The battery woes: 2010 update

hillbilly

Well being that time of year again for off the grid living; where the limited sunny hours, and added loads really put our energy system to the test. It's been about a year now since I found that I had some issues developing in our 24V battery bank (8 surrette s-460 6V; series/parallel arrangement). All in all things have fared a bit better than I had feared, but not as well as I had hoped... so far anyway. Now I am in a bit of a quandry over how to maximize what life may be left on these batteries.

The are two main issues that I'm dealing with now:
1) one cell has been getting slowly lower in it's max SG and is always about .040 points below the highest cells (and that's after EQ'ing a few times over the last 2 months, it's been much worse a few times after a deeper discharge).

2) one cell that has had the highest SG levels typically is now quite murky during EQ cycles, or under a higher charging current. It's a redish brown tint, and I'm assuming that this sediment being stirred up is from excess plate shedding? Not sure about this, nor am I sure how big of an issue this may be (gut feeling says not good).

So on the one hand it seems that the spread of SG levels is too far out of whack to leave alone, especially since it means that the one cell reaches some pretty low SG levels well before the rest of the cells (making my reserve capacity quite small for this time of year). On the other, I'm very hesitant to do much aggressive charging or corrective EQ'ing for fear that I'm basically toasting the one cell. The one idea I have is to split the battery bank in two, and EQ the one set that has the weakest cell and leave the other set alone for a bit. I'm thinking this is probably only a minor and short term help... any other comments, or suggestions are most welcome as always.
Thanks

niel

Re: The battery woes: 2010 update

for specifics concerning the batteries you should approach the manufacturer, but it doesn't sound good. all you can do beyond manufacturer's recs is try to baby them. it's always difficult when you see the potential demise of the batteries coming and that's a cost of being aware and caring for batteries.

hillbilly

Re: The battery woes: 2010 update

I did forget to mention that I do also have a query in with Surrette's tech support, but I also like hearing what some of the good folks here have to say. There has been some dramatic differences at times, and I usually try to distill it all down to what makes the most sense given my own application.

niel

Re: The battery woes: 2010 update

i sometimes wonder if the manufacturer waivers at times in the electrolyte mix causing some to come up a bit on the short side from the get go. unlikely as that sounds, it might explain some of the unexplained differences at times.
do let us know what surrette says.

mike95490

Re: The battery woes: 2010 update

hillbilly wrote: »

2) one cell that has had the highest SG levels typically is now quite murky during EQ cycles, or under a higher charging current. It's a redish brown tint, and I'm assuming that this sediment being stirred up is from excess plate shedding? Not sure about this, nor am I sure how big of an issue this may be (gut feeling says not good).

I see this after I water my batteries, crystal clear, add water, and it's like mud soup. But there is a large cavity (supposed to be) under the plates to hold all this gunk, and in older batteries, I guess it happens.

hillbilly

Re: The battery woes: 2010 update

mike90045 wrote: »

I see this after I water my batteries, crystal clear, add water, and it's like mud soup. But there is a large cavity (supposed to be) under the plates to hold all this gunk, and in older batteries, I guess it happens.

Just to make sure I take your point correctly; do you mean to indicate that you don't think that the sediment issue is as big of an issue as I had feared? To be honest, I certainly would feel more comfortable just dealing with the sulphation issue. "when all you have is a hammer, every problem looks like a nail" right?

Still waiting to hear back from Surrette :-( but I will post anything noteworthy that they have to say.

At this point, I figured the safest bet was to charge the bank up as best as possible yesterday and then disconnect the one string of four batteries (including the murky cell). The resting voltage on those batteries is quite high 6.43v, 6.44v, 6.44v, 6.44v, and the SG levels are all pretty darn close (1.258-1.263) after sitting all afternoon and overnight.

The other set I put through a 2 hour EQ at 32V keeping the current rate between 15-20 amps... with slight improvements on the SG levels but nothing that was beyond the margin of error in measurements. After discharging about 70ah last night and checking a couple of cells I put the batteries back on a charge.
Ran a 2.5 hour absorb at 29.4V, then put them back on an EQ charge at 17amps... 3 hours later the voltage has topped out at 31.6V, and is now starting to dip a bit to 31.4V.
Hopefully we'll have some improvements to speak of, but the one cell in particular is certainly being stubborn.

mike95490

Re: The battery woes: 2010 update

hillbilly wrote: »

Just to make sure I take your point correctly; do you mean to indicate that you don't think that the sediment issue is as big of an issue as I had feared?

