quick question for Midnite Classic owners

solarpowernovice

My batteries are full and I want to force a float charge i.e. skip the 2 hour absorb time... is this a possibility with the classic? I ask this because, I am currently only using the system on weekends and want to keep the batteries in float as long as possible until next weekend.

I updated to the new firmware and have the localapp installed on my laptop. I see the option to force float but it is greyd out and I cannot click it.

Photowhit

Re: quick question for Midnite Classic owners

I think you can but you'll still have loads on the system, the Classic by it's self draws 30-35 watts, I'd reduce absorb to 1 hour and be comfortable...

I'm sure others here may have other opinions, and you could ask on the Midnite forum.

solarpowernovice

Re: quick question for Midnite Classic owners

thanks for your input. I have one more off topic question... If my battery manufacturers spec sheet says absorb gets battery to 95% and float brings it to 100%, does this mean I will have to let it stay in float for a while after absorb is done? how long would you recommend?

http://www.interstatedealers.com/pdf/201535.pdf

I have 4 of the GC2-XHD batteries @12v 464AH in series/parallel and 5% of that is 23 amps

it seems like the float function only puts 0-2 amps into the batteries periodically.. is this enough to get the batteries to 100% if its only in float for a few hours?

westbranch

Re: quick question for Midnite Classic owners

You can also raise the End Amps setting to number greater than the recommendation of 1% to shorten the absorb phase. The higher the value the sooner Absorb limits will be met.

solarpowernovice

Re: quick question for Midnite Classic owners

Can I raise the float amps too? (because of my last question) seems like it will take a really long time in float to get to 100%??

Cariboocoot

Re: quick question for Midnite Classic owners

solarpowernovice wrote: »

thanks for your input. I have one more off topic question... If my battery manufacturers spec sheet says absorb gets battery to 95% and float brings it to 100%, does this mean I will have to let it stay in float for a while after absorb is done? how long would you recommend?

http://www.interstatedealers.com/pdf/201535.pdf

I have 4 of the GC2-XHD batteries @12v 464AH in series/parallel and 5% of that is 23 amps

it seems like the float function only puts 0-2 amps into the batteries periodically.. is this enough to get the batteries to 100% if its only in float for a few hours?

Float Voltage is above resting Voltage so therefor the battery is receiving a tiny charge amount. It is not necessary to hit 100% all the time every day, and some days you may not even see Float. You don't really "let it stay in Float" so much as try to maintain Float against load demands. It is the stage where the batteries are not called upon to supply any power, and the actual Voltage point isn't critical so long as it is above resting Voltage.

Interstate's description may be "lab correct" but in the real world finishing Absorb is "100% charged".

Cariboocoot

Re: quick question for Midnite Classic owners

solarpowernovice wrote: »

Can I raise the float amps too? (because of my last question) seems like it will take a really long time in float to get to 100%??

Float does not have an Amps setting. It is a fixed Voltage stage like Absorb.

solarpowernovice

Re: quick question for Midnite Classic owners

thanks again guys you've always got the answers :-)

H2SO4_guy

Re: quick question for Midnite Classic owners

I have a few Classics. The absorb time can be changed in seconds, very quickly. I change it from time to time, like if a battery bank is going to go unused for a period of time, I'll set it to 15 minutes, but more if I am going to be using it for any length of time.

Awesome controllers, I would like to have more!!!

Cariboocoot

Re: quick question for Midnite Classic owners

You realize that is a maximum Absorb time limit, not and absolute Absorb time right?
In general if the batteries are not in use they don't take long to reach Absorb and therefor don't stay in Absorb for long either. Setting End Amps makes it even better (in case Bulk took a long time due to weather conditions for example) and adding the WhizBang Jr. is the coup de grâce for charge controlling.

Unlike some other controllers where 'X' hours for Absorb is the start and finish of it.

Vic

Re: quick question for Midnite Classic owners

s p n,

That US Battery data on charging GCs is really for charging from the grid. For charging from PV, we do not have a constant current Bulk charge.

As Coot mentioned, for almost all Flooded batteries, when Absorb ends, charging should be to 100% SOC.

Do not run the Local App on the Classics here, so do not know why the Force Float is greyed out, but if you have a standard Classic (not the Lite), you can go to the Tweaks menu, use the Soft Right key - more - and scroll left to Force Float and use the up arrow button to activate Float ...

