removing surface charge

Can I remove surface charge on a maintenence-free or VRLA type battery the same way I remove surface charge on a typical non-sealed car battery? By turning on the high beams for five minutes, then waiting like 15 minutes after that.

AFAIK, that should be fine.
Except for the dryness of VRLA/AGM batteries (hence no overcharging and don't leave them discharged), their behaviour should be similar.

Question - does it take as much as 5 minutes on high beam (ie, 150W - 300W) to remove the surface charge? Is it a typical auto battery (300-600CCA; 40-120AH etc)?
If it does, that will certainly blow audio "stiffening" capacitors to kingdom come (with the possible exception of one parameter...)!   

Nice to hear someone else mention surface charge. I sometimes have difficulty explaining why people's batteries really are ~12.7V & not 13.7V etc....

thanks for the feedback oldspark......and dont worry.  I will disconnect the power cap when the high beams are on.  Even though it would be kinda cool to see one blow up (from a safe distance).

Excuse my ignorance Oldspark but is this related to disconnecting batteries for 20 minutes to remove static when playing around airbags, or removing both leads and touching them together?  Honest question, please remove my ignorance?

Calitech - forgive my bad!
My "that will certainly blow audio 'stiffening' capacitors to kingdom come" was not intended as literally destroying them (though I do enjoy people destroying their multi-$hundred super-caps because they didn't pre-charge them as per instructions!).

I was referring to those that insist on the electrical requirement for caps close to the sub/amp.
I am one that suggests (or knows?) that a much cheaper small battery next to the sub/amp is as effective (if you call having 1,000 to 10,000 times the stored energy for 1/3rd to 1/10th the price as merely being "as effective").
I am not appealing to those that like their bling & show, merely those think they need a cap.
Anyhow, I reckon that a battery's surface charge alone has more energy than a cap.
The only other parameter of interest is their ESR (Equivalent Series Resistance) which even for a small $35 Yuasa NP7-12 AGM/VRLA battery is 25 milli-Ohms which is less than or similar to many cap ESRs.
I'll leave that there - it gets real tech and complex, but I do have a good link somewhere....

And BTW - I wouldn't want to be around an exploding supercap. An old thumb-sized 12V electolytic was bad enough (pop, smoke, sticky gel and some schrapnel).


Now for Howie's excellent question...
(Ignorance? Nice try Howie - even though I interpret (continued) ignorance as NOT questioning something.)
There is no harm asking a question - especially if it clarifies an ambiguity. (Not that I am ever ambiguous, except when "blowing" caps, or whenever I write or say anything.)
And here we have a lovely ambiguity - "surface charge" as in static electricity or capacitor-plate stored charge, and battery-jargon's "surface charge".

As to airbags? Sorry - my ol'Dear doesn't use batteries...
Oh - airbags.... I get it --- they weren't even an option on my old T-model....

No - a battery's surface charge is not static or capacitive charge.

A fully charged 12V battery is usually about 12.7V
But charge a battery at (say) 14.4V and then remove the charger (or kill the ignition and engine etc).
If you observe the battery voltage, it will quickly drop but be much higher than is "full" 12.7V; perhaps say 13.7V.

This is due to the "surface charge" and it can stay for quite a while. (Hours, days - I'm not sure.)

It takes a discharge to remove it. EG - a reasonable load should see its 13.xV surface charge voltage drop to its "full charge" voltage of about 12.7V (ignoring the battery's internal resistance voltage drop) where is should remain for quite a while (I guess for about 1/10th of its discharge rate before dropping to 12.6V etc). Otherwise a battery's self-discharge will eventually remove it.

Geez - you got me dusting off various "old issues" there!
And I haven't really defined surface charge - I've merely explained its behaviour.
I/we could look that up on www, but I never trust anything I read out there!
Alas like many things, I have forgotten the theory but recall its reality. (That's where there is little difference between the experienced "trained" person and the "uneducated" experienced person - noting that both are usually far better than an inexperienced but qualified "expert", IMO.)

