Stress-testing old batteries...

[RandomJoe]

I was given six Trojan J305P (very close to an L16 in size and specs) batteries today.  Cool!  Of course, TANSTAAFL applies - these things came out of a floor polisher that, as best anyone can remember, sat unused (and uncharged) for over 5 years!  One of the maintenance guys at the plant pulled them and checked them out.  They needed a LOT of water, and surprisingly did take some sort of charge.  Then they figured out they'd never fit the things into the golf cart they wanted to refurb, so set them aside and forgot about them until I showed up.  They know I piddle with solar power, so the offer.

Can't beat free, so I figure even though they are likely junk they will at least give me cores (or salvage value?) in case I want to buy something else.

However, I thought I'd play with them a bit, see what (if anything) they can do.  Might as well have a little fun, and maybe learn something in the process!  I do have a few questions about that though, as I've never worked with old batteries before.

Primarily, what would be the best charge / discharge rates?  Whatever I can manage?  High?  Low?  Not sure whether to be gentle while they are weak or just kick 'em hard and see if they can handle it!    For charging, I can supply anything from 750mA to 55A.  If the sun would ever show up again, I may also try connecting a set to my 12V panels.  (It's been nothing but overcast and severe storms all week!)

I'm going to be working with these in 12V banks (two in series) - four of them are usable, two have decent SG and actually pretty close to each other, the next two are a little farther off but still serviceable.  Those four were holding at 6.1V today, after sitting on the dock for a week or two untouched.  I probably will need to equalize them at some point - the SG readings are somewhat out of balance.

The last two intrigue me - hopefully someone can perhaps explain this.  Their resting voltage was 4V.  When I checked the SG, one cell in each measured 1.0!  Plain water?!?  The guy who worked on them did say he had to add a lot of water to some cells, but the cases aren't cracked and the batteries hadn't been spilled - so what happened?  Is it actually possible for enough of the electrolyte to react with the plates that you'd read 1.0?  The maintenance guy did try charging them, not sure for how long.  Anyway, I'm figuring those two aren't worth messing with at all, unless someone suggests otherwise!

SG readings I measured after carting them home and before charging:

1) 1.225 / 1.150 / 1.225
2) 1.150 / 1.150 / 1.225
3) 1.225 / 1.225 / 1.230
4) 1.160 / 1.225 / 1.225

I've paired 1&2, and 3&4.

The "dead" two:
5) 1.000 / 1.100 / 1.240
6) 1.200 / 1.000 / 1.175

All thoughts and suggestions are welcome! 

[TomW]

I am no expert but use batteries daily for a good decade.

I say you need to pump some amps into them and let them simmer awhile (equalize). Get them gassing good for a few hours and refill with distilled water.  Assumption being they are f/ooded lead acids and not gel or other sealed type that don't like equalizing  Since you are checking SG they probably are flooded lead acids.

Start with the dogs and see how they recover. Then go to the better ones.

Just what I would try. It may be they are scrap but a good way to learn some about batteries. Get a couple gallons of decent distilled water because they can get thirsty doing this.

Be sure to keep the plates covered. The gasses are both explosive and corrosive so do it outside or where there is good air flow out of the area. equalizing both stirs the fluid and dissolves the sulphation back into solution in the acid. Both are good things.

Others may have ideas but that is where most would start I think.

Have fun and don't get blown up or drenched in acid. It is good practice to keep a pail of water easily to hand when messing with acid for flushing any spill or sticking your head in if you get sprayed in the face with it somehow.


Tom

[Bruce S]

First: those if good: are some nice batteries!! :-)

I'm with TomW on this one, the first 4 seem like they need a good charging, but I would charge them individually and retest the first 4 to make sure you don't have a cell going bad that could muck up the whole set.

The last two: I'd grab a charger or PVs overcast or not as see if you can shove 10 - 15A into them, even at 12Vdc to see if they'll come up to the 6V and stay, the the voltage drop back under 6Vdc they're core material .
Let them bubble and see  if the SG come up over 1.1 if any of the internal cells don't stay above 1.17 then, again core material, or recyclers may give $$ since these are up around 100lbs.