But, at midnight, a new charge day begins, and the Classic will begin looking for enough power to start charging your batteries.

If you wish to avoid Bulk and Absorb stages for a certain number of days, do this;

In the Charge menu, scroll over and down to the Advanced menu. At the right of this page, you will see Skip Days. This is the number of days that Bulk and Absorb stages will be avoided. Once you set a number that is not zero in this day setting, the FOLLOWING day the Classic will begin counting down that number of days that you entered. When this number goes to zero, that is the day that a full charge sequence will be run. On the following day, the day number you entered will be re loaded, and this sequence will begin again.

Personally, I would try to get the batteries charged to 100% SOC in Absorb. This would normally be represented by a Charge Current value into the BATTERY of between 2% and 1% of 20 hour Capacity (in Amps).

If you have the WBjr and a Shunt installed in your system, if is very easy to see just what the charge current into the battery actually is.

Float current INTO THE BATTERY is determined by the SOC of the battery, its temperature, and the Float voltage. The only way to increase this current (into the battery) is to raise the Float voltage. Normally, Float voltage is set at the lowest point that will just barely keep the battery fully charged.

As an aside, the Classic, with Firmware updated within the past two or so years, no longer will use the Bulk charge time to determine the Absorb time (thank goodness!!). When the End Amp setting is zero, the Absorb time set in the Charge menu will be the Absorb time. With a non-zero EA setting, the Absorb time is the longest time that the Absorb will last. If the EA setting is reached before this time is reached, the Classic will go to Float.

Some opinions. Vic

mike95490

Re: quick question for Midnite Classic owners

solarpowernovice wrote: »

.... I see the option to force float but it is greyd out and I cannot click it.

In the local app, go to CONFIG SETTINGS, last item is Enter unlock code CL ________ That's your serial #, enter the digits, and it unlocks, and
then you CAN manually force FLOAT. (ignore my voltages unless you have a NiFe bank)
Attachment not found.

solarpowernovice

Re: quick question for Midnite Classic owners

This is some great info you all have provided to me, I really apreciate it. kudos :roll:

2twisty

Re: quick question for Midnite Classic owners

Can you explain End Amps? I have a Classic 150 with the WhizBang. Us Battery says I should float for 3 hrs on these 1800XC2s.

Because of this, I often only BARELY make it to float most days. Some days, not at all.

My End Amps is set to 0. The manuals tell me how to change the settings, but there is precious little on the theory of operation that will give me the info I need to make informed choices.

Please advise.

Alaska Man

Re: quick question for Midnite Classic owners

Rule of thumb is End Amps = 1% of total Battery Amp Hours or so I've been told. In my case that would be 17amps, but I set my "End Amps" to 1. So I go into Float at the 160 minutes set Absorb Time or when the "End Amps" input value is reached which ever comes first. I have been told it is okay to set End Amps to "0". Most days I'll time out before I hit the End Amps value.

Vic

Re: quick question for Midnite Classic owners

Hi 2,

OK, normally, with a reasonable Absorb voltage, the approximate correct EA Setting for Flooded batteries, will be between 1 and 2% of 20-hour Capacity. So try 2% or so to start with. If these batteries are Flooded (FLA), you can monitor the SG just after the transition to Float.

Have not taken the time to find those batteries. But with a min Float time, perhaps they are AGMs ...

There is a way of determining the approximate EA value, by setting a long Absorb time, and monitoring the rate of change of battery charge current in Absorb ... that curve will get flatter and flatter. At some point when the rate of change is quite small, you are near the correct EA current value for your batteries, given that the Vabs is reasonable for those batteries, the EA current is affected to some extent by the battery temperature.

As you know, with EA set to 0 on a Classic, the Absorb Time setting in the charge menu will be the Absorb time, and EA will NOT be used. FWIW. Vic

Vic

Re: quick question for Midnite Classic owners

TooTwisty,

OK looked at the US B specs for your FLA GC2s.

Float time is unlimited, with no minimum noticed.

Typical Absorb = three hours, but the correct time depends on the Depth Of Discharge.

