department of energy breakthroug for lead acid batterys

[truckerzero]

just thought id pass this on they took deep cycle batterys and gave them a voltage 5 to 20% higher than the standerd on a 5 sec on 5 sec off current interup cycle and got 700 cyles istead of the normal 200 cycles out of a optima battery beeing deeply discharged and this paper pdf was on a department of energy website must have some kind of merit

 

[TomG]

http://www.eere.energy.gov/afdc/pdfs/inter_charging.pdf

 

[deardancer3]

Very NIce----But A March 2002 document?

What happened with this data over the last 6 years?

 

[safe]

From the pdf...

There are two reasons why a VRLA battery reaches its end-of-life prematurely when subjected to a conventional constant current/voltage charge: (1) insufficient recharge at the negative plate, and (2) interference with recharge of the negative plate by the “oxygen cycle” or recombination reactions, which cause oxidation of sulfuric acid into sulfate. The new technique involves applying a current to the battery for 5 seconds, overcharging it slightly, then interrupting the current for 5 seconds to cool the battery and prevent its going into the oxygen recombination phase. Tests on a pack of 24 Optima yellow-top batteries verified that the VRLA battery can sustain 700 deep discharge cycles with this method, four times more than when it is charged with a standard constant current/voltage system. The research team hopes to eliminate the battery management system, further lowering the cost of producing and using this battery.

I suspect that doing this improved charging and combining that with cell monitoring to be sure that you aren't draining a cell too far and don't know it (because you have them in series) would extend SLA a great deal. Throw in some ultrcapacitors to soften the Peukert's Effect a little and design around a 1C dischage rate and you have a very economical system.

There seems to be a "panic" to rush to build something to fill the urgent need we have now and in that rush there's a tendency to throw practicality and reason out the window in favor of the most expensive thing out there. Hopefully we can all settle down and put some more hard work towards perfecting what is cheap.

It's easy to go exotic and expensive... the real genius is in taking the mundane and making it pragmatic and useful.

P.S: On my SLA's I've found that an occasional high rate charge shakes up the cell and brings it back to life. Sulphation and Oxidation are opposite problems, so this 5 on, 5 off idea deals with both problems at once. Good posting.

The best scenario would be to have cheap SLA batteries when you first buy a vehicle and then have the option to upgrade to more expensive options as an alternative. That way the poor can have their basic "entry level" vehicle and the rich can have their Tesla's and other such things.

Maybe in a few years Lithium prices will come so far down that they will be the same price as lead.

Why not?

Lithium is plentiful... it's just a matter of getting the manufacuring price down.

Remember how expensive flat panel tv's were a few years ago?

 

[PJD]

I recall that when the e-max electric scooter venture was going south due to prematurely failing "silicone" batteries and failing chargers on every scooter delivered, they kept promising a miracle charger that would fix the problems. They want out of business altogether before any of these chargers materialized.

Later, I finally got one of these chargers from an owner of what was the same generic Chinese e-scooter being sold under a different name. The charger has a very odd protocol. On at 15 amps or more for about 5 seconds, off for 5 seconds, repeating through the CC cycle, with occasional longer pauses, The CV cycle was similar, but decreasing current of course.

It seems this is where they got the idea from.

Unfortunately, true to it's Chinese origins the charger failed after only a dozen uses - probably failure of the programmable microprocessor chip that ran the protocol. So I was unable to see if there was any benefit to either of my scooters both have 300 to 400 cycles and are down to only 50-60% or the new capacity.

At any rate, SLA's still suffer from their very poor energy density. Their sheer weight limits the range any kind of EV using them could have. And 700 cycles still doesn't cut it.

AS far as lithium being cost competitive with lead, they already are. An SLA pack for my scooters is up to $700. A LiFePO4 pack is $1400 to $1600, but will last even pessimistically, 3-4 times longer.

 

[safe]

And 700 cycles still doesn't cut it.

But this provides a new "baseline" to work with. The standard way to measure when a cell is "used up" is when the capacity drops to 80% of original. If you combine this charging method with an ebike design where your peak current needs are waaaaay down compared to the battery size then as the battery ages you still have a "functional" system.

So if you follow my logic... rather than using the 80% figure (the standard) you could design your ebike to only use about 1C of current and since SLA can pull 5C peak (or more) and 2C pretty easily your pack could still be functioning normally at double the cycles. (because at 60% you can still function)

So rather than: 300 -> 600 (what I've done on Project #001)

You could have: 700 -> 1400 (using 5 on, 5 off charging)

...there's always an "easy" argument to just get expensive stuff and use it, but the real trick is to figure out how to do the "hard" stuff. It's harder to find "tricks" to exploit to your advantage all the possibilities.

It's like gears... in the beginning of EV's everyone thought that gears were no longer needed, but you're starting to see them pop up more and more now because it allows a smaller motor to achieve the same result.

Every little advantage helps... you just need to exploit all the advantages all the time...

