rebuilds, cost of replacement batteries, replacement fuel, replacement generators.

We can do our best and strive to be close... take notes, learn, and try to do better. But that's about it... a man has to know his limits, try to break them to do better, without failing and doing destruction while trying. It's all about trade offs, even with my little Honda and single telecom battery. I charge hard, it's not the money issue or cost of repair to me... my priority while camping is quiet time... more than listening to any generator... so when mine runs, the sooner it gets shut off, and I get quiet time back, the better... my priority... YMMV on what is important to you.

[BFL13]

Sounds good, but I expect "SG lag" to ruin that plan. Worth a try at home for a test run though.

http://www.engineersedge.com/battery/specific_gravity_battery.htm

[NinerBikes]

BFL13 wrote:
So, if you don't have enough charger/generator to get the batts to instant Vabs, can you apply this idea when there is a time while the battery rises to Vabs and then starts the absorption stage? I think I missed that info exactly.

So if I am doing my 50-90 and it gets to 75% when the battery reaches 14.8, I should lift the caps and start looking at bubbles. If it is only bubbling hardly any, I can keep going at 14.8 till it is bubbling "lightly" and then drop the voltage. So now I am at maybe 80% SOC, then do the 80-90 at the lower voltage? (but same amps into the battery so no time is lost?)

Or is it too late because it will already be bubbling "lightly" when it finally gets to 14.8?

Just experiment and take notes on when your battery starts bubbling, and how gentle to how vigorous your battery is bubbling, and add in a few specific gravity readings on the cells. By the time your SG is at 1.250, look at if it's bubbling. Keep reading SG until it's 1.260 and note the level of bubbling, Read the SG at 1.265 and look at how it bubbles, all at 14.8V. Somewhere in there, in that range, you'll know what point to shut off the 14.8V and charge at a lower voltage, say 13.8 to 14.0V, for absorption charging. Also note the time spent charging at 14.8 V when you do your SG readings. It should be clear from the above when the time spent charging at 14.8V is over.

You should very clearly notice a change in the level of, or how vigorous the cells are bubbling, at those states of Specific Gravity at 14.8V. Then compare it with how the battery bubbles at 14.8V with a Specific Gravity of 1.240.

If a SG of 1.210 is 50% charged and a SG of 1.275 to 1.280 is 100% charged, what would you estimate the SG to be at 80% SOC? 90% SOC. 80 to 90% is where the battery starts getting stubborn, showing resistance, and needing time at lower voltage instead of brute force voltage/amperage... the chemistry inside the battery is that it gets harder for sulfur on lead plates to find free hydrogen and oxygen in the electorlyte to bond to. Hence, bubbling is stirring up the electrolyte so that the free hydrogen and oxygen can find the sulfur on the lead plates, bond with it, and remove it. There's less sulfur to bond with, hence the charge rate and ability to take amps is reduced. Now it's a time issue, not voltage or amperage issue, to finish off charging the battery, it can't be rushed. The generator is inefficient at this point of the charge cycle.

That's the Dummy's version of how it works... MW could give you the full blown Calculus and derivative model of finding the area under the curve on that charge cycle... me, I just know that like most things in life, the closer you get to full, or 100% perfection, the harder it gets, the more expensive it gets, to get the least amount of percentage of gain. Just the way it is.

Batteries bubbling while recharging is a qualitative judgement... voltage, time, amps, and specific gravity readings are quantitative. Until you get a better feel for how all the quantitative readings mesh together, and some experience, it makes qualitative judgement difficult, just looking at bubbles.

[BFL13]

So, if you don't have enough charger/generator to get the batts to instant Vabs, can you apply this idea when there is a time while the battery rises to Vabs and then starts the absorption stage? I think I missed that info exactly.

So if I am doing my 50-90 and it gets to 75% when the battery reaches 14.8, I should lift the caps and start looking at bubbles. If it is only bubbling hardly any, I can keep going at 14.8 till it is bubbling "lightly" and then drop the voltage. So now I am at maybe 80% SOC, then do the 80-90 at the lower voltage? (but same amps into the battery so no time is lost?)

Or is it too late because it will already be bubbling "lightly" when it finally gets to 14.8?

[Salvo]

I got my BS meter on high alert.

Again, we're only talking about first-order approximations. No need to go into any mumbo-jumbo.

I use the two-tier dc load method to calculate battery impedance. It is accurate and well accepted in the technical (battery) community.

BTW, you've side-step my question. What's the dominate factor causing battery voltage to instantaneous rise when a current step is applied to a battery?

MEXICOWANDERER wrote:
Ummmm this is to assssume the electrolyte is not a component in determining impedance? The great error is this assumption. The resolving of which would require perhaps 20 samplings per minute to compensate and develop an algorithm. Are you ready to develop an impedance sampler/controller for the process of charging? I'm not. Try Sandia National Labs.

[MEXICOWANDERER]

PT. Impedance? Measures and CONTROLS selectable voltage?

All the E=MC2 workups in the world do not prove or disprove a flooded battery charge regimen. It takes actual authentic molecules in action and measuring devices. This was the epitome of hard earned lessons that I had to swallow some forty years ago. Theory makes for a great start-off guideline. Actually performing the protocol reveals hidden flaws and permutations in a seeming simple theory. Quite a revelation for a young smartass engineer.

[pianotuna]

Hi,

The smartgauge samples a huge number of per second. It works well with everything except LI jars.

[MEXICOWANDERER]

Ummmm this is to assssume the electrolyte is not a component in determining impedance? The great error is this assumption. The resolving of which would require perhaps 20 samplings per minute to compensate and develop an algorithm. Are you ready to develop an impedance sampler/controller for the process of charging? I'm not. Try Sandia National Labs.