why an equalization charge

[dinges]

G'day,

Because of my recently acquired batteries, I have been delving a bit into the datasheets of the manufacturer.

Somewhere, it gives the correct voltage for an 'equalization charge', about 14.5-14.8V, from memory.

I have read about this before on this board, but never found out why this was necessary, and when. How do you know it's about time for such a charge?

Has it to do with batteries being in parallel, or is it something that needs to be done to every battery once in a while. I suppose only gell-cell lead batteries, or NiCds and ordinary lead batteries too?

Peter,

The Netherlands.

[wpowokal]

http://www.otherpower.com/otherpower_battery.html

[dinges]

A subtle way of saying 'read the bl**dy FAQ'. :-)

I had seen this page a long time ago on otherpower, will read it now much more carefully.

Thanks.

Peter,

The Netherlands.

[dinges]

Ehm, according to this info equalization shouldn't be done on gell-cells.

Yet I have datasheet of a gell-cell that does specify equalization voltages...

I'll stick with the manufacturers recommendation, but this is one difference I note.

Peter,

The Netherlands.

[wpowokal]

Peter, as I understand it an  equalising charge is done simply to mix up the electrolite, a bit like areating a fish tank, and bring all cells to as equal a voltage as possible.

Gell bateries have very different requirements to lead acid, since the electrolite is in a gell I don't see how it could stratify. They are sealed for all intents.

allan down under

[Flux]

From what I have been able to find for flooded batteries the main reason for equalising is to stir up the electrolyte to remove startification. Also as no two cells have absolutely identical capacity or discharge characteristics some cells will eventually reach full charge before others. If you charge to the minimum value required if all the cells are the same then the slow ones will never fully charge and the others will gas gently. The slow cells eventually form sulphate.

With flooded cells there is no problem letting all the cells gas occasionally to make sure the slow ones reach gassing volts. The bubbling also stirs the electrolyte.

With sealed cells you can't replace any water that is lost so you have to be more careful. Fortunately the Gell and AGM cells do not stratify, there is so little free electrolyte but there is still the problem of slight differences in the cells.

The charging seems to be a compromise between enough charge to deal with the slow cells and gassing enough to remove water.

In stand by duty these batteries are floated at a voltage high enough to maintain their charge without sulphating ( about 13.8v )

If the battery is used much as opposed to stand by then 13.8v is not enough to fully charge them and every so often it is still a good idea to bring them to a higher voltage to make sure they are fully charged. For the pressurised batteries (VRLA) an occasional short charge to about 14.3v seems to be ok. As long as gassing is slow the gas seems able to re-combine without loss of water.

With gel batteries the latitude is much reduced and It seems that generally they go for a slightly higher float voltage and minimal need for an equalising charge.

Too high a float voltage causes corrosion of the grid bars and it is all much of a compromise.

All you can do id follow the makers advice, each manufactures processes are slightly different.

If you have no makers advice, then I would say equalise VRLA to 14.3v for an hour every few months but with Gel I wouldn't go over 14v.

I don't think you can win, batteries will always die, all you can do is avoid the worst forms of abuse and hope for the best.

[PaulJ]

   Peter, are these the Sonnenschein batteries you mentioned in an earlier post? Do you have a type number?

   I'm pretty interested in this, as I run my house off a bank of used 12V Sonnenschein wheelchair batteries, type "dryfit A200" and "dryfit A500 cyclic", varying in capacity from 28Ah to 38Ah. I have 48 of these in a 48V series/ parallel configuration giving about 400Ah (12 strings of 4 batteries).

   My understanding of these is that they are AGM's with an unusual chemistry; as well as sulphuric acid, they also contain phosphoric acid which somehow keeps the internal resistance low all the way to complete discharge (this is from memory, can't find the reference now). The 38Ah units are rated by the manufacturer to deliver 1500A for 5 seconds!

   On occasion I have used 2 or 3 of these in series as an arc welder, simply hooking one side to ground and the other to the welding electrode, keeping a steel door between myself and the batteries as a token safety gesture. The batteries don't even get warm.

   The information I have been able to find from the manufacturer's website reccomends charging at between 14.1- 14.4V for a 12v battery for up to 12 hours, followed by a float voltage of 13.8V(at temperatures from 10 to 35*C)

   I never let the voltage on my battery bank exceed 57V (14.25V per 12V battery). This is my "boost" setting.

   The "equalisation" setting is 56V (14V) for 2 hours.

   The "float" setting is 55.2V (13.8V) in summer and 56V (14V) in winter.

   I'm a bit conservative with my maximum voltages due to the difficulty in matching used batteries in series strings,some always sit at higher voltages than others.

   Where did you find the info on equalising these batteries? I would be most interested if it applied to the ones I am using, I'm fairly sure they could cope with a higher voltage, just haven't had the courage to try it!

   Thanks,

   Paul.

   

[wooferhound]

If an equalization charge is basicly stiring everything up and destratifying the electrolytes, then, will shaking my single battery do the same thing without applying the higher voltage equalization charge ?

