Need help - batteries not reaching full charge - adding more

[robbertwilliams]

New to forum but have been searching the archives for awhile and have not found a solution to my specific problem.  It could be as simple as a hardware mismatch. 

I've had a set of 8L16 (4qty) hooked up for about 6 months.  I've only monitored the SG a couple of times since the install (nothing unusual).  However, just was about to add 4 more to the bank and checked the old...they were sitting around the 75% charge state while the WBjr said fully charged. 

I'm a bit worried to add the other ones into the mix until I figure out my current settings.  If there's anyone out there that would have an idea of where to start?  I will acknowledge to you that I am not as well versed in this area of life...as I should be.  We just moved off grid and would love to have a bit of help. 

Hardware:

4 (current) Deka 8L16 6 volt 370ah batteries
4 Hyundai s250mg 250watt multicrystalline panels (series/parallel)
Midnite Classic 150

Settings:

EQ: 28.4
ABSORB: 28.3
FLOAT: 27.0

ABSORB Time:  1hr30min
Temp Comp Charge: -5.0 mV
Output Amps: 48
Input Amps: 60

Ending Amps: 7 (based on a midnite classic video - so probably part of my problem...)
Rebulk: 8volts

Please feel free to email me or send a message.  I don't have extremely good internet at this location of service...so, what I can research is done on memory and notes.

[Vic]

Hi robertwilliams,  Welcome to the Forum.

So,  the target SGs for fully-charged batteries is 1.275.

In looking around on the web,  for charging specs on these batteries,   seems like a good starting point is about 29.4 V.   This should be Temperature Compensated at -- 5 mV/Cell/C.   This is customary for Flooded batteries,   perhaps for your batteries,  it could be as low as -- 3 mV/Cell/C.

The Absorb time required for full charge will depend upon the Depth Of Discharge (DOD)  that the battery has experienced in the previous discharge.

An Ending Amps setting of 7 A may be good,  bu the correct value will depend upon some monitoring and adjusting this value,  and/or the Absorb voltage.

How long have the present batteries been in service?  It can be a bit of a problem adding batteries to some that have been in service for some time.   About six months age difference may be about the limit of what is desirable.

Will look further for charging specs on your batteries.

FWIW,  Vic

[robbertwilliams]

Thanks for the reply Vic. 

The current batteries were installed I believe in mid June.  I was aware of the disparities of adding batteries of different dates/ages of use.  However, I need the extra capacity.   

So, when you say a good starting point for charge - I understand that as an absorb voltage of 29.4?  Is that correct?

I just downloaded the Midnite Local App onto a laptop.  Would this be of any use?  Such as recording a log of amps in the absorb stage so that I can adjust my ending amps.

Reading a couple of other posts you have made, it seems I should have my absorb time set out quite aways in time while I'm observing the amp curve.

Also, the batteries I picked up today were supposed to be fully charged (I called a week ahead - and they were in fair condition).  Anyways, upon the SG readings of the new batteries, I thought I shouldn't add them to the bank until they were up to charge as well.  So, currently, the new ones are on the CC, while the old ones sit.  Can I take SG readings right after they are pulled from the system (ie. just got done charging) or should I wait awhile.  I'm currently under the impression I should wait a day.  If this is the case, I will probably be babysitting this system in the dark for awhile...or is it better to find ending amps while using normal loads?

Thanks again Vic!

[ClassicCrazy]

East Penn Deka absorb range
28.80V â€" 29.40V
Float
27.60V â€" 28.20V 27
Temp compensation
-3 mv

If they are new batteries you may start with lower voltage of the range above.

I would put at least 2 to 3  hours absorb - and ending amps 5 or 6 and check SG to confirm they are charged .
So you want to watch SOC and watch system amps - easiest way is to monitor on MyMidnite - system amps should start to level off around 100% SOC. That would be your ending amps - confirm with SG readings .
What efficiency do you have for your SOC setup ?
Here is East Penn Deka specs
http://www.eastpennmanufacturing.com/wp-content/uploads/Renewable-Energy-Charging-Parameters-1913.pdf

Local Status app is great monitoring tool , so is Grahams Classic Android app if  you have android device.
Also you can set everything up with Local Status app and save copy of parameters so when you do firmware update you can easily restore everything .

