Sulphated VRLA

[zap]

I picked up a Schwinn electric scooter off of craigslist.

It had 2 batteries@12v, 10ah VRLA for 24v.  Zhongshan Hengli Elec. Enduring Battery CB 10-12. Stamped into the case of both batteries is "OBMHT2" on one end and "0309 06" on top.

The batteries were toast.

The craigslist ad ended up being a pawn shop so the available history of the scooter was slight but if the code "0309 06" is a date code, 2006 would seem about right.

When they had taken the scooter in it ran.  I haven't been able to find out when they received the scooter but they told me someone had come in to look at it and it's green light on the throttle came on but that's it. They put it on the charger overnight and when they tried it again the 12inch wheel did about an 1/8th of a turn and that was it.

We hooked the charger up to see if it ran at all, it did so I snagged it.

When I got it home I took the battery bag out of the scooter's deck and then removed the batteries from the bag and stuck a meter on them.  Hooked in series for 24v, the batteries measured 320milivolt... not good.

I plugged the batteries into the supplied charger and left them overnight, about 20 hours of charge time, and measured them again.  The meter read somewhere around 1.5 volts then immediately dropped back to 320milivolt.

I separated the batteries and tried hooking up a Black&Decker/Vector smart charger in the desulphate mode, the charger shut down immediately so I hooked up a good 12v 9ah SLA in parallel to keep the charger happy and running.  24 hours of that did nothing... the now familiar 320milivolt.

I tried zapping them a few times with a 50v 10000µF capacitor charged up by the pedal gen but that also did nothing, as did hooking the pedal gen straight to the battery.

The scooter needed some work.  It looked to have had the front end built backwards, possibly from the factory, and a flat rear tire so I got busy working on the scooter, figuring the batteries were a loss.

As I was tinkering with the scooter my mind pondered battery sulphation.  I started thinking about it in a more physical sense versus a chemical sense.

A thought popped into my head that the sulphation was a blockage that wasn't letting the battery do it's thing, kind of like a spit wad stuck in a straw, and I thought "Why not hook the battery up backwards and try pushing the blockage backwards, such as you might try to do with a spit wad if it had gotten stuck in a straw.

With the batteries behaving as they were, I figured I had nothing to lose and all I had to do was bypass the pedal gen's blocking diode and pedal backwards.

With the pedal gen it's easy to gauge how much power you're putting into something by how hard it is to pedal/turn the cranks.

I could tell the pedal gen was pushing current when I reversed the polarity to the batteries.  I pedaled  the  voltage to about -12v with the batteries still in series then tried hooking them up and pedaling with the correct polarity and still nothing.  The batteries just wouldn't take a charge.

Since they had seemed to be doing "something" with the reverse polarity, I pedaled them again but this time to about -18v but pedaling again with correct polarity still produced nothing.

I decided to hook them back up to their charger, leaving the meter hooked to them, and get back to work on the scooter.

As I worked something caught my eye... the meter, which had been frozen at 27.8v, float voltage of the charger, was starting to drop.  It worked it's way down to around 26v then started heading back up.

I took them off charge and the pack showed 6v.  I had a 12v automotive test light near and hooked it up and the bulb glowed for a bit then died out. Hmmmmmmm

After a few more tries back pedaling and seeing things getting a little better every time, I drained the batteries as near to 0v as I could then hooked them up to the scooter's charger with reverse polarity and took them all the way to the chargers float voltage of around (-)27.8v.  I did this a few times, the longest time leaving them on the reversed polarity was about 5 minutes.  Every time the batteries were hooked back up with the correct polarity they showed a better standing voltage and gave a longer run time on a 24v handicap scooter motor.

The batteries now get pretty warm during the charge routine and last night they never would get to the point where the scooter's charger would shut off.  They kept pulling amps from the charger for over 4 hours and although not hot, they did get warm.  I took them off charge and let them sit for about 8 hours and the pack measured 24.6v this morning.

The handicap scooter motor ran for about 15 minutes pulling around 2.5amp and brought the pack down to around 20v and once disconnected, the pack came back up to 23.6v.

