lemmiwinks
100 W
(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!
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!