Battery Score!!!

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Sharkey
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Battery Score!!!

Post by Sharkey »

Today's big news is that I had to go to the city for some business, and took along some Trojan T-105 deep cycle batteries to have the "combination" screw terminals cut off and "automotive" round posts cast in their place.

When I dropped off the batteries at the warehouse, I noticed a stack of Alcad brand Nickel-Cadmium batteries by the roll up door. I asked the guy who was working there what the story was with them and he told me that their employees are idiots. Apparently, when new batteries are delivered, they are supposed to pick up any old cells that they see, and these had been collected some time in the past. I asked him what they were going to do with them, and he indicated that they were "just old, dead batteries", and that they were a problem for them, because of the toxic pollution potential of the cells. The business didn't have any way to get rid of the batteries, so they had just left them to sit by the door.

I asked if they wanted me to take them away. Of course they did!

So, when I went back to pick up my Trojans, I loaded 25 Alcad UHP65 Nicads cells, 24 military issue 25 ampere hour cells, and five Alcad VB4 cells. Here's the stack after I unloaded them from my truck and stored them in the wood shed:

Image

I don't really need any more projects, but over the next few weeks, I'll carefully clean the tops of the batteries individually, top up the electrolyte with distilled water, and give them each a controlled charge. I'll then build a battery of ten cells, and discharge it fully, then recharge. This will condition the cells and determine the overall health of the batteries.

My hunch is that they are fine, at the worst, they might have some loss of capacity due to needing the electrolyte changed.

Last time I got a load of free UHP65 cells, I let them lay around dead for six or eight years, then finally got around to adding water and charging them just before I moved. Those batteries are now installed in a bank of two paralleled sets of ten series cells, and are running the lights and electronics on the Housetruck, recharged by some PV cells on the garage roof. If the new cells are in similar condition, I'll add them to the existing bank, and at least double my storage capacity.

Image

Here's the first set of 20 sitting exposed under the Housetruck. They need to be re-cleaned after sitting out for a year, but they are electrically healthy Guess I'll have to buid some kind of a battery room before this winter.

Not sure what I'll do with the military cells. They look to be in the roughest shape. The VB4 cells only add up to 6 volts, but they look to be fully charged. Wish there were more of them.

Anyhow, when someone offers me $7,500+ worth of indestructible rechargeable cells, I usually take them up on the offer...
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Dennis The Bus Dweller
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Post by Dennis The Bus Dweller »

Cheap is good but free is great
Peace along the way
Dennis the bus dweller N.Y.
AccordGuy
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Post by AccordGuy »

Gosh, I wish I could find stuff like that...

There used to be a "magic skip" at the back of the engineering department of my university. It was magic because no matter how much stuff they put in it - it never got full. Engineering students would routinely scavenge stuff from it (old electric motors, bits of VAX minicomputers, 8" disk drives, dead osciloscopes, etc.)

I dug out the two other car batteries I had in the garage to see what kind of shape they were in and I'm sure they used to be rectangular... they are now round-ish... bulging out at the ends. Not good. One read 2v and the other looked more promising at 10v but lifting the caps, all the water had gone somewhere (don't ask me where!). The cells were half empty and the tops of the plates had disintegrated into a pile of rubble... Oh well, they can join the two dead SLA packs from my UPS that need to be taken to the recycler.

I reckon NiCads pretty much live forever, provided they don't leak. I found an old Epson PX8 CP/M notebook at a car boot fair last year and the NiCad pack in that was still good after 20 years.

Li-ion packs just rot by themselves in a couple of years. Worst thing is they hate being full charge floated as it accelerates their natural chemical breakdown. Of course that's exactly what you do to them when you install them in a laptop that spends most of it's time on the mains... The Sony ones are the worst - I swear they've got use-by dates programmed into the management chips in them. After almost exactly 4 years they just stop working one day and that's it - dead. Not just a little bit dead but actually switched off. In contrast my HP laptop Li-ion battery just gets worse and worse (it now holds about 10 mins of charge) but it still works.
Sharkey
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Post by Sharkey »

Well, my "free" batteries weren't completely without cost. I had taken three lead-acid batteries in to have the posts modified. The shop told me in advance that they would be careful, but if the used batteries failed while being altered, that they wouldn't be responsible.

Today, I put one of the three batteries back into my electric tractor and connected it up. When I ran the tractor, the voltage seemed low, so I checked the battery that I had just replaced. One cell was smoking when I removed the filler cap. Apparently, that cell was shorted by something during the process, and the almost-new 6 volt battery is ruined!

I put the other two back into the electric car, and they seem alright, so I guess my lucky day just wasn't perfect after all.