Yep. Can't do anything about it, so I'm ignoring it. Unless someone has a filter for acid....

hillbilly

Re: The battery woes: 2010 update

Well I finally got a call back from the technical support guy at Surrette, who was pretty helpful and encouraging. Still no hard solid answers (I'm becoming convinced that batteries are essentially a form of voodoo science), but a couple of points that I thought I'd share:
He agreed that I shouldn't really worry much about the sediment in the one cell, that there wasn't anything that could be done for it and that any sulphation in the other cells was a MUCH bigger issue to attend to. Also of interest was his firm insistence that my max absorb time (3hrs) was too short, and that 4hrs should be considered minimum (a previous tech had suggested 6hrs). I even commented that my batteries often reach a 1.5% acceptance charge level before the 3hrs, and he still said that he thought it would be best to just let them continue to absorb for another hour or so.

The suggested action was to split the bank up to focus my efforts on the string that has the weakest cell (and a few other lowish cells), which I had already initiated. He was pretty certain that I should be able to get the SG level back up to 1.265, which really surprised me and ran somewhat counter to other info that I'd read/heard. His opinion seemed to stem from two main factors: the voltage of the battery at rest (6.32 rested overnight), and the fact that the cell is gassing while under absorb or EQ charge. I wish that I shared his optimism, but I figure I can give it a few more EQ cycles and see if it helps...So I'm now doing a few deep discharges followed by full recharge/EQ cycle, and we'll see if the SG levels actually improve much.

niel

Re: The battery woes: 2010 update

at this point it appears you've nothing to lose and the manufacturer feels you've much to gain. go for it and here's crossing my fingers for you.

hillbilly

Re: The battery woes: 2010 update

Niel, it would appear that we need more voodoo than just finger crossing. Thank you anyways for the sentiment.

This week I've done three EQ cycles, and a couple of deeper discharges since the last update and overall I'm not seeing any real conclusive improvement. There has been some benefit, but on a very small scale; the real problem cell is barely budging with it's SG levels topping out at 1.232 or so (if I look REAAALLLY hard it sometimes looks like it's almost 1.234... almost). This is up from readings in the 1.228-1.230 range, but still kind of within the .005+/- level of accuracy range. The thing that kind of keeps me trying here is that some of the other cells that were also a bit low have been steadily getting to higher levels (the other 3 low cells have gone from 1.248 -> 1.256, 1.242 -> 1.250, and 1.250 -> 1.260).

I'm thinking that the one cell must be more resistant to change due to more established sulfate formation on the plates, which I'm hoping might mean that as the other cells reach a fuller charge that the problem cell might start to move a bit more??? I'm drawing things down a bit deeper right now, and then I'll start yet one more EQ cycle and am hoping that we'll see a more conclusive change at the end of it. I'm curious, but not overly optimistic at this point.

Which puts me in a real quandry, and I'm wondering what the wise folks here think might be the best path forward. If the one cell doesn't come up any further, and seems stuck with a SG reading of 1.232 I'm weighing out a few options which all seem less than ideal:

1) I could just leave things as is, and know that basically things will likely continue to go downhill for all 8 batteries. The big question here would be how quickly might the "problem child" drag the whole bank down I suppose.

2) I could cut the bank down to 4 batteries, as the one string seems quite strong and healthy (although I've probably lost some capacity over the last 4 years, these all show strong resting voltage with high and consistent SG levels. Thinking is that these batteries would likely last a fair bit longer with out the weaker ones connected, but it does make for a more limited capacity during the winter months.

3) I could add in another new battery, which would also likely increase the overall lifespan of the battery bank. While I know this is a typical "No-No", it's kind of tempting due to the comparatively small cash outlay. This seems like it could really help prolong the life of the whole bank, but I'm worried that in another 6-12 months, I'd be in a similar situation with yet another battery (two other low cells are from a different battery).