Ta for the answers, I'm the second type in your last sentence, but even after 35+ years in the game, I still believe in gaining extra knowledge or asking advice. I still use a Snap-On test bulb for most of my work, when I'm unsure I'll use a DMM but then I've probably triggered 2 airbag lights in all that time, I do know when not to probe, though I still say you can't beat Mr. Snap-On for finding lock triggers or radio mutes. Hell I even use a Mac 120 tester with LEDs for finding tach, it's fast and it works.

Howie - yet again you impress me.
And because I have always had a multimeter and know how to use it, I never use a test light.
However, if not for my MM, I would surely have a test light. (As to modern mechanics that function without one...!!???)

As to the number of times I think I'm being really stupid powering up a multimeter and reading some digits or dial when a test lamp would be so much easier....
No - maybe I'll paraphrase another forum - it's much better buying a $10 brake bleeder with a valve that seizes and rubber that perishes than using a bit of tubing (preferably clear plastic).
I presume that is because it costs more and is more complex (and breaks down), and is therefore a superior tool.
Else it is because professionals use it for their everyday work, therefore we need it twice a year, or bi-annually etc.
(Is this an appropriate point for my new term "SLAM"? In this case I prefer my common term akin to fornicators with a sense of humour - aka F-wits - with F is as in PhD - Doctor of Filosphy - very clever wits.)

Anyhow, no hijacking! I wanted to supply the "stiffening cap" link I was thinking of above...

Although there are many like this site's (closed topic) "Capacitor Information", one I did like was at the MobileElectronics site as reproduced from an original article by Richard Clark (CarSound) - an apparent guru in the audio field.

What is said in the MobileElectronics link below IMHO is good - both Richard Clark's writings, and others in support.

I also like the "non-arguments" of the so called knockers (of Richard's cap debunking).
I will usually recommend the much cheaper small AGM battery alternative (read: far superior solution!).

And FYI - although that site's Pulse-R puts up some seemingly reasonable counter arguments.... No - I'll rephrase that - some seemingly valid debunks - he is way off track whether it be misinterpretation or confustigation. (This becomes apparent at the link he provides at the end of the link below.)
If readers herein do not accept or understand that, I could explain what Richard means by half the charge being under 12V; provide the correct Nyquist Sampling Theorem; etc.
Mind you, like Richard,, I'd want to keep it it basic - one step at a time - not introduce transient and Fourier analysis (frequency or time-domain) as Pulse-R does later on.
Let's just deal with DC and low frequency (sub) stiffening capacitors behavior for now. If that isn't grasped, the high frequency & Laplace have no chance!

To quote the Chinese: Enjoy!
See "Capacitors, Taken From The Writings Of Richard Clark..".

Howie - "incandescent bulb" - you greenhouse gasser!
Incandescents are banned here. Well, soon anyhow - we much prefer those high crestfactor low powerfactor CFLs (Compact Fluorescent Lamps) that take a bit more manufacturing energy than incandescents, and then emit the usual hazardous items (especially if broken) - all to reduce inefficiency by 1/20th from 95% to 90%.
Luckily it only applies to our 230VAC domestic lighting - not automotive DC lamps.

And thanks for clarifying the names. I'm a noob to them, but already I have been impressed! I intend to get Richard's original article(s) one day....
Amusing isn't it - the cap issue seems to have been solved long ago, yet it still survives. Money & bling?
It reminds me of a recent response from a group that confuse a safety function with engine preservation, and still use an engine kill technique known to be damaging. Having rejecting a person's solution (despite underpinning his/her argument(s)), they then ask that person why people still use that old damaging method! (Please - ask Lemmings why they jump - not me!)

Howie was worried about sidetracking.
I have totally turned this into an Oldie & Howie conversation. For that I apologise.
But I'm certain CaliT's original post/question has been answered.
A related ambiguity was clarified (surface charge & static).
Likewise the ambiguous "exploding cap (myth)" was clarified.
And I think a few useful methods and techniques were covered.

Now, if I would desist slipping in political comments....
(Whether as revenge or to provoke awareness....)

