[RE-wrenches] intermittent battery problem; ...Battery Sulfation

Allan Sindelar allan at positiveenergysolar.com
Mon Oct 24 03:35:33 PDT 2011


Ron,
You have made a connection that I would not have made, and while I may be
wrong here, it has got me thinking. I have never equated low water level
with SG, nor have I ever read in battery maintenance guides that I should
maintain a particular water level before measuring SG. I'm not convinced
that electrolyte level has any connection with measured SG, although it
would seem logical on the surface. I have always thought that if the correct
concentration of acid was installed at the factory and not lost thereafter
(such as due to a spill or chronic overfilling), the SC is only a function
of SOC. I'm interested in others' opinions here.

Allan
Positive Energy

On Mon, Oct 24, 2011 at 1:49 AM, Ron Young <solareagle at solareagle.com>wrote:

> Hi Larry,
>
> I immediately assumed sulphated battery when I heard the customers
> description a couple of weeks ago but the hydrometer readings didn't jive.
> Any sulphated battery I've encountered, and I defer to your greater
> experience, has always revealed itself with a simple S.G. test and these
> batteries were reading above 1.265. I then thought the possibility of a
> defective hydrometer and had them test with another but we just got
> confirmation of the same thing.
>
> The weird drop in voltage also isn't explained by your description. Why
> would this just happen without loads or charging present (except maybe the
> DC Sunfrost load) at the same predictable time at 4 a.m. The fact that when
> the generator was turned on and sent a surge of current into the system and
> the problem went away made the detective in me think there had to be another
> explanation. The bank was at rest for several hours through the night and
> the voltage dropout was cured by a brief application of charge current.
>
> When I arrived on site my discovery that the client was under watering the
> batteries and this chronic condition resulted in a very rich electrolyte,
> reading well above 1.265 - into the 1.280 range made me think that was the
> problem and it seems to have gone away now that the electrolyte level was
> raised and the batteries given a good charge. But it still nags at me that
> something else is lurking in the shadows. Your description of the sulphate
> converting to a crystalline form has me worried because if this is the case
> this expensive battery bank is in danger. I would have to camp out at the
> site and monitor the charging over a day or so. I'm going to forward some of
> your comments and those of others that have generously offered suggestions
> and we'll see if I can convince the client who now believes everything is
> A-Ok.
>
> Best Regards,
> *Ron Young*
> earthRight Products - Solareagle.com
> Alternative Energy Solutions ~ Renewable Energy Products
>
> On 2011-10-22, at 12:06 PM, Larry Crutcher, Starlight Solar Power Systems
> wrote:
>
> Hi Ron,
>
> As many on this list have suggested, it sounds like a sulfated battery
> condition. In your last message you revealed something to me that absolutely
> confirms this but perhaps you didn't recognize it.
>
> Battery voltage readings are deceiving because they do not indicate
> capacity. 25.7 volts sounds like a fully charged 24 volt bank, but is it?
> Only if the battery was at rest for 5-6 hours could you have some confidence
> that the bank was full at this voltage. But this is not the case because the
> bank is in daily use, always charging or discharging. However, there is one
> useful indication that voltage can be used for: detecting a sulfated
> battery.
>
> You mentioned that the the battery drops to 24.5 in the early AM without
> any heavy loads on. For the 4KS25 battery this equates to about 800AH at the
> 72 hour rate. Then you said that the customer ran a 2500 watt generator for
> 5 minutes and drove the voltage up to 29 volts. Here's the Ah-Ha moment:
> That is EXACTLY the behavior of a heavily sulfated battery bank. A fast rise
> in voltage indicates sulfation.  It is impossible for that tiny generator,
> or any charge source they own for that matter, to replace the hundreds of AH
> it would take to drive a healthy battery up to the absorb voltage of 29
> volts. The bank is about 45,000 watt hours (72h rate). There would have to
> be over 20,000 Wh removed to be at that voltage. How many Wh's are replaced
> in 5 minutes by a 2500 watt genny? I'm sure you are getting the picture.
>
> Why did this happen to these expensive batteries? Glad you asked. Battery
