Rolls batteries struggling to hold voltage - advice

[cottonpickers]

I've got 2 6v Rolls Surrette 350ah cells in a solar setup. I don't take much juice out of them (2 laptops that the family use) but equally don't put much juice in (180w of solar)
In the summer they were mainly at 100% charge, but even then over night the voltage would drop to 12.35v with no power coming out of the cells. 

They are about 6yrs old I guess (bought second hand where they behaved like this from when I got them) I've never properly equalised them though they do bubble in the summer just not vigorously. Got the voltage up to about 15.1v a few times but no higher.  Specific Gravity readings are (from memory around 12.25 on the worst and about 12.5 on the best) I am planning to get another 80w-100w panel as I know they can't cope in winter.


Questions:
I'm interested in general thoughts on batteries that fall from 13v to 12.35v overnight without any use - I guess it could be a few things but my guess is that its likely sulphation would you agree?

I'm thinking I need to do a good equalization but I don't have enough solar to do that. Would you agree equalization is worth trying?

For equalization, I do have a 5amp 12v battery charger. Could I use this to equalize a 6v cell? If its not powerful enough, could I use a 20amp car charger on a single 6v battery to get it bubbling? (I'm trying to avoid getting a large 30amp 12v charger or a dedicated 6v charger.

All other comments welcome :-)

[dnix71]

One of the two is bad and dragging down the other. Even one bad battery in a string of 8 or more will drag down the whole string. Disconnect them and let the rest apart at the end of a charge. After an hour check the voltage again and you will know which one is bad.

[ghurd]

Do not connect a 12V battery charger to a single 6V battery.
Keep them in series and charge the 12V bank with the 12V charger.

Will need to use the 20A charger to get the volts up.  Even then, when the voltage increases, the charger amps decrease.
My 20A charger output is around 4A(?) when the battery gets around 13.0V(?).  I don't think I ever saw a 20A charger actually put out more than about 12A (except when trying to start a car).

I have paralleled 2 or 3 chargers to get large banks bubbling.
Maybe could get another 20A charger from a friend for a day?

No need to get a 6V charger.

"general thoughts on batteries that fall from 13v to 12.35v overnight without any use"
13V?  That's not very high.  Could be they are not fully charged.
I'd like to see them up around 14.4V for a several hours before deciding if they are nearly full charged.

What kind of charge controller?

No need to separate them to check the individual voltage.
I'd check them individually before sun rise, at noon, at sundown, and maybe midnight.  Strings can do funny things.
G-

[Simen]

I've got 4 S-4000 530Ah batteries from Rolls, and both from what i've heard and in my own experience; these batteries seem to fall fast down to 12.3V-12.4V with only light load... (But not with no load at all!) But - Once there, they stay around there a long time before going further down during discharge/use...

An SG of 1.225 to 1.250 would indicate around 75-90% charge (not knowing your battery temp), so i'd agree; a good equalizing would be good. Do not give up before you're at atleast 1.265SG @ 25deg. C. on all cells. After that, you can adjust with distilled water on those cells that are higher...

Edit:
During your charging and equalizing process, you'll might find the SG Log program i wrote useful: 
http://fieldlines.com/board/index.php/topic,144770.0.html

[Rover]

I'm agreeing with the rest... Not fuly charged, needs equalized, etc.

But also don't ignore temperature differential from initial read to the low reading. If temp falls 20 deg F, expect a .2 V drop (roughly .1 per 10 degree F)

It all adds into the equation.

Rover

[ChrisOlson]

For equalization, I do have a 5amp 12v battery charger. Could I use this to equalize a 6v cell? If its not powerful enough, could I use a 20amp car charger on a single 6v battery to get it bubbling? (I'm trying to avoid getting a large 30amp 12v charger or a dedicated 6v charger.

You're not going to equalize and desulfate those batteries with any automotive style charger because none of them will hold the voltage high enough.  You need to hold them at 16.5-17.0 volts for several hours to do a corrective equalization.  Your batteries are suffering from what is called "deficit cycling" due to not having enough charging power available to properly charge them and they have become heavily sulfated.