[wooferhound]

These battery links will teach you more than you want to know about Batteries...

http://uuhome.de/william.darden/carfaq.htm

http://www.batterystuff.com/tutorial_battery.html

http://www.buchmann.ca/faq.asp

http://www.uuhome.de/william.darden/batlinks.htm

[Flux]

Some of the very large batteries use gas jets to mix the electrolyte.

I wouldn't risk shaking it, there is usually a lot of crud at the bottom and you risk shorting the plates.

Flux

[dinges]

Hi,

The batteries I'm using are Sonnenschein A400 series, 12V 12Ah ones.

Rechecked the datasheet (see my file-uploads, a .pdf-file at the bottom of my files) and it does specify an equalization voltage. I must further study this datasheet though.

Am checking the last batteries; of the 8 A400's, one was a dud; another one was at only 88%, but perfectly useable. The other types of batteries I took are all defect.

So I'll be going back to get me more Sonnenschein batteries; 20 to 30, I'm planning. If only 50-60% of these are ok, I'm happy :-)

Have just modified my UPS to connect external batteries (installed two battery plugs).

After the tip from wpwokal (I think it was him) to check the faq & otherpower site, I've learnt alot more. Also, there was an interesting link to another site, that was entirely on batteries; it had a downloadable file called 'battery.zip', the entire website in one zip-file.

I'm learning more & more on batteries; thanks for all the links, will check them out ASAP.

Funny how quickly you get to know your batteries; for the first three Sonnenscheins, I've made discharge curves (measuring voltage vs. time, 2 hour test, load 4.5A (.375C). Normally this test takes 1h40' to complete (for a battery at 95% capacity) (it's de-rated because of high discharge current; all in the datasheet, you end up with 8Ah instead of the 12Ah). But I can tell in the first 10 minutes of testing the battery whether it will be a good or bad one; even tell its capacity, to an accuracy of 1-2%... Was amazed by this myself. So I'm sure that you guys with RE-batteries get to know your batteries pretty well (perhaps like you know your pets ?)

Paul, you have a different battery-series from mine, but if you look at the Sonnenschein website, you should be able to find a datasheet for the A200 & A500; I found one for mine somewhere on the internet, think it was the Sonnenschein website but not sure.

Hope my batteries will die of old age, and not be murdered :-), unwillingly.

Peter,

The Netherlands.

[dinges]

more clearly:

of the 8 Sonnenscheins (lit. 'solarshine' :-), so the must be useable for RE)

1. was a dud
   
1. was at low capacity (88%)
   
6. are at 93-115% cap. (most are at 95%)
   
   

not too bad eh?

Peter,

The Netherlands.

[dinges]

PaulJ,

Where/how did you get these batteries? From a place that sells/repairs these wheelchairs? If so, I might see if I can find one of these places and offer to relieve them from their batteries (they won't even have to pay me :-). Are they replaced as routine maintenance, before problems occur, or after the fact (i.e., will the batteries usually still be ok or defect?)

My car had to go for the annual inspection last friday; all was ok, but asked if they had any defect lightbulbs lying around (for testing the batteries); scored me some of these, with only 'dimlight' defect. The big one (name?) of 12V/5A are usually still ok. Even have a 24V one. I think my new batteries will be in two 12V banks, for 12V and 24V that I need for the UPS. With my current batteries, I have now 862Whr; this should provide plenty of light during the next blackout (very rare here in NL); can't wait to see the looks on the neighbours faces when everything in the street is dark, except for our house :-)

Things are getting weird over here; the place I get the batteries from said they couldn't sell; so I offered them a donation and said I would steal the batteries :-)

The garage installed zinc weights on one tire, because lead is no longer allowed (though you can use up old stock).

With soldering, starting from 2006, no lead-based solder may be used in new electronic products (ROHS-compliance); the alternatives are not good, so I've heard. And all my old parts are still lead based... Must get me as much lead-based solder as possible to last me the rest of my lifetime, I'm afraid :-(

What's next? Ban aluminium, because cooking in aluminium pans can cause mental illness (is a fact).

Sorry, couldn't help myself; I suggest we stick to batteries (how long before lead is banned here too; NiCds are already hard to get, now NiMH are more common) (d*mn, did it again)

Peter,

The Netherlands.

[PaulJ]

   I read the pdf, they look like a good find, meant to last 12 years! Page 8 is where your charging info is, looks like your equalisation voltage is 14.25V for a max 12hrs if it's over 15*C (higher at lower temps).

   My A500's are rated for 5 years, but they're also designed to be run to pretty much full discharge, so hopefully they'll last a bit longer the way I use them.

   Yes, they come from a wheelchair repair place, they mostly maintain the scooters people use when they're having trouble getting around rather than the para- or quadriplegic type wheelchairs.

   They change the batteries when the customers complain about reduced range, so no doubt the ones I get are down a bit on their original rating. I only take the ones which show more than 12.5V when loaded with a 60W headlight globe for a couple of minutes; like you said, once you've done this a few times it's pretty easy to get a feel for the good ones. Reduced range for some of their customers can be a drop of as little as 5%, this is apparently often due to inadequate charging on the customer's part and with a decent charge the batteries can be almost as good as new.