They mention Ending Current at about 3% of C, THEN held for 3 hours of Absorb, but this probably only applies when the Bulk charge meets their spec, which looks like Constant Current at 10% of C, which really never happens with Solar charging.

BUT, good news! You can use your high quality glass Hydrometer, the Gold Standard for determining how well your charger settings are working. This plus the Great WBjr,, should direct you to Nirvana without delay. Good Luck, Vic

2twisty

Re: quick question for Midnite Classic owners

There is a checkbox to use the Whizbang for end amps and I have that selected. But it seems that it always wants to absorb for 3h (I set it to 3 from the default of 2 based on the info I got from US Battery)

The batteries are not AGM. There is no glassy mesh in the cells. They are a flooded lead-acid.

My bank is 12v nominal 832 AH. So, you're thinking that End Amps will be between 8 and 16?

I've got the spec sheet that I was sent from U.S. Battery in PDF form. I've ot to run for a neighborhood BBQ now, but I'll try to dig it up later so you can see.

2twisty

Re: quick question for Midnite Classic owners

Well, I have your general low-quality plastic hygrometer... And only know the basic theory of operation, nor does it give me the ability to correct for temp.

Since my system has only been online for about a month, (and my batteries were brand new) I have not yet gone through a maintenance cycle. I guess I'm gonna have to get on that, I guess.

How would I use the hygrometer and the WbJr to get to nirvana? Any suggestions on what changes I should make to which settings in the Classic?

Vic

Re: quick question for Midnite Classic owners

YEP, looked up the specs on your batteries ... our posts crossed, so you did not see the post above.

That 3% number is not useful as an EA value. So would guess that the correct EA IS still between 1 and 2% of that 832 AH value, when using the suggested Absorb voltage -- 14.7 V IIRC for your 12 V system. It would be good to watch your system charge the batteries for a day or so, and be able to measure the SGs when the CC transitions to Float.

WOW!! Four strings of batteries ?? You may have heard this before ... but hope that you have a good amount of PV to charge those batteries, and a Clamp-On DC ammeter to watch the current balance between strings FREQUENTLY!

So why not try about 1.5% -- about 12 A as the EA value -- enter 12 under the EA label in the Charger Advanced menu page. Also, in this Advanced menu, the left "Soft Key" will toggle the Classic from using its own output current for EA, or when you push this soft key again, it will use the WB's Shunt reading. You should see the label toggle between Classic, and Shunt (IIRC - it has been a while). But the included instructions for the WBjr are quite clear and complete.

Hope the BBQ was good. More later. Vic

Rybren

Re: quick question for Midnite Classic owners

I have USB 2200XC2 GC 6V batteries. When I first got them, I queried USB about how to best charge them. The Senior VP for engineering replied and said:

"Since you are off-grid, I would suggest a bulk and absorption charge setting of 2.40 volts per cell (28.8 volts for a 24 volt system).
If the specific gravity does not come up to full charge regularly, you can move it up to 2.45 - 2.50 vpc (29.4 - 30.0 volts).
Float charge voltage would be 26 volts and equalization charge voltage would be 30 - 31 volts."

I run my absorb at 29.4V and then use 2% of C as my EA value (with the WBJr). This works perfectly for my setup.

2twisty

Re: quick question for Midnite Classic owners

Yeah, I know that 4 strings are bad juju. I plan to move to 24V as soon as I can. I was limited by finances when I bought my cheap Harbor Fright inverter, so as soon as I can make the jump over to 24 (pure sine inverter and a 24v charger) I will.

I know it's not optimal; but it is what it is, and it powers the refrigerator that keeps my wife's insulin cold. Oh, and this laptop that I'm using right now.

boB

Re: quick question for Midnite Classic owners

I am not sure if this was mentioned here but the latest firmware allows you to skip so many days
of Bulk/Absorb cycles. In the ADVANCED charge menu, it is the menu item on the right end
of that screen. Disabled is zero (0) days.

Taking out amp-hours from the battery is discharging and putting those amp-hours back in
(with A-H inefficiency taken into account) is considered fully charged again... BUT without
an Absorb cycle once in a while the batteries will sulfate and go bad. This is the latest thinking
anyway.

And along with that thinking is that Absorbing every single day will wear out the batteries
prematurely. This all sounds pretty understandable actually.

