SLA vs. LiFePO4

[Toorbough ULL-Zeveigh]

Vindication


http://endless-sphere.com/forums/viewtopic.php?f=7&t=857&p=23364

It would be great to get 10,000 miles out of the batteries if that's possible. I'm usually not going below 12 volts on the discharge so the batteries are being taken good care of. We will see...

"Dreaming is free."

- Deborah Ann Harry


So you've finally realized that you were wrong then about your SLA.
Accept that you're wrong now about LiFePOOOO.

 

[D-Man]

Safe buys the cheapest batteries available. Probably not tested at 1C either. Don't buy a battery unless you see the manufactures cycling testing results.

 

[rf]

The best comparison between SLA and LiFEPO4 is that there is no comparison.

Hold your horses there impatient one. :wink:

Let's think for a second... every single battery chemistry that's ever been invented so far (NiMh, Nicad, SLA, Li ion etc...) have all had lifespans that were normally measured in a few years. Some can be made to last longer (like decades) if you do special things like keep them at a constant cold temperature (below 60 degrees F) and do certain things to reduce the damage caused by cycling. NiCads have been know to last for 10 years.

If all examples from the past point to some measurable constant of decay why would we expect things to be any different with LiFePO4?

I mean it's great that you are so excited about the new chemistry, but until we get some more solid evidence of incredibly long life I'm going to remain skeptical. Cycling seems to be a big improvement, but the underlying decay processes are still likely to be there.

All I'm asking for is some testing... some data... that prove that the decay rate is so low that it's effectively infinite. From what I've discovered so far LiFePO4 seems to decay by having the Lithium detach from it's desired location and drift off and attach itself where it's not supposed to be.

Your ability and desire to spew pointless, groundless conjecture is breathtaking.

 

[memy]

I know this is slightly off topic RE SLA vs. LiFePO4, maybe it should be renamed Lead Vs lithium.
I've been following altairnano batteries for a number of years now, I don't have the information at hand but I seem to remember they are talking +20-year life, many deep cycles ECT.
The chemistry is very stable. Google altairnano.

I can’t remember seeing anything definitive on the life of LiFePO4 chemistry.
I suspect my “ping” battery will die of old age well before I kill it with cycles.
But who cares?, 2 to 3 years in battery technology at the current pace I’ll be trying to kill the cells so I can justify my next battery purchase.


For what its worth, my experience with SLA’s/lead in telecommunications (Australia) is we get about 10years from SB40 or SB100’s (fibreglass matt),… if they spend most of their life on float.
Flooded cells in exchanges usually have a service life of 15+ years. Depends on how much work they have to do and environment (temperature).
Using well-constructed batteries 10 years for gelcell 20years for wet, are deployment standard.
If they see discharge events then service life slightly affected, deep discharge their service life is crippled.
I have to admit I struggle with the concept of lead on a pushbike, though most of my mates struggle with a battery on a pushbike.

 

[safe]

So you've finally realized that you were wrong then about your SLA.

I've discovered that one cell is dead. My suspicion is my experiment with "SLA Battery Warming" caused it. Seems that the other two cells are okay and it was the one that got the most heat from the heater that failed. It will be interesting to see how far they go after I replace the cell.

10,000 miles is likely too far... but I'm already past 3,200 and 5,000 seems reasonable after replacing the "runt" cell.

Initial Cost with Shipping - $138 (they were likely old already)

Total Miles - 3,200 miles (after 2 years)

Cost per mile - 4 cents

So even if I have to replenish my cells right now I've still done very well.

Anyone want to try to beat that with REAL data... (and pedal assisted kind of screws up the data because mine is pure motor) SLA is still the lowest entry price and equal to the best out there in terms of long term cost.

Seriously... let's see some people do their numbers here.

My guess is that I'll see something like:

Initial Cost LiFePO4 with Shipping - $600

Total Miles - 5,000 miles (after 5 years)

Cost per mile - 12 cents

Which would still make LiFePO4 "good" compared to something like gasoline, but it's still going to cost more compared to SLA based on normal usage.

