Interesting battery observations

[lemmiwinks]

(Matt is going to love this!)

I've got a few 65Ah SLA batteries that I picked up for free. They've been sitting in various states of discharge for an unknown amount of time (I think years). Only one had enough juice to produce a spark when the terminals were shorted.

Now it just so happens that one or more of my EVT batteries appear to be giving up the ghost. I dunno if I somehow screwed up cleaning the hub, but now I can ride to work, ride downtown in the afternoon and on the way home the batteries collapse totally on a hill. The red light comes on and speed is down to 40kph (25mph). Take the load off and all is well again, so I'd say it's batteries...

Anyway, Matt is a big fan of adding acid to SLA's (http://community-2.webtv.net/MATTGRU/more/index.html). A while back I added demineralized water (not sure I agree with acid) to my "sealed" motorcycle starter battery with no ill effects (I worked at the motorcycle shop for a while and I know they are shipped dry and acid is added before being sold. I assume it is absorbed into the matting but can dry out). Encouraged, I decided to experiment on the 75Ah batteries before attacking my EVT batteries, after all, they still work at this stage!

So I grabbed a 65Ah at random (it was reading 8.3V) and popped the caps (the "sealed" part of sealed lead acid is a misnomer). Using a torch I could see down into the cells and look at the matting which holds the electrolyte, not surprisingly it was all dry. So I added demineralized water to each cell until I could see a very thin layer of water above the plates/mat.

Right away I could smell sulphur, not strong, but it was there. The voltage didn't change, so I threw it on my "dumb" 6A charger. The voltage went straight up to 14.4V indicating some pretty high internal resistance. This battery is probably very badly sulphated, but demineralized water is cheap

I tried my 1.6A smart charger which right away went green and settled into float charge mode at 13.3V. With no charger connected the voltage was staying around the 12.3V mark, but I knew it was faking it because the chargers had only been connected for a few minutes total.

I hooked up a 500W 36V motor for a load and the voltage dropped to 0.7V. No real surprise there. If I hooked up my 6A charger the motor would run but only because the charger is acting as a power supply. I disconnected the charger but left the motor hooked up to the battery figuring to "cycle" it a couple of times and see if it might come back to life.

Now if you've managed to stay awake this long, this is where the interesting (to me anyway) stuff happened. The motor gradually started running. Very slowly at first as the volts were around 6V, but gradually built up to 8V.

While the motor was connected but not running I could hear a very faint hissing/sizzling noise. I thought it was just the motor because it was only getting a few volts and not able to convert the electrical energy into movement. After it started running I fiddled with the battery some more trying to get it to draw some current from the charger, and connecting and disconnecting the load (motor) and charger.

I noticed that after a while, sometimes when I hooked up the motor it wouldn't run, but after a few seconds it would start and run slowly, but if I left it connected it would suddenly pick up speed and run much faster. Now I was curious. Also there was a strong smell of sulphur coming from the battery now.

I decided a light would make a better load and I scrounged around and got a sealed beam headlight of uncertain origins. It worked so I started using it for my load. I noticed the same thing, hook the light up and sometimes it wouldn't light, but wait a while and it would glow red for a while, then suddenly come up full power.

Because the light was silent, I noticed that I could hear the strange hissing/sizzling noise again. The noise corresponded to the power output of the battery. It went like this, apply load to battery, hissing/sizzling noise coupled with low power output. When the power suddenly shoots up (bright light), the hissing/sizzling stopped.

I narrowed the noise and strong sulphur smell down to the third cell along from the negative terminal. I think it's fair to say this cell is probably shorted out but I'd love to know what's actually going on inside it under load. It sounds as though there's arcing happening down there but I don't know how likely that is. Also I'd love to know why it will suddenly come good.

Anyway, this battery will probably head off to the recycler/scrap metal merchant but it's encouraged me to see if I can revive any of the others. If I can get three or four working that might be enough to power my conversion project temporarily.