And the logic (that's my most obtuse pun this month) behind the incandescent bulb was that it "safely" tests things and draws enough current to trip things like lock triggers. Yes all my bulbs at home are low energy and yes unlike the US colonies we run 230AC, but do you know the reason why Europe went 230/240 as against 110?  I know house voltage is 220 in the US. But they split it and while HVAC runs at that, the actual wall outlets are at 110. Those low wattage bulbs remind me of the spurious reasoning behind the Prius. In fact build to scrappage you'd be better off in a BMW/VW/Focus diesel.

https://www.jgdarden.com/batteryfaq/carfaq.htm

I'm bumping this for this worthwhile reference (IMO), and 'cos it's a good place to put it....
Ironically, I now think I know where calitech got the OP "turning on the high beams for five minutes, then waiting like 15 minutes" info for removing surface charge.
But do AGM/VRLA batteries have surface charge...? (See below.)

Regarding Surface Charge, I have extracted the relevant text below from 4.3. Remove Surface Charge which is part of carfaq4.htm = Car and deep cycle battery FAQ (as updated 2nd January 2010).

This is Bill Darden's famous info that is often referenced as being at https://pweb.uunet.de/william.darden/carfaq.htm which is now https://www.jgdarden.com/batteryfaq/carfaq.htm

(I have an older uunet copy (of Part-9) and went looking for Part-4 - finally finding the new & updated site.)

I was glad to see so far that my advice has not been wrong.
Like, last night I saw someone saying batteries should NEVER be paralleled when idle (ie, when not charging or supplying) because even when matched, they will differ and die prematurely.
Mind you, if I read the lot, I'll probably find some of my bads!


The following is extracted from Bill Dardner's carfaq4 "4.3. Remove Surface Charge" (with my added bolding):
Surface charge (or "counter voltage") is the uneven mixture of sulfuric acid and water along the surface of the plates as a result of charging or discharging as the electrolyte has an opportunity to diffuse in the pores of the plates. It will make a weak battery appear good or a good battery appear bad. Larger wet lead-acid batteries (especially over 100 amp hours) could also have electrolyte stratification where the concentration of acid is greater at the bottom of the cell than near the surface. The Open Circuit Voltages (OCV) will read higher than they actually are. Stratification can be eliminated by an equalizing charge, stirring or gently shaking the battery to mix the electrolyte.

So will an electrolyte-less AGM/VRLA have Surface charge (counter voltage)?   
I'll have to read more.... (or does anyone else know?)
And despite years of intent, I have yet to charge one of my 10 year old AGMs and find out! (They have been charged yearly, I just never tested for surface charge - though I can't recall the +1V often seen on wet batteries.)

But I can imagine some surface charge - even if literally "surface" - ie, plate capacitance (even though this should self-discharge in seconds...)


And herewith the rest of the info under 4.3....

A surface charge can be eliminated by one of the following methods after recharging a lead-acid battery:
- Allow the car or deep cycle battery to sit (or rest) without discharge or charge for between two and eight hours at room temperature, if possible, to allow for the surface charge to dissipate. (Recommended method.)
- For car batteries, turn the headlights on high beam for five minutes and wait ten minutes.
- For car batteries, apply a load with a battery load tester at one-half the battery's CCA rating for 15 seconds and then wait ten minutes.
- For car batteries, disable the ignition, turn the engine over for 15 seconds with the starter motor, and wait ten minutes.
- For deep cycle batteries, apply a load that is 33% of the amp-hour capacity for five minutes and wait at least ten minutes.

Note that all state wait ten minutes (except the recommended 2-8 hour wait).

I like the 15-second cranking (plus 10-minute wait) as this is fast and convenient (for vehicle mounted batteries).
And I expect that the voltage reading immediately after cranking will be far more indicative than the typical +1V seen after charging, though the post-cranking will be pessimistic.
(After removal of their load, batteries self-recover to some extent - ie, their voltage increases.)


Anyhow, for any battery related information, I highly recommend Bill (JG) Darden's info.

