CC affecting morning V readout

[Brian53713]

As I was saying I didn't think there was a problem, I'm trying to do the evil thing of guesstimate SOC using the CC battery monitoring capabilities .
AGM. I did adjust the absorp,tion to 14.6, and Float to 13.6. But I see my charge controller has been raising it to even higher to compensate for the cold, like PN Junction chart that he provided shows. I have the luxury of turning off the lights at night when I see the battery Bank getting down to 12.56 for example, like last night, recuperated to 12.71 this morning. And I do see by the convenient monthly log Victron has, I'm getting between 5 and 7 hours of float or longer most days. Thank you all for all of the help, and quick responses.

[Sunking]

You only use temp comp on Stationary Batteries in Float Service.

[Brian53713]

Are you saying I should not adjust the absorption or float settings for the cold weather? Because the temperature compensation seems to be happening automatically from the charge controller, being located right next to the batteries.

[Mike90250]

You only use temp comp on Stationary Batteries in Float Service.

I'll disagree. I think Temp Comp should be used all the time, with the sensor mounted on the battery case or bolted to the metal terminal (follow the charge controller instructions for the final word) My batteries are 90F in the summer and 29F in the winter, and the mfg suggests temp comp for them.

[PNjunction]

As I was saying I didn't think there was a problem, I'm trying to do the evil thing of guesstimate SOC using the CC battery monitoring capabilities

Right - but it is useful to a point as long as one doesn't take it as the ultimate gospel. However, it may want you to take another look at things.

Since we know you are the original owner of a pretty fresh agm that isn't being abused, the 12.7v ocv after your normal solar charge indicates that it is not being charged back up to 100%. That means walking it down in capacity cycle by cycle as it sulfates.

Part of the problem is that it may have never gotten a decent first charge in the first place. And that retail storage, even if only for 30 days does take a toll. Most consumers don't care and just repurchase batteries sooner than later with improper maintenance. Sometimes that is the best they can do since they aren't in control of how the battery is charged, but you are!

Quick fix: grab an ac charger, which can be a chore to vet for proper performance if you are a stickler for staying within the specs.

Tell you what, if you want a quality charger that stays within the East-Penn specs, and is just a simple 3-stage charger with no funny business going on behind your back without you knowing it, grab a COTEK BP1210A charger. 10A CC, 14.4v CV, and 13.6v float. Just a plain *quality* charger, (with very high PFC, so good for use with a genny). Let it charge and sit on float for at least 12 hours. Now rest battery for 12 hours and recheck. Within the "one battery" budget project too. There are scads of other chargers out there, but this would be great to have on hand. It even has a switch - fancy that!

Test load for 50% DOD discharge test:

45w incandescent ac bulb. Or any other bulbs at the grocery store that add up to 45 watts with the REAL and not "equivalent" wattage ratings, like halogen, CFL's and the like. Get a small inexpensive msw inverter, like 100-200w or so. Run for 10 hours. If you only have a 40 watt bulb, run for 11 hours. This is for your 92ah battery, being test-discharged for 10 hours at the C/20 rating. Why?

45 watts / 10 = 4.5 amps. Now run for 10 hours to pull 45ah from your 92ah battery to see how close your 50% DOD really is.
Where did the 10 come from? From the cheap inverter with losses. This is why you don't divide wattage by 12, but by 10 to compensate for the inverter loss.
Run for 10 hours (half of the C/20 total timeframe), and compare the no load ocv against the chart, since were pretty sure your battery isn't totally knackered.

If done properly with a "freshening" charge, (14.4v held for 12 hours or more, despite the current being nearly zero) new East-Penn agm's (and JCI's too for that matter) have about 13.0v ocv resting voltages for days.
A decent charge with say something like the Cotek mentioned above - about 12.9 - 12.95v for days.
12.85v? After it gets old.
12.7v like yours? Big red flag man! But you have time to fix the undercharging problem now that the flag has been raised. Or just buy batteries more often.

[Brian53713]

Sorry to keep beating this up, I don't think there's a problem as I already stated after I use the battery for several hours at night to approx 12.56 .then settles in at 12 .68 to 12.72 in the morning after not using 5 to 7 hrs. Floating for five to seven hours most days these days. And I can adjust the absorption and Float, but it seems like the charge controller is already compensating for the temperature .like the voltages listed in the East Penn manual PN. provided. Temperature compensated automatically, not a probe available but right next to the batteries it is.

[PNjunction]

Sounds good - we're just trying to tweak things for best possible performance, limited at this distance by forum communications.

Big question: How accurate is your voltmeter, either handheld or are you relying solely upon the controllers metering? Could it be that one or both is slightly off leading to either better or worse conclusions? Hint: Find a Fluke, or other reputable measuring device and compare. Add compensation if necessary, either mentally or by calibration adjustment.

I note that your ac charger is probably of the simplistic "taper" type. Watch your regulation when in float, as poco ac differences can result in large current excursions behind your back if you aren't watching it. Most agm manufacturers point out that while this is ok for one-off type of charging, for regular use, it is the least desirable. Ie, the charger does not follow the classic CC/CV routine, but tapers during bulk instead of during absorb and wandering float voltages due to the simplistic design are not the best for long term usage.

Not a show stopper, but hey, while we're talking batteries and such.....

[Brian53713]

I am not, and would not use that basic charger on my AGM. The basic AC charger is for my other batteries, topping off once in awhile.