[RE-wrenches] intermittent battery problem; ...Battery Sulfation
Ron Young
solareagle at solareagle.com
Wed Nov 16 00:20:28 PST 2011
Hi Daryl. I've got other KS25's in hybrid systems (wind gen & solar) that seem to do fine over the last several years. The Ouback 3524 has an 85 amp charger. There was no problem getting to 32 v and holding it for eight hours. This has been done twice now. Larry and others attribute the ability to get to 32v to a sulphated battery condition and I'm thinking that a healthy battery could get to 32v as well, especially one that's been regularly EQ'd... am I wrong?
I'm listening to every opinion here and trying to sort it out but I think John may be on the right track with an intermittent failure of one cell. I just can't seem to find it.
Ron Young
On 2011-11-13, at 3:51 AM, penobscotsolar at midmaine.com wrote:
> Ron,
> What comes to mind for me is that Surrette 5000 series batteries like
> to have a regular charge of C10. KS25 cells are rated for 1350 ah,
> creating a need for a somewhat regularly occurring charge of 135 amps.
> I do believe the batteries are not ever getting that, except for very
> rare occasions. We have seen this before in undersized systems.
> Is the bulk charge set to 29.6? I would try a couple more eq's over the
> next month to loosen likely sulfation. Get it up to as close to 32
> volts as possible and taper the charge down, then eq at that voltage
> for four or five hours, even more if the client will do it.
> That would be how we would deal with this. It does seem ultimately to
> be sulfation that is the problem.
>
> Daryl DeJoy
> NABCEP Certified PV installer
> Penobscot Solar Design
>
>
>
>
>> 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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