Getting back to my EVT batteries, I'll probably add some demineralized water when I get a chance (hopefully this weekend). I'm also considering this additive as well http://www.inox-mx3.com/product_detail.php?productID=2 which is mostly (totally?) Cadmium Sulphate (super secret "doping" chemical??) http://www.inox-mx3.com/product_detail.php?productID=2&pageID=MSDS in an effort to break up the sulphation that has undoubtedly been formed from sitting all day at work in a partially discharged state. It may be snake oil, but a $15 per bottle per battery it's got to be worth a shot compared with around $300 per battery for new ones. Provided of course it doesn't make the batteries any worse!

 

[Matt Gruber]

take the lead scrap to a recycler and swap them for usable ones.
don't take anything home that fails a hygrometer test or amp/volt test.
i did just that yrs ago and was charged $1.50.
got a 6v for a 66 VW, out lasted the car(several years)!

 

[Mathurin]

Yeah I noticed fluttering readings when playing with a dead SLA, that was pretty cool. In charging it would suck a small amount of ma's, shoot up to three fold as much, come back down... It wasn't the connections either, and whacking the battery didn't seem to change anything. Really weird man.

 

[lemmiwinks]

I just wish I knew what the heck cadmium sulphate is supposed to do. Ok, let me rephrase that, I know what it's supposed to do, I'd like to know what, if anything it does (other than lighten peoples wallets). Google doesn't draw any links between it and lead acid batteries.

 

[xyster]

If you didn't try it already, you might try spelling it the more common "cadmium sulfate"
Looks like there's some stuff about it here...
http://www.google.com/search?hl=en&q=cadmium-sulfate+sla+OR+lead-acid&btnG=Search

 

[lemmiwinks]

If you didn't try it already, you might try spelling it the more common "cadmium sulfate"
Looks like there's some stuff about it here...
http://www.google.com/search?hl=en&q=cadmium-sulfate+sla+OR+lead-acid&btnG=Search

Ahhh, the good old English language eh? :lol: See what happens when you spell things correctly, you get no results!! :wink:

P.S Thanks!

 

[xyster]

Ahhh, the good old English language eh? :lol: See what happens when you spell things correctly, you get no results!! :wink:

Just like how driving on the right side of the road down under gets you nowhere :wink:

 

[lemmiwinks]

HA! I suspected Deafscooter was simply adding cadmium sulphate to his batteries as his mysterious doping agent but because of my damned correct spelling :wink: I couldn't prove it. Not that this is technically proof, but it's a step in the right direction:

http://www.fieldlines.com/comments/2005/5/31/181953/697/16#16

 

[lemmiwinks]

Just like how driving on the right side of the road down under gets you nowhere :wink:

It'll get you into a head on collision! 8)

 

[Mathurin]

I got some Rust Check Rust Converter stuff
28-35% Phosphoric Acid
7-9% Tannic acid
22-28% Isopropyl Alcohol

I also got an old dead 12-12 SLA leftover.
(Not the same one I added tap water & sulfate crystals rained out of)

Been thinking about combining these two items to see what happens,
I'd rather wait 'till summer so I can do so outside though...

 

[lemmiwinks]

Even better - get someone (preferrably someone you don't like) to to it while you video from a safe distance :wink:

I know that rust converter stuff chemically turns iron oxide back to...err something (steel?) No idea what it would do to the inside of a battery though. Could be an interesting reaction between the residual sulphuric acid and the phosphoric...

 

[fechter]

The sizzling sound might be from a cracked connector bar.

If a battery is severely sulphated, it needs to be charged for a long time to try and convert some of the sulphate back into active material.

I've seen batteries come up in voltage while under load also. I suspect it has something to do with chunks of sulphate falling off the plates and exposing more plate area.

I've heard an "urban myth" that you can give a dead SLA a high current reverse charge for a short period of time to bring back partially shorted cells. I'm not quite sure how you would do it though...

 

[TylerDurden]

I've heard an "urban myth" that you can give a dead SLA a high current reverse charge for a short period of time to bring back partially shorted cells. I'm not quite sure how you would do it though...

Readers are duly notified that some participants like to "blow things up".