???

keyturbocars

Re: The battery woes: 2010 update

In option #3, is the problem of adding a new battery that the new battery would be degraded, or is the rest of the bank damaged by the new battery?

If just the new battery is dragged down (degraded) by the rest of the older bank, then that's the option that I would choose. If the rest of the bank is still in good shape, then it seems it would be a cost effective way to try to get more life out of the rest of the bank.

I've got some similar issues with my Lifeline Concorde AGM bank, and the tech told me that even though it's not recommended, he'd personally replace 1 bad battery into a bank that was otherwise good in order to get more life out of it. Hard to know for sure, because you never know what will happen tomorrow. Another bad cell could develop shortly after replacing a battery. Sort of a gamble. Seems to me that it might be justified if the cost savings are big enough.

Interested to see what you find out, as others will be learning from your experience as well.

Edward

hillbilly

Re: The battery woes: 2010 update

No, I don't think that a new battery would hurt the others; more like the other way around. I would hope that the new battery would help the whole set out, but clearly it would be rather quickly degraded to the same condition as the exsisting ones.

niel

Re: The battery woes: 2010 update

now i don't recall you saying just how old of a battery bank this is as that may influence your decision, but batteries do fail at times and even new ones can fail. i lean replace the offending battery and hope for the best, but this is purely your call.

it may be partially or even all covered by a warranty and even surrette should understand that cell isn't right if that's the case. could it happen to the other batteries? yes, it could, but i think it's worthwhile to chance the others are fine amongst one failed cell and you don't want the others to become bad so if replacing then it should be soon. i guess it's a half full/half empty possible viewpoint and assume it to be half full aka a positive outlook unless proven wrong down the road.

is it voodoo? i wouldn't go that far, but you do almost need a sixth sense with batteries and it's just not good for somebody to say, " i see dead cells." sorry, couldn't resist.

hillbilly

Re: The battery woes: 2010 update

niel wrote: »

now i don't recall you saying just how old of a battery bank this is as that may influence your decision, but batteries do fail at times and even new ones can fail. i lean replace the offending battery and hope for the best, but this is purely your call.

Thanks Niel and everyone else for your thoughts. The batteries are over 4 years old now, and after further EQ'ing the absolute best that I ever got the one cell up to was 1.236. This seems like very small improvement indeed, and the amount of charging that I had to do to get it there was pretty impressive. The thing that had made me most hesitant on getting a replacement battery was my wondering just how "healthy" the other batteries are. Not that I really "know" any better for certain, but I'm more suspicious now that I have another battery that is likely not far ahead of the weakest one. One other cell was pretty stubborn about coming up too, and the resting voltage on that battery was always a tad lower than all others... meaning that I would be looking at replacing 2 batteries instead of 1.

I think that's probably a deal breaker for me, especially when I consider that at best case I would be extending the life span of a battery bank that already has a bit of a smaller capacity. At this point I'm keeping my eye on things, with all batteries connected but at some point I am thinking that it would be best to remove one string and just run on half the bank until it goes south (which is really hard to say just how long any of this might be). We'll just call this battery bank my "learner set" I suppose; which is certainly an appropriate term, as I am learning a lot along the way here.

The only downer of all this really is that during the winter months it will mean having to fire up the generator a lot more frequently. One little detail that I sort of "learned", or rather had illustrated much more clearly; with a smaller battery bank (1/2) it means that I end up having to run the generator a lot longer to recharge the same level of discharge due to a much lower max charging rate. One of those kinds of moments where the light bulb goes on and you realize something obvious that you "knew" all along. In part I've posted some of the details her in the hopes that others might glean some info too; I'm a firm believer of learning from other's mistakes.

Here are some the big lessons that I've been having my nose rubbed in:
#1: "ready, fire AIM!" (thanks Tony, one of my favorites) I did NOT get the best help/recommendations from a few of the dealers in the very beginning when designing and installing... wish I knew then what I know now.

#2 have appropriate charging options (preferable more than one), in my case I didn't have a way to fully charge my batteries for over a year and a half! (Iota chargers, while nice and handy will not reach full charging voltage or EQ). So it wasn't really until I got an Outback inverter/charger that I was able to use the generator in full capacity (which had been a key in buying a "larger" sized battery bank)

#3 get a battery monitor day 1! I've been very happy with the education that the $100 or so dollars that I spent on this, and should have done so right off the bat.