What I hear is that most flooded LA batteries can go many weeks or months without an Absorb charge
and not sulfate but I would do a complete Bulk/Absorb more often. Just skipping several days inbetween
is probably helping the battery life a lot but I do not have actual data... Just (believable) hear-say.

Sounds perfect for a cabin that is not used all the time though.

boB

2twisty

Re: quick question for Midnite Classic owners

My cabin is where I live. So... Is the current thinking that I should skip absorb for a few days to help the batteries live longer? What is the thinking? Set Skip to 2? so on every 3rd day it absorbs? Or should I set it longer? Most days I am able to get to 100%, or at worst, 95%. Since some of my electronics are too hefty for the solar, I will fire up the genny when I want to watch movies, and that has a battery charger hooked up and can get me back to 100% easily if I fall behind.

I need these GC2 batteries to last as long as possible...

westbranch

Re: quick question for Midnite Classic owners

there are lots of posts on this topic, its like your brain, exercise is good for a long life, sort o use it or lose it, keeps all the cells working, deep down...


hth

Alaska Man

Re: quick question for Midnite Classic owners

I wouldn't think anyone is suggesting that. You don't need to get 100% everyday, but I would definately recommend into the mid 90% everday. I make sure I get to 100% + once a week. Absorb to 14.4 - 14.5 everyday for my 12V system.

Vic

Re: quick question for Midnite Classic owners

We all have opinions on this.

I was one of those encouraging MidNite to add this Kkip Day function to the Classic.

Have tried it for almost one year. In general, NOT doing a full Absorb on FLA batteries every day reduces the average heat that of the battery bank, and increases, somewhat, the average Depth Of Discharge -- which are both good things.

BUT, for batteries that have had issues with recharging, low cells, need of frequent EQs, and batteries/systems that are not monitored often, etc, would suggest NOT Skipping Days. Also, for aged batteries, it is probably best to try to get then charged every day if possible.

It is unknown just how much PV power 2twisty has, but he has a fairly large battery bank, composed of FOUR parallel strings, so, would suggest that perhaps trying for a full charge every day may be good for the batteries, until, perhaps the switch to a 24 V system is done. Very personal opinions. FWIW, Vic

2twisty

Re: quick question for Midnite Classic owners

Lol. Oops. Forgot to put the panel sizes in the sig!

Each of my panels are 230w, total of 920w

Vic

Re: quick question for Midnite Classic owners

Hi 2twisty,

Thanks for the info on your PV array. You are in somewhat better shape with PV power than I had guessed. You are about in the middle of the suggested range of battery Capacity vs PV power.

Please check your SGs regularly, until you find a good combination of Absorption voltage, and Shunt End Amps on the Classic. It is a very good idea to start a Battery Logbook, where you record SGs of each cell, every month or so, the amount of water added, and using a DC Clamp-on Ammeter, keep a record of the current into each string during fairly heavy Bulk charge current. Also looking at discharge current under fairly heavy (but constant) discharges. This will help you to TRY to keep strings fairly well balanced.

Hope that you can move to a 24 V system fairly soon.

Nice blog, will read it further. Nice looking new cabin. Have fun, Vic

2twisty

Re: quick question for Midnite Classic owners

So... What conditions in SG would make me change absorb voltage and end amps, and by how much in which direction? If SG is low, increase absorb voltage or end amps or both?

Vic

Re: quick question for Midnite Classic owners

First, just paying attention to the SG is important ... many pay some attention to SG at 11:00 PM just after the power "went out".

According to the US B Data Sheet for your batteries, the target SG is "above 1.270" IIRC.

Try using Rybren's 14.7/12 V (which I believe is the standard US B guidance), and 2% of 20-hour C, as a starter. Ryrben's batteries appear to be a slightly different battery, but why not try that.? You will probably want to set the Absorb time in the Classic to 4 - 5 hours, or so. Just want the typical Absorb time to exceed the typical time spent in Absorb when using Shunt EA to 50% or so greater +/-- .

If you are unable to maintain SGs at target, then decrease the EA value somewhat, and watch SGs. In Winter, with short days, an increase in Absorb voltage may be needed to get as much charging done in the shorter time. It is all a bit of a balancing act, just keep an eye on SGs, plus some intuition, and experimentation ... all part of the fun! YMMV, Good Luck, Vic