Not a TriMetric, but for $20 might be worth trying out...

You are right.

Generally, if you are getting near full early in the day, drop to float for the rest of the day; but if you are not getting to near full until late in the day, just leave it at Vabs till dark and start over in the morning.

If you want to keep the voltage high as long as possible, you can also adjust your float voltage to as high as it will go so the drop from Vabs will be small.

For storage the batts will be full so you want to drop to float right away. With an adjustable voltage, you can make your storage Vabs the same as your float voltage so it won't spend any time at the higher voltage.

As you indicate there is no "set and forget" in this solar game.

Thanks for the feedback. My setup is 2x6V GC batteries for just over 200 Ah capacity. With my PWM solar charging setup, I can see 15A of charging under ideal situations in the summer but only 5A or so in winter (storage). Panels are mounted fixed and flat. When thought about from a duty cycle standpoint, I feel like I should be thinking about the two seasons differently with respect to transitioning from absorption to float.

ewarnerusa wrote:

MrWizard wrote:
....6v flooded GC, i would guessitmate 2amps at 14.0v means totally full...

Sorry to thread jack, but I'd like to ask a follow up to this statement. Any guesstimate of fully charged amp acceptance for pair of 6V flooded at a 14.8V (temp corrected) absorption setpoint? My PWM controller uses time at or below a percent duty cycle for the absorption to float transition and it seems like I could use this info to make a meaningful full SOC transition to float.

I'm using 3A at 14.8V for ~400Ah, four GC2s.
3A tells the solar charger to switch to float.

IOW my batteries are sitting at 14.8V a lot longer than most folks. And when we're using Amps, the batteries can take all day to get there, or not. Of course at night, they can rest (settling down to 12.x depending upon what we're doing).

Only check and fill the water twice a year. And I do equalize after a particularly long and brutal period of cold, grey skies, furnace usage and incomplete charges, when Sol lets me.

Think I do this (14.8V down to 3A) because of Mex's "Top Charge" diatribe. Don't have a charger or power supply that can do top charging, so this is my approximation?

I understand the question, but another factor is how much 6s gas, especially older ones like mine (5 years)

I found in summer on solar with long sunny days in a row and set to 14.8, that the batts got to 14.8 mid-day so that left a long time still to go in daylight at 14.8 while amps tapered. I was losing "water" more than I liked, so I dropped to 13.6 soon after reaching 14.8.

The batts still got to full that day as measured by hydrometer, but did not lose nearly so much water per week.

A side note-- my old rule was they were at 90% SOC when amps had tapered to 5 amps per battery at 14.4/5 volts. When I increased charging with 14.8v, the amps per battery at 90% was more, but I didn't have a measurement. I have enough evidence now to use 8 amps per battery as my new "marker" for when to stop the gen at estimated 90% SOC instead of 5.

Essentially that means the taper curve is steeper with 14.8 getting to full but by the time you are at 98% or so nearing 100, the amps will be so low the amps difference will be small between 14.4 and 14.8 by then.

MrWizard wrote:
....6v flooded GC, i would guessitmate 2amps at 14.0v means totally full...

Sorry to thread jack, but I'd like to ask a follow up to this statement. Any guesstimate of fully charged amp acceptance for pair of 6V flooded at a 14.8V (temp corrected) absorption setpoint? My PWM controller uses time at or below a percent duty cycle for the absorption to float transition and it seems like I could use this info to make a meaningful full SOC transition to float.

Both of the last two posts indicate that AGMs do need an "overcharge" every so often. Been a lot of threads about that arguing if true or not, depending on the brand or type of AGM etc etc. Maybe time for another go round on that topic in a new thread with this latest actual measured evidence.
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Even the Trimetric AH counter gets out of whack between its AH counter and the SOC of the batts. It has a way to adjust the default heat loss allowance during a recharge to make resets needed less often, but it is still going to get off track. Outside temps keep changing and battery capacity keeps changing with age.

While on solar with the batts getting full every day, I reset the Trimettic AH counter every evening when it gets dark--by then the counter is well above zero into positive numbers.

I have checked and when the AH counter is above about plus 15, the SG is at baseline which is True Full. So I could adjust for that. But that amount above zero is a variable for complete accuracy. Don't need that much accuracy while camping. Everything is a variable. Every day is different for how much sun how much battery usage.

The way to tell you are really "full" with flooded batts is with an hydrometer. AGMs require more indirect evidence that most RVers probably aren't much "into" gathering. Still, the AGMs do have many advantages. In winter I would keep mine inside the RV where it is warm in cold weather to keep their capacity up. (Ignoring any risk of them venting) Can't do that with Wets (fumes)

Even with more professional battery monitors, The human who believes the readings without any occasional supporting evidence is misguided.

I always look for how much amps the battery is accepting at absorption voltage on my AGM.

Sometimes the Ah counter is very close, other times it drifts and I reset it.

Also of consequence is how many cycles it has accumulated without a true full charge, or in the case of my TPPL AGM, how many cycles without the higher amp recharge.

Still a great tool to have, even if I don't trust the % from full or AH from full screens completely

the only problem i had with mine, was i tried to calibrate at low amps
and threw it out of whack

after i reset it, and left it alone it has been find

last week, i noticed, i was having problem returning full amp hrs,
charging was tapering before ampHr capacity had returned to the set amount
but it was not the meter, it was the batteries

after i zapped the batteries at 15.4v for 15 minutes, they accepted the ampHrs and recharged to the full capacity count and reach the 1amp per battery at 14.4v, that is my indicator of full charge

it was the batteries not the meter

its a straight matter of Physics and chemistry

if you remove 100ampHrs it will take 105~110 amphrs to reach full 'SOC Chemical balance'
this meter will Not indicate going over aka returning extra (the counter stops and says XXXamphrs 100%
BUT it will indicate the amp flow, and that the batteries are still accepting amps after the capacity counter says full, and show how many amps the batteries are taking (its just the counter has stopped)
not a problem for me, i just watch the amps charge rate they are taking,
(5)AGM batteries, so when at 5amps or less at 14.4v, they are full

(2) 6v flooded GC, i would guessitmate 2amps at 14.0v means totally full

right this minute, the amp counter has returned to full capacity, showing 100% ,
BUT 14.18v, and charge rate of 4.2~5.3 amps,, I know they are not at peak SOC and have a tiny ways to go, but very very close

Yes, I did calibrate them. But they seemed to wander. They are not bad as long as you like to tinker. I just wasn't satisfied.

Snowman9000 wrote:
I have not read the whole thread.

I installed two meters about the same as Mr Wizard got. I had a 200A one and a smaller one, 30 or 50A, I can't recall exactly. One for the whole house and one for the solar by itself.

After using them dry camping a few weeks last winter, I feel they are not all that accurate at measuring amps, unless you are in their sweet spot for current draw. I mean, they are "okay", barely. They will give you a rough idea of what you are charging or drawing.
...

Their Amp reading does have to be calibrated.

When I first installed my 100A version I only roughly calibrated to ~15A max. It was fine for our first outings, but now with our heavier loads, the Ah are way off.

One of my first projects when we return from this trip is to recalibrate, especially closer to our max expected load (~90A). I have a clamp-on Ammeter that will hopefully be a good reference.