I don't know if these batteries will ever be any good but coming from, more or less, zero voltage to a half way respectable voltage of 24.6 impressed me.

I'm also working on a tired and abused pair of 6v Powerwheel batteries that were left drained and uncharged in a garage for about 5 years and they are starting to show similar signs of coming back to life.

When I first started seeing results from reversing the polarity I was more than surprised.  I've read quite a bit on desulphating over the years and not once... have I seen anything about reverse charging.  I decided to see if I could find anything online and found 2 interesting sites.

http://www.candlepowerforums.com/vb/showthread.php?t=28498

and another post here

http://www.electro-tech-online.com/340094-post12.html


-- W A R N I N G --

Batteries are inherently dangerous and even more so when reversing the battery's polarity.

Do NOT attempt this if you are unfamiliar or uncomfortable with batteries and high current or voltage.

Don't experiment indoors or near the batteries and wear protective clothing.

-------------------

[Bruce S]

Zap;

 Thanks for the reverse voltage trick. I have a "few" of the 6V large so-called kiddie batteries, people keep giving me. They have 20A fuses in them and will not take a charge for anything. I will give this trick a try before using them as core-charge material.

Cheers

Bruce S

[zap]

Hey Bruce, I hope you post back with some results... as for mine...

I haven't had time to baby sit the 12v ones.  They may still be toast although I've left them for around 30 hours off charge and they're still showing 12.1v each so that can't be all bad.

I hooked them back up to charge for now.  The one thing I notice is they come up to around 14.8v on the Black&Decker but never get any higher.  From that point on it seems like all the amps going in just start heating up the batteries.

The other day I took them off charge, put them in series and hooked them up to the handicap scooter motor.  I left it running about 30 to 40 minutes(was over at a neighbor's house) and when I came back they were still showing something like 24.2, the motor was warm, and spinning away happily.  I was kind of happy too!

I'm thinking of doing a very deep cycle and see what that does to them.

The PowerWheels batteries are slowly getting better although I think I need to take them back down into the negative range at least one more time.

[Madscientist267]

Keep the loads low till you get it sorted out... It seems like every time I get a little cocky with a resurrect, it kicks me in the head with a shorted cell because of heat from too high of a charge or discharge rate.

Also, I've been playing heavily with this pulse charging thing lately... Might want to give that a try. I made a simple charger with a 32V 750mA power supply for an old HP printer, a couple 4700uF caps in parallel, and an IRFZ44N MOSFET driven by a parallel port from a laptop. It has taken 2 of my lab rats to almost full capacity, one of which was virtually hopeless in the beginning!

I'm still playing with the software; going to try and work in several feedbacks for checks and balances, but in the mean time, requires some babysitting. I'm excited about the results so far tho... looks very promising, although for larger batteries I'm going to need much bigger caps... heheh

Let me know if you're interested... I could use a partner in crime.

Steve

[zap]

Steve, my problem is... I usually fry 'em after I get tired of the bricks showing no progress and then crank the heck out of the pedal gen.  I can spin it to around 60v.... doh!

So far these are showing much more promise than the dozen or so I messed around with in the past.

I ducked when I started reading you're second paragraph but I didn't need to.  I looked up at the ceiling and it wasn't there either... it was way over my head.

I wonder if using Windows to desulphate a battery ever crossed Bill Gates' mind when he first started programing it.

What size batteries are you working on?

[zap]

Charged the 10ah batteries for about 4 hours yesterday at 12v@10amp and they would get to 14.4v, but no further using the B&D.

After about 8 hours off charge, both are sitting at 12.24v this morning.

Hi ho, hi ho...

[Bruce S]

Looking good.

I'll be giving the 6volt ones a try this weekend. Will let you know if anything comes of them.

Cheers

Bruce S

[Madscientist267]

LOL actually using DOS and QuickBASIC, it's quick, dirty, and effective; Windows (or any other multitask environment) would cause timing issues due to CPU 'distractions' because of the way the code is written...