   I'm pretty happy with these batteries. They are FREE, they have a very low self-discharge, and I've never had one fail with a shorted cell which is very important in my situation with so many in parallel.

   Paul.

   Off-grid 9 months and still married.

[nothing to lose]

Shorting the plates or spilling acid all over yourself too perhaps.

Anyone know the easiest least destructive way to open the case on a Trojan L16P?

 I want to look inside, but I may also want to put it back together again too.

 I know the dangers, but we clean and play with lead posts and cable ends all the time, should not be that much more dangerous (with good ventilation of course, outdoors) to remove an entire dead cell and replace with a good one. Haveing some batteries with 2 good cells and only one bad cell I may be willing to give it shot. I have 2 L16p's with 1 dead cell each. Curious if I can swap out a whole set of plates in just the dead cell and get a good battery.

 No grinding, melting or other really bad stuff, no trying to rebuild a plate, just easy swapout and simple soldering is what I want to try.

[dinges]

Thanks for the info. Will check out some dealers here in the area, perhaps I can help them out :-)

I agree that shorted cells would be very bad indeed in your case.

9 months off-grid eh? You're not 'expecting' something, are you?

Over here, it's common wisdom that 9 months after a power blackout, there's a (small, but measurable) rise in child births :-)

Peter,

The Netherlands.

[PaulJ]

   Ha! No, not expecting! Anyway, the power hasn't gone off since we've been off grid, it's nice and reliable now.

   Paul.

[dinges]

Thanks for the links, Wooferhound, esp. the one at uuhome.de is very interesting!

BTW, the gell-cells aren't suppose to be re-filled with water, but it is usually very easy; pry off a cover and refill. Don't know if this ever should be necessary, though. But when excessive gassing occurs, it might help to prolong life (though preventing excess gass would be better, of course).

Peter,

The Netherlands.

[Ungrounded Lightning Rod]

Shaking it won't do a bit for the cells that have slightly high leakage and as a result aren't fully charged when the rest are.  You HAVE to equalize to correct that (unless youre float volatge is too high).

Since the difference in charge level between the lowest and highest charge cells come straight off the top of your battery capacity (since you start killing it when the lowest one goes too low and your inverter's low voltage cutoff will shut it down when that happens to protect the battery), equalizing effectively increases your battery's capacity to the best for its current age and condition.

[Gordy]

NTL,

A neighbor of my dad's ( down in AZ) rebuilds batteries. He showed me how, he cuts them open and welds them shut with a trigger type (Weller) soldering gun. With a flat - thin blade type tip for both cutting and welding. He liked to use plastic coffee can lids (cut into strips) for welding the cases closed.

Gordy

[dinges]

I see; is it because the crud that they advice to use batteries upwards, even for those that can be installed in all positions? That would make sense, since I see this in some datasheets.

My trouble is, if I know WHY they advice something, it is much easier for me to remember later on... I don't want to know what I can and can't do, but why.

Peter,

The Netherlands.

[nothing to lose]

Thanks,

 I was kinda hoping to break the factory seam and reseal it that way. Cutting and welding back together will work I geuss.

[bob g]

as batteries age, and especially if they are in strings they begin to not charge to full capacity on all cells.

the cells that lag behind having not fully charged, have not returned all the sulfation back to the electrolyte, if left in this condition for extended periods this sulfation hardens and becomes increasingly difficult to return to the electrolyte. The end result is loss of capacity in that cell.

equalizing charge regimes are used to basically apply a controlled overcharge to effectively break down the sulfation on those weaker cells, and bring them back to as full a capacity as possible.

mixing of the electrolyte is a byproduct of the process, but not the primary goal.

each manufacture has equalizing regimes/guidelines for their batteries. i would follow them to the letter if i was hoping to get the most out of the batteries.

flooded cells are fairly easy to determine if you have them brought back to as good as you can get by taking spec gravity tests on each cell, noting when the peak has been reached on a lagging cell.

gell cells would be a different matter as i am not sure how you could test spec gravity of the cell, probably all the more reason to follow the manufactures procedures to the letter.

bob g

[dinges]

I see;

So if no periodic equalisation charge batteries will sulfate; I've built a desulfator a while ago (in 'Elektuur', or internationally 'Elector') some years ago. Haven't really used it yet (only for a few days on one battery), but the stories I hear indicate that desulfating is a process that can take weeks/months, not the 3 days I did it. Besides, the article in Elektuur stated that the designers themselves weren't sure whether desulfating actually worked...

Peter,

The Netherlands.

[bob g]

desulfators as you describe are typically used to break down sulfation that has been allowed to harden, this can take a very long time. i am not convinced that these desulfators work any better than an equalizing charge, but that is another discussion.

the equalizing charge is designed to break down the sulfation before it hardens, and return it to the electrolyte.

whichever method you use, it is a good thing to do, because if the sulfation is allowed to harden, loss of capacity will result. sulfation that is allowed to harden on the plates effectively insulate that area of the plate.

bob g