New batteries to install

[asdex]

I have some new batteries to replace my failed ones. They are not idea but were very cheap second hand.
They are 12 volt AGM and 100AH so I will have to have 4 parallel strings of two batteries =24volt 400AH. Not the best design but I have 20 batteries to play with.
The float voltage is 2.25-2.3vpc
Cycling 2.35
Max 2.4vpc
I'm not sure how these figures translate to the Midnite 150 settings.
There are in an offgrid system.
Can someone translate please. I guess cycling is float?
Thanks,

[Westbranch]

you  may find the info here useful...http://www.cdtechno.com/pdf/ref/41_2128_0212.pdf

[asdex]

Hi, thanks for the link. I'll have a read. It looks quite technical.
My problem is I'm installing the replacement batteries this weekend at our remote farm and won't be back for a few weeks. I'm hoping to get the figures correct so the batteries aren't boiling away which happened to my previous batteries.
If in doubt, I'll leave them disconnected.
Thanks,

[Vic]

Hi asdex,

I am NO expert with AGM batteries,   But,  AGMs,   fairly often have an Absorb voltage that is speced for batteries that will spend 99.9 or so percent of their sitting at the specified Float voltage,  provided by Grid power.

For off-gridders,  we Cycle our batteries daily or almost so.   So,  the 2.35 VPC for Cyclic use,  is what one would use for off grid,  or perhaps for Grid Backup power,   where the batteries are cycled daily or nearly so.

Be certain that you use the BTS on half-way down the side of one battery,  near the center of the pack.   But with four parallel strings,  there could well be some variation in battery temperatures across all of the batteries in the bank.

It IS very good news that you are not planning on running ten strings of two batteries.

Hope that you do have a Clamp DC Ammeter,  as you will probably want to measure how well each string of batteries are sharing charge and discharge currents.

Make certain that you set the recommended Temperature Compensation value,  in the Charge menu,  and so on.

EDIT to add that 2.35 V X 12 cells = 28.2 Volts ...

Just some general comments from a non-expert.   Good Luck,   Vic

[asdex]

Thanks, that's good advice I can use. I'll take a clamp on tester with me. I can hopefully get the string resistance similar using the charge current as you suggest.
My current bank was 440 AH and running a fridge and freezer though the night took it down to around 90% (10%DOD) and it was usually back to 100% by 10am.
If I can I'll only use 3 strings.
The classic uses bulk, absorb, and float. which voltage would the cycling be? Bulk?
Thanks,

[Vic]

   ...   The classic uses bulk, absorb, and float. which voltage would the cycling be? Bulk?
Thanks,

Hi asdex,

That 2.35 Volts Per Cell  --  28.2 V will be the Absorb voltage.   Would suggest that you use about the center of the stated Float voltage range (about 2.27 VPC)  X the 12 cells as a starting point for your Classic Float voltage setting.

Does this make sense?   Vic

[asdex]

Yes that looks good.
Absorb 28.2v
Float 27.24v
Bulk would be the initial charging rate which would be under the max of 28.8v so maybe 28.5v?
These are pretty precise voltages so I'll need to check battery voltage with a meter and adjust the controller offset.
I have done this before but didn't get consistent results. The voltage error changed at different voltage from what I remember.

[Vic]

Hi ascex,

Most Solar Charge Controllers,  like the Classic,  have NO setting for a Bulk voltage,  so there is no setting for Bulk voltage.

And,  YES,  we have one tenth of one volt resolution in setting voltages,  so,  why not start with a Float voltage of about 27.2 V.

If you have a good,  accurate voltmeter,  then you should check the accuracy of the Classic's voltage readings,  verses what you measure with your meter.

Good Luck with the new batteries.   And,  again,  I am not an expert,  especially with AGM batteries.   Vic

[asdex]

Thanks, I'm only working from memory as I have been overseas for three months but I'm sure it sometimes says bulk on the display. I see in the manual it's also mentioned:

Bulk MPPT
This stage of the Classic means; that the Classic will be putting out as much current as it can trying to
charge the batteries to the absorb voltage set point. This is also known as constant current mode.

Battery
Voltage
12v  24v  36v  48v  60v  72v
Bulk MPPT  14.3v  28.6v  42.9v  57.2v  71.5v  85.8v
Float  13.6v  27.2v  40.8v  54.4v  68.0v  81.6v
Equalize  14.3  28.6v  42.9v  57.2v  71.5v  85.8v
To adjust these voltage set point see page 25 of this manual.

