Specific Gravity varied widely after topping up.

[landyacht318]

The other day I checked my 9 month old Crown batteries and found the plates exposed slightly on a few cells and cursed mightily. I hadn't checked them in about 3 months. I covered the cells with distilled water and charged them.

The next day I got more distilled water and filled the cells to proper level and charged them again.

The day before I added water, they were holding 12.6+ volts overnight using 20 amp hours out of a 230 hour bank.

The day after topping up the cells they dropped quickly to 12.2 using the same amount. An Hour ago I pulled out the hydrometer.
I found:
1 cell at 1.290
2 cells at 1.250
4 cells at 1.275
2 cells at 1.265
1 cell at 1.270
2 cells at 1.255

The thermometer on my hydrometer said -2 for temperature compensation.

So, I disconnected the batteries from the RV, managed to force my Schumacher charger to go into it's EQ mode and adjusted my solar setpoints upto 16 volts and tilted my panel at the sun.

Right now they are taking 17.3 amps at 15.5 volts, bubbling away aggressively. I am monitoring temperature and they are at 75f. The ambient temp is 75f.

Obviously I am hoping for the best, yet expecting the worst, and wishing I had the money to go with AGM 9 months ago. It is not really easy to check my batteries and I went too long and let a couple cells drop too low.

Hopefully this EQ cycle restores the performance.

My questions are: Can I get the SG back upto what I recorded when they were new(1.295 to 1.285)? Is that what I should hoping/ aiming for?

Does the max SG level determine how sulfated each cell it, never to return even after an aggressive eq cycle?

I've been plugging into the grid much more with these batteries, which is no doubt why water consumption increased, but the cycles on these batteries have been very shallow and not very many of them. No cycle went below 55% SOC and most were above 85% SOC. So if i killed another set of batteries by letting them get too low I will really be cursing up a storm.

I don't know how long the Schumacher is going to allow the eq cycle to continue, and the sun is dropping. It was not easy to get the schumacher to go into EQ mode. Since I started typing voltage has dropped by .1 and the amps by 1 but the temp has increased by 1.5. I had to try 3 times by turning on 40+ amps of load and waiting until the voltage dropped below 12.3.

I'll check the SG again after it shuts off and report back.

[landyacht318]

These batteries are still performing fine for my usage. Rarely plugging in, 35 to 55 A/h removed each night on average, alternator and solar recharging only. Very seldom Schumacher assisted.

Strangely, well perhaps not so strange, is that when the electrolyte levels fall to half way between topped up and the tops of the plates, they hold more voltage.

Like last night with 15a/h removed under a 3.7 amp load, they were reading 12.7 v. I am used to seeing 12.4. It is rare to see over 12.6 once the sun goes down. I've noticed this trend nearly every time. When the electrolyte level falls, voltage remains higher at least until I goto bed, and after topping up it is reduced.

Being afraid to let the plates get exposed again, I will likely top them up soon and watch the overnight voltages suffer again. Perhaps the diluted electrolyte is less corrosive to the plates. Since they still provide all I need overnight, I guess no big deal if I wake up to 12.2 or 12.0.

[landyacht318]

I am happy these batteries are still holding on. All the cells took about the same amount of water, and the one cell which read low SG, has always read low, at least since October. The highest reading cell was average on previous readings.

I am not sure about the 115% return number. The equipment is not that precise. I just have the non temp compensated acceptance voltage set at 14.5 for 2 hours and 13.7 float. I know this is not returning them to a true 100%, but I think my attempts to get that last 3% to 7%+ daily, last summer, contributed to me letting them get low on water once and prematurely reducing the capacity of 8 month old expensive flooded Crown batteries.

The long sunny days this time of year, and higher overnight temperatures certainly make the batteries appear to perform better. Nice to see the solar performing in the 11+ amp range around noon, but I deal with partial shading before 9:30 am and after 6:30 pm this time of year

The few times I have plugged in, the Schumacher pretty much agreed with the 0 amp hour from full point, at least when it went into float mode providing less than 0.8 amps to hold 13.7.

The Amp hour from full can go into the positive territory, yet it just says 0 from full. Lately on the few occasions when I plug in after dark, I reset the IPN pro remote by hitting my circuit breaker before going to bed, and unplug the Schumacher.

[HiTech]

How often are you able to return more than you take out, by at least 15%? Using all that water makes me wonder if the low cell is still heavily sulfated and you are having to do a lot of overcharge on the stronger cells to charge it. If you are losing water while only returning the amp hours used, you are recharging less and less each time. Out gassing takes extra amp hours away from those that charge the battery. A third of a gallon is something like 5500 watt hours (figure something like 350 amp hours) consumed that were not charging the battery, but were producing gas and lowering electrolyte level instead.