It's sort of an unrelenting pursuit of perfection.

(like an endless sphere?)

 

[truckerzero]

so us tinkerers can play with this idea ouselves we could use a adjustable voltage/amperage dc power supply but im at a loss for how to turn it on and off at 5 sec intervals does any body have any ideas on how to turn the voltage on and off like that?

 

[safe]

...but im at a loss for how to turn it on and off at 5 sec intervals does any body have any ideas on how to turn the voltage on and off like that?

My charger has a desulfation routine that it runs through at the beginning and I really don't know what cycle rate it uses, but I suspect that it's pretty fast. (like many cycles per second)

You could build a "desulfation machine" and just do that part separately and then connect your regular charger... but I suppose that might not give the best results because you would be reverting to the method that is not as good.

A very good question...

You still need to get the CC/CV stuff figured out right. Maybe some of the ideas that the "Doc" is doing with DC DC chips might be usable. You could built your own circuit basically to do the cycling and then use the DC DC stuff to set the right voltage level.

Getting a five second cycle is a good electrical circuit design question...

 

[truckerzero]

hey safe have you noticed any differance using the desulfanator from what i heard if a battery is still doing ok just has less ah capacity than when it was new it can healp get your ah capacity back up and make your battery last 3 times longer i thought about getting one of the pulsetech products as these can be ordered locally at my batteryies plus store

 

[fechter]

The same kind of protocol may benefit other battery chemistries too. Perhaps a different, but non-standard charging method involving some kind of pulsing.

Somebody want to try this with some lithium batteries?

 

[truckerzero]

fetcher from what i read it works with lead acid nimh and nicad but not with lithium just out of curioity do you notice a better life span with lithium cause were i work we had nextell phones with nimh and nothing but problems keeping them charged after 1 year of age but the newer lithium powered units have not had 1 problem and i bet those batterys are 3 to 4 years old at least of mcorse they are low drain charging them up every other night or so but the nimh after a year of age would go dead half way through my shift

 

[safe]

hey safe have you noticed any differance using the desulfanator from what i heard if a battery is still doing ok just has less ah capacity than when it was new it can healp get your ah capacity back up and make your battery last 3 times longer

Normally I apply my 10 amp charger in parallel to my three 12 volt cells so that each cell is getting 3.3 amps. But if I want to desulphate I run the charger (which has a desulphation startup routine) on each cell one at a time so that's 10 amps per cell. When I do that it definitely wakes up the cell and brings it back to life. I'm not sure if you want to do that all the time though because there's a balance between the oxidation and reduction reactions. (they both do damage)

What is the secret of the 5 on, 5 off routine is that it's giving the high powered charge and then letting the temperature come down again to prevent the negative reaction of oxidation. When you revive your battery after not being used for a while it seems worth it to do the high current ONCE... but I'm not going to do it all the time with conventional charging.

So my answer is that we just don't have any way to be sure that we are able to do this right. You would need to study the desulphation device to see what it does... I suspect that many might simply introduce an AC current (variable DC actually) which is not what they are doing.

What you want is:

Full power forceful overcharge (5 sec)...

Rest (5 sec)...

Full power forceful overcharge (5 sec)...

Rest (5 sec)...

...

 

[safe]

Electric Circuit Behavior

The circuit should work like:

5 second full power on...

Measure voltage, if less than "stop voltage" set timer for 5 sec...

5 second off...

5 second full power on...

Measure voltage, if less than "stop voltage" set timer for 5 sec...

5 second off...

5 second full power on...

...

finally

...

Measure voltage, "stop voltage" attained... extend timer delay to 10 sec...

10 second off...

5 second full power on...

Measure voltage, "stop voltage" attained... extend timer delay to 15 sec...

15 second off...

5 second full power on...

etc...

No need for current limiting (you don't really even want it) you just increase the delay between power stages to such a length that pretty soon there's a minute or two between them. This charger would be fairly simple to build... you just need to have a good timer.

 

[HAL9000v2.0]

I think that's the way that my Cristalyte 36V 3,5A charger work.

 

[safe]

Download This Pdf !!!

http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/evs17pres.pdf

There is a gold mine of information in it.

Just some things to mention... apparently as the cells get older you need to hit them harder with high voltage and current to break up the desulfation. You do NOT want to hit new cells very hard because that just wears them out. So you need to have the ability to adapt to conditions if you want to extend the life of your SLA cells.

Here's one of many charts from the pdf:

 

[safe]

A second valuable pdf... (click back to read #1)

http://www.ipenz.org.nz/ipenz/publications/transactions/Transactions98/emch/2wilkinson.PDF

"A simple ‘unintelligent’ invariant pulse charging approach was shown to dramatically decrease charging time but is also capable of gassing the battery and must be applied with care. In this technique specific pulse widths and/or magnitudes must be chosen carefully to fit each lead-acid battery and may need modification with battery age.