Do NOT charge a 6 volt battery with a 12 volt charger.

I have a 2,400 amp-hour Rolls bank, and this is copied from the manual that came with my batteries:

• Equalization
Individual cells will vary slightly in specific gravity after a charging cycle. Equalization or a “controlled overcharge” is required to bring each battery plate to a fully charged condition. This will reduce stratification and sulfating, two circumstances that shorten battery life. Equalization of the battery bank is recommended every 60 to 180 days, depending on the usage of the individual system. To equalize the cells, charge the batteries until the voltage elevates to the “Equalization” voltage shown in Table 2. Charge parameters and maintain for 2 to 3 hours per bank. A constant SG for 30 minutes is a good indication of cell equalization. It is recommended to water the battery cells halfway through the equalization. This will assure the water is mixed with the electrolyte.

• Frequency
It is recommended to equalize the batteries before usage. Corrective equalization needs to be performed if symptoms arise such as a constantly running generator (low capacity) or the battery bank will “not hold a charge”. These symptoms are typical of a heavily sulfated battery. If a battery is not being fully charged on a regular basis or limited equalization is performed using a generator, sulfating will occur from “deficit” cycling. This undercharge condition can take months before it becomes a major and noticeable problem.

Method
Corrective Equalization can take a very long time depending on the degree of sulfating.
1. If you have a recombination cap, remove during equalization.
2. Set the charging controls to the highest voltage allowable by the charge controller (inverter). Temperature should be monitored very closely and kept below 50ºC.
3. Charge at a low DC current (5 A per 100 AH of battery capacity). If grid power is not available, use solar panels or a good DC source when possible. At high voltages, charging with generator can be difficult and hard on the inverter.
4. Once every hour, measure and record the specific gravity and temperature of a test cell. If the temperature rises above 46ºC and approaches 52ºC, remove the batteries from charge.
5. If severely sulfated, it may take many hours for the specific gravity to rise.
6. Once the specific gravity begins to rise, the bank voltage will most likely drop, or the charging current will increase. The charging current may need to be lowered if temperature approaches 46ºC. If the charge controller was bypassed, it should now be used or put back in line.
7. Continue measuring the specific gravity until 1.265 is reached.
8. Charge the batteries for another 2 to 3 hours. Add water to maintain the electrolyte above the plates.
9. Allow bank to cool and check and record the specific gravity of each cell. The gravities should be 1.265 ± 0.005 or lower. Check the cell electrolyte levels and add water if necessary.

It is recommended that a specific gravity reading of one pilot cell is measured and recorded on a regular basis when it is thought that the bank is fully charged. The measurement should be compared to previous readings. If the measurement is lower than the previous reading, a longer absorption time and/or higher voltage setting should be used. The longer the absorption time and the higher the bulk voltage, the more water will be consumed but less equalization will be required.

--
Chris

[B529]

How much water do you add to them? How often?

6yr old batteries bought second hand, never been EQ'd properly, most likely your batteries are shot.

[Rover]

"6yr old batteries bought second hand, never been EQ'd properly, most likely your batteries are shot." Yeah it does bring some questions to ones head.

Shot...? I'd say probably not... Behave like new after some work?  Probably not. Worth the effort to assertain state, probably

 I just dealt with some "shot batteries" .... after 2 months at rest 9-10V (that's shot)  .. considering the were fully charged before their forced respite. (Course the hurricane did some mean things to them)

Rover

[cottonpickers]

Thanks for the feedback -very much appreciated and nice to get a number of suggestions/input.  To provide a little more information.

In summer (maybe like June -Sep/Oct) they were at 100% most days. (meaning they got to 14.6v and then floated at around 13.6v)  Now its darker they aren't doing that but then I'm not drawing on them currently until I can get the voltage up.

