Schneider SW2524 - Charging questions

[robbertwilliams]

Hey,

I know most of you aren't using any Schneider products.  However, maybe someone can give me some insight. 

I'm using the charger to bring my batteries up to their finishing stage - in the 90's.

What is going on here...

(background 370ah bank)

The charger inputs only allow for amps - so, I have (Bulk - 46amps max), (Absorb - 37amps max), and (Float - 2amps max).  However, when I'm monitoring the charge via my WBJr and Classic 150 (PV panels are disconnected), Bulk voltage seems to be fine (as I have no idea what a normal Bulk voltage is from the PV panels), but when the CC reads Absorb and you can clearly see the amps have dropped to the 37amp max (via WBJr), the voltage is at 29.6 (whearas my setting for absorb on the CC is 28.6V). 

Is there some inverse relationship between max charge amps and the voltage?  If I lower the max absorb amps, will the voltage go down, or up?  I guess, I'm just worried that using the generator/charger for the absorb stage is putting too much voltage to the batteries (and this starts to happen around the 85% SOC). 

Also, at the max, what percentage SOC should I stop using the generator and switch to PV/CC?
Please, I welcome your feedback. 

Thanks

[Vic]

Hi Robert,

So,  IIRC you DO have two strings of 370 Ah batteries,   but are charging them individually,   perhaps via a battery switch ...

YES,  am unfamiliar with the Schneider SW inverters.   Many Inverter/Chargers have charge current settings that are in AC amps,   not DC ...  perhaps the SW has either,  both or DC only,  dunno.

When you said,   "I'm using the charger to bring my batteries up to their finishing stage - in the 90's",   assume that the 90s is the approximate SOC.

Schneider and some other inverter manufacturers have a provision for using a Bulk voltage that is different from the Absorb.  Personally,  have always set the Vblk and Vabs the same.  You need not worry about a good Vblk on the Classic,   as the Classic does not need a Vblk setting,   and will produce the maximum amount of power available from the PVs.   The Vbat will increase until the Vabs is reached,    THEN,  a Constant Voltage stage begins,   where the Absorb voltage is maintained as a constant,   and the battery Acceptance will cause the battery current to taper.

46 Amps DC is probably a fine current maximum for Bulk and Absorb when charging a single string of 370 Ah batteries.

With "the PVs disconnected",   am surprised that the Classic would read "Absorb",   and not Resting.

From what you have stated,  do not know just what is the setting that causes the 29.6 volt reading when charging from the SW.   But,  most likely,   the batteries are cold,   and the  BTS on the Schneider should be increasing the Vabs (or Vbulk)  to compensate for a lower battery temperature.

If you DO lower the Absorb Amps on the SW,  then in early stages of Absorb,   the battery voltage should drop below the Vabs voltage,   and revert to Bulk,  until the battery Acceptance drops to the DC current that corresponds to 37 A DC (or whatever you have as the Max setting).   Then the battery voltage will increase,  in time,   and still reach Absorb ...   it will just take somewhat more time.

Regarding the relationship twix Max charge current setting in the SW,   and battery voltage,   the relationship is a direct one (NOT inverse)  --  reduce the charge current available,   and  the battery voltage will drop,  when in Bulk,   and when in Absorb,  only when the battery Acceptance is greater than is the DC current available   ...    if this makes sense.

SOC readings on any battery monitoring device are approximate.  The decision on how long into Absorb should generator charging continue,   is a very grey area.   Would run longer into Absorb,  if it had been a number of days since a full charge,   especially,  if the following several days were forecast to be relatively poor solar charge days,  and so on ...   it all depends.    But this is a good question,   as much of the Absorb stage is not a good use of fuel,   if good sun might be available later in that same day,  or on the following day ...   depending ...

FWIW,  Vic

[WindFarmer]

Robert

It's good to hear from an off-grid guy close to where I call home in the Pine Ridge Forrest of NW Nebraska. At the moment I am working for Doctors Without Borders (MSF) based out of Bordeaux France.

I just came back from a mission in Haiti where I installed some Schneider XW gear so I can understand the difficulties with this gear. The manuals were very ambiguous to say the least.

I see in your signature block that you have a combox. This a SE combox correct?

If it is, have you tried programming the SW through this device? I assume that programming the SW is similar to the XW. Do you have a laptop hooked to the combox?

Could you take some screen shots of the "charger section" to include the "custom settings? Maybe I could help.

Marc

[mike90045]

As soon as it's light enough, I'm going out to start the generator, it's been off a couple of days and needs TLC for "initial startups" (like pre oiling the main bearings with a squirt in each port on the con-rod)

I run the genset in the AM. and charge at least though Bulk  (60 min at my 30A charge rate), and when the amps in Absorb have dropped off to (20A-15A) where the generator is no longer operating in it's efficient range, I let solar finish off the charge.  (or come back at night for another boost so I don't have to go out at crack of dawn the next day to really flat batteries)

I have both the Combox and SCP,  I find monitoring with the combox to maintain good loading on the genset, and data recording is useful, and the SCP is handy for throttling back charging amps to let the Alternator cool for a couple minutes before shutdown.