Not sure where you are but it can be tough this time of year up north to get batteries topped up with short days and cloudy weather especially if you are running batteries way down. You should have generator to charge in your system to keep batteries healthy .

With settings you had ending amps was likely too high , absorb time too short, absorb voltage too low .
Larry

[robbertwilliams]

Thanks Larry.

The new batteries will hopefully get juiced according to the old settings, better than nothing.  I won't get back over to the site until tomorrow evening.  I hope all works.  When I had left it, there was still daylight but the controller kept going into resting mode once I hooked up the new batteries.  I didn't see any odd voltage drops on the PV in, or Batt V.  I have encountered this once before...and I don't recall what the culprit was. 

I will make some changes tomorrow evening.  I will also hopefully be able to log some of the charge rates - 2 days from now - on the local app. 

Thanks for the charge specs.  Would it help to equalize (I've never done it before) the older batteries before connecting them all together?  I guess, what I'm asking, what would be the best sequence of events for adding these newer batteries to the system? 

[ClassicCrazy]

You want to make sure your two parallel strings of batteries are wired correctly so they both get same charge.
See this
http://www.smartgauge.co.uk/batt_con.html

I guess I would charge each series string up on their own to 100 % , then put them together .
But it won't hurt to charge them up together now if they are both low.
It also doesn't hurt to equalize . See those specs I posted - and equalize with temp compensation for 2 hours.  There is check mark on equalize to use temp compensation for that . But you won't be able to get them equalized until you have good sunny day when the batteries are not too far down. You really only need to equalize if some cells are getting lower than others to balance them but once a month is what is often recommended for maintenance.   Or more or for longer if some of the cells are lower than others and are taking longer to get the same as others. Check every cell with SG readings.

How many amps are you taking out of your batteries - what SOC are you going down to ?

Larry

[Westbranch]

Whether you start using the new ones or the old ones you need to bring them both up to FULL charge. 
Do you have a charger that you can power with your generator? If so put it to use soon as possible, both sets of cells need to be as similar in charge-state as possible before combining them.  The results of checking the SGs will let you know if there is an issue...

Make a chart to record your SGs and number all the cells.  This will be invaluable at a later date, monthly or so checks should also get recorded.

hth

[robbertwilliams]

Another quick question - Objectively, I understand that ending amps should be reflective of when the amps start to taper of at a rate of <.10amps/hr.  Subjectively, are they are based on a number around 1% of the battery's aH rating?  or the battery BANKS aH rating? 

Once I get both sets topped off this week, I'd like to know where/when I should be looking to end amps?  Specifically, after I join the (2) 370aH banks together, collectively 740aH.

[Westbranch]

are they are based on a number around 1% of the battery's aH rating?  or the battery BANKS aH rating?

If you are calling a BANK a string of cells, they are one and the same...

Do not mix different Ahr rated cells in a bank or parallel strings of cells...  big NO NO...  mucho problema...

your target should be in the neighbourhood of 7A per string, and you will have 2 strings,and each string will vary somewhat around its number..

If you think about what you are using , it is WATTS and Watt hours, so you need to replace these
Watts = Volts x Amps

[Vic]

Hi robbertwilliams,

First,   assume that each string  of batteries in your bank are  8L16LTP-DEKA,   or,  perhaps 8L16LTP.

Yesterday,   did poke around on the Net,  and found several Deka Docs on charging.   The ones that I quoted above,   were for Flooded Lead Antimony batteries,   and therefore the --5 mV/Cell/C spec noted in that document.


It appears that Deka has changed to Lead-Calcium for their Flooded batteries  --  this changes the charge voltages and the Temperature Compensation value to -3 mV.

Did find only one reference to the SG for fully-charged cells,   at 1.275.
What are you using as the SG for a full charge?

What brand,  or type of Hydrometer are you using to measure the SG of each cell of the battery bank?

