Getting the ending amps set correctly

[ClassicCrazy]

Thanks John for the Excel sheet  - I was able to get it from Dropbox link also and inserted my data and it worked graphing it.

Larry

[Resthome]

Thanks John for the Excel sheet  - I was able to get it from Dropbox link also and inserted my data and it worked graphing it.

Larry

Glad it worked Larry...

I think I need to lower the efficiency on the SOC as I was pretty close to matching my Link10 meter but it seems to be off since the update to the Alpha Firmware. And it is hitting 100% SOC way before the WBjr Amps level off. Batteries are only on their 2nd year so the S/G have always been good. And with my deep 2v cell they need to be stirred up. I also need to drain them down more they don't get much below 90% SOC and in the winter we don't get to the boat so usually use the nice Skip Day function of the Classic.

Good luck with finding the right end amps it's a science project but much nicer since the addition of the WBjr.

[ClassicCrazy]

Now that I have been watching the system amps closely , comparing it to the SOC , and checking the specific gravity it also seems that the point of 100% SOC is off. I think I will lower the efficiency from 94 to 90 or 92 % and see what happens. My batteries are still quite cold 52 F  and I wonder how that effects some of this. It would be nice to really trust the refractometer and hydrometer . I have not equalized the batteries yet - probably do that tomorrow.

Here is when the manufacturer says to end absorption
End Condition Charge until change in current < 0.10A per Hr / Max Time: 12Hr 

[vtmaps]

My batteries are still quite cold 52 F  and I wonder how that effects some of this.

Quite a bit.  A cold battery has lower capacity and higher Peukert coefficient (which makes it less efficient).  I am not sure to what (if any) extent the WhizbangJr accounts for this. 

For example:  you draw down 37 amphours from a fully charged, cold, 370 ah battery.   A SOC that is calculated by counting amphours will be 90%.   The actual SOC is less than 90% for no other reason than the battery's capacity is not really 370 ah.   In addition, the internal resistance of a cold battery is higher, so more energy is lost to I²R heating.  Thus the higher the amperage while you draw down the 37 ah, the lower the resulting SOC will be.

Another factor to consider is the efficiency of charging.  During bulk charge, the lower the charging current (within limits), the more efficient the bulk charging process is.  During late bulk and absorb (when above the gassing voltage), the charging becomes still less efficient.  As far as I know, the whizbangJr does not yet account for this.

--vtMaps

[ClassicCrazy]

Thanks vt ,
The more I dig into the battery stuff the more I learn !
I just tried making the 27.25% sucrose battery calibration fluid for the refractometer-  but it is way off for me - might be due to that I only have a digital ounce scale that goes to 0.1 digit . The sucrose mix  only gave me 1.21 on refractometer scale which I had already calibrated the other way. When calibrating with distilled water to the 32 degree line as directions say it compares more closely with hydrometer with its temperature compensation.
It is fun to experiment with these things to gain greater understanding.
I have concluded I need to do a good equalization cycle to bring cells back in better balance.
Larry

[vtmaps]

I just tried making the 27.25% sucrose battery calibration fluid for the refractometer-  but it is way off for me -

Calibration of hydrometers and refractometers is over-rated in my opinion. 

As an analogy, consider 'end amps'....  your whizbangJr does NOT need to be calibrated to work.  If two WhizbangJrs disagree on what that 'end amps' current is (for a particular battery), then so what? ... you simply set each whizbangJr to go to float at what it thinks 'end amps' current is.

You can take the same approach with a refractometer or hydrometer:  Keep equalizing your battery until the SG no longer increases.  That number represents 100% SOC for your battery.  Different hydrometers and refractometers may disagree on what that SG is, but that doesn't matter as long as you use the same instrument each time.

Another thing... if the SG after equalization does not APPEAR to be as high as the manufacturer's specification, it MAY represent some permanent sulfation.  Even so, that low SG is 100% for your battery and is the number you should use for monitoring your SOC.

--vtMaps

[ClassicCrazy]

Those are practical realistic observations vtmaps .

Going beyond that and trying for scientific accuracy and perfection could drive a person crazy !  I am coming to this same realization that you have just stated about testing instruments. Hopefully others with less experience can absorb this knowledge and save some frustration and be ready to apply these insights before they even start playing with the battery acid.

Now if the sun would just be a bit more cooperative so I can get a decent equalize day or two in !

Larry

[Garret]

I just tried making the 27.25% sucrose battery calibration fluid for the refractometer-  but it is way off for me - might be due to that I only have a digital ounce scale that goes to 0.1 digit . The sucrose mix  only gave me 1.21 on refractometer scale which I had already calibrated the other way.

Yeah, you need a balance with at least 0.01g precision unless you are making a bucket of it.
Weight percent = weight of solute/(weight of solute + solvent) x 100%.  Mine agrees well with the hydrometer Midnight solar sells [CORRECTION TO POST] a really nice German-made hydrometer that agrees along with my refractometer and standard 1.265 electrolyte.