I have a steca pr3030 pwm controller.
I have added 7.5 litres of water since I had them (around 2 years)

When I said they go from 13v-12.35v over night with no load , I guess to be fair that should really have been 13.6v down to 12.35v with a very light load.

So general concensus is that a good equalizing could be beneficial - NOT using a 12v car charger on a single battery :-)

Question: A 20amp car charger will probably cost me about £20-£30 and sounds like even that isn't ideal as it will not get me up to 15v.  What could I get that would get me up to 15v?
Would I be better off putting that towards another panel and perhaps connecting the (nomimal 12v) panels to one (the likely weak) battery? (one battery does have lower specific gravity than the other in most cells) and then do the same with the other? - I'm assuming that solar behaves a little different to a car charger and will meet the batteries voltage. Is this something I can do? or must I equalise together?

[ChrisOlson]

In summer (maybe like June -Sep/Oct) they were at 100% most days. (meaning they got to 14.6v and then floated at around 13.6v)

Just "getting to" 14.6 volts does not fully charge the battery.  If you just "get to" 14.6 volts, then drop to float, the battery is only reaching, at most 80% SOC.

I think it would be best to refer to the Rolls RE battery manual and study the required charging voltages in Table 2.  For instance, at 20 degrees C the cells have to be charged at minimum 10%, maximum 15%, of the ah rating until the voltage gets to 2.50 volts per cell (bulk stage).  Then the voltage has to be held at 2.50 until the amperage required to hold them at that voltage drops to 2% of the ah rating (absorb stage).  Then you drop them to float voltage of 2.19 volts per cell.

Failure to charge those batteries any other way will sulfate them and they'll die an early death.  It sounds like you don't have even close to enough power available to properly charge them.  So it's not surprising that the at-rest voltage drops very quickly with a light load.  Those batteries will last 15 years if they're properly charged and cared for.  Deficit cycle them repeatedly and they'll be dead in 6-7.

Edit: You said you got 180 watts of solar.  At 75% of the watt rating of the panels, that's less than 1/3 of the required charging capacity for those 350 ah batteries.  You're killing them by not feeding them properly.
--
Chris

[birdhouse]

cotton-
what chris is telling you is the best, and what should be done under ideal conditions. 

however, with what you've got you may be able to help these batteries.  first off, don't pull any more loads from your batteries until after you've tried to revive them.  i'm not familiar with your stecca pr3030 controller.  does it have adjustable set points for battery voltage cut-offs?  can it be set in a "permanent" equalization mode? 

if the answer to both questions is yes, then i'd peg your controller for the highest voltage setting and try to keep it in equalize mode for days on end.  note: you'll have to keep a very keen eye on your water levels, as this procedure may make them eat some water.  do this for a week, and record the resting voltages in the morning. 

of course, more panels would help.  and a fully adjustable battery charger would work also.  problem is, most battery chargers are too "smart" to allow you to get the volts as high as they should be for a proper equalize.  your controller may be too "smart" as well. 

whie cant thang's bee jost plane dum any-moore??

adam

[thirteen]

I do not know your system. Maybe as a side question do you have an inverter or something else that is using power just sitting there without anything being used. A power robbing ghost (Casper) might be in the system. I have an old inverter that does that. I have a throw switch that totally disconnects my batteries. As a suggestion when you get done charging them be sure and completely disconnect them before testing.
Sounds like you will have to really charge the batteries to bring them back to full life.

To others; would he need to get them fully charged and then maybe draw them down with a heavey load and then fully recharge them again to help bring them back? I've read something like that on this board but it might have been for a certain system or batteries. Not sure just a question. An idea to play with or toss.

[Simen]

The Steca controller will perform an equalizing charge at 14.7V@25deg.C. for 2 hours every 30 days, or after a SoC of below 40% are detected...(Note: the Steca does temperature compensate.)
But ofcourse, if there's not enough solar power available, i guess the controller never reaches equalizing...