Tragically I suspect there are people that are getting:

Initial Cost LiFePO4 with Shipping - $800

Total Miles - 2,000 miles (2 years then something bizarre malfunctions)

Cost per mile - 40 cents

 

[Ypedal]

If " cost " is the only factor you care about .. then sure.

 

[safe]

If " cost " is the only factor you care about .. then sure.

Cost is very, very big on my list. I know that right now everyone is soooooooo excited about the idea of "Going Green" and making really fun electric bikes, but at some point reality is going to sink in and the bottom line is going to matter. I really like the idea of LiFePO4 but every time I seek real answers about how long they will last I get nothing. Seems that all the manufacturers are afraid that if the shelf life issue is presented (and it's not as great as people hope) then they will not sell their expensive products.

Just look at the car manufacturers... some of the hybrid car makers have been looking at LiFePO4, but they seem content to stick with NiMh because it's been working well for them. Is it cost? Dependability? Stupid Executives that don't know what is "cool"? I don't know.

What I do know is that there is not enough information about how LiFePO4 performs over the long term.

I will welcome the data as it comes in...

(and heck, maybe the wildest dreams of everyone really will come true)

 

[safe]

An Observation

I am different.

If you've seen my "Safe's Ancient History Thread" in the photo's area you know that my central focus has been "bicycle road racing" as a concept for over 20 years. Adding the battery and motor is just an extension of that older vision that I've been shaping on my own.

For me the "battery" is a secondary focus... it's not the thing that gives me pride or a feeling of being significant in any way.

Last time I was at the welding gas supply place I was talking with the guy there and they want to push the idea of hydrogen as the "new fuel" and so he was presenting it as an "either or" proposition. (battery or hydrogen) But for me I really don't care... if fuel cells are the cost leader I'll dump the battery and go for that. If supercapacitors do it better, then I'll go that way. My vision is centered around something OTHER than the battery so I'm a truly objective person.

I really don't care...

 

[EMF]

An Observation

1. I am different.
<<Snip>>
2. For me the "battery" is a secondary focus... it's not the thing that gives me pride or a feeling of being significant in any way.

1. Granted

2. Here is why you are different than me. As far as "shelf Life", chemical decay, purity of chemistry, Ultra-capacitors, Fuel Cells, DiLithium Crystals ( or anything else that does not yet exsist in the marketplace ) assorted theories and graphs pertaining to storage charge, chilling my garage, etc. I find no need to discuss these things in the battery forum. I live in the here and now. Not in some hypothetical 2 dimensional ether - so for me there is no "dilema".

To me, it's real simple. I have a machine that has two wheels and a light frame. It's not designed for a powerplant of any sort. But, I need a motor to make it go. It likes at least 48 volts and to do what I want - it "needs" 66 volts or better. I'm not going to stack lead on it to get there. I also want to go at least 20 miles.

I want an ebike that looks and rides like a regular bike and does not draw any attention whilst I go down the road. I want a bike that handles well and does not feel like I have some lard ass riding on the rear fender. I've got it.

We all have two choices: lead and all the other chemistries that blow lead out of the water.

Even if I made a heavy frame and I just wanted to go fast, I would avoid lead like the plague.

I am fortunate that I can afford to get what I want, so I did. If I was broke, I would have got lead and not met my design goals. But I still would have had fun with the bike. In the meantime, I would have saved my pennies for anything else.

But, it's good we are all different, or we would all be chasing the same girl.

 

[safe]

I want a ebike that looks and rides like a regular bike and does not draw any attention whilst I go down the road. I want a bike that handles well and does not feel like I have some lard ass riding on the rear fender. I've got it.

When you think about the total weight of bike and rider the battery weight becomes less of a problem.