I'm reviewing my options for the tractor, and they will probably involve the EV's batteries as well, so I'll post up something in the EV forum tomorrow, once I've made up a plan.

If you asked me if I would have traded one of my Electrak batteries for the large pile of NiCd's that I picked up, I think I probably would have, but damn, I just don't need any additional probelms in my life right now...
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Post by AccordGuy »

That's really bad luck...

Why did you want to change the posts anyway? Were the combination ones too small to take the current?

Oh and yesterday while surfing about EVs I found out about new Lithium Titanium batteries. You can't buy them on the open market yet (although there's a new EV sports car that uses them) and they are hugely expensive.

They can accept huge charge currents. The car maker is talking about them accepting a full charge in 10 mins from a chunky 3 phase supply at a garage (or 80% charge in 3 mins!). They cure most of the problems of current Li-ion batteries used in laptops (like they catch fire at the drop of a hat and destroy themselves if discharged to below 2v per cell and generally rot pretty quickly all by themselves). The Li-Ti ones also have a cycle life of an estimated 25,000 deep cycles. Normal Li-ion cells use graphite as an electrode and the battery works by pushing lithium ions into the graphite when charging and pulling them out when discharging. Problem is that the ions are pretty big (physically) and they stretch the weak inter-layer bonds in the graphite until after about 1000 cycles the bonds break down and the graphite rods are shattered at the atomic level. This makes them go progressively high resistance and the cell dies.

The Li-Ti type use an electrode constructed with nano technology that has lithium ion shaped holes in it's strong crystalline structure. So the ions can move in and out of the crystals as much as they like without stressing the crystal, so no breakage and very high cycle life. They also don't depend on the usual formation process to make the barrier coating that stops the electrolyte from reacting with the graphite. That's a common set of failure modes for Li-ion cells - over charging / fast charging / fast discharging heats the cell to 120C and the barrier layer melts, exposing the graphite to the electrolyte which reacts with it and gets hotter and so more of the layer melts and... BOOM! They also do the same if you drop them... the plates / rods buckle or snap (coz graphite is so weak) and the barrier is cracked, the graphite is exposed and... BOOM! Because the LiTi ones don't use graphite at all they are much less prone to thermal runaway and much more resistant to high temps and vibration / abuse.

You can check out a white paper here:

http://www.b2i.cc/Document/546/NanoSafe ... 060920.pdf
Sharkey
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Post by Sharkey »

Today, the Academy of Battery Rejuvenation graduated it's first cell:

Image

The cell on the left is sitting at 1.617 volts after being charged at 2.6 amperes for 48 hours. The cell on the left is 24 hours into it's initial charge.

I'm using regular automotive-type battery chargers (the old kind, that don't require any voltage in the battery to turn on the output) set for 6 volt battery charging. To lower the voltage enough to keep the current in the proper range, I am running the AC power input to the chargers through individual Variac autotransformers, which allow me to dial in the current exactly.

The first cell displayed a perfect NiCd charging profile. It started out with the terminal voltage going very high (1.7 volts or so), then it quickly dropped to 1.38 volts, and very slowly gained voltage through the first 30 hours of charging. At about 33 hours, the voltage of the cell began to rapidly rise, indicating that the cell had reached about 90% charged state. All of this tells me that this particular cell is probably quite healthy.

Right after this photo was taken, I took the left hand cell off the charger and stored it away, moved the right hand cell to the left hand position, and cleaned the top of another dead cell to begin it's charging process. At this rate, I will have one cell coming off the charger each morning.

I also disassembled the battery of military-type cells, and began charging one of them at 1 ampere. Research on the 'net shows that these are indeed Mil-Spec cells. There are three manufacturers represented in this battery, SAFT, Gulton, and Marathon. All three cell manufacturers produced a basically identical product, so much so that one has to look carefully to tell them apart. My guess is that these cells were produced for aircraft use. Four of the cells are destroyed, with cracked open cases. Many more are totally dry inside, and still more have very low fluid levels. It will be quite a challenge to get all twenty of the remaining cells operable. I might have to settle for making up a single 12 volt battery of ten cells, and recycle the rest, we'll see.

I had the posts on the lead acid batteries changed because the round automotive posts are purported to have lower resistance to current flow, which is important in the EV, as it can draw 275 amperes over sustained periods. That and the fact that all of my interconnecting cables have round lead connectors, and I didn't want to have to change them to use the extra batteries. It was a good plan, but now I have some dancing around to do to get my tractor back in good nick.
AccordGuy
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Post by AccordGuy »

Nice production line... :)

Just watch them though... I almost burned my previous apartment down charging a duff NiCd pack for a drill a few years ago.