One thought:
Have you checked your controller if the 'battery type' are set correctly? It should be set to 'Li' (Liquid); if set to 'Gel', it will never do a proper equalize charge...

If you can get your batteries up to 'normal' charge voltage (14.4V), you could connect your solar cells directly to the battery the next sunny day; that should get the bank up to equalizing voltage (15.0V+) But you'll need to monitor the battery voltages and SG closely during this process...
Edit:
And watch your water level also... The 180W of panels won't be enough to do any damage to your battery, as long as you don't overdo it...

[ChrisOlson]

Well, here's a suggestion that will work to equalize those batteries properly, but it will take some building to construct it.  Using the controller is obviously not going to work, and neither is a regular battery charger.  The only convenient way is an inverter with a built-in charger running on gen power (like an Outback or Xantrex unit).

Failing that - there is another way.

You can build a gas charger for a 12 volt system with a small gas engine and an automotive alternator.  Drive the alternator at 1:1 with a 3,600 rpm engine and full field the regulator on the alternator so it doesn't regulate the voltage output.  Then you adjust the voltage and amps with the throttle on the engine.  I equalized my 12 volt bank for years with just such a setup, and it takes constant monitoring and reducing engine speed to hold the voltage where it should be during equalization as the internal resistance of the cells comes up as they get desulfated.

I highly doubt those batteries are shot - they just need a corrective equalization charge, which will take many hours (could be up to two days) of holding them at 16.5-17.0 volts.  And from experience with those batteries, it will take many hours of charging with about all the gas charger can put out with a 40 amp alternator to even get them to 16.5 volts.  But once they get there and the amp requirement starts to come down, then you'll have to back of the throttle to supply just enough amps to hold them at 16.5 or so.

Constantly monitor the temperature of the batteries and if they start getting too hot, stop the equalization, adjust the water level, then go back to doing it after they cool down, and just continue the process until the required voltages and amperages are reached.  It's a smelly, messy process that won't have to be repeated as long as the batteries are maintained properly in the future.  Those batteries have the plates to handle it as long as you keep the plates under electrolyte and don't boil them down too much and expose the plates to the air.

I assume cottonpickers does not have grid power, and this is one way to accomplish the task in the absence of enough solar power to do the job, and without having an inverter/charger that can do it.  And if you do live off grid, the time spent building the gas charger I describe is well worthwhile anyway because it can be used to make up the difference between what the batteries need and what you get from RE sources on a weekly basis to keep the batteries in good health.  And you can also use it to do a normal equalization about once every 60 days to keep them happy.
--
Chris

[cottonpickers]

Thanks again, all. A wealth of knowledge here and I'm certainly going to use Simens SG Logger - Very nice!

I do have mains power. I have a small phantom load in that I have a car adapter laptop charger than takes a small 150ma all night and a voltmeter sucking a small 15ma - otherwise thats it.

In the summer I'm pretty sure they went beyond full charge and 'tried' to equalize (hitting 15.1v for maybe an hour) but whilst they visibly fissed they certainly didn't get warm. So per suggestions I will up the solar wattage. Its only a hobby so at this time- I think I can take (afford) wattage up to perhaps 300w, but not really much more currently.

Is it OK to directly connect 12v solar to just one 6v cell to help me push more amps in? I think it is... but looking for confirmation :-)

[ChrisOlson]

Is it OK to directly connect 12v solar to just one 6v cell to help me push more amps in? I think it is... but looking for confirmation :-)

You can - as long as you watch the voltage as the battery charges up.  But it will limit how much the panel can make as far as power because of being "clamped" at low voltage.
--
Chris

[ghurd]

Is it OK to directly connect 12v solar to just one 6v cell to help me push more amps in? I think it is... but looking for confirmation :-)

You can, but it is pointless.
Connecting a 12V PV to a 6V battery will not increase the amps much...  No increase in amps worth mentioning.
With a decent controller (low Vf), the amp increase is maybe 3~5%?
Might as well leave the pair of 6V connected for 12V, and it will send the same charging amps through BOTH batteries at the same time.