Human Weight - 185 lbs (more or less)

Bike Weight - 40 lbs to 50 lbs

Battery Weight - 30 lbs to 100 lbs

If you use the lower weight the batteries are:

185 + 40 + 30 = 255

30 / 255 = 12%

If you use the higher weight the batteries are:

185 + 50 + 100 = 335

100 / 355 = 30%

...so the battery weight increase doesn't translate into the big increase as a percentage that you might expect. What matters is whether it's located at the center of mass or if instead it's hanging off the rear.

And this is my "ancient" bike (1985):

...so looks are not something I'm trying to hide.

 

[EMF]

I did think about it and I decided lead was too heavy for my needs - especially considering it is perched over my rear fender/axle. I even lost some weight, about 20 pounds, ( because I needed to and yet, in the back of my mind, I was thinking - wow, this is going to lighten the load on my bike ).

My bike has a total of 17 pounds of batteries and this includes, 2 onboard chargers, circuit breaker protection, isolation circuit, wiring harness, battery box, etc. I can easily hit 30+ MPH and safely pull 40 amps without causing a significant drop in voltage. My pack keeps giving the proper current and voltage until it is almost exhausted, instead of a continual degradation in performance over the course of my ride. Lead can't do this. I would find that annoying.

If I keep my speed under 20mph I can exceed 25 miles, no problemo. I can re-charge an almost dead pack in about 1 hour, or slow charge for 8.

I can pull one plug to my controller and lift the entire power pack/ charger system out of my Swagman, hold it in one hand to take it to the bench if needed.

IMHO, folks can overthink things sometimes and end up doing nothing, or worse yet, go down the wrong road.

On another note, that bike above would make a nice ebike with some lithium cells.

 

[safe]

My bike has a total of 17 pounds of batteries and this includes, 2 onboard chargers, circuit breaker protection, isolation circuit, wiring harness, battery box, etc.

Are you willing to accept the challenge and do "the calc"?

What was the total cost of all the parts?

How many miles have you gone on it?

Now divide the cost by the miles and let me see what number you get....

At least that way you give "fair attention" to the penny pinchers in the audience that care about the "bottom line". I'm willing to guess that if you sum up all the costs that you are riding around on something that is not nearly as cost effective as my bike.

My total bike cost was roughly $800 for "everything" and I've done 3,200, so at this point I've spent:

$800 / 3,200 = 25 cents per mile.

Typical car:

$20,000 + $10,000 (gas @ $3) + $5,000 (other) / 100,000 = 35 cents per mile.

 

[EMF]

No, I do not intend to calculate anything. You made your decision...I made mine. I would do it the same if I had to do it over too.

 

[Toorbough ULL-Zeveigh]

So you've finally realized that you were wrong then about your SLA.

I've discovered that one cell is dead. My suspicion is my experiment with "SLA Battery Warming" caused it. Seems that the other two cells are okay and it was the one that got the most heat from the heater that failed. It will be interesting to see how far they go after I replace the cell.

10,000 miles is likely too far... but I'm already past 3,200 and 5,000 seems reasonable after replacing the "runt" cell.

Hell yeah, if you continuously swap out the weak/ded cell you can go forever.
A dirty bit O' cheetin' that is.
Once you replace a cell, that's it, the odometer resests, it's not the same pack anymore.
The weak link (sorry Hyrule) in the chain will always shift to a fresh runt.
So that's it, the jury's in, SLA good for ~3000 miles, which would be about center of the bell shaped curve.

I don't know how hot you got your cell, I wasn't there, but I think you're jumping to a wrong conclusion (yet again) that the cell failed as a result of a heater.
It died at about the right time cheep AGM's typically die, the others can't be far behind.
You will let us know when the last of them have been replaced later this year won't you?

Initial Cost with Shipping - $138 (they were likely old already)

Total Miles - 3,200 miles (after 2 years)

Cost per mile - 4 cents

So even if I have to replenish my cells right now I've still done very well.