Also good the have some baking soda around, it'll nullify the acid quick.

Best of luck on a hopefully great find!!
Bruce S

[RandomJoe]

Thanks for the tips.  I'll try some things over the weekend.  Hoping for enough dry time to get stuff out on the back patio - rather not be in the garage with "unknowns"!

I currently have two of them on a small charger (10A max) which brought them up overnight.  When I got home this afternoon, it was "floating" at 13.5V and 1.7A.  I don't think it actually does the absorb phase correctly - it doesn't appear to get the voltage up high enough - but if these things were really down to 50% DOD (according to the SG and Trojan's charts) I don't think the voltage should have gotten anywhere near 13.5V for a long time.  The meter only showed about 16AH put in, clearly a long way from fully charging a 50% DOD battery...

Have to see what happens when I hit them with more amperage - I have a 55A Iota that will do the full 3-stage charge algorithm properly, so hold 14.2V or so for a good while.  (It'll equalize, but I can't manually tell it to, it just does it automatically once a week.  That's going to be a problem...  Have to figure something out for that!)

Worst case, I can shut down the Outback system and reconfigure the FM80 to 12V and feed the things with the 1080W array!

[Bruce S]

Joe;
 Actually that charger is right, first thing it'll do is bring them up to voltage, then a deep current charge. Are these the ones who's Sg was 1.00? might let then cook for another day-ish, let them rest 1/2day check SG. Will tell you quick if they're toast or not.

Back patio is a good idea, never now when something's gonna reach right up and say "SURPRISE!!"

Next step is getting those others to a good bubble then start checking what they have left in them.
Still even if you come out with only 1/3rd of them being any good still a NICE set!!

Cheers!!
Bruce S

 

[RandomJoe]

Are these the ones who's Sg was 1.00? might let then cook for another day-ish, let them rest 1/2day check SG. Will tell you quick if they're toast or not.

No, these are a pair of the better ones.  I haven't done anything with the really bad ones yet.  They're the ones I really wanted outside before trying out!

Still even if you come out with only 1/3rd of them being any good still a NICE set!!

No doubt!  I've often wished I'd gone for L16s instead of the T105s I bought first, and I have been toying with the idea of a second battery bank at 12V, ever since I converted my primary bank to 48V.  If these work well, I'll be set - although I could use some more solar panels on the 12V side...  (Currently have a single 135W panel on a 100AH AGM there.)

This hobby really is an addiction, you know...! 

[RandomJoe]

Finally have a decent weekend, and am carting batteries out on the patio.  Had the first pair on the Iota charger for about an hour and a half, and already have more questions!

First, this is rather odd to me.  Anyone know why this would happen:
The first pair is the "middle quality" of the three sets.  Over the past couple of weeks I swapped a 10A-max 3-stage charger between the two better sets and this one would sit forever at about 13.6-13.8V, 2.5-3A.  Never got above that.  Today I lugged these two out first and checked SG.  Five of the cells are higher than before, which is good - but one cell now reads 1.000!  Eh...  What?  How'd that happen?  It was the lowest in this battery, but no lower than two other cells in the other connected battery.

I have had it on the Iota for 1 1/2 hours, after the first hour I took the charger off and took more readings.  The voltage had come way up - 6.30V - but the SG readings haven't changed at all, including the 1.000 center cell.  How quickly does SG respond to charging?  The second battery was holding at 7.30V.  (Granted, there will be surface charge.  But at least they didn't immediately dive to 4-5V!)

I'm still not getting a whole lot of current into these things.  The Iota pushed 40A for a brief period, then tapered down to 20A at 14.65V.  After 20 minutes it dropped to Absorb and sat at 10A / 14.14V.  (It is still there now.)

Happily, it appears I do have one set that'll work somewhat well.  The best pair was actually reaching float stage with the 10A charger, has been off the charger for a few days, and is still holding 12.67V.  I'll have to do some load testing with that pair.

[zap]

Today I lugged these two out first and checked SG.  Five of the cells are higher than before, which is good - but one cell now reads 1.000!  Eh...  What?  How'd that happen?  It was the lowest in this battery, but no lower than two other cells in the other connected battery.

