Mex's Flash?

Yeah I can just imagine me paddling around in Englishman Falls B.C. I took a drink in August and it made my teeth hurt. Solar is excellent for topping off the batteries. Like it or not, that last few few hundredths specific gravity to be gained is a scream and yell session but cannot be constantly ignored. I am going to use the six panels atop Quicksilver to power an inverter, then a transformer and send 600 volts up the hill (330') to be reduced then feed a 600 watt DROK at 20 amperes top-off. Less than 2-hours a day thanks to rain-forest shade, but heck it's better than nothing, right?

Shaded off grid is misery incarnate when sunshine is available 33 meters straight up. But I do not want the dominant sunlight vegetation taking over cleared sunlit patches. It's a sticky vine with hairs that sticks to everything like glue. Will not grow in the shade. Liberal application of crushed oyster shell and rock salt keeps Quicksilver free of this nightmare. Oh yeah I forgot, the local fingernail-length red ants use the sticky vine for an elevated highway. I pay the girls to make careful rings of diatomaceous earth around each nest entrance but the fight is continuous. I don't want the salt to turn the property into Bonneville Flats so I am careful how much I use. Danged hens consume the oyster shell grit.

Life in a rain-forest...

My gen time motivation is different as to why I want to keep it short.

First, there is the campground time limit of 9-11am to do my 50-90 so I don't want to slow down the recharge half way along as I was worried the Flash procedure might require. I think I now see how that really works.

Second motivation is where in a different campground in summer we are allowed gen from 10am-2pm. This is lots of time to do my 50-90 but I don't want to be stuck there battery charging all that time. Once it is done I am free to go up to the lake for a swim :) So get the gen recharge over with ASAP.

Solar in summer means hardly any gen time needed at all, so more swimming or whatever.

Connect enough chargers to obtain 14.8 volts INSTANTLY

ABSOLUTE FACT different batteries different banks, will take a different amount of time to achieve light bubbling at 14.8 volts. This is specifically why I denoted "CHECK BATTERIES TO DETERMINE WHEN LIGHT BUBBLING IS EVIDENT"

My battery bank requires more or less 408 amperes to achieve 29.6 volts (my vmax voltage is less because of high ambient temps - but let's skip that for now).

It takes what it takes. Obviously doing this takes a suitable generator and charging system. The larger the generator the more relevant this becomes because of run-time cost. In my case it is a water cooled 6-cyl Kubota twisting a 12.5 Kw KATO. The generator is laughably de-rated and the Kubota is a 38 HP engine but operating at 1,200 RPM, with turbocharging added for low end power.

About 14,600 VA total. The gen has to go online slowly - about 12 minutes of ramping-up using the 4024 Trace as a lead-in to get oil temps stabilized. Remember I am starting with an average 88F ambient air temp. This is no cheapo setup. The generator has a lube oil cooler, with a 24-volt .5 HP pre-lube pump, a six row push radiator. A C750L Luber Finer element works in conjunction with an oil filter adapter and B88 oil filter for an 855 Cummins engine (the same as Quicksilver).

REGARDLESS! Diesel fuel down here is $3.33 gallon at the present exchange rate. When the Kubota gets cranked up it goes to work. The 400-amp charging rate can be supplemented by the Lombordini 385 amps engine if the batteries were discharged more than 60% SOC.

I've run the numbers on this and other Vmax charging installations so many times it isn't funny. Should diesel prices drop to $2.05 gallon or cheaper the tradeoff would become less clear, at $1.60 gallon, the crunching favors a 50% Vmax charge rate to increase battery life SLIGHTLY.

Now, someone running a teeny Honda 2000 and charger, and a single or dual RV batteries isn't going to go bananas, over savings. As a matter of fact, pseudo deep cycle car-jar batteries do not like to be Vmax charged nearly as much as thicker plate "genuine" RV batteries.

One of the components of safe and sane battery charging is cell temperature. It is safe to raise cell temps to 110F but not above this. Cell temperature is a must-check when configuring a Vmax charge regimen. But and consider this a BUT BUT BUT, high cell temps and "LIGHT BUBBLING" do not fit into the same space.

This formula was worked out during innumerable trial and error workups. It isn't derived from E=MC2 wishful thinking or conjecture. Nor is or was the number crunching for expense.