You've don't an interesting & sneaky little shift of your position here.
You're now arguing operating costs when the sole point of contention, (for me at least, but most others as well it seems) is your simplistic & flat out wrong assertion that no battery can last more than 5 years under any condition, calender life, shelf life whatever label you decide to put on it.
I can't decide if these unfounded assertions you continue to post in large bold letters of proclamation springs entirely out of a self centered arrogance.
That no one's experience counts for anything except yours like when your battery dies then you do an extreme flip from 'SLA last 10k miles' to 'all batteries must die when the gemstone in their plate turns dark at the end of the calender'.

OR are these misleading proclamations fulfilling your masonic obligation to spread doubt & confusion amongst the great unwashed.
After all, you can't go strutting around in smug enlightenment when everyone else is on the same page, no gradient to differentiate yourself with.
BTW, good of you to come up to speed what the rest of us that have been trying to tell you since forever, that temp is time's arrow (entropy law) & kills batteries.
Saves me from having to prove it to you which means you are going to have to accept accelerated life testing data as valid.
Just another example how you don't believe it until our saviour discovers it on his own, that he's the first to make the grand realization & delivers us from the darkness.

You like to identify yourself with the great lord garth.
But I see you more as the changeling, nomad.
Thinks he's perfect (enlightened) but doesn't realize how fawlll...teeeee he really is.
Either way, stop with the dis-information pls.

And I thought this was kinda cool, even tho I don't golf.

 

[CGameProgrammer]

Regarding weight, let's conservatively say a 12V 12Ah B&B SLA battery actually yields 8 Ah. That's 96 Wh in a 9.5 lb package, or 10.1 Wh/lb. A 10s pack of A123 batteries (i.e. the DeWalt configuration) delivers 33V and, from my testing, 2.1 Ah. That's 69.3 Wh in a 1.6 lb (?) package, which is 43.3 Wh/lb. So A123s are about four times as dense as sealed lead-acid, which is nice.

But let's look at cost now. The above battery packs would be $38 for the 96 Wh lead-acid, or $100+ for the 69.3 Wh A123. That's $0.40 per Wh for lead-acid versus $1.44 per Wh for A123. For a 400Wh pack, that would be $160 vs $576, so the A123s are almost four times as expensive, and that's at the cheapest price you're likely to get for new ones. The DeWalt packs actually retail for $160 each, or $2.31 per Wh.

Of course A123s almost certainly last more than four times as long as lead-acid, but I think people usually overestimate how much that matters. I got my first e-bike running a bit over a year ago and I'd estimate I've no more than 400 miles on an e-bike. Could be 300. Maybe I'm unusual, but I've spent far more time working on it than riding it.

 

[D-Man]

Thats right, your pack is done Safe if you replace any of those batteries. Looks like I might get the "most miles" if you throw in the towel now. Only 500 more to go. :lol: I wish I would have got the better sla's that were good for 300 cycles instead of 180. :x

 

[safe]

10,000 miles

10,000 miles from SLA...

10 years for LiFePO4...

These are dreams of optimal performance.

Under perfect circumstances I would think that either one of these ideals might be attainable... but the more realistic performance is usually less than the ideal. In my case I think I may have caused a cell to fail by using external heating on it. I don't know for a fact that this is the case, but that's the "working theory" until new data changes my opinion. (I'll know after replacing the "runt" if another fails shortly after)

The main lesson out of all of this is that SLA does produce some pretty nice cost/performance numbers ($ per miles) so no matter what the final number ends up being it's going to be hard for something that costs four times as much to compare with it.

If cost matters.... SLA is pretty good... but if you have other criteria (like wanting a super light weight bike at any price) then you have to look into other options.

 

[Link]

The weak link (sorry Hyrule) in the chain will always shift to a fresh runt.

LULZ, I wouldn't have even noticed that had you not pointed it out.

If cost matters.... SLA is pretty good... but if you have other criteria (like wanting a super light weight bike at any price) then you have to look into other options.

