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

[Larry Crutcher, Starlight Solar Power Systems]

Hi Ron,
Accurate SG readings are not simple. Was temperature compensation properly employed? Have they been keeping a log book to identify changes? How accurate is the hydrometer? How skilled is the person taking the reading? 

Most of the Battery Wrench responses suggest equalization but I don't see from any of your posts that this has been done yet. I suggest this to be the next step and I recommend that you carefully watch voltage and current. This will tell you a lot. I use a Fluke ScopeMeter in the TrendPlot mode and track voltage and current over time. It provides a good visual understanding.

In case others are using this forum to glean information, attached is a chart for illustration of the charge cycle. You should see a constant, somewhat linear rise in voltage until the constant voltage setting is reached. If you see a sudden rise: suspect sulfation. If you see a quick reduction in current: suspect sulfation. The current should drop to about 8-10 amps at the constant voltage towards the end of charge cycle. The health and DoD will determine the time this takes, expect many hours. Begin equalization.



A couple other points: Is the MX absorb voltage at 29.6V? Did you program the MX controller for an extended absorb time (advanced menu, absorb time limits)? The default setting is poor for large batteries. I use 90 minutes minimum and 4 hours max. This can greatly reduce the possibility of undercharging the battery but it may use more water. The timer (ChgT) will determine how long it stays in absorb each day.

Larry Crutcher
Starlight Solar Power Systems

On Oct 24, 2011, at 12:49 AM, Ron Young 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
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20111024/fad5cc2f/attachment-0003.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 3s-chart.gif
Type: image/gif
Size: 27707 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20111024/fad5cc2f/attachment-0006.gif>