Battery Charge Voltage

[SM-Viper]

Hi all!

I'm trying really hard to get a good handle on the charge voltage settings for my battery back with the Kid CC. My main question relates to hearing a "bubbling" of the battery electrolyte while charging. How much of this sound is normal?  I'm mostly concerned with safety and not overcharging my batteries too much. I also don't ever want to under charge them either.  Right now they are floating at 14.1v-14.2v. This seems a bit high, but I'm not sure.  The battery specs indicate that the "maximum charge voltage is limited at 15 d C (59 F)" ().  This is what I'm using for my battery specs: M&K or Deka http://www.mkbattery.com/documents/3379Form%201913.pdf

My questions are:

1. Do my settings seem correct?
2. should I be hearing the electrolyte "bubble"?
3. Is this the sound of the batteries Gassing?

* I have a small bank of two 215ah batteries in series for a 12v system.

* Currently, I have my ABS voltage set at 14.4v, Float voltage at 13.8v. My EndAmps is set to 3.2A.

* TComp is set at -3.0mV/Degree C/Cell

* Current battery temperature is 9 degrees C.

* Batt Efficiency is 94%, 25dC Ref, 1%/d C Change %

-Thanks!

[Vic]

Hi SM..,

Carefully looked at your post and Sig line,  BUT,  could not find weather your batteries are AGM or Flooded.

For Flooded batteries,  this bubbling during Absorb,  and EQ  is quite normal,  and really required for full charge and a good EQ,  as well.

Are your batteries Flooded?  There ARE some GC batteries that are AGM,  but not too common.

Thanks,   Vic

[SM-Viper]

Thanks for the reply Vic!  Yes, they are flooded. The specs on these batteries were very hard to locate, and the company rep I spoke to referred me to the PDF I attached. This was the closest I could find. Do you think my settings look okay? I am still a bit confused by the "maximum charge voltage" statement in the documentation specs though. 

-Thanks

-SM

[Vic]

Hi SM,

Thanks for the info.  Yes,  it seems very,  very difficult to find charge data for most of the GC batteries.

So gurgling and bubbling is normal,  and required for full charge of Flooded batteries.

Regarding the limits of temperature,  believe that in that Data Sheet,  it only applied to AGM batteries -- there appears to be a very small,  light "  1  " for the data,  and Footnote 1 apples to AGMs ...   should go back to look at that data.

The Temp Comp value seems more like that for AGM,  and not customary Flooded Lead-Acid (FLA)  batteries.  FLAs generally use --5 mV/C/Cell.

Will try to look again at that PDF data ...

And,  YES that Float voltage appears high to me.  For Flooded batteries,  that are cycled,  as in an off-grid system,  the Float voltage is almost always set at the lowest voltage that will just (barely) keep the battery fully charged.

All just my opinions.   Have Fun,  Vic

[SM-Viper]

Thanks again Vic.  Regarding the TComp value, I started it out at -5 mV/C/Cell, and changed it due to the specs and the seemingly high charge voltage.  Do you have any ideas as to why my charge voltage is climbing so high? I've exhausted my searching and research for this, and really am concerned.

Isn't the TComp values the temperature compensation control?  That seems off to me.  I figure .003v x 6cells x (25-9) = 0.288 volts.  14.2-13.8v = 0.4v.  This looks to be double what its supposed to be. Is that right? do you see anything different here? Is this a problem I should even be concerned with?

btw, I checked the spec doc and did not see where footnote 1 was referring specifically to AGM. Not sure what that means.  Should I leave it at -3mv/C/Cell ? or change it back to -5mv/C/Cell? What kind of difference should I expect to see there?

-Thanks!

[Vic]

SM,

First,  YES,  the spec does note that the Temp Comp be limited to the noted range for ALL of the batteries covered in that Data -- Gel,  AGM,  and FLA.  My Laptop has trouble resolving that small grey text,  as do my old eyes.

And that --3mV/C/Cell Temp Comp does cover the range of Gel,  AGM,  and FLAs.

We always DO say to follow the manufacturer's data.  And if the MK Rep says that this IS the Data,  then guess that you should follow it.

Are you saying that your present battery temps are 16 C?

FWIW,   More later,  off to an appointment.   Vic

[SM-Viper]

Thanks again Vic.  No, My current battery temp is at 9dC. The difference is 16dC.

[Bob D]

Took a look at the PDF, and it seems to me the necessary info is there.
I agree that the float voltage seems a bit high, but if that is what Deka specifies, I'd use it.
In your calc, the difference between the temp corrected voltage and the measured voltage is just over 0.1V - this might be measurement error, but in any case it is not a significant difference.
From what I understand, the voltage correction for low temperatures is to ensure your batteries get fully charge, as opposed to the high temperature correction use to protect the batteries from overcharging.
I was advised by my battery supplier to not get to excited one way or the other about the low temp compensation.  they were not at all concerned with 5mv/dC, which in my case let the voltage run up by 0.25 volt per cell when the batteries hit -25C.  They did say that if I was going to lose sleep about it then turn off the low temp compensation; I left it on.
All fwiw - might help your learning curve.

[Vic]

SM,

Yes,  agree with your calc for the amount of nominal Temp Comp.

Are you using the MN Battery Temperature Sensor,   attached to one of the batteries?

Have you checked the voltage Calibration on the KID?  If you have an accurate DMM,  this can help the accuracy to the Temp Comped charge voltage. It is probably best to try to check this Calibration,  when the KID is delivering only a smll amount of current,  in Float,  perhaps -- this will reduce the effect of any voltage drop in the cables between the KID and the battery.

It is just my opinion,  that charge voltage Temp Comp is very important for batteries that are cool or cold,  and those that are warm or HOT.  The more extreme the temp of the batteries,  the more important is an accurate comp value.

Just my opinions,   FWIW,   Vic

[SM-Viper]

Thanks Vic and Bob for your input.  I do have a MN Temp Sensor, and it is right at the level of the batteries. Also, I have checked the voltage values with a DMM and I don't recall there being much difference betweenthem. I will check them again next chance I get.  I'm beginning to feel better about all of this, but still not real confident yet in my current settings.

I'm now okay with the gurgling during charge, (namely the ABS charge state near the end when the batteries are nearly full), but I was not expecting it in FLOAT.  Not sure that's right.  Thoughts?

Thanks!  -SM

[Vic]

SM,

First,  believe that you are saying that the BTS is not attached to a battery.  If that is the case,  please attach the BTS to one of the batteries,  about half way down the outside of the case.  If you do not wish to use the adhesive on the BTS,  then just tape it down with some blue painters tape,  or similar.  This will help track the real battery temperature.  Batteries have a lot of thermal mass,  and track the ambient temperature fairly slowly.

Batteries will continue to gurgle long after Absorb or EQ has ended,  and while your Float voltage is on the high side (IMO),  it appears to be below the normal Gassing voltage.  But believe that this highish Vfloat could mean that it will take more time for this gurgling to cease.

The gas bubbles stick to the plates,  and coalesce into larger bubbles,  and eventually break loose and rise to the top,  where the bubble breaks and makes the noise -- this can take several days,  especially with tall batteries (your GCs are not tall batteries,  however).

Just the way I see it.   Have Fun,  Vic

[SM-Viper]

Thanks Vic! You da man! I'll do that tonight. Thanks for all your advice.