The main point is to CHARGE THE BATTERIES CORRECTLY meaning not under nor overcharged. The gen charging runtime (Vmax) is a derivative, to minimize fuel and wear and tear expenses. In my case it saves many hundreds, sometimes more than a thousand dollars in annual fuel cost. The nearest diesel is a 78 mile round trip drive. Times the fuel savings by the 22-year lifespan so-far of the system and you'll get the idea quickly.

I have never quite understood the notion of "how many amps does it take to support the voltage"

I set the charger voltage and how many amps I get depends on the battery at anything below charger max amps limit. I have no way to change how many amps that is except to change the voltage on the charger which also changes the voltage on the battery.

I don't know how you can see voltage falling off when the charger is set to that constant voltage.

I can see how the "marker" for when to stop the gen could change when you use the amps amount as they taper, like my 5 amps per 110AH = 90% SOC at 14.5v rule of thumb. 220AH would be at 10 amps. If the battery has lost AH, then the amps at 90% would be lower than usual. But that is still at 14.5 volts.

I think the actual time it takes to get the gassing a happenin will be different for each battery, and charging amps, and temperature, and battery health. So any data collected and reported here, might not have much validity for another system at a different point in time and place.

The beauty of an Ammeter on an adjustable voltage charging source is one can see the results, directly of raising or lowering voltage. But one needs a voltmeter on the battery terminals, not one just inline on the possibly undersized overlength cabling.

I've been finding that a while after I first get my AGM to 14.46, and amps start tapering into the low 30amp range, if I reduce voltage to 14.0 the amps flowing at 14.0 are not much less, perhaps 2 to 3 less, than what was required to hold 14.46.

Same general test on the screwy31 and the amps it accepted at 14.0 was perhaps half of what it took at 14.9v iirc.

I think for generator charging, you'll still want to hold absorption voltage at the battery terminals for as long as you are willing to run the generator. But next time your amps are tapering at 14.8v, try lowering voltage to 14.0 and see the difference on your trimetric. If it is not a huge difference, then perhaps 14v would be less abusive and only marginally slower.

I move my 10 turn pot way past 15volts as measured by the 8awg leaded wattmeter when I am seeking to get the battery to 14.7 as fast as possible as I have some 8 gauge and a few connectors in route to battery terminals from the Meanwell.

If I set it to 14.7 unloaded, then plug into the batteries, amps start tapering earlier, So I crank it way past its unloaded voltage to keep that 40 amps flowing until the battery terminals read 14.7, or Whatever voltage I choose.

I'll bump off the voltage as the amps taper and the voltage drop becomes less of a factor, IF the time I have to recharge is limited.

Turning the voltage dial higher is easier than upgrading the charging circuit in my case. A little less convenient.

Now, if I had an Amperage potentiometer that could go from 0 to 40 amps, I'd never stop laughing maniacally.

Perhaps the Fanless Meanwell hep-600-15 which claims to adjust current from 18 to 36 amps and also has constant current limiting on overload:

http://www.meanwell.com/search/HEP-600/HEP-600-spec.pdf

My 500 watt meanwell will output 600 watts so I imaging this 600 watt unit will also be able to exceed its rating

My observations with a 150 AH Trojan T-1275 that was beat up when I got it free, and I got another 2 years out of it, all on Honda Eu2000i generator time and solar panels, with an Adjustable Voltage MegaWatt 30 amp power supply unit, and an RC watt meter.

I'd pull 35-50 amps a day out of the battery... 60-70 SOC most mornings. RC watt meter told me voltage, and amps the battery was taking and cumulative amps charging.

Usually an hour at 14.8 to an hour and 15 to an hour and 20 was enough to get my amp charge rate to drop to 9 or 10 amps, off from the 29 to 30 amps it would take at first charging for 3 or 4 minutes.

Tiny bubbles after the first 15 or 20 minutes, very, very very tiny bubbles. At an hour to hour 15, when the amps charging rate was 9-10 amps, I shut the generator down. That was it, the end of bulk charging.

150w Solar panel was then employed, usually set at 14.0V. 8.8 Amps was possible from the panel, but more normal was 6 to 6.5 since the panel was portable and aimed almost always at the sun. 2 or 3 hours would drop the amperage down to about 4.5 Amp being taken. At this time, a peek inside would reveal slightly bigger champagne bubbles, a little bit more vigorous. Time to reset the charge controller to 13.6V for the rest of the day on solar.