I disagree that 180W of 12V solar is insufficient to equalize 12V 350AH.
I have seen unregulated 3A 50W smoke a 12V 110AH, more than once.  It certainly would not do it in winter here, or if the battery was regularly powering a load, but it will do it.

I agree with Simon.
The shop has 180W-ish of 12V solar.  Usually around 880AH of 12V (8 x 6V golf cart).  A few days of good sun in summer to get the bank 'actually full', and after that equalizing is not a big issue.  But we would never intentionally let them get anywhere near 15.5V, let alone 17.0V.  (the battery bank is at room temp)


About "If you just "get to" 14.6 volts, then drop to float, the battery is only reaching, at most 80% SOC."
I could agree or disagree, mostly I 95% disagree. 
Case in point.  My truck. 
If the alt is cold it charges to 13.9 to 15.1 but just for a very few minutes.  Warm it charges to 13.5 to 14.3. (from Chilton's #8163, page 2-17)
The truck sat for almost a year a little while back, maybe ran it a half hour every month or 2.  Sometimes had to charge the battery to get it started, meaning it was sitting while severely undercharged for a long time.
Often had an inverter clamped to it to power drills or saws, when it was not running (the other guys could help me push it started if the battery went dead).
Anyway.
Changed the battery about a month a ago.  It was a prorated for 12 months battery (cheapest they made at the time, $28 back when lead was cheap, and they don't even sell anything in the same class now).  It was in the truck for 9 years and 10 months.
Turns out the battery was still OK.  Not great, but OK.  The issue was the alternator amp output was low, and couldn't keep up with the heater fan and headlights at the same time, unless on the highway.

There is a good chance leaving it as it is, and adding a cheap (the cheaper and older, the better) 20A car battery charger (or 2) for a day (or 2), will let the PVs and controller do the equalization charge.
You bought a controller that equalizes and accounts for the temp.  Might be a good idea to let it do its job by itself.  Steca is not my favorite brand, but they have engineers to figure out this stuff so they can make a controller that can do it by itself.

Adding more PV power would be money well spent.  Good bang for the buck.
No need to upgrade battery, controller, etc.
Just add the PV(s), mount, and some wire.  That's cheap $/W.
Plus it will let the battery supply more power per day, especially in winter.
G-

[ChrisOlson]

In the summer I'm pretty sure they went beyond full charge and 'tried' to equalize (hitting 15.1v for maybe an hour) but whilst they visibly fissed they certainly didn't get warm. So per suggestions I will up the solar wattage. Its only a hobby so at this time- I think I can take (afford) wattage up to perhaps 300w, but not really much more currently.

I just spent $9,600 on a new Rolls bank back in August when I discovered that several batteries in our 8-1/2 year old bank were going south.  I was told by the dealer in no uncertain terms to not trickle charge those new batteries.  He said to work 'em and work 'em hard, and when I recharge them do not repeatedly do it partly one day, and try to finish the next or they will die young.  He said do not make them live on constant float because they will stratify and die young.  He handed me the manual and told me to read it cover to cover to learn how to take care of them to keep my 7 year warranty on them in effect.  So I'm just passing on what I was told and read in that Rolls battery manual.

The 350 ah 4000-series S-460 battery requires 150 amp-hours of charging capacity from 50% SOC to 85% SOC during bulk stage.  180 watts of solar power is barely enough to bulk charge those batteries in one good day if they get cycled to 70% SOC, much less get them thru absorb.  In fact, if you have an idling inverter hooked up to them with no loads on it, I'd consider 180 watts of solar barely enough to maintain the bank doing nothing except running that idling inverter.

Oh sure, on a perfect day it might be more than enough.  But how many perfect solar days do you get?

Those are expensive batteries and they're only in their middle age years.  I would not mess around with trying to move a boulder with a toothpick.  Put a crowbar under that boulder and do it right.