8)

 

[Matt Gruber]

take the lead scrap to a recycler and swap them for usable ones.
don't take anything home that fails a hygrometer test or amp/volt test.
i did just that yrs ago and was charged $1.50.
got a 6v for a 66 VW, out lasted the car(several years)!

don't wast $$ on additives.
swap them for working ones

 

[lemmiwinks]

The sizzling sound might be from a cracked connector bar.

Good suggestion. I thought about cutting the battery open (carefully) to have a look but it's more effort and mess than I want to be a part of at the moment.

If a battery is severely sulphated, it needs to be charged for a long time to try and convert some of the sulphate back into active material.

Yeah, I've currently got battery #2 on the bench. It was also showing about 8.5V no load, but dropped to 0V with a load. It's been on the 6A charger for about 15 hours now but not pulling any current. The voltage has been slowly coming down from around 14V yesterday to about 13V this morning. If I understand correctly this is a good thing, because it means the resistance is slowly dropping. If it keeps up it will hopefully take a charge eventually.

I've seen batteries come up in voltage while under load also. I suspect it has something to do with chunks of sulphate falling off the plates and exposing more plate area.

Sounds plausible to me.

I've heard an "urban myth" that you can give a dead SLA a high current reverse charge for a short period of time to bring back partially shorted cells. I'm not quite sure how you would do it though...

I've heard that too and like you I'm not sure how you'd do it (or that I'd want to try it!)

 

[lemmiwinks]

don't wast $$ on additives.
swap them for working ones

I live in a small(ish) country town, we only just got a scrap metal recycler. The chances of swapping a dead battery for a working one is SFA.

Anyhow, I checked my EVT invoice last night and it says the batteries have a 6 month warranty with a further 6 months pro rata, so I think I might be in line for some new ones. I've emailed the importer to see what they say.

 

[Matt Gruber]

have u visited the recycler? or just ASSuming.

 

[Reid Welch]

New question:

Does the electrolyte stratify in the AGM battery?
If the battery is always on end (mine are in the currie's bat box), isn't it liable to be water in the topmost of the mats, and too-strong in the bottom? There's not much percolation possible in these things, is there?

If so, I should charge sealed batteries in various positions,
and uh hang my bike inverted when unused,

I guess! Or is this horsehockey?

 

[lemmiwinks]

New question:

Does the electrolyte stratify in the AGM battery?

Dunno, good question though. I'll do some guessing too :wink: Since it's Absorbed Glass Matt, I'm going to assume that the electrolyte is absorbed and therefore suspended, not free to move around. I will therefore further assume that upending them as Currie have done on our bicycles shouldn't prove to be a problem as there should be no liquid to move around (I am of the understanding that upside down is a no-no though **edit** no it isn't: http://www.answers.com/topic/absorbent-glass-mat).

I had planned to allow the demineralized water which I added to the deceased batteries as an experiement to "dry out" during charging so that (hopefully) the electrolyte would return to it's original consistency within the matting. Since I'm yet to get one of the batteries to take a charge I haven't been able to put my theory to the test yet :wink:

 

[lemmiwinks]

Hmmmm, seems Ethylene diamine tetra acetic acid-tetrasodium salt is the goods for chemical desulphation of lead acid batteries. Now where to get some without being "renditioned" :x

Then again, maybe an electronic solution would be best. From Wikipedia: "Many vendors sell chemical additives (solid compounds as well as liquid solutions) that supposedly reduce sulfate build up and improve battery condition when added to the electrolyte of a vented lead-acid battery. Such treatments are rarely, if ever, effective.

Two compounds used for such purposes are Epsom salts and EDTA. Epsom salts reduce the internal resistance in a weak or damaged battery and may allow a small amount of extended life. EDTA can be used to dissolve the suphate deposits of heavily discharged plates. However, the dissolved material is then no longer available to participate in the normal charge/discharge cycle, so a battery temporarily revived with EDTA should not be expected to have normal life expectancy. Residual EDTA in the lead-acid cell forms organic acids which will accelerate corrosion of the lead plates and internal connectors."

