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

Ron Young solareagle at solareagle.com
Sat Nov 12 20:57:41 PST 2011


Folks, this one really has me puzzled. The client has done regular two hour EQ's, at least once a month. When did a site visit and I topped up the electrolyte (they'd been starving the batteries for water but always just above the plates) the problem seemed to go away. They were satisfied that the problem was solved but I wasn't and I told them what I had been hearing from this group - essentially that the batteries needed a deep EQ, discharge, recharge and EQ again two or three times to scrub the sulphates. They declined until just a few days ago when they said the rapid voltage drop was back. Here's a quote:

We had another rapid voltage loss this morning ---it was 25.2 when we got up and it dropped rapidly to 22.8.  We turned on the generator and charged the batteries until our display showed 30.2  for awhile with the generator running.  We turned off the generator and the voltage settled at about 26.4.  We turned off all loads and wind and solar.
  
At 9.15 our batteries were at 26.4
At 9:16 we turned on an 8W light bulb, a1600W hair dryer, and a 1.5HP (120V 5.75A) shop vac
The display showed a load of 1.9kw
At 9:40 the inverter shut down---display showed batteries at 18.4
By 9.47 the display showed the batteries at 25.2----the solar and wind were still shut down.
We turned everything back on (a light, Sunfrost RF16, phone)  and all seems to be normal.

They agreed to do the EQ process but only have a 3kw generator so we started with 8 hours with the EQ voltage set for 32v (24v system). They completed that yesterday and here's what resulted:

Before starting EQ the batteries were at 25.8, hydrometer reading 1283 with temp. correction
Began EQ                                            32.6 v                                                                        		Buying 1.5 kw
Hour 1                                                  32.4 v                            1283  with temp. correction       Buying  1.4
Hour 2                                                  32.4 v                              1285  with temp. correction      Buying 1.5
Hour 3                                                  32.2 v                                                                       			Buying 1.7
Hour 4                                                  32.2 v                              1290  with temp correction        Buying 1.8
HOur 5                                                 32.0 v                              1290   with temp correction        Buying 1.8 
Hour 6                                                  32.0 v                                                                       		Buying 1.9 
Hour 7                                                  31.8 v                               1292 with temp correcton        Buying 1.9
Hour 8 complete---turned off Gen and turned on loads ---Batteries dropped to 25.4 within 30 minutes and stayed there until this morning---fridge was running, telephone, internet, wool carding machine, lights.  This morning hydrometer reading  was at 1290.
> 


Then today I just got this email:

Just experienced another rapid voltage drop.  As soon as the voltage hits 24.8 the voltage drops like a rock if we don't have any input (no solar or wind).

This is not what I expected after a lengthy EQ. I'm getting them to do another one tomorrow after a discharge cycle and charge but I'm really beginning to think we have something else going on here, something electrical, not chemical. The rapid voltage drop is puzzling. 

To review, it's an Outback 3524 on an Epanel, Whisper 100 & controller, 6 4KS 25 Surrette batteries in 24v configuration - 4.5 years old, .7kw solar. I know the charging end is undersized but they have been compensating with the generator and they get lots of wind in the fall, winter, spring.

Any more thoughts on this anyone?

Best Regards,
Ron Young
earthRight Products - Solareagle.com
Alternative Energy Solutions ~ Renewable Energy Products


On 2011-10-24, at 6:50 AM, Larry Crutcher, Starlight Solar Power Systems wrote:

> 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.
> 
> <3s-chart.gif>
> 
> 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
>> 
> 
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