CC affecting morning V readout

[Brian53713]

Does the small amount of power mppt uses while not charging ,overnight ,affect the battery not being under load? When getting a ballpark of what the voltage is ,while not being used for 5 to 7 hours?

[Sunking]

You cannot use voltage as an State of Charge. Only way you can use voltage is to disconnect the batteries and let them rest 24 hours. All those battery monitors are not worth the box they come in. Only a hydrometer can tell you what is going on and anyone with batteries should have a hydrometer and know how to use.

[inetdog]

You cannot use voltage as an State of Charge. Only way you can use voltage is to disconnect the batteries and let them rest 24 hours. All those battery monitors are not worth the box they come in. Only a hydrometer can tell you what is going on and anyone with batteries should have a hydrometer and know how to use.

Make that "anyone with FLA batteries" and I will agree with you 100%.

[PNjunction]

Yes it does affect the battery, BUT it is up to you and the capacity of your battery to determine if it will be a factor in 5 - 7 hours as you stated.

Instead of looking at voltage, just multiply the current draw of the device in standby mode X 5 or 7 hours.

Would this represent in insignificant discharge to a 250ah battery in that timeframe? Most likely insignificiant.

Would this represent a significant discharge to a puny little 2.5ah battery? Could be!

Example: You have only a puny 2.5ah battery, but at night your charge controller pulls a little current, and OH, you forgot to turn off the humongous 1kw inverter, and it pulls 500ma in standby. You'd be totally discharged in a few hours just based on current consumption alone. No need to even think about SOC resting voltages!

In the real world, unless you go to extremes of using very small batteries, and a controller with high standby or idle current - relative to the size of your battery, the 5-7 hour timeframe would be insignificant.

[Brian53713]

AGM. CC daily low & high battery monitor . If no load other than self consumption of CC for 7 hours is it somewhat of an indication?

[PNjunction]

What size agm? For my own knowledge, what model - don't worry I wont bag on you if you are using an Intimidator or the like as a learner.

Are you just witnessing normal self-discharge, or in this case the "settling" voltage of a battery no longer under charge? A very healthy agm, even an east penn should settle after a few hours to no lower than about 12.8v. If it is healthy with only about 7-8 hours, I'd like to see 13v actually. What are the voltages you are seeing?

Essentially, the draw caused by your CC under only 7-8 hours of idling is insignificant. UNLESS it is totally sulfated, where what was once a 55ah battery is really only ten times less than that, say 5.5ah internally due to undercharge!

[Brian53713]

Blain Farm and Fleet branded Duration Extreme 4-year warranty 2-year full replacement 27magmdc92 Amp
$ 145. Successful Daily use , appears ecactcly same as Intimidator . 5 To 7 hours of LED light is the load at night. Everything appears normal I'm encouraged by the 12.72 it is almost every morning. And it seems to have between a 30 minute or two hour absorption every day and so many hours of float.

[Brian53713]

And yes at the end of the day after a good floating charge, it does settle at 12.8 or higher.

[PNjunction]

Ok, gotcha on the classic East-Penn agm rebrand. More on that later. I'm running some Duralast rebrands myself for just simple led lighting with an ac inverter...

Note that I'm assuming you are the original owner, have not cooked it with some super agressive high voltage speed-charger, and was less than about a year old retail worst case when you got it.

And yes at the end of the day after a good floating charge, it does settle at 12.8 or higher.

That doesn't really count. It is the 7-hour resting voltage of only 12.7v that worries me. That is actually not good and assuming the battery isn't decrepid, used, or already abused, we can do something about that. I'll bet if you let it go 12 hours (the real minimum, and 2 days is what REALLY counts!), the voltage would be even lower.

We know that voltage alone isn't the best indicator, but *for now*, that's all we have to go on.

I don't know if I pointed it out before, but here is your manual for that battery. Ignore the "gel" voltage charts and stick to the agm:

http://www.eastpenn-deka.com/assets/base/0139.pdf

What this signifies out of the gate, is that you are undercharging that agm. AND quite importantly, it probably never got a good "freshening charge" upon receipt. But what consumer knows about this? You will now, but instead of going too far into that, we'll take some baby steps.

