FLA Battery Charging Questions - Looking back over the First Year

MrM1 · October 2018

I have learn a lot over the first year of battery ownership. I have 4 Trojan L16H-AC 435Ah batteries. When I purchased them new, I did not receive a manual, I was not part of any forum and so I did not even know I should do a commissioning charge and EQ. But I did the first EQ in the first few weeks, and started a battery log the first few days. Also had a glass temp compensated Hydrometer in hand. (now I have 3 different SG measuring devices)

I became a forum member of 3 solar forum about the same time I commissioned my system. I thank all the members for your patience and time spent teaching me so much about charging. The batteries have never seen less than 50% SOC (and that was only a few times and by design as suggested by some members). They have never once been low on water and generally allowed to fully recharge daily.

A few lingering questions after a year:

I have one cell (out of 12) that has sediment in the draw every time I check the SG. Some other cells may have a spec or 2, this one cell has a lot. I did do several draws in that one cell and forcefully returned the acid back in while holding the tube of the hydro as deep as possible to try and remove the sediment which seemed to have settled on the top of the plates in that cell. This seemed to work (or help) as I do not get the sediment in the draw now.
BUT ... that same cell is also lagging in SG by about 20 points. Unfortunately, It has been lagging for about 6 weeks (according to my log). But Trojan says in the manual (yes I downloaded it back in Nov last year) NOT to EQ until you have a 30 point gap. So I was trying to limit EQ.
Question: How do you fully charge the bank, with a cell or two that has a 20 or more point gap? Seems if you charge the highest cells to 100% (for Trojan that is 1.277) Then the low cell gets only about 90% charged (at 1.257). If you charge so that the lowest cell gets to 100%, Then the higher SG cells could reach 1.297 (as mine do sometimes). What is best practice?
Question: What does the sediment I saw mean? Is that cell shredding apart more than normal? Or did it just happen to have some of the sediment land on the top of the plates? I looked at several cells plates thru the fill tops and they all look the same, and looked good.
Question: EQ. So over the weekend I decided it was time to close that 20 point gap. I did the EQ at night after the bank was fully charged from the sun. Disconnected all loads. My SW charger only goes up to 32v for EQ. (Trojan calls for 32.4v). I EQed the bank for 6.5 hours at 32v. I checked the SG every hour. The low cell only rose to 1.287 while all other cells where above 1.290 up to 1.297. The bank temp never rose above 27.5*C. Went to bed. Started again the following afternoon, again with the bank already fully charged, I EQed another 4 hours checking regularly, and the lagging cell finally made it up to 1.292 (might go higher but I stopped). Highest cell was now 1.303. (NOTE: I use a hydrovolt for easy reading. I have tested it against a temp comp glass and a refractometer and find the Hydrovolt to be 5 point higher than the others, so my readings are actually 5 points lower). Should an EQ take that long (over 10 hours total)? Should I continue to EQ that cell now that it is within 7-10 points of all other cells?

Thanks

Mike

mcgivor · October 2018

Don't become obsessed with perfection, there is no such thing, the guidelines of 30 points allows enough for leeway between measuring devices, additionally there are natural variencies between cells which is normal, excessive equalization can do more harm than good, reserve such remediation for when the SG is way out of normal.

The sediment question is probably related to the sacrificial nature of lead acid, as the cells accept charge and discharge some of the material is lost from the plates, much of which falls into the wells at the bottom, however during equalization they may be suspended in solution falling on top of the plates, which can, in extreme circumstances, provide a path for current to bypass the cell, this is a phenomenon with stationary applications, less so with mobile, which get a sloshing effect which minimizes this. Perhaps agitation of the batteries may help putting the sediment where it belongs, in the bottom.

Estragon · October 2018

I agree with Mcgivor that you don't need to be too concerned with getting all cells exactly equal. EQing (and long/high voltage absorbs) is a bit of a trade-off between not letting undercharged cells harden sulfate, and excessively charging already fully charged cells.

The objective is to get, to the degree possible and practical, the sulfate back into electrolyte solution. In practise, I EQ (within reason) until the lowest SG cell stops rising. For my banks, this generally happens after 5hrs or less of EQ. 10hrs seems long, but if it's the first EQ in a year, maybe not. Mine seem to need it about every 3mos.

The dark bits might concern me if there's consistently a large difference in quantity combined with that cell having lower SG. I also see bits, but just the odd couple in some cells - likely just the random movement of a few bits in vigorously charging cells. It could be that with that cell now fully charged, it mixed enough to get the sediment to the bottom where it should be. I'd keep an eye on it though, in case there's a problem with the cell.

MrM1 · October 2018

mcgivor said:

Don't become obsessed with perfection,

No doubt I do. And I am trying to dial it back, which is why I had not EQed the bank yet ... I have probably over EQed them in the first year (no this was not the first time). I have EQed probably once a month or more up to this point. I have been dialing my charge regimen way back in the past 6 weeks or so. I plan to even start using "Skip Days" with my MN Classic CC to skip days between bulk/absorb. What will happen in practice is, I will Bulk/Absorb one day to full, but with my discharge daily only being down to about 88% SOC, on the days I skip, if solar conditions are decent, I will float charge back up to 100% (+/-) on the days that get skipped.

But still wondering, when charging in general, and you are using SG, do you charge to the lowest cell, the highest cell or somewhere in between? That is, if the lowest cell is 10 points under do you charge until that cell hits 1.277 or do you just kinda hit somewhere in the middle?

@mcgivor , I plan to try the agitate idea. In a few days I will disconnect all the batteries and move them all close together for the winter to help keep them warm, and will gently rock them back and forth to "stir" them some when I do.