That's my .02 cents  on it.
--
Chris

[Madscientist267]

Going to tend to agree that 180W for 350AH is plenty, provided a few contingencies are met:

I can ALMOST equalize my 8D (~220AH @ 12V) with "60" watts of solar. Not quite, because the losses start to add up quickly as the voltage increases. I don't have a plot on it, but from what I've seen, I could hit "normal" equalization with probably somewhere between another "20" and "40" watts. I put these figures in quotes, since I've yet to see a panel that puts out what the sticker says. Usually, real world availability is somewhere around 75% thanks to temperature/azimuth issues. Things we all face. So the moral of the story is, if that "60" watts were REAL world 60 watts, I'd probably have no problem whatsoever hitting and holding the EQ.

Another issue is, by the time I've recovered the losses (along with tapping some of the solar for use during production), there's little light left in the sky on any given day to do anything like equalization. Only the best days will even come close. A cool, summer day comes to mind. You know, IDEAL conditions.

But, stopping use by "killing service" for a couple days shouldn't prove to be a problem even if you WERE off grid and had no other source of power to hit and hold with. Even during the winter, if you started the day with a "full" charge from the previous day, all but the most extreme latitudes should provide you with enough light on a clear day to get you at least close to where you want to be.

Even with all that said, I will also agree that it never hurts to add some more panels. I'm looking into the idea myself as soon as a few things settle down and I'm a little more sure I wouldn't be throwing my money away...

More power, Captain!

Steve

[ChrisOlson]

Going to tend to agree that 180W for 350AH is plenty, provided a few contingencies are met:

How many hours of sunlight do other parts of the world get?  And are these like turbo-boosted panels that put out extra amps?  Because these "recommendations" go against everything Rolls says about those batteries, and I don't think cottonpickers is looking for bad information.

Maximum time limit for equalization is three hours.  Minimum 2 hours.

I don't believe cottonpickers batteries are even getting thru absorb, which is the most important part of the charging cycle, because bulk only gets them to 80-85% SOC.  From the manual for the S-460:

t = 0.42* C/I

t= time required to absorb charge them
C=20 hr rated capacity
I= charging current

Assume those panels can put out 12 amps constant at absorb voltage of 15.0.  All day.  That's 180 watts.  The time required to absorb charge them, assuming they've made it thru the bulk stage, is 12.25 hours @ 12 amps.

Required equalization current is 17.5 amps @ 16.02 volts for a series pair of S-460's and a two hour equalization, according to the manual.  Can 180 watt panels put out that much power?

You might get them to equalization voltage with 180 watt panels on a perfect day, but there's no way on earth you're going to hold it there long enough to get the cells to a constant 1.275-1.280 SG for 30 minutes, which the manual says is the required parameter for equalization to be complete.  Equalization is not something you can start today, let the sun go down, then continue tomorrow.
--
Chris

[birdhouse]

Required equalization current is 17.5 amps @ 16.02 volts for a series pair of S-460's

maybe my battery bank of trojans (450ah @ 24v nom) is WAY different than the rolls brand, but for me, it takes very little amps to continue equalize once the high voltage mark has been hit.  my controller (ts-60) dials the amps WAY down once the required equalization volts have been hit.  my panels are 390w 36 Vmp (although ive got more i'm waiting to install). 

i agree that cotton's panels are undersized for his bank, but i don't think hugely. 

to cotton:  *i think* your most simplistic way to get a good equalize on your bank may be to  pick up that 20-30 dollar (pound/quid/whatever) charger.  run it along side your solar for a week, and put your charge controller in equalize mode as often as possible in the early afternoon to try to get decent amounts of equalization time in.  monitor battery water levels, and buy some more panels as soon as your budget allows.  afterall, i'm guessing you got your batteries for cheap/scrap/salvage pricing?  just do your best to send as many amps as you can to get them to equalize as long as possible with your current resources (within reason of course).