Unfortunately that cell and battery is probably toast
It might have come around pushing fewer amps through it but chances are it was already a lost cause.

[Devo2]

I had 1 trojan battery with a cell that always read "recharge" when the other 2 were "good". I put a load on it until all cells were at "recharge". I then carefully dumped the weak acid into a suitable HDPE container. It was very dark. Then I pressure washed the dry cells out & dumped the dirty(& I mean dirty) water into another HDPE container which I will neutralize. Then I poured the weak acid through a coffee filter back in & charged it-it has been fine. Careful with a pressure washer though as to much power will ruin some of the cell material. If I did it again I would just fill the battery with water from a hose & shake it & dump a few times. Of course nitrile gloves & eye protection.

Devo 

[RandomJoe]

Well, dumping acid and washing cells is a bit more than I care to do, especially with batteries that apparently sat completely discharged for years!  I'm not quite up to that sort of endeavor - I also don't really have the facilities / space for it...

My "experiment" such as it was had a bit of a handicap - I just don't have a way to actually equalize the things.  The only device I have that will equalize on command is my FM80, but it's running my 48V bank and I really don't want to rearrange things...  Especially, again, for batteries that I have very little hope of recovering anyway.  The Iota supposedly will (eventually) equalize, but only after some period of time (can't remember if it's a week or month).

But I did learn a few things yesterday, some of which simply puzzle me!

First, I kind of expected lots of agitated bubbling and such when I hit completely-dead batteries with the 55A Iota charger (the batteries are rated at 305AH, so I'd be nearing 20% charge rate) but it just didn't happen.  First, I only ever got to 40A max, the voltage almost immediately hit 14.65V, then the current tapered off to about 20A pretty quickly.  Within a half hour it had dropped to the Absorb voltage of 14.14V and sat there pretty much forever, and the current was down around 10A.  When I went out to shut things down late last night it was floating at 13.87V / 3.80A.

The batteries had very little bubbling.  Just some tiny ones occasionally.  I might have had one cell that had very many.  The cells that measured at or close to 1.000 SG didn't bubble at all.

Is the charging current being limited by the 1.000 cells?  Or perhaps just by the (I'm sure) heavy and hard coating of sulfation?

What baffles me, though, is the fact that the 1.000 cells would apparently "take a charge" at all, when the SG didn't change a bit?  At least, the voltage across the two batteries in series was roughly equal the whole time even though one of them had a "bad" cell.  Maybe 1/2 volt off from each other.  I had always figured a bad cell would either show open or short, thus causing nothing to happen or for the remaining good cells to be WAY overvoltage and boil aggressively.

What completely baffled me is, as I mentioned above, a cell that read a low SG (1.150) when I first brought it home dropped to 1.000 (or so close to it I can't tell on the float) after being on a charger for a while.  And it stayed there all day yesterday too.  I suppose I could have read it wrong, but the battery had a higher terminal voltage beforehand as well.  Maybe that cell developed an internal short and discharged itself completely?

In the end, I wound up with these SG readings:

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Bad Battery #1:
Brought home :  1.000  1.100  1.240
Start of test:  1.000  1.050  1.220
End of test  :  1.000  1.105  1.230

Bad Battery #2:
Brought home :  1.200  1.000  1.175
Start of test:  1.175  1.050  1.150
End of test  :  1.230  1.105  1.200

"Middle" battery #1:
Brought home :  1.225  1.150  1.225
Start of test:  1.240  1.000  1.270
End of test  :  1.250  1.000  1.275

"Middle" battery #2:
Brought home :  1.150  1.150  1.225
Start of test:  1.230  1.235  1.255
End of test  :  1.235  1.250  1.270
Terminal voltages this morning, after sitting disconnected all night, were:
"Bad" pair: 11.89V (5.72V and 6.17V)
"Middle" pair: 12.31V (6.0V and 6.31V)

The second of the "middle" set looks promising, and the second of the "bad" set - while still quite low - at least has all cells going up.  Guess I should pair those two and see what happens.  Maybe with all cells "working" they will actually take a decent charge current...