Here is a good Article on measuring SGs,  from Surrette Battery.   The SG for fully-charged batteries is one difference between the Chart in this article,   verses your battery SGs:
http://support.rollsbattery.com/support/solutions/articles/4347-measuring-specific-gravity

Regarding the EA setting,  Deka suggests a value between 1 and 2 % of 20  Hour Capacity (370 Ah).   The proper value of EA will depend somewhat on the Absorb voltage setting that is being used.

For EA,  would suggest beginning at about 1.5% or your bank's total Capacity  --  370 for a single string or,  740 for two parallel strings,   if your Absorb voltage (Vabs) is in about the middle of the suggested range from Deka.

When using EA to terminate Absorb,   you will want to set the Absorb time to a value that is above the longest Absorb time you would ever expect.  Absorb time varies directly with the Depth Of Discharge (DOD)  that the battery experienced in the previous discharge.

In general,  it takes a number of discharge/charge cycles for Lead Acid batteries to develop full-capacity,  and become stable.  You may have some difficulty using EA,  particularly with a six,  or so month difference in the ages of the two strings of your battery.  Usually,   the number of cycles  will be from about 20,  to about 70.   The shallower the cycle,   the longer it may take.   You may not notice this effect,  but perhaps if could cause some unpredictability when using EA.

Better Post this now,   the Inet may crash soon.    Vic

[Vic]

 ...   MORE,

It is unfortunate,  that for Renewable Energy (RE) charging specs,   Deka  suggests using Rate-of-change as a suggested terminator for Absorb,  as almost NO RE chargers,  like CCs can use this method.   However,   they do also state between 1 - 2% of 20 hr Capacity.

There is still some Jitter in the battery charge current,   as measured by the WBjr,   and the WBjr current display on the MNGP may not be updated  for each reading that the WBjr sends to the Classic.   boB did reduce this jitter,  several years ago,  but if it were further-reduced,  it would make watching the rate-of-change if battery much easier to read with one's eyes.   But,  still,  the WBjr is a great addition to the MN CCs.

Then,  regarding your battery bank going from 370 Ah,  to 740 Ah:
Depending upon your location,   your 1,000 PV array might be able to provide about 25 Amps charge current to the battery at peak sun,  on a clear day.   This is about 7 percent of battery Capacity (C),  when you double the battery C,  this charge current is diminished to about 3.5% of C.   For a weekend cabin or similar this is not too bad,  as  the battery charge state can catch up during the week,  of little or no battery use.   Although,  we do not know your approximate location,  solar conditions,  now,  or the intended use of your system.

For systems that are cycled daily,  the suggested range of charge rates for Flooded batteries is around  10% of C,  with 13% being about the maximum charge rate,  recommended.   Deka  does have specific recommendations on maximum charge rates that are a bit different,   but,  you might want to increase the size of your PV array,   or,   at least have a genset  and a charger that can charge the battery bank, should if not get sufficiently charged from your PVs.

Vic

[robbertwilliams]

Thanks everyone for your help and interest.

Just switched settings on the charge controller.  Eq=28.8 Abs=28.8 Float=27 EndingAmps=4 Absorb Time=4 hrs Temp comp = -3mv

Since I swapped to the newer bank to charge it up (note, both times I've monkeyed with it have been in the late afternoon - no direct sun), the CC goes from Float in Resting, and then vice versa.  I ended up doing a complete reset today.  Tomorrow is going to be overcast, snow, and 6F.  So, this figuring stuff out is going to take a bit of time.  I need to find a "no" job.

I should add a little more info to help in finishing the picture, and maybe painting it too.

We are moving into a 20ft yurt in the Black Hills of South Dakota.  No water (at least not running) and minimal electric needs.  The site gets full sun for 3/4 of the daytime hours (today 1/10/2017 - visible at 9 and invisible at 3:30).

Currently, we have:

9 LED lights (all 9w/piece) with all hooked up to a dimmer
A small dorm size refrigerator (not currently on the system)
An HRV - 50watts and is programmable(heat recovery ventilator to help with our air quality in such a small space, definitely needed in such a small space with only wood heat and humidity issues) - also not currently installed, hope to run a laptop (or two)
Energystar TV
Internet modem
Router
Schneider electric Combox
Schneider Electric SW2524 Inverter/Charger
A coffee pot that runs for 5 minutes and then shuts off
Occasional use of a small vacuum (650 running watts)
AND possibly a 4 cu ft chest freezer which would be outside in an outbuilding in the winter months

That is all that I can think of, off the top of my head.  It's currently still under construction.  So, it's hard for me to imagine something I haven't lived in. 