[robbertwilliams]

Some Schneider's coming out of the shadows...

Well, I think I found out what I was wondering.  I am using the Combox to change all these settings.  I have my voltage inputs correct but there is one input that I CANNOT change - that is the battery temperature compensation coefficient (always set to -54).  The manual states that it is set to -54 for a 24v bank (54mV x (25 degree C - BTS degree C)).  Well, the only thing that I can figure is that most battery temp comp numbers are stated per cell.  So, in my case I have 12 cells and times that by the -3 (Deka's recommended temp comp coefficient) and I get -36 (not -54). 

If I find some time before the end of the week, I may call Schneider and figure out why this is the only value I cannot change.

MIKE - are there features that the SCP has that the Combox does not?  Is it worth the extra money?  I currently just have a laptop pretty much devoted to being connected to the combox via wifi.

MARK - thanks for chiming in.  I wish I could get some screen shots but will not be able to for a few days.  How long are you back in the states?  I'm sure I'll have a couple of questions later on.

Also, when using the generator/charger, is it best to disconnect the PV panels?  or does it matter?  It's one extra switch to flip and thing to remember but I am already starting/shutting off the generator. 

Thanks a bunch.

[WindFarmer]

Robbert

I am back in Bordeaux now but  i'm always happy to help out by e-mail and share my limited experience with SE gear.

It should not be a problem to leave the PV on when charging through the SW and it's one less thing to forget to turn back on. Though it is possible that you would be throwing more amps into the battery if the sun was out and running the gen at the same time. That could be a good or bad thing depending on your situation. I guess that could be a whole different discussion.

Good luck and look forward to hearing from you.


Paix, Marc

[mike90045]

I leave the solar charger connected all the time, the generator does not affect it.
SCP is another tool, no more settings than the combox, but I monitor with the combox, and adjust my charging amps
(I have an old diesel genset, have to ramp up load slowly, and cut load off to let alternator cool down at shutdown)
with the SCP.

There have been issues with the combox memory filling up and it locks up, the latest firmware is supposed to fix that, but
the version before that was supposed to fix it too.  So when combox is down I only have SCP to adjust settings with.
Beware the firmware update procedure, you have to wait additional time to allow a FULL intake of all the new firmware, it signals an early end, and you will brick it if you stop early,

[mike90045]

Adding a couple pics of generator I use the SCP to adjust the warm-up and cool-down loading.

2 ports on either side of connecting rod, get a squirt of oil, if it's not been run in last 48 hours, splash lube only.
Valve train gets a squirt daily, as does the injector pump and pushrods.

[grgdgreek]

What is that , a Lister?

[mike90045]

Listeroid  - Clone from India, since the British ones are rare as hens teeth.  Works great

[robbertwilliams]

I just paralleled (2) 370ah banks, the voltages were identical, Mike...Anyways, I went in to change the charge specs in the combox under charger settings.  I changed the Battery Bank capacity to 740ah, and it automatically changed the Bulk, Absorb, and Float Current settings to 65amp (all of them).  I had the bulk set to 48amp, absorb set to 36, and float to (I can't remember).  I have Deka L16 batteries and I can't seem to do the math off of the spec sheet for the bulk amp setting. 

Here is the link (if you know what all the abbrev. mean): 
http://www.eastpennmanufacturing.com/wp-content/uploads/Renewable-Energy-Charging-Parameters-1913.pdf

I have changed the settings in the CC to 740ah bank and Ending Amps to 7.4.  Anyone know of any other settings that I am missing? 

[Westbranch]

Robbert, What time have you got Absorb set to?.... if it does not reach the time limit EA is used, if the time limit is used that will end it....it's an either /or statement, which ever comes first... 
I you want to max out Absorb in the winter set EA to 0.1A or 0.0A if you don't like the results of extra long Absorb set an appropriate time you feel is right for your bank, if it turns out not to give you the  desired results increase it.. it's an ART not a SCIENCE

[robbertwilliams]

My time limit is set to 5.5hr, but have been (when charging single string) relying on EA to finish the charge.  I guess I'm not sure what you're getting at with your reference to "winter results".  Is there simply a period of time in absorb that is too long?  I haven't been having any problems getting through a full absorb cycle with EA being the end all.  And yes, I am realizing it is an art and NOT a science...however, as with every field of interest, including art, there are fundamentals and starting points.  My question with regard to the Schneider charger and where to set the Bulk amps for a 740ah bank, that is more a fundamental/starting point question.  (Edit: the charger's max is 65amps.  So, I don't think it matters what I have it set to when charging the 740ah bank.  If anything, it's charging a bit on the low end.)

Thanks for all the feedback.

[Westbranch]

Is there simply a period of time in absorb that is too long?

In my experience so far, it is the opposite, a lot of time the Absorb is too short... and then battery performance starts to fall.... with an early death pending...