And FYI update on my AGM Surface Charge.... after intense scientifically controlled testing....

Last night I charged my two ~10 year old Yuasa UXH38AH-12V AGM batteries from an 8A charger in the bathroom.
They had been ignored for an indeterminate period starting last decade (probably at least 12 months ago) and had voltages of 12.34V & 12.66V respectively.

After charging each for an unrecorded time, the charger was disconnected after reading ~14.8V for one, and noting 15.4V on the other whilst brushing teeth (mine; and in situ). (NB: The electric tooth brush used an independent power source.)
In the first "disconnect charger" case, I thought of MY Golden Rule never to exceed 14.4V when charging AGMs.
In the second "disconnect charger" case, I chose not to think of my nee-Golden Rule.

However, in both cases it was observed that their OC (open circuit) voltages quickly approached ~13.7-13.8V (about 1V above "full charge" voltages).
From there they slowly reached ~13.2V within a few minutes.
I then connected a 0.44A fan and later a 3A water pump to hasten the "surface removal" process. (Ignore teeth enamel and brushing - that was in the previous block & over 4 paragraphs ago. That subject is closed - no further decay etc puns.)

Although the loads increased the rate of decay, I got bored around 13.1V, disconnected the loads, and kissed the terminals goodnight.
[ The official record states that at 13.1V, "extreme fatigue caused by rigorous scientific testing took its toll and the esteemed tester retired for the night (without recovering expenses)". ]


Approximately 12 hours later and the OC batteries are 12.76V & 12.80V respectively. (Ambient temperatures: Currently 21C. Last evening 32C. Overnight 19C minimum.)


My conclusion is that AGMs do exhibit surface charge similar to wet cells, however:
- the AGM's initial surface charge decay is much faster (my estimated real 5AH "12V-40AH" car battery holds its surface charge MUCH longer!)
- I strongly suspect that Bill Darden's explanation of Surface Charge being cause by an "uneven mixture of sulfuric acid and water along the surface of the plates" is not correct for AGMs, however the root cause may be the same.

I further suspect that the AGM is more likely to exhibit capacitive behavior than wet lead acids due to less conductive medium between plates (ie, electrolytes).


As to how AGM and wet lead acids compare against each other in accessing their (audio/stiffening) capacitor equivalence with respect to "charge" is inconclusive.
Wet cells seem to have more initial surface charge due to uneven plate-electrolyte distribution.
AGMs may have greater "plate capacitance" (ie, like a capacitor).
AGMs may also have uneven plate-charge distribution after charging similar to wet cells.
AGM surface charge (or equivalent/other) may increase closer to their idle (steady state OC) voltage - in particular - relative to wet cells. (IE - AGM voltage initially decayed faster, but then seemed to hold up well.)

Certainly from observation of voltage decays above "full battery voltage" above (ie, above 13.0V) and from observations or wet cells elsewhere (ie, Le Co-Pit of my car), I suspect the combination of capacitive & surface-charge charge in an automotive battery to be the equivalent of a VERY VERY large capacitor.


Suggested next test: power/charge capacity of a wet cell, AGM, and large capacitor (eg, 1F - 10F etc) above 13.0V or 12.8V from 14.4V or 15.4V be compared.
The lower voltages should be above the system voltage/s where the battery determines the system voltage (ie, by chemical conversion).
The upper voltage/s should be the system's charge or operating voltage - ie, 14.4V max for normal vehicles; 15V or higher for SPL competitions etc.

Then: Testing of "battery lag" - ie, any hi-load voltage dip whilst the battery changes from capacitive & surface charge energy to chemical energy.

And Then: If the above suggest real-performance inferiority of the battery, compare ESRs and its dynamic effect in real-life extremes. Note that battery and capacitor costs must be included (as well as their size, manufacturer, model, batch etc as done with all above testing).

Then there are comparisons for batteries that are under full charge - say at 70-80% capacity for crankers, or 20% capacity for deep-cyclers.
But lets crack those Chinese Take-Away games first.