It was a 12v pack and was not accepting charge very well so I decided not to use the drill's slow charger but a lab supply. It's voltage variable but sadly doesn't have current limiting and has no fuses in the output. It's also very powerful and can put out 25A continuously.

I ran it up to like 15v and not much was happening, very slow uptake. I then did something stupid. I forgot it and fell asleep only to wake with the apartment full of smoke!

While I was dozing, the battery revived a bit and suddenly started accepting charge - lots of it. Only the fact that I was using puny 6A flex and that melted and went open circuit before the cells exploded or the carpet caught fire saved me :shock:

Amazingly the cells didn't even pop their seals. The ABS pack housing had all melted though.

It looks like a 10A charger from the photo but hopefully with the variac and any fuse / thermo-breaker in the charger you'll be saved from anything dramatic happening if the cell plates expand/buckle and short out.
Sharkey
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Post by Sharkey »

A lot of which is the reason that I am charging the cells individually instead of in a bank as a battery. It will take ten times a long, but be at least ten times safer. I can also better control the voltage on a single cell, and make sure that it remains within the manufacturers recommended guidelines. Charging a battery of multiple cells results in much greater swings in voltage and current as the cells begin to accept a charge.

Yesterday, I checked the AC voltage going into the chargers, and it's around 17 volts, so the chargers are loafing on this job, no heat to speak of. When I charged the original set of 20 UHP65's I used this technique, and didn't see any unusual behaviour. Yet another caution is that I put the new cells on to charge in the early morning, and watch them for the next 12 - 15 hours, adjusting the current as needed. By bedtime, I have a pretty good idea whether the charging is stabilised and if it's safe to leave it to go overnight unsupervised.

There's now three chargers and variacs, with the Mil-Spec batteries now on line and getting the treatment. Got to do something useful with all the excess solar electricity. Yesterday, my dump load (the electric water heater) came up to 150 degrees F, and the thermostat switched it off. That meant that any excess production was entering the utility grid and I was being charged for the privledge of sending power to my neighbor's homes. After finding this problem, I cobbled up a three-way thermostat so that when the tank is up to temp, the excess power is burned off in an electric space heater, but that's a waste in the middle of summer.
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Post by Sharkey »

Well, so after crowing about how safe my charging regime is, I just had my first mishap.

When I went into the garage about 30 milutes ago to check the progress, I found that the Mil-Spac cell (this one is a Gulton brand) was disgorging small amounts of electrolyte out it's vent cap. I had been watching the liquid level in the cell with some concern, as it seemed like the cell was getting overly full, as if it had been manufacturing it's own electrolyte. Had I known this was going to happen, I wouldn't have added some distilled water before beginning the charging process.

Anyhow, I dumped the small amount of KoH off the top of the cell into the bottom of a cut-off water bottle, hosed the top of the cell off with the garden hose, then gave it a swabbing with a rag soaked in vinegar to neutrilise any remaing base. I then use an eye dropper to remove some of the excess electrolyte, and put the call back on charge.

This might be normal. I read a series of posts on the Electric Vehicle Discussion List a few weeks back about someone who had acquired some Nickel-Iron batteries that were completely dry. The were sealed batteries, and the user was wondering what to do about this before charging. He ended up just putting the dry batteries on the charger, and as if my magic, liquid appeared in the cell, eventually filling it to capacity!

The next one of these cells I charge, I'm going to leave it alone after cleaning it and let it make it's own electrolyte.

I do wonder about one thing, though. NiCd cells are supposed to have a layer of mineral oil floating on top of the electrolyte to prevent contact with the air. Seems that atmospheric carbon dioxide can contaminate the electrolyte, and carbonate it to the point were it no longer works properly in the cell. None of these batteries I'm fooling with seem to have any oil at the top? More mystery...
Sharkey
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Post by Sharkey »

The last UHP65 cell went on the charger yesterday. Every cell I charged reacted the same to the charge regime, taking the same number of hours to come up to a terminal voltage of ~1.600 volts. This tells me that they are all either good, or all exactly the same amount of ruined. Only a load test will tell.

Here's the last cell on the left, with one of it's fellows after cleaning and charging. Yes, external cosemetics don't count for much, it's the chemical reaction inside the battery that matters, but at least there won't be cigarette butts all over the tops when I recycle them...

Image

Now to finish off the Mil Spec cells. They are in bad shape, many of them have cracked tops from rough handling and stress on the terminals, and spew electrolyte when charged, the internal pressure escaping through the cracks. Jury is still out on whether or not I'll get ten useful cells out of the 24 I was given.

Just started charging the Alcad VB4 cells, which I have not been able to find any information on whatsoever. I expected that these cells were in a charged state, and the first one came up to 1.600 volts after about 4 hours of charging. Wish I had 24 more of them instead of the Mil Spec cells...
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