Jim

[BFL13]

Interesting update, thanks. It seems they have settled at some lower than original capacity but are not getting worse, and that capacity is meeting your needs.

IMO the clue they are at lower capacity is the low "loaded voltage" figure for only 4 amps draw. However the SG is not bad--you must be pleased how that is holding up.

You must be doing something right to have dug yourself out of that one! 🙂

[landyacht318]

Checked SG on these same batteries today after solar had them in absorption for an hour. They were taking 3.8 amps at 14.5.

Of 12 cells, most cells were 1.280 or 1.285 one was 1.275, one was 1.300.

They took about 1/3 a gallon of distilled h20 afterward.

I raised the acceptance to 15.5 for the rest of today. They are taking 10.1 solar amps at 15 volts at 2:30 pm at 75f has not risen above 15 after an hour at 10+ amps

I have not been plugging into the grid much at all. Perhaps 2 times in the last 3 months. The solar with occasional alternator contribution has been more than sufficient to return the 25 to 65 amp hours I use each night.

At 60 amp hours from full, while still supplying 4 amps, they will read 11.9 volts. I don't know what they rebound to once I stop streaming movies.

Regarding my nearly 6 year old engine battery, I cycled that once or twice too mistakenly, but not very deep. Once, my Fuel pump relay's contacts crusted over, and after 7 seconds of cranking it slowed down significantly revealing its reduced capacity. Normally the engine cranks for no more than a second before catching. I usually feed it some solar amps in the afternoon when extra are available.

I have not put water in the engine battery in years. Have not had to and I check every month.

[wa8yxm]

One thing about SG after topping off but NOT yet equlizing....

When you add Distilled water (SG 1.0) it normally starts out sitting at the top of the battery, in time through normal action some acid (higher SG) mixes in and raises the SG but this may happen at different rates depending on the cell. I would expect wildly differing readings right after topping off.

[HiTech]

Did you try Mex's trick for recovering from having the plates exposed, using Epsom salts?

The Unisolar docs do say not to walk directly on the little bumps down the sides which are diodes, if some of them broke you could drop capacity (but I think it would be shaded capacity only). But it sounds like you are getting a lot more solar now that the sun is higher in the sky.

It should be normal for cells with a lower specific gravity to bubble less. They are still working on converting lead sulphate to acid. The other cells are done with their chemical reaction to they use the energy toward hydrolysis. Does a long equalizing session get them closer to the same specific gravity?

Leaving your engine battery in parallel with them is what is convincing your alternator to put out more in the morning. The engine battery is lower voltage, and triggering the alternator to higher voltage output, until it charges back up.

When using this trick, I always l liked to keep a jump start battery in the coach on its AC charger. I never needed it, but it was good insurance. If you cycle the 5 year old engine battery too deep for too long, it will take a vacation on you. A shorter cycle in the morning or shortly before driving should achieve a similar effect but be More SLI battery friendly (a quick recharge after a discharge).

Jim

[landyacht318]

Okay Thought I'd add an update.

I resigned myself to the fact that I was overcharging the batteries and once let them get low on water and shot myself in the foot.

These batteries are still going, and seemingly with no further loss of capacity. I am not checking hydrometer readings any more, nor letting my Schumacher charger float them all night long or forcing equalization sessions. I added a small amount of water once since the late October. They are being cycled 25 to 65 amp hours a minimum of 5 nights a week, and grid power assisted only on the evening of some the cloudy days if I have not driven and solar did little that day.

I've lowered my acceptance voltage to 14.5 for an hour and float to 13.6. Non temp compensated, but San Diego weather 38 to 75f.

They drop fairly quickly to 12.4 but then level off the rate at which they decline and in this regard they seem to be behaving better than a few months ago.

I've been feeding them alternator amps by driving a fair distance in the morning before the solar has returned much into them. At 1750 engine RPM, They have been able to pull 90 amps on their rise to 14.5v. The belt starts squealing on the more humid mornings.

I parked on a few hills so my panels more directly faced the sun and saw the performance I have not been seeing since the last post and close to the maximum expected. A drive right before sundown is not requiring much at all from the alternator but the batteries really seem to hold their voltage longer that next night.

I am surprised at how much amperage these 2 flooded batteries can ask for from the alternator in the morning. They really seem to love this morning blast of high amperage, physical agitation followed by cool sporadic solar amps all day long, even when the monitor says they are a dozen A/h from full when the sun goes down.

