Absorb time setting

[Corndog]

Hello,
Two Questions

I have searched and read the replies associated with this question with some mixed answers. Being brand new I would like to make certain my absorb settings are close to the best they can be.

Off Grid
2 x Outback Flexware- VFX3648 Inverter
Mate 3
Power Hub 10
14 x Hanwha solar panel 345 watt
Midnite CI150 Charge
13 KW Diesel Gen
Batteries- Surrette 550 6V x 16
48V

Is there more information required ?

Absorb is set to 57.8 for 6 hours

 2nd question - Being in Ontario Canada our summer and winter sun amounts vary A LOT should I have different settings per season for this reason ?

Thank you

[Vic]

Hi Corndog,

Six hours of Absorb is a very long time.

The proper Absorb time varies,   depending upon the Depth Of Discharge (DOD)  in the previous discharge.  There is no set answer for Absorb,  when recharging from Solar.

57.6 V seems a bit low for Absorb.   Absorb voltage and Absorb time is a bit interactive.

There is a Surrette Battery Manual for these Flooded batteries,  on the Surrette Battery site.

Did you Commission this battery bank,  per that Manual?

Regarding the difference twix Summer/Winter,   often in Winter,  the Absorb voltage needs to be increased,   to try to get as much charging done as possible in the short Winter days.

Does this help?   Vic

[Corndog]

Thank you Vic,

This does help thank you !!

Yes this was set very close to the Manual from Surrette .
http://support.rollsbattery.com/support/solutions/articles/237882-calculating-proper-charge-settings-for-rolls-flooded-lead-acid-batteries

I am going to revisit this

[Vic]

Hi Xorndog,

Thanks for the added info.

Looked at your Link,   this is an improvement from just having the older Bat Manual.   But,   it looks like the battery in the example was discharged to about 58%   State Of Charge (SOC),   as a rough guess.   This is a fairly deep discharge for daily cyclic use.

Do you know what is your DOD  of your battery on a typical day?   If you discharge to about 80% SOC (Discharge of about 20% of battery Capacity),   then,  about 2.25 - 2.5 hours of Absorb,  at 58.8,  to as high as 60 V Absorb should be about right.

Assume that you are using the MidNite Bat Temp Sensor,   attached midway down a battery in the center of the pack,   and your  Temp Comp value is --5mV.

Your accurate Hydrometer will help you tell how well your batteries are being charged,   as will the amount of water that the bank consumes per month.

Later,   thanks,   VIc

[Corndog]

Thank you ..

Assume that you are using the MidNite Bat Temp Sensor,   attached midway down a battery in the center of the pack,   and your  Temp Comp value is --5mV.

Temp Sensor as stated
Is this the temp comp setting value here ?

Also what is the best way for me to calculate my DOD ?

[Vic]

Hi Corndog,

YES,   that  is the correct compensation for your batteries

If you have a Whizbang Jr Current Sensing Module on your Classic,   you would see the approximate SOC,   and (to me) the even more important and accurate reading  --  Net Ah.    This the Net of all Ah  put into and removed from your battery,   on each cycle.   It is reset to 00 Ah,  when the Classic transitions from Absorb,   to Float (on its own).

You could measure Specific Gravities in the early morning to  give a good read on actual DOD/SOC.   This is often done,  using Pilot Cells  --  at least one per battery string,   usually chosen from the cells with the lowest SG readings when the battery is judged to be fully-charged.

Vic

[Corndog]

If you have a Whizbang Jr Current Sensing Module on your Classic,

I will have to get this. Learning again. Thank you

Can I ask you about Equalization ? I have not done this in over a year , my batteries are all very close in specific gravity. Should this be done anyhow every so often ?

[ClassicCrazy]

There is some good info on here regarding how to determine end amps.
http://www.midniteftp.com/support/kb/faq.php?cid=1

Larry

[Corndog]

Great Link,
Thank you

[ClassicCrazy]

Also a lot of good info in the series of youtube videos Ryan made on how to use the Local Status app
https://youtu.be/uyPcDvNXMCI

Larry

[Vic]

Hi Corndog,

Surrette has changed their stance on EQing their batteries.   Their present take begins on page 20 of their present manual revision:
https://rolls-battery.com/wp-content/uploads/2019/11/Rolls-Battery-User-Manual.pdf

Perhaps one reason that Surrette no longer recommends a periodic EQ,  independent of a significant variation in SGs among all of the battery cells,  is,  perhaps due to their increase in recommended Absorb voltage,   for systems that are cycled daily (to 60 V for 48 V batts).

Out of curiosity,  what are your nominal SG readings  in Float,   after what you judge to be a complete charge.  AND,   what is the maximum variation between all cells?  Do you notice any difference in the average SG readings,   between each of your two battery strings?

BTW,   have been a proponent of using EA,  to end Absorb.   BUT,  the Surrette banks here evidence a variation in optimal EA values,  depending on the DOD of the battery in the previous cycle.   This can add some uncertainty in how well the batteries are being charged,  in systems that do not have a repeatable DOD on each day (IMO).

EDIT:  Also,  how are you measuring SGs?   Hydrometer,  Refractometer etc?   Please tell us about the type of device you use,   and,  if possible the name/manufacturer,   and perhaps a Link to it.

FWIW,   Thanks,   Vic