I always knew that no matter what, my trailer was always drawing 1 AH in parasitic draw, all day long, with nothing on or running.

A week of this, and time to mix things up, charge on the generator first thing in the cold morning at 15.0V, for 2 hours on the generator, a "top" charge and 16.0V with the solar panel for 90 to 150 minutes, for desulphation or equalization charging.

This almost always tuned up the battery, Specific gravity would be 1.275 to 1.280, with the weakest cell, doing 1.250 to 1.260. The T-1275 was an anomaly with this.

This battery saw 500 -600 recharge cycles in a golf cart before I got it. I'd say in 2 years since I got it, at the end, I added 100-120 recharge cycles to it.

With generators, I don't worry about tiny champagne bubbles when recharging at 14.8V. I begin to get concerned when they get soda pop sized like soda water in a clear glass, that's when I try to time it to drop the voltage. That or when the battery won't take something like a c/15 charge rate, or 10 amps on the RC watt meter. Time to go to the solar panel, drop the voltage then and slow the take rate down, letting the battery pass a 90% state of charge without bubbling and a c/15 charge rate for a few hours.

My observation with an RC watt meter is that the take rate in amps will tell you a lot about when to drop the voltage, further dropping the amp take rate. About 9 to 10 amps at 14.8V on a 150 Amp Hour battery with my 30 amp Megawatt was that cut off point, regardless of time on the generator. When it got that low, it was time to cut the generator and go solar. This was with a high 6% antimony sweeper /golf cart battery, that was very beat up. They will bubble, a lot, and they will use water, but a lot less water if you only use voltage and amps as stated, the RC wattmeter, for me, worked almost as well as the acid dip and an SG reading. Taking some regular notes and responses tells one a lot. So does the stench of rotten eggs when a battery is dying, or surprise corrosion that starts growing on the battery terminals all of a sudden, from sulfuric acid off gassing. Of to the recycler it goes, then.


Now I have a Telecom AGM "acid rich" 1.300 SG battery. And a 10 turn pot on the MegaWatt. Voltage sits at 14.4V... and I watch the amps drops that the MegaWatt puts out, while at home, on the grid. When the RC watt meter says .13 Amps for take rate, she's topped off and ready for storage. Usually takes 3 to 4 hours to do this after a 2 week long trip in the travel trailer.

AGM batteries are a whole other world, compared to flooded lead acid batteries, which seem to have huge losses while recharging, due to resistance to charging in the battery.

Didn't see my question (poorly asked) answered. Try again here---

I can't get the battery voltage to spike to 14.8 as my Vmax unless I hit a 50% SOC battery with maybe a 45% charging rate or so. Lower charging rate will mean it accepts the charger's max amps steady (constant amps with current-limited charger) for a time and then it gets to 14.8 at a higher SOC later on. (The lower the charging rate, the higher the SOC before it gets to 14.8, and longer time before it gets there and vv)

I have a bank of four 6s, call it 440AH, and I can muster 155 charging amps, so that is a 35% charging rate. I will not spike to 14.8 right off, I would need more charging amps going in.

But let's pretend I have enough charging amps and generator to run that many amps on my size of bank so it does spike to 14.8 right away.

I got from above reply that bubbles will not start yet, but I know amps will be tapering at the constant 14.8. No problem so far for fastest charging.

The question is---how far up in SOC will the battery bank be by the time the bubbles are enough to reduce the voltage and so the amps?

I am worried that it might only be 70% SOC (half of a 50-90 done) and I am shooting for 90%. I think Mex is saying that since it is already gassing, some of the amps is being wasted making heat, so it doesn't hurt your charging time to reduce the voltage and lower the gassing.

BUT--then how can you monitor that you are still getting the 70-90 part done just as fast by using AH counting? You do have an AH counter (Trimetric) but you don't really know how much goes for heat either way ( leaving it at 14.8 or dropping to 14.2) so how do you know when you get to 90% and can stop the Gen?

Mex says try it at home and get some before and after measurements till you get it right, and then just use the same "markers" (times, etc) when actually doing this away camping, because it will come out the same.

Has anybody done this (including Mex if he has the data) with some examples of how far you got up from 50% SOC at the 14.8 before the bubbles got going so it was time to reduce the voltage?