Geh? I've got 4.5Ah of lead strapped to my back. They're crap, so I can only get about 1.5Ah out of them before the LVC on the controller (and this is a 36V controller, mind) starts cutting in and making a grinding noise in my motor. I got them free, but new they cost about $25 apiece. $100 of lead. For 72whrs. Not including sag. A DeWalt holds 76whrs for the same price (at least the old price, anyway). Some of the highest performing lithiums end up being cheaper than my crap SLAs that barely take me 4 miles. If I didn't have to pay for shipping, PingPacks would come out to $50 for an equivalent pack.

Granted I'd need a bigger pack to be able to sustain the amp draw, but for me, lead is twice as expensive as cheap lithium, not even factoring in cycle life.

 

[safe]

I've got 4.5Ah of lead strapped to my back. They're crap, so I can only get about 1.5Ah out of them before the LVC on the controller (and this is a 36V controller, mind) starts cutting in and making a grinding noise in my motor.

Yeah, well 4.5Ah is simply too small for SLA... I'm sure you and everyone else realizes that...

My experience with 38Ah SLA has been pretty good because you have to think in terms of "C" rates. 1C for my bike would be about 40 amps... right where my current limiting is. This produces about a 50% efficiency based on the Peukert's Effect and that's about as good as you can hope for.

So you should "reverse engineer" your system:

Step One: How many amps will you draw?

Step Two: Translate discharge amps to Amp Hours.

Step Three: Find the appropriate batteries at the lowest price.

Step Four: Build bike that can handle the batteries you plan to use... this means custom design. It's really the LAST step that get people into trouble... if there was a mass produced bike like mine then more people would think positively about SLA.

...for 4.5Ah you should not draw more than 5 amps or you have made a mistake in your design.

(5 amps * 36 volts = 180 watts maximum... more like 150 watts in practice)

 

[safe]

This produces about a 50% efficiency based on the Peukert's Effect and that's about as good as you can hope for.

I'm quoting myself, but it's a separate thought so why not...

Maybe the easiest way to make the comparision is just to say that whatever price you pay for SLA you need to double it to get a satisfactory comparison figure to LiFePO4.

So if SLA costs $100 then it's "true cost" is really equivalent to $200. In order to equal or better the performance of SLA you need to buy LiFePO4 at a cost of less than double the SLA. However, the lifespan for LiFePO4 is much longer... so the first few years you struggle with LiFePO4 to "pay off the debt" and then it's only after that point that you actually might see an advantage. Many people might never see the benefits of LiFePO4 until some future date. (it might take 3,000 miles or more to return a profit from LiFePO4)

The "break even" point for LiFePO4 is way out in the distance... thousands of miles...

 

[TylerDurden]

So you should "reverse engineer" your system:
Step One: How many amps will you draw?
Step Two: Translate discharge amps to Amp Hours.

Will you only ride in warm weather?
Do you have lots of time to recharge?
Will you never need to pick up and move your bike?
Do you only ride on flats with no hills?
Is buying batteries again in 1yr acceptable?

Lead my be perfect for you.

 

[D-Man]

Hey Safe, how many miles did you get on a charge when the batterys were new ?

 

[safe]

Will you only ride in warm weather? Yes.
Do you have lots of time to recharge? Yes. (it takes about 4 hours after short rides)
Will you never need to pick up and move your bike? I've had to load it in my truck.
Do you only ride on flats with no hills? I have gears.
Is buying batteries again in 1yr acceptable? No, but every 2-3 years is okay if it's cheap.

 

[safe]

Hey Safe, how many miles did you get on a charge when the batterys were new ?

About 20 miles at full throttle.

That started really going down last summer to about 12 miles. Until I replace the bad cell and retest it to see if the other two are usable I won't know their state of health. I'm hoping that the "runt" cell took the brunt of the damage on every cycle and the remaining cells are in better shape. I'm hoping that the 38Ah cells are at about 18Ah now. Since I'm going to get two 18Ah in place of the 38Ah I'll be able to test at 36 volts and at 48 volts. With some luck I might even break some of my old speed records because the spreadsheet shows that 48 volts will give me a top speed of about 47 mph compared to 40 mph with my 36 volts setup.

My highest speeds occurred when I was using a different gear setup that was taller... so