At least I can get hold of epsom salts easilly 8)

Pity I'm too dumb to build this: http://www.shaka.com/~kalepa/highpower.htm :?

 

[TylerDurden]

Pity I'm too dumb to build this: http://www.shaka.com/~kalepa/highpower.htm

They might rendition ya for building that, too.

Thanks for that link. The setup looks pretty good for big EVs and home solar... gonna save that page.

 

[fechter]

There's some already built ones. Here's one place:
http://www.survivalunlimited.com/desulfator.htm

I built a small one on a breadboard and played with it. It seemed to work, but the batteries I was trying to recover all had shorted cells, which stayed shorted.

One techinque I've used is a constant current power supply set to around 50ma and the voltage on max. The terminal voltage on the battery goes sky high at first, but comes down slowly as the sulfate dissolves. On smaller batteries, use less current. I left it charging for about a week, then cycled it a few times and it seemed to recover pretty well.

 

[lemmiwinks]

I'm going to have a go at making the http://www.homepower.com/files/desulfator.pdf one on a breadboard. I bought one of these: http://www.duo-regen.com/ (MAXI-Life Pulse) a while back off ebay which I am convinced was a complete waste of money. Chalk that one up to experience.

Battery #2 was retired on Friday since it wasn't going anywhere. Initially I thought it would be a good candidate for treatment with EDTA but then I read that it (EDTA) removes the active material (sulphate) which needs to go back into solution for the battery to work. I will try an electronic desulphator on it if I can make one.

On to battery #3 then. The OCV was about 8V and all the cells were bone dry (which might be how they're meant to be since I've never opened a good battery I don't know). I threw a load on just for fun and predictably the voltage dropped to 0 then jumped up slowly to around 6V. This one also has a sizzling cell.

To my considerable surprise, after messing around for a while applying and removing a load, not only did the OCV come up to 10V then finally 12V but the voltage under load also came up as high as 11V. This is on a battery that I hadn't even tried to charge yet. Weird!

For battery #3 I decided to try something different, I decided to drown the sizzle. I kept adding distilled water to the sizzling cell (actually there are two) until the sizzle became a gurgle then chucked it on the charger.

I cycled it a few times with the voltage under load jumping around, and eventually it started taking some current from the charger. After more fiddling last night, I got very excited when the battery started pulling 4A from the charger. Unfortunately it didn't last and went from 4A suddenly down to 0.5A.

I will persevere with this one a bit longer as I've added enough demineralized water that I can check it with my hydrometer and I've noticed that the specific gravity is sloooowly creeping up indicating that the sulphate is returning to solution.

 

[Eric G]

Don't know if this helps found it surfing around for battery chargers and came across this home made 3 dollar current based charger,the diode rectifies the voltage giving a pulsed DC to the battery,to help prevent and break up sulfation.I'm not well versed in electronics but thought in may be applicable to this thread.Hears the link....

http://www.alpharubicon.com/elect/3dollarbattggn.htm

 

[lemmiwinks]

That's pretty neat Eric, thanks. Being the electronics moron that I am though I'm way too scared to mess with AC, especially since we're on 240V down here.

I spent yesterday being frustrated at how dumb I am, trying desperately to bash the attached circuit diagram into my thick brain, but no luck. Eventually my girlfriend who has more electronics smarts than I sat me down and showed me what all the bits are (I had no idea what L1 and L2 were but now I do).

To make matters worse, there's a whole web forum devoted to it, and improvments to it, full of people sharing stories of the free batteries they picked up from a scrapyard and have now recovered to 100% Ah capacity. And here's me with 4 50Ah batteries just about cactus (I only just made it home (12.5km) yesterday). Talk about frustrating!!
http://p198.ezboard.com/Lead-Acid-Battery-Desulfation/bleadacidbatterydesulfation

Anyway, now armed with just enough understanding to be dangerous, a breadboard and a handful of components (well I'll have them soon I hope), I'm going to make one ASAP. If that works, I'll make another 3 so I can desulphate all 4 scooter batteries at once.