I've used the pulser on a 2.3AH and a 4.5AH with excellent results. I've tried it on my 48AH bank but the charger can't really keep up with it. And actually, the 48AH set doesn't really need desulfating, but I ran it to see if it could elevate voltages high enough on a battery that size just for giggles. I couldn't get those above about 14.25 without the MOSFET getting uncomfortably hot.

From what I am gathering from circumstantial, the pulses peak out at about 5A. I still need to investigate with the scope, but in the mean time, it very visibly flexes a 3A fuse each time it pulses, but doesn't blow it because the duration is so short. Also, there's soft but definitely audible clicking emitting from the smaller batteries when it's running, but 5A isn't really enough to do much to the larger ones.

Pulse currents of about 1C work well for the small batteries, so I figure I need to go up for higher capacities. I run them no longer than about 1 or 2 mS each; the MOSFET starts getting too hot above a 0.25% duty cycle (its the surface mount version and I haven't bothered with a heatsink yet, difficult to do).

From what I am reading with some of your other posts in here, 'desulfation frustration' sets in easily. I feel your pain. The biggest thing is the temperature. Watch the degrees, all around the battery. If it ever becomes warm, you're pushing (or pulling) too hard. Patience is the key to getting it done. Its an awesome feeling when you finally figure out that you've beaten one, equally crappy when you end up with a shorted cell because you rushed it...

The 3 things that seem to make the most difference in the desulfation process are:

1. Time. It takes plenty of it to get rid of a problem that took time to make. Desulfation is a slow process, probably very similar in nature to the rate that it sulfated at to start with. If you have greater than 12V after 24 hours sitting, you have hope. Don't blow it by trying to cram it full of juice too fast. Somebody said it's like a beer. Fill the glass nice and slow and a certain way, you get an enjoyable drink. Turn the bottle over and let it all fall out, you'll end up with nothing but head, and not the kind you like either... LOL
   
2. Deep cycle - It's counter-intuitive for most battery maintenance, but for desulfation, you have to 'connect' the layer that is disconnected by sulfation back to the active plate material. The visualization in my mind reminds me of killing the memory effect in a NiCd. You have to go past the point (in terms of SOC) where the sulfation took place so that you have homogeneous lead sulfate all the way to the grid. With this in mind, see rule #1. A very slow discharge (over the course of about a week seems to do it) is the key. At first, when the sulfation is still rather significant, don't be afraid to go down to just a few volts on a 12V battery. Just do it slowly! Avoid below 12V after the first couple of cycles. You'll do more harm than good.
   
3. Slow, steady charging. This might be the most important of all. Pulse or Constant Current, doesn't matter. The average energy inflow rate needs to be kept very low so that all of the material can absorb the charge, and you don't end up with surface charge. With pulsing, you can get away with 1C pulses if your duty cycle is 0.01% (equivalent to C/100) or lower. If you don't do this, you'll not only defeat the purpose of #2, but may actually leave behind more damage than you started with, since #2 in it's very nature is a destructive act to perform on a battery. Keep in mind, you not only have to undo previous damage, you're also undoing any damage you did during the deep discharge cycle. My most successful runs have been where the charge rate was about the same as the discharge, with a few extra days at the end to make up for inefficiencies.
   
   

Repeat 2 and 3 a few times until you get something resembling the rated capacity of the battery. Also, don't be afraid to let it sit (fully charged, of course) for a couple of days to let things equal out a bit.

Hope this helps some.

Steve

[zap]

I'm going to try a combination of Steve's #1,#2, and #3.  I hooked them up to the main solar bank to try and get some PWM into them but all they did was try and bring the rest of the bank down with them.

I now have them "on a slow boat to China" using a taillight bulb.  I really don't like the waiting though.

[Madscientist267]

Yeah, unfortunately, thats what seems to work. I wish myself that it could be sped up but it just doesn't seem to happen.