Instead of biting off more than we can chew at this point, I recommend the following no matter what, since you using solar for charge. Instead of getting totally involved with max-smoke types of charging, do this:

Baby Steps:

1) Change your CV/Absorb voltage to 14.5v instead of 14.4v. That makes a difference. Ordinarily I'd recommend maxing it out to East-Penns highest at 14.6v, but I'm not sure if you are using a temperature compensation probe at the battery. I think you are relying on ambient compensation if I remember correctly, so we'll split the difference.

2) Up your float voltage to 13.7v. Again, small changes can make a difference.

If your led lighting is not mission-critical, give this a few days of no load operation like this.

You can see the chart at the bottom of page 11. Your controller is probably set to default to the 68-70F values as a starting point, and will change and follow this chart more or less when the temperature changes.

See the top of page 11, where they recommend for longest life, to try and achieve 0.3C (which is the max current recharge value). Babying an agm will walk it down in performance and capacity.

I don't know what your array is, but this means that for longest life, try to get near 0.3 * 92ah = 27.6 amps. If that is not possible, the *minimum* would be 0.1C, or 9.6A from your array. A nice middle of the road boost would be 0.2C, or 18.4a charge current. 0.2C is about the sweet spot for charge efficiency health vs panel / infrastructure economy for standard lead-calcium agm's. Pure-leads are a whole different story!

Want to be a Jedi-Master of AGM? Know this:

By design, agm's are VERY prone to being sulfated, *especially* in a solar undercharge environment. Why?

Unlike a flooded battery where the amp-hour capacity of both the negative and positive plates are the same, in an agm, the negative plate is actually slightly larger in capacity than the positive! This has to be to make the whole sealed recombinant thing work. If the positive plate never gets a slight overcharge in order for the negative to get charged fully, the negative plates starts to become equal to the positive plates in capacity, and now it more or less emulates a flooded battery, with attendant higher levels of gassing! Not good. Dont' baby agm's. Unfortunately most consumers do, and manufacturers don't want you messing around with slight overcharge, fearing quite rightly that someone will just go overboard with it.

You can accomplish this by *enabling* the so-called 30 day "EQ", but that is a misnomer and no-no for most agm's. What you want to do, despite the "EQ" name in the controller, is set it to a *low-absorb voltage that the agm can handle*, not the high-voltage 15.5v or so called for with flooded! We're talking around 14.4v, just a hair under your 14.5v setting normally for absorb.

So if set properly, this so-called "EQ" in your controller should be thought of as a "Refresh" for agm.

Very simply, set your EQ to 14.4v, just a hair under you did above for your CV absorb. Now what happens is that every 30 days, instead of dropping to float as it normally would, it will HOLD the 14.4v voltage for a few hours longer than normal before dropping to float. That's good for an agm.

Ideally, one would hold this for 12-24 hours for a "true" 30-day refresh, but in most cases we simply don't have that much time with solar, so you just enable it and it will do the best it can every 30 days. It isn't perfect, but it helps.

If I haven't bored you to death, can I ask what amount of power your led lighting pulls? Are you using an inverter etc? There's more to this agm story - and it isn't ALL bad, as long as you know the ropes of what these "dual purpose" agm's can do.

[Brian53713]

Here is the daily log proximate past 30 days. Been using battery successfully for six months. 3 months old brand new in the store.
getting quite a bit of nighttime LED direct to DC usage. And running one of my flat panels and the fans to pull air out of my solar space heater during the day when it's sunny. thank you for the manual on AGM from East Penn, I've seen that before from you or my own stumbling on it. But it really validates my charge controller has been basically charging for the temperature that the chart shows. Charge controller located right next to batteries. I have the absorption set 14.4, but it has been charging a little higher than that basically the same as what the chart shows it should. Battery does call for His Highest 13.6 float, I have it set for 13.5 and it is automatically been going higher than that for the temperature compensation. I really appreciate the personal attention you gave this. I don't have a concern that the battery charging correctly. Was just curious how accurate it might be with the self consumption of the CC for the 5 to 7 hours that the battery does rest every night after being used seven eight hours evening use.