> plates are not uniformly efficient in the electrochemical process leaving
> some portions with lead sulfate even after 8 hours of charging. Unless these
> portions are cleared off regularly by achieving 100% SoC and occasional,
> thorough equalization, the amorphous sulfate will convert to a crystalline
> form and grow. 99% charge, if not corrected in time, will always cause
> premature battery failure.
>
> Undersized RE charging systems, or perhaps oversized batteries, is the
> culprit that contributes to this all too frequent phenomenon of chronic
> undercharging. I say contribute because there are other factors. Fact: it
> can take 10-12 hours to fully charge a lead acid battery. Fact: The time
> element of battery charging is a highly misunderstood part. With only a few
> daily sun-hours to work with, how do we get a battery charged with PV solar?
> Properly sizing the PV array to the battery AND consumption is critical. One
> method I think is essential for nearly all PV systems is use a generator and
> charger, appropriately sized to the battery. By bulk charging early in the
> AM you can reduce the finish time to perhaps 5-6 hours of constant voltage
> charging, something easily done with a PV system.
>
> Ron, you might be able to recover some capacity in this bank if the sulfate
> has not formed hard crystals by now. You can try a very long charge time, up
> to 24 hours, at high voltage, about 31 volts. You will need a larger
> generator. Monitor the temperature and reduce current if they get up to 125F
> internal. In our shop I have recovered sulfated batteries with high voltage
> charging, as much as 3Vpc (do not do this with any loads connected), at
> reduced current, about C*.05, and a 1 kHz pulser that I built. My findings
> over the years is the current will begin to rise very slowly, peak then drop
> if the recovery is working.
>
> Sorry that this post is getting so long. There's just so much. OK, one last
> thing. In my last post to you I recommended a battery AH monitor. This
> problem could have been detected and perhaps prevented if they had one.
>
> Larry Crutcher
> Starlight Solar Power Systems
>
>
>
>
> On Oct 21, 2011, at 11:39 AM, Ron Young wrote:
>
> Hi Maverick & everyone,
>
> I visited the site a couple of days ago and load tested the batteries,
> checked individual voltages in the string of six Surrette 4KS25's (4.3v
> each), checked all connections etc. The client told me that when they would
> go to bed battery volts read 25.7. Through the night this would seem to stay
> steady. About 4 a.m. as far as they could tell the voltage would drop to
> about 24.5. This happened without a load present and with no charging
> present (calm, no wind, no sun). They would start up the generator for five
> minutes in the morning and see the voltage come up to just above 29v then
> turn off the generator (a small Honda 2500) and the voltage would settly at
> 25.7 and remain there most of the day even when using their light loads,
> some lights, phone system, laptop and the Sunfrost.
>
> When checking the batteries I noticed they needed watering and mentioned
> this to the customer. The electrolyte was just over the plastic screen above
> the plates by about 1/4 inch. He said he had just watered them and always
> kept them filled. I replied that they were low and when he looked he said
> no, that's where I keep them! When I checked the specific gravity reading it
> was very rich reading around 1.275 - 1.280. I topped them up properly to
> about 1/4 inch below the bottom of the cell channel which took about 5 cups
> per each battery. Of course as soon as I topped them up the s.g. dropped to
> around 1.175. I told him to put the generator on for about ten hours and
> call me in the morning.
>
> I heard from the client today and in the last two days the voltage has only
> dropped from 25.6 to 25.4 overnight and s.g. reading is at 1.260 or better
> so problem seems to be solved.
>
> So it appears the battery was under watered for several years. I'm still
> not sure why this would result in a sudden voltage drop, especially in the
> middle of the night with no loads present and no charging. Any additional
> thoughts appreciated.
>
> Best Regards,
> *Ron Young*
> earthRight Products - Solareagle.com
>
>
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive:
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>
>
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive:
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20111024/fd52dc01/attachment-0003.html>


More information about the RE-wrenches mailing list