I think once I can get the CC dialed in, then both battery banks up to full charge, we should be in good shape.  After taking the SG readings tonight, the older bank looks like it may need an equalize.  But for the next few days to a week, I will be playing with some adjustments to charge times, etc.

Question:  With the midnite local app, do I or don't I need internet?  Or is it possible to just network it to the router (just like I have my Schneider Electric Combox currently) and talk to it that way?  Or can I directly plug the ethernet into the laptop (that didn't work with the combox). 

The current generator that I have is a 3000 running watt machine, with a 220 20amp output.  I could do one of two things; buy an external charger to top the bank off or wire up the inverters' built in charger.  What would be most effective?  If I need to buy an external charger, any recommendations?

Thanks again.  I'm very happy to have some people to help me with this.  I've also attached an excel worksheet with my SG readings from tonight

[Vic]

Hi robbertwilliams,

Thank you very much for all of the added detail about your yurt,  location,  settings,  SG readings,  and loads.

IMO,  your charge settings need to be changed:
Would suggest setting the Absorb voltage at the high end of the recommended range  --  29.4 V,  because,  your SG readings show that your batteries are NOT being fully charged.

In Winter,  it is common for us to need to set the Absorb voltage a bit higher than the Summer setting,   as the number of hours of good sun are short,  and higher Vabs will allow more battery charging to be done in fewer hours.

YES,  it appears that each string of batteries need an EQ,  based upon the variation in SG readings.

Your EQ voltage setting is too low.  Would suggest at a minimum setting for Veq at about 30.6 V.   This is the high suggested setting for Veq.   IMO,  the EQ voltage should be Temperature Compensated  ...  set the Classic to YES for compensating the EQ voltage.

Would set the Float voltage (Vflt) to the middle of the range  --  27.4 V.

The SW2524 should be a good battery charger,  when using the genset.  So try this.  You should not need any other battery charger,   is this inverter/charger is setup correctly.

Normally one would try to charge the batteries from the genset,  starting early in the morning,  and allow it to charge the batteries into the middle of the Absorbtion stage,   shut off the genset,  and try to finish th
e charge with PV,   when the sun is due to shine most of the day.    This should save fuel.

There is a Video,  where the procedure of setting up a Router,  connected to a Classic,   is shown ...   will post that Link.   Using a Router with the Classic is quite simple ...   even I could figure out that!!
Link to the Router setup Video:
http://midnitesolar.com/video/videoPlay.php?video_ID=39&videoCat_ID=3

Black Hills in Winter !!   You folks are tough!

...    Vic

[Vic]

OOOoooppppsss,  Just edited the above post,    but notice that you are now online,   so please note the Link to the Router setup video,   and did also edit the body of the post a bit ...   Thanks,   Vic

[ClassicCrazy]

You don't need internet to connect with Local Status App - just plug Classic into router, then your computer into router and Local Status App should find your Classic and connect to it. I have used both DHCP and also set up Classic with static address -- both work fine and depends on how you want to set up network or other stuff on there.

If you want to use the MyMidnite online graphing then you do need to have internet because it sends data to their server. You need to log in and set up account there and get your Classic registered, etc. That is really nice to view accumulated data on graphs you can change to your liking.

If you have Android phone or tablet look up Grahams Classic app on forums or available on Playstore - great interface that  you can select F temps and change between watts and amps and see system amps more easily as compared to general output amps of classic. This app will find Classic on the network - no internet needed for this either.

You want to use your inverter for charging if possible - save a lot of $$ on a charger if you already have inverter charger and it has smarts built in to regulate charging.

I should add that the Classic on some firmware versions or for whatever reason sometimes does mess up and need reset to work right with Local Status app or Mymidnite. There is a setting in Classic to reset automatically at midnight ( time ) . You may want to enable that if you have problems and save some hassle  .

Larry