to chris: i, in no means mean this as an attack on your (thorough and free) information.  just trying to help out a guy who seems to struggle to get his batteries "on the level"  not everyone has diesel gens, propane gens, PTO's, 12g turbines ect.  some of us can't hit manufactures specs on EXACT charging specs, and do what we can with the resources we have.  it may not be ideal, but it's all some can do, and it tends to work very well for many.  again, no disrespect.

adam 

[ChrisOlson]

maybe my battery bank of trojans (450ah @ 24v nom) is WAY different than the rolls brand

Yes, they are different.  The dealer where I got mine showed me a cutaway of a Trojan L16 vs a Surrette L16/1380.  The Trojan is designed for 5-7 year service life.  The Rolls is designed for 12-15 year service life and roughly double the 80% DOD cycles that the Trojan is.  The dealer handles both brands and told me the Rolls batteries, even thought they cost roughly half again more than what the Trojans cost, will cost less over the long run.  I went there all set on buying Trojan T-105's and he told me don't even look em.  They're not suitable for anything but golf carts and very small RE systems.  So we got Rolls T12-250's.

When my inverters equalize the bank, it don't build the voltage slow until it finally gets to equalization voltage.  It takes it directly, bang right now, to 32.0 volts when I press the equalize button.  Whatever amps is required at that voltage is what it delivers, and  both inverters combined can deliver 240 amps.  The bank, from fully charged, usually pulls 120-130 amps initially when the inverters take the bank up to 32.0 volts, and that tapers down to about 40 amps or so when equalization is complete.

some of us can't hit manufactures specs on EXACT charging specs, and do what we can with the resources we have.  it may not be ideal, but it's all some can do, and it tends to work very well for many.  again, no disrespect.

Of course, but how long do you want your batteries to live?  My dealer, who's been in the business for 35 years, told me that it doesn't hurt those batteries to work them.  He said what will kill them is not discharging them below 50%, it's not having enough power available to bring them back in one charge cycle.  He said Rolls stresses that the #1 killer of batteries is improper charging and what they call "deficit cycling".  He told me that if my batteries get discharged and my solar and wind doesn't bring them back to 100% within 24 hours, do not go, "Oh, they're at 80% and we'll make it to the next day."  He said start the generator and finish the job that the solar panels and wind turbines didn't complete, and they'll live really long and happy.

So I dunno.  That's what I was told, and that's what it says in the manual for them.  Rolls has been building deep cycle batteries for 80 years so I would think they know what they're doing.
--
Chris

[ChrisOlson]

I can ALMOST equalize my 8D (~220AH @ 12V) with "60" watts of solar. Not quite, because the losses start to add up quickly as the voltage increases

Steve, kind of an interesting observation there.

Just for giggles I called Rolls-Surrette tech support this morning and asked about equalization charging rates and voltage.  The tech support guy told me DO NOT use insufficient power to equalize because it will hold the battery in an overcharge condition too long.  He said from a fully charged state, when equalization is started the inverter (or controller) should immediately take the batteries to 2.58-2.67 VPC.  The initial amp requirement will be very high and approximately equal to the 6 hr discharge rate, but should gradually drop to 15% of the 6 hr rate as the cells stabilize and start to gas, and remain just about constant at that current during the cycle.

This is all assuming a healthy battery that just needs a normal equalization and does not need corrective equalization.

The 6 hr rate on those 350 ah batteries is 43.2 amps.  Those 180 watt panels can't deliver sufficient power to get equalization going.  It will take too long to get them up to equalization voltage, which puts the battery in an extended overcharge state just trying to get there, and will shorten its life or wreck it.

He said equalization is a controlled overcharge under very precise parameters, not an extended overcharge that eventually gets to the required parameters.

That's right from Surrette tech support.
--
Chris

Edit:  I forgot to add that for cottonpickers, those panels could possibly provide the required power to equalize if they had a "boost" (like maybe an automotive battery charger?) to help them deliver the initial power to get the equalization going.  And that's assuming the charge controller can be set for high enough voltage.  15.1 volts will not work.  15.48 is minimum and best for 25 degrees C, 16.02 is best for colder batteries.  I think I read a post from Simen about that controller doing an equalization charge at 14.7 volts @ 25 degrees C, and that's not high enough for the Rolls batteries.  14.7 is barely above their absorb voltage at 25 degrees C.