[PNjunction]

Sounds good then, but remember this....

You are in the honeymoon phase where you won't see the immediate effects of undercharge, but will see it sooner than later.

Just doing a normal CC/CV charge is not enough. Eventually one needs to slightly overcharge in a controlled way. If you have an eq setting, then set it to the same voltage or maybe a tad higher 14.4 - 14.6 for a 30-day extended hours absorb, aka "refresh" and not really an eq as we think of it in flooded terms.

Float for 3 hours or so? That's not enough! The last 1% of an agm charge is the longest to get in - no matter what you set your absorb voltages to or how fast you get there. There is no way around it that you need at least 8 hours or more of float just to do the "normal" cc/cv charge, nevermind the slight monthly overcharge that is needed. With cyclic solar you'll never get there.

Advanced solar users with agm's and daily discharges do away with float altogether and just make their CV/Absorb AND float voltage the same, ie 14.4v. Now you may not have to do the "refresh" at all since you are basically just in extended absorb every day until the sun goes down. Daily discharge users only. The "max smoke" model.

This is akin to what wheelchair users experience - nice peppy performance when the batteries are new, but due to insufficient float time when they charge the chairs at night and get the "finished" indicator, the battery rapidly declines in performance. Cycle by cycle, it takes it's toll right behind your back. 8 hours would be the *minimum* for float to actually finish the charge before going into maintenance, assuming the charger / controller hasn't dropped out of CV/absorb to float mode too soon to begin with!

In the end, the moral to the story is that it is better to slightly OVERcharge an agm, rather than to let it undercharge. Sadly, most don't realize that a normal cc/cv routine IS undercharging by itself. Hence the short life of agm's in most consumer's hands.

Moving forward ....

You know that despite the "heavy duty", "deep cycle", "marine" or "dual purpose" descriptions of these batteries, they are not "true" deep cycle. What that simply means is that if you want to get decent cycle life out of them, NEVER go beyond 25% DOD. Stay within the 10 - 25% DOD window.

But wait - their docs tell me that I can go to 80% DOD and still have robust, full-flavored performance!

All that means is that the beefier ones made with better materials will just have the ability to recover from that occasionally, and not be damaged outright. It does NOT mean any improvement over cycle life.

Basically they have thin plates, which means the material just gets eaten up faster. Some of the better ones won't trash themselves at the outset, but again, it is not an indicator of improved cycle life under normal conditions, just the ability to withstand occasional abuse.

Just so you know..

[Brian53713]

Thank you very much for that detailed explanation.

[PNjunction]

Voltage is misleading!

Taking the long trip back to what Sunking and others mention about voltages NOT being the real indicator of battery health, especially agm:

Imagine this - the guy that sold you the battery swapped date of manufacture stickers to some old stock sitting on the shelf for a year or more. It just sat there sulfating, eventually to the point where it is hardening and no recharge will bring the hardened sulfate back. But it isn't totally dead.

You bring it home, attach to your controller, and what do you know? Superb fast-charging performance that seems to follow all the voltage rules in the charts. Great right?

Uh oh, that 92ah battery is in reality about 60ah internally due to the hard sulfation that has taken place. But the voltages all line right up on my meters during charge!!

This is what we're talking about when relying solely on voltages with agm, and the importance of not babying them, especially if the "honeymoon" period right after purchase seems to be doing great!

Do a discharge test to at least 50% DOD. Not all the time. Pull 46 ah from it at a normal rate, 4.6a per hour for 10 hours or close to it. Let it rest for 12 hours or more, and see if the voltages line up something along these lines:

East - Penn Deka ballpark ocv values:

12.8v 100% (new should be 13v actually!)
12.6v 75%
12.3v 50% < should be near this
12.0v 25%
11.8v 0%

These ballpark figures may let you know if the honeymoon is over.

[Brian53713]

I take it the capacity should be Approximately 50% after using 50% ?

[Brian53713]

Nevermind, I see you marked that on the indicator. Thank you.

[Sunking]

And yes at the end of the day after a good floating charge, it does settle at 12.8 or higher.

So what is the problem, that is normal?