#4 take accurate records from day one, something that would have been really helpful in being able to monitor any trends and understand the health of the batteries.

#5 contrary to what some might say, I am now a believer in buying a quality Hydrometer day 1! I'd heard some advice that any old hydrometer will do the job and that a $10 cheapo would be fine, but in all honesty this may have turned out to be one of the worst things that I ever did to my batteries. It produced months of faulty SG readings, and therefore inadequate charging.

I know, nothing new here... but hopefully this might save someone else from making some of these "classic errors".

hillbilly

Re: The battery woes: 2010 update

Greetings all. I thought I might update this saga for educational purposes; who knows maybe someone other than I will learn from my experiences with batteries. I decided not to add any new batteries, but left them hooked up "as is" to try and limp along as long as possible. Actually, relative to our needs, they've performed reasonably well: GREAT in the summer months... fair in the winter (frequent generator use).

For the most part all the SG levels hold up pretty well, within a few points of 1.260 on average. Two cells tend to lag a bit; on "normal" charging they tend to get up to 1.235-1.245, although they will come up a bit more with extra absorb time or EQ (but this means really "boiling" all the other cells). One cell is quite low always: comes up to about 1.205 or so :-( grrr!

Interestingly the voltage levels are very even and consistent; charging and discharging. I haven't done any really deep discharges, so I don't know if there would be a sharper drop in the voltage readings once they get to a lower SOC like I had observed last winter. I'm not quite sure just how low I could discharge them before the one cell would drop too low??? So we're keeping them fairly charged, which has been easy during the summer/fall months. Winter on the other hand can be much more challenging to keep them charged...

Then "Murphy's Law" struck: fortunately/unfortunately our old propane fridge died, and we were able to replace it with a nice new efficient electric one (LOVE IT!). Of course this additional expense and load would come right before the worst possible months of winter, AND just when we were already concerned about whether or not our batteries were still up to the challenges of winter charging. Long and the short of it is that we are looking to replace them (hopefully SOON!).

So we got about five years off this bank, and my guess is that most of the batteries would be just fine for another 3-5 years, with 1 or 2 maybe fading a bit sooner than that, and the "problem child" being a total wild card... Had it not been for the additional load on the system (averaging out to about 500WH/day), we probably would have limped through this winter with them, coasted easily through another summer and looked into replacing them next fall. Overall I can't be too unhappy with the performance we got when I consider some of the folly we committed along the way.

Now we need to decide what to do with them when we replace them....

mike95490

Re: The battery woes: 2010 update

hillbilly wrote: »

...... Now we need to decide what to do with them when we replace them....

The new battery supplier, should take take them for recycling or core charge.

Blackcherry04

Re: The battery woes: 2010 update

Sell them to a recycler yourself, you'll get 3 times more out of them.

SCharles

Re: The battery woes: 2010 update

Just sold my old batteries to a recycle business yesterday. They gave me 21 cents a pound [lead price]. I know it was 26 cents there a few months ago. But I had over a ton in those six cells. The price, they said, fluctuates almost daily, or can. But they were happy to take them, didn't care whether they were still full of electrolyte [they were].

hillbilly

Re: The battery woes: 2010 update

Yeah, we had thought about selling them to a recycler. The hard part for me is scraping them while they still have some life in them, particularly 6 of them seem to have decent use still. I am tempted to perhaps work out some sort of a back up system with them maybe? Or perhaps sell the best ones super cheap to someone who could use them, which would likely add up to more than I could get from the recycler. They are 125lbs +/- when wet, so I'm guessing that they have less than 100lbs of lead: 8*100*$.20= $160. Not exactly a huge incentive to just scrap them. I don't know, I'm still rolling it around in my head a bit.

mike95490

Re: The battery woes: 2010 update

I've got the same issue, 400ah bank, down to about 80ah, but still working.

Maybe I'll try to sell them as a "starter pack" which is what I bought them as 3 years ago @ 100 A Should have the Ni-Fe bank online at the end of this month.