[Westbranch]

Asdex, have a read of this thread, http://kb1uas.com/mnsforum/index.php?topic=2563.15....

The thing to watch for is the sharp rise and then leveling off (maintaining) of the voltage and dropping of current which is what is supposed to happen...  the sharp jump is/can be caused by the batteries internal resistance..  there are several graphs in around posts 30 and 56 or so....

hth

[asdex]

Thanks, will have a read tonight.
Cheers,

[Vic]

Thanks, I'm only working from memory as I have been overseas for three months but I'm sure it sometimes says bulk on the display. I see in the manual it's also mentioned:

Bulk MPPT
This stage of the Classic means; that the Classic will be putting out as much current as it can trying to
charge the batteries to the absorb voltage set point. This is also known as constant current mode.

Battery
Voltage
12v  24v  36v  48v  60v  72v
Bulk MPPT  14.3v  28.6v  42.9v  57.2v  71.5v  85.8v
Float  13.6v  27.2v  40.8v  54.4v  68.0v  81.6v
Equalize  14.3  28.6v  42.9v  57.2v  71.5v  85.8v
To adjust these voltage set point see page 25 of this manual.

Hi asdex,

Must say that I've never seen that reference to any BulkMPPT voltage setting,  and look at the Menu Map on pp 85 of the 2056 version of the Classic manual.  Under "Charge"  there is no place to set BulkMPPT voltage,  but the customary Absorb voltage does have an entry.

Furthermore,  with "BulkMPPT" ,   the MPPT suffix means that the Charge Controller has NOT reached a voltage setpoint (where the voltage would be maintained),  additionally,  there does not appear to be a way to set the Time for this Bulk voltage to be maintained,  as is the case with ALL  (EDIT OOOppppssss   obviously (even to me,  at times)  that Float does not have a time parameter) other voltage regulating stages  --  Absorb,  and EQ.   Although,   it could be possible that if there WAS a Bulk voltage setting,  that it could run for a fixed length of time,  I guess.

IMO,  you have found a slight error in the Classic Manual ...  on page 32 of the 2056 manual there is the how  to set the Absorb,  Float,  and EQ voltages,  but nothing for Bulk voltage ...

FWIW,   Thanks,     Vic

[asdex]

Hi Vic, thanks for your reply. It looks like I have all the info I need then to program the charge controller. I understand what you saying regarding no settings needed for the bulk charging. I'll have a further read of the manual and make sure I have the latest one although I think my controller needs a couple of upgrades of the software.
Bye the way my water heating using waste not high is working very well. I have also used SOC to turn on aux 2 which activates a SSR to put battery power to a 24 volt element. The 40 gal tank takes about 9 hours to heat. In summer, no other water heating is needed for us.
Cheers,

[Vic]

Hi asdex,

Yes,  you will want a Classic manual at the site.   One that matches the FW version in the Classic will be a bit less confusing,  probably.   Documents,  including Classic Manuals are on this page  -- choose the CC that you have,  and then, scroll to the manual that best suits your needs:
http://www.midnitesolar.com/doc_prod_list.php?menuItem=products&productCat_ID=21&productCatName=Charge Controllers - Classics

When you feel the need to Update the FW,  if you have never done it before,  it would be a very good idea that you have some way to access this Forum,  if needed during the Update.   Hope that you have the Net at your Solar powered location.

Saw your Post about WasteNot doing a great job heating water.   The Classic is certainly a very flexible and capable CC.

Have fun,  and good luck with the battery swap.     Vic

[asdex]

Hi, I have my 6 Haze batteries in and going now.
One thing I'm not sure about.
The are in float but at 97% capacity.
Battery voltage is 27.6v
From the PV panels are 85.5 v and 22 watts.
there is 0.8 amps going to the batteries. This is all from the Classic screen.
I though it would be taking the batteries up to nearer 100% before it went to float.
I have the absorb voltage set at 28.2v and float at 27.2v.
I set the AH in the WBjr screen to 300AH
on Saturday the batteries had been on float for about 5 hours but were still at 98% capacity.
On Sunday morning the batteries were at 90% so I think they are not charging up enougt.
My version is 1849 and mngp is 1821. Should I update thsi?
Thanks,