@Estragon , thanks, I will keep an eye on that lowest cell with the sediment. I did a deeper discharge today and we have perfect clear skies so I will get a really good charge on the bank today and tomorrow. So I will monitor that one cell thru the weekend and see if it is keeping up within reason, and see if the sediment returns.

Thanks

Mike

Estragon · October 2018

For day-to-day charging, wbjr end-amps terminates absorb at a bit over 1% of capacity, generally after 2-3hrs absorb. Seems to work well so far (4yrs). I normally only check SG during regular (roughly every 2 mos) maint (water, EQ, clean) cycles. At ~1% most cells should be pretty close to full, so I suppose that would be sort of an average of cell SGs. If you were to target the lowest SG in daily charging, you'd essentially be EQing at Vabs daily.

Using skip days may take some playing about with settings. In particular, you may get bulk/absorb cycles on skip days if rebulk voltage gets hit with a pump load or whatever. It's just a question of finding the right number so it skips when you want it to.

I also had to adjust some trimetric settings so they don't complain about not getting a full charge for too long.

MrM1 · October 2018

My bank today in perfectly clear skies and a starting SOC of 72% got 2hrs 40min in Absorb with my EA set to 1% (4.3) and my Vabs set to 30.7v. I am going home now to check my lowest cell to see how hi the SG rose in that one cell.

Vic · October 2018

Mike,

Agree, that being too obsessive about cell balance, etc, is just too tedious for our FLAs. Given time, divergence in SGs among cells will grow. And, often, the low cells will most always be the low cells regardless of what we do.

EQing can help the low cells, but that often takes L O N G EQ times.

Too bad that the CSW cannot deliver the EQ voltage (Veq) suggested by Trojan. Perhaps trying to charge overnight, and use the Classic to EQ at the suggested voltage, to see what that does.

Almost certainly, the debris that you see in the Hydro samples is eroded plate material. We do see that when measuring SGs during Absorb or EQ. This is also visible on the top of the Moss Gaurds at all times. I do wonder is this fine debris will give false high SG readings when using Hydrometers, although, if you note that SGs are rising during Absorb and/or EQs, then this trend should be correct (just the absolute SG reading may not be correct). This may be one of the reasons that it is oft suggested waiting to take actual SG readings after the bank has been in Float for an hour, or so ...

Do you notice a sulfur aroma during EQ? If so, do you smell this aroma when EQ is ending?

Also, do you note the WBjr battery current at the point where Veq is reached? Does this current diminish significantly during the EQ process?

Is the Veq Temperature Compensated by the CSW? (you can Compensate Veq with the Classic, if you choose).

Some opinions, FWIW, Vic

MrM1 · October 2018

No noticeable odder Vic, but I do have a VERY ventilated (with fan) battery box. I checked today while in absorb and smelled at the exhaust vent of my box ... no odder at all.

I think you are right about the sediment and times. I see less or none now. And the bank has been in float for over an hour.

I don't use any Temp comp with the SW while doing EQ because it does not do the 32.4vEQ anyway. It only does 32 ... and even that is sketchy. It usually runs between 31.8 and 32v

I just checked, and having really good charge conditions today, I had the Vabs set to 30.8 (temp compensated) and the EA set to 4.3 in the classic. Checked my lowest cell, and after running absorb for over 2.5 hours (it did not time out but hit EA) ... the SG in the lowest cell was 1.263. The highest cell in the bank was 1.275. If I compensate for my known 5 points too hi of my HydroVolt, that means I was at 1.258 and 1.270. That is why I run my Vabs so hi. If I use 29.6v abs, I never use any water, and I never get fully charged, even if I set the bank to 1 amp for an EA ... it just drones on all day.

Should I adjust the Vabs up ... OR ... lower the EAs?

Also, the bank tested at 27.2*C as a max temp during charging. Today's hi outside air was 28*C

Estragon · October 2018

FWIW, my banks used very little water for the first year or so, and now use a couple gallons/year. I added small arrays to ensure charging over the winter which might account for a small bit of water use, but I suspect it's mostly because they're ~4yrs old now.

2.5hrs to 1% end-amps sounds about right. Personally, I would leave end-amps at 1% and wouldn't increase Vabs past 30.8 for now. 1.258 is pretty full IMHO, and not worth pushing all the others too much harder on a daily basis just trying to get a few points of SG on the laggard.

MrM1 · October 2018

Estragon said:

Personally, I would leave end-amps at 1% and wouldn't increase Vabs past 30.8 for now. 1.258 is pretty full IMHO, and not worth pushing all the others too much harder on a daily basis just trying to get a few points of SG on the laggard.

Thanks. I am still just figuring it all out thru the first year. I would have thought 1.258 was down to 90% and thus not good on the cell. I may just let it ride.

jonr · October 2018

You could remove some mix and add some acid to bring the low SG cell up to the same SG as the others. No idea if this would be a good thing.

MrM1 · October 2018

jonr said:

You could remove some mix and add some acid to bring the low SG cell up to the same SG as the others. No idea if this would be a good thing.

Image: https://us.v-cdn.net/6024911/uploads/editor/hh/qmktqnf83m82.gif

Estragon · October 2018

Assuming the 1.258 is accurate (may not be for a number of reasons), 90% may be right. It may be that this is going to be a weak cell for much of its life. Like a problem child, worth keeping an eye on, but not worth constantly punishing the other kids because the one can't always keep up.

I have a small 6/12v automotive charger that I've occasionally used to tweak a problem battery.

FLA Battery Charging Questions - Looking back over the First Year

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