I'll be running these batteries till they can't safely provide 65 amp hours overnight. Wonder how long they have?

[BFL13]

I found that Voc didn't match up with rating very well compared with Isc. They have different temperature co-efficients, so I was getting full Isc but lower than rated Voc.

The only way I know to benchmark my solar is that I know it gets Isc at high noon pointed (at 13.5v or below on the IV curve). If it didn't, I would say something is wrong.

You would need a similar known target for when it is working right with your set-up.

[landyacht318]

If the controller is the solar bottleneck wouldn't it get hotter than normal? Which is not the case, it is barely warm.

The test you outline would be an absolute curse fest due to tight spaces, and thick inflexible wires shoehorned into undersized receptacles.

Guess I could run temporary wires from panels to battery to bypass the curse fest.

I think the unisolar 68 watt thin film has a few dead cells. OPen circuit voltage should be a good and easy test for that.

[BFL13]

Ok, so three batts are say 300AH whatever. 12.4 is 75% so AH is 225. so add the 33Ah used that is 258 before dark or 86%

With two house batts it is 12.1 or 50% with 33 used. So if 200AH down to 100 and 33 used, that's 133 or 66% before dark.

So yes, the two house batteries are hurting compared with the engine battery, however old it is. if those figures are correct.

If the solar is in question, IMO as a fist step, go panel direct onto the house batteries and see how that comes out--no controller. Then compare with controller on line. Next step depends on results of that.

[landyacht318]

Well the 5+ year old engine battery is a group 27 too. I have a hard time believing it is still viable.

I agree that the results during charging are not really making sense. Something somewhere is just not right. It is as if the batteries have a large amount of internal resistance, or some current is going somewhere bypassing the shunt.

When I had all three in parallel, and removed 33 amp hours from them overnight, the lowest voltage recorded was 12.4.

Without the engine battery in the mix the batteries hit 12.1. Note that this is not what they stabilized at, just what the ~2.5 amp cycling fridge was able to pull them down to, just before sunup.

Frankly, the underperformance of the solar is a bigger concern than the poorly performing batteries.

[BFL13]

If the batts are at half capacity, then it would take less time for the solar to raise their voltage. As voltage rises on a 12v panel you get fewer amps (as per IV curve), but not a lot fewer until voltage gets closer to 15. So I am not understanding this very well.

The lower capacity should make the battery charger taper sooner, not later. Again this is confusing.

Without some measured numbers using say a Trimetric, it is hard to get a grip on the situation.

Not being able to get the voltage higher than 14.5 using the same amps on half the capacity seems counter- intuitive.

Paralleling the engine battery with dubious house batteries is very brave! 🙂 I don't know what that means where the "morning voltage" on the whole bunch is then " ok" What is "ok" in voltage? If the house batteries are shot, ie they would otherwise sink to a low voltage overnight, then how can the teeny weeny engine battery hold them up?

Very confusing situation! Anyway, the main thing is you are still in business, so something must be going right.

[landyacht318]

I have not bothered to check SG readings again. Even after I was able to get the SG higher, the batteries really did not perform any better. If I leave the 5+ year old engine starting battery in parallel overnight, then the voltage stays where expected.

While it is inconvenient to check the batteries, they are in the best location for my modest DIY class B, without major modification, which I am not willing to go through. AGM's would be cheaper/ easier than modification, and I might look into reducing the bank size with group 65's or 24's when replacement cannot be put off any longer. Depends on the pro rated warranty too, whenever I get around to asking about that.

Really I can only blame laziness for letting them get low in the first place. I'm estimating they have about 45% of their original capacity, so I am dragging around a 62 pound paperweight.

I am wondering if they have something to do with my Solar seeming to be underperforming by at least 30%. We had a nice cool sunny day last week and the amperage is just not there, even with a tilted panel. There is 2 hundred of a volt drop over the solar circuit breaker, but I don;t believe that would account for 30% less performance. Would be nice to have a clamp on DC ammeter.

The solar, and Schumacher, are having a hard time getting the voltage above 14.5, no matter how long I leave them to charge, and the amps with the schumacher are not tapering at those higher voltages. It just seems to plateau at 7 amps for a few hours, then give up and revert to float.

[MEXICOWANDERER]

Next time you need to water, mix up a tablespoon of epsom salts for each cell. Let it dissolve thoroughly in the distilled water. Maybe not the best for a battery going in for warranty consideration but it'll add a little zip for awhile.