If you think it sucks checking on a light bulb, imagine trying to tweak software! LOL It's WORSE than watching grass grow! Hahahaha

Oh well, good luck man. I finally built a more suitable 'box' to run the desulfating software, and as I get it closer to tweaked, I'll see about putting up a schematic and some code for others to try for anyone who's interested. In the mean time, the waiting game persues... I just put one of mine on for the final run after a long slow drain.

Steve

[Bruce S]

Zap;

No luck on the 6V batts . first I blew the inplace fuse, no biggie thats what they make wire coat hangers for .

Did the little Zap trick, still no luck.

However they will take on new life for a few golf cart batts soon the be acquired:).

Cheers

Bruce S

[zap]

Sorry to hear they're bricks Bruce.  Mine took about 4 or 5 tries at reverse charging before they would take any charge but they finally started.

They've been sitting for 48 hours and showed 12.64v (hooked in parallel)and with a small automotive trouble light as a load, dropped to 12.33v and stayed there!  Weeee!

If you need some fuses I have a few extra! =)







The 10ah have fared just about as well.

They've been resting now for 24 hours and showed 12.57v, not great, not bad considering.  They were charged and discharged hooked in parallel.

I took them down to 0v with a automotive tail light bulb, took around 18 to 20 hours.  I then did a slow recharge of around 1.5amp till they reached about 14v, about 8 hours, then did a bigger charge of around 4 amp which didn't take long and then let them rest.

I just did a half arsed load test with a headlight bulb, 7amp IIRC, and they dropped quickly from the 12.75v to around 11.9v... but held there for the 3 or so minutes I had them hooked up.

They're still not healthy but a far cry from how sick they were.

One more deep discharge may be in their future... we'll see.  But they're still too sick to use for anything but experimenting.

I tried the reversing trick on 2 sets of "Gates Energy Products" "Cyclon" "804471"???(hard to read) "Sealed Rechargeable Battery" 6v 2.5ah

Stamped on the bottom of each 3 cell pack is "8412W".  I think these were in a burglar alarm box and I wouldn't doubt if these were made in '84... the alarm was ancient.  They've both been sitting on the back porch for about 4 years or so.

Both showed 0v and wouldn't take any type of charge even sitting on a Schumacher 612-A-PE on the 6v setting for 24 hours and both still showed 0v.

I tried reverse charging each separately.  One set started accepting a charge after about 6 reverse/forward charging cycles of about 30 seconds each.  After a small load test and then a recharge, it's showing 5.5v and will run the little automotive test light at half brightness for about 20 minutes.  Amazing considering it's age.

The other set never would take a forward or reverse charge even after a few dozen tries.

[Madscientist267]

Wanted to check up on this and see how it was going...

I just got done with the 2.3AH after almost 4 weeks on the pulse charger. Talk about boring..

The good (more like excellent) news is that it is holding 13.47V after sitting for 24H! I'm going to be doing a load test after it sits for a few more days; I kinda want to see where it ultimately settles out at. Looks very promising as it sits right now, the scope showed very good absorption of the pulses at the end of the charge (spikes hitting about 15V, with rest voltage floating around 13.9V). This is excellent considering that I believe the current spikes to be much higher than I initially estimated. Won't know for sure until I rig up a shunt to use with the scope. Unfortunately, I cant seem to get a pic of the screen... I tried and tried to capture a pulse, but the camera didn't want to cooperate with me...

Then, a few days ago, we were cleaning up around the shop, and I hit the motherload of freebies that were just begging to be experimented on. It's an old 26AH PowerSonic SLA, 'brand-new-in-the-box'; too bad the box was dated 1993. LMAO. To my surprise, It was showing 12.35V! When I got it home, I started it on a super light trickle regime, all of about 10mA, and it slowly came up to about 12.4 within 15 minutes or so. Definitely sulfated.

Looks like I have my new victim, and I'll keep you posted on what happens, but if this thing reacts like the 2.3 has, I will have a sweet new addition to my collection to tell my story about.

I'm going to modify the desulfating code some more for the computer and get the shunt for the scope made so I can gather better data about what is actually happening for this one.

Until next time...

Steve