A new pulse charging approach is proposed with variable pulse width controlled by feedback resistance free battery voltage, presenting an average current to the battery that is similar to conventional charging profiles. This approach is shown to dramatically improve the charge rate outside of the constant current region (typically around 50% state of charge). In addition, it appears to eliminate gassing at these high states of charge, and does so without the need of additional sensors. A practical observation is that high currents applied during the initial part of the charging cycle cause consistent but limited temperature and pressure rises that may require monitoring (particularly for sealed VRLA lead-acid cells). If the battery is placed at elevated temperatures then higher currents than specified by the battery manufacturer should be used with care.

The inclusion of a small discharge pulse gives a slight improvement in charging efficiency without reducing the charging time, despite the initial lower average current. Both variable pulsing methods show significant improvements in charging time compared with conventional means, illustrating the potential to rapidly improve the useability of lead-acid batteries in EVs by opportunity charging."

This pdf also has an abundance of charts...

 

[truckerzero]

ok i confirmed this on the tower hobbie web site some of their nimh chargers for rc cars youse the zero delta voltage algorythem since there was benifit to yousing this for the lead acid batterys mayby we could experament with these type of rc car chargers ill look and see what the highest voltage anm amperage is avalible and post it

 

[andrew]

The PDF doesn't really say anything substantial. 700 cycles---thats super great, but what's the DOD? Without that information, then "700 cycles" means nothing. At 50% DOD this is probably about normal for Optima yellow tops.

The pulsing may have lessened the damage done by overcharging when charging a string of 24 optimas. It's no mystery they got poor life when charging this many batteries in series with standard CC/CV charging without any form of balancing device.

My Zivan charger has a kind of pulsing algorithm at end of charge too. It wouldn't shut off (would pulse for hours), and took the batteries too high. It probably killed one of them. The pulsing messed up the battery equalization at end-of-charge, because the powerCheqs I was using have a lag time. Beware of doing a pulsing type algorithm if you are using powerCheqs and maybe even BattEQ devices as well if they have a lag time. Probably a voltage regulator like Rudman regs would work much better when doing this.

The best scenario would be to have cheap SLA batteries when you first buy a vehicle and then have the option to upgrade to more expensive options as an alternative.

They aren't cheap anymore. My motorcycle pack is worth $720 for good quality B&B chinese batteries. Not cheap, unless you are delusional.

But this provides a new "baseline" to work with.

There's no new baseline based on the information in the PDF. There's not even anything substantial that can be concluded with the information given.

rather than using the 80% figure ... your pack could still be functioning normally at double the cycles. (because at 60% you can still function)

You don't get double the cycles from 80% to 60% capacity. More like 25 additional cycles. Check some cycle graphs on B&B spec sheets.

 

[safe]

The PDF doesn't really say anything substantial.

You've got to be kidding!!!

If you actually read both pdf files you would gather a better understanding of why some people fail with SLA when others do very well. I'm in the "doing very well" category and given their low price compared to the exotic chemistries it's still a good starting point.

There is a long list of mistakes/guidelines which people need to be aware of:

You must design the EV to use no more than 1C discharge if you want to avoid the worst of the Peukert's Effect.

Sulfation occurs naturally and the way to break it up is to hit the battery with a powerful pulse. You cannot hold that pulse for too long because you will start to gas the battery and so there is "just right" and "too much".

Batteries change as they age. You need to apply a totally different charge with older batteries than younger ones.

It's important to make sure that no one cell becomes the "runt" cell and is repeatedly overdischarged. This is sort of a balancing issue or a cell monitoring issue depending on how you want to achieve this result.

And on and on...

The main idea is that if you are really "smart" with your SLA usage they can get upwards of 700 cycles. (absolute best case) If you make a lot of mistakes you might be stuck with 300 cycles or less. Also, sometimes individual cells go bad early and you can replace them and the rest still can go on a lot longer. You have to think in terms of average total output and not a static pack, which might have defective cells ("runts") that need to be taken out.

I've been using this product by Vector. It has desulfation built in and uses a microprocessor. Unknowingly my product pick seems to have given me better results than many who might have been using simple CC/CV chargers. Every single time I charge it goes through a little desulfation routine for about a minute or two at the beginning. A really nice product for an ebike and a great price.

It even says "smart" on it... so they are broadcasting their design priorities with their labeling...

 

[Eric G]

How about the "Flexcharge" charging algorithm...

http://www.flexcharge.com/flexcharge_usa/charge_method/flexcharge_charge_method.htm

Eric

 

[safe]

It appears to be targeted for solar power... but it's interesting...

 

[Eric G]

It looks a bit like the pattern of the float charge stage of my sla charger.My charger manual calls it a special wave form.
Basically it shoots the voltage up to ~14v and rests til the voltage drops to 13.5v then shoots back up again.During the cycle where the voltage shoots up it draws about 1 amp.current.The longer it's on the charger the longer the rests between voltage spikes.It starts by spiking every second or so to about once every 5 or 6 minutes after being on float charge for ~6 or more hours.

Eric