If it was at 90% anyway, then who cares? But if it was at 70% then it matters for how you can get from 70 to 90 as fast as just leaving it at 14.8 and never mind all the gassing.

BTW this would be another great excuse for having the adjustable voltage charger, so you can lower the Vabs to whatever you want when you want! :)

CHEMICAL REACTION

You will bring a discharged antimonial battery immediately to 14.8 volts AND IT WILL NOT BUBBLE. Not right away.

But you can take the same battery under the same conditions and apply a voltage LIMIT of 14.2 with LIMITED AMPERAGE and three days can pass and the battery will be actually gassing freely.

This is a battery generator charge issue. With power pole voltage time is not an issue. With solar it can become an Alice In Wonderland guesstimate which I will not touch with a twenty foot hotstick due to limitless permutation possibilities.

No calculation will arrive at the same conclusion as my advice. It is an electrochemical phenomenon that has to be observed by trial and error innumerable times.

Charging a battery formulae is every bit as intricate as Peukert's is for discharge. AMPLITUDE (voltage) and TIME. There are conclusions that can damage a battery. Other conclusions WILL NOT WORK. TIME SPENT AT VARIOUS VOLTAGE is the key. It cannot be done accurately with amp hour resolution but kWh is workable but too complicated except for nerds and it really is in the end, not necessary.

Some cherry pick phrases, and statements out of one of my battery charge rants and come back days later with a statement that is soooo out of context it makes me want to cry.

The instant absorbsion voltage limit recipe for charging is for GENERATOR CHARGING

BUT WAIT! THAT'S NOT ALL! THERE'S MORE

The recipe is specifically designed to reduce generator run time to a skeleton bare bones minutes.

But all of the components of the recipe must be followed without fail. A setup designed to produce instant vmax is not something that can be changed to "Well yup I'll crank 'er up and I figger three hours otter do it, then I'll come back and check for bubbling (in reality the aroma of Yellowstone National Park). A person has to pay attention, and follow advice. A SMART PERSON will realize this formula is REPEATABLE, so they check the TIME that has passed between initiation of vmax, 14.8 bubbles, and the amount of time that passes after voltage is reduced to second stage v/intermediate, and bubbling. It is REPEATABLE and PREDICTABLE. I can take a weak sister cell dip and spin the dial on the Intermatic timer, and the percentage of charge will be so close to full when I return, it freaks people out. Two stage vabs. The EXACT same protocol I have designed with BORG with.

Charging is something like deciding "Gee my car gets 12% better gas mileage at 55 than it does at 70 mph). But a three day trip turns into a four day drip and an extra hotel bill is involved. Save forty dollars on fuel and blow ninety bucks on the hotel. In this case it's fuel cost AND HASSLE versus battery life.

A GUESSTIMATE has arrived at a conclusion that a battery will live 85% of the life as a battery given manufacturer recommended 20% of amp hour vabs charge. Compare this to fuel cost. I have and I am NOT going to spend a HUNDRED DOLLARS PLUS in extra fuel to afford fifteen dollars worth of life to a battery. This does NOT COUNT the money spent and time lost to go buy more fuel or time spent and money lost to learn an early generator rebuild is going to cost hundreds perhaps a thousand dollars or more.

Charge Efficiency Ratio. Books to keep tabs of expenses. A run hour meter. And an intangible - how much does a person love to hear excessive generator use, in the case of lift and run away generators, the extra hours spent nursemaiding their safety?

When electrolysis occurs, it is a dead giveaway that excessive energy is being consumed in a battery. Some of it is a necessary abstract by-product. But when it reaches a certain point it becomes a waste, and excessive heat enters the picture. So vabs MUST BE MONITORED to make sure excessive bubbling does not occur. A Lawrence Welk Bubble Machine Bubble Counter isn't necessary. Common sense is. The 2nd stage is just as critical. When bubbling is light, the battery is telling the world, "I've had enough". Just like it did at the 14.8 volt 1st stage. Time to revert to float.

This is where a solar panel or two is par excellence. A 13.6 volt third stage for even as much as 6 hours would top the batteries off astonishingly full. So tah-dah, the generator charging should be done earlier in the day along with chores that demand 120vac appliances be used. This allows the solar to do it's chore which the fickle battery petulantly demands - that last 4% to 6% that electrochemistry resists with a jutting lower lip.