Might require a different charge controller.

[SamoaPower]

All of the advice given thus far concerning equalization and charge levels is certainly well deserved. However, one parameter that hasn't been mentioned is the ACTUAL existing capacity of the bank. Being that the bank is six years old and has been less than well treated, I suspect there may be less to work with than thought.

Actual capacity can be determined by a timed discharge test using the rated 20 hour current level, preferably at constant current. Don't be surprised if the timed discharge test shows less than 30% of rated capacity remaining. If it's down near this level, resurrection may be like  beating a dead horse.

[ChrisOlson]

Actual capacity can be determined by a timed discharge test using the rated 20 hour current level, preferably at constant current. Don't be surprised if the timed discharge test shows less than 30% of rated capacity remaining. If it's down near this level, resurrection may be like  beating a dead horse.

That's right.  From the description of how they drop voltage right away with very light loads, I suspect that's the case.  But for cottonpickers' sake, everybody I've talked to about Rolls batteries claims they're the only ones capable of being resurrected if they're heavily sulfated at that age because they got the plates, and big enough sumps below the plates to hold "sludge" that's going to come off the plates to do it.

The problem, I think, for cottonpickers is that he does not own the equipment required to do a corrective equalization on those batteries.  My Xantrex inverters will go up to 34 volts, and that's one way it could be done (with a 12 volt Xantrex that goes up to 17 volts).  But he doesn't have one of those.  The other way is an unregulated gas charger.  And that could be built.

cottonpickers - if you decide those batteries are junk and you're going to haul them off to the scrap yard, I'll take them.  I'll pay shipping to get them here.  And I'll resurrect 'em.  
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Chris

[Madscientist267]

I thought about the SoC thing after I posted... I probably was a bit more vague than I intended.

A lot of variables to consider with all of this. I think you're right about the whole "reaching equalization" part; and definitely didn't mean to infer otherwise.  I think the other aspect of this is the difference between maintenance and corrective. I personally don't use the panels for either, but rather a hefty charger I put together some time ago. You're absolutely right, attempting to reach it when the equipment at hand can't pull it off could very well do more damage than good.

I guess my whole thing with the wattage vs amp hour rating thing was just that it is theoretically possible, not that it is the best method. One of the many arenas where "just because you can doesn't mean you should" applies.

I guess my only real angle is that the load should be completely discontinued while this entire process is taking place, so that the condition of the batteries could be ultimately determined, and no "stepping back" taking place from outside influences.

The idea was to reach as full of a normal charge as possible (allowing them to pass through absorption with as little cycling as possible), then once they are essentially floating at somewhere between 14.2 and 14.4 for several hours, prepare to take them on up to full on equalization before self discharge brings them down too far.

In theory (and this is where I was heading before), at that point, the solar alone would potentially be enough to do maintenance equalization. But rolls is calling for quite a bit more apparently, and corrective will probably take considerably more energy above that to do good sans evil...

Eh, FWIW.

Steve

[ChrisOlson]

I was reading in the manual for my batteries about corrective equalization.  Rolls is the only manufacturer that recommends that procedure.  Basically you do a controlled cook on the battery at 16.5-17.0 volts until it smokes, smells real bad, and gets hot.  Rewater it, let it cool, and do it again.  Repeat until it comes back to life.  It says it will take many hours.

I'm pretty sure that would totally and decisively destroy any other battery.

Symptoms indicating that a corrective equalization is need is low SG at rest after a maintenance equalization.  They got a battery trouble shooting flow chart in the manual and one of the tests is a constant rate discharge at the 20 hour rate to determine the actual ah capacity and degree of sulfation to determine if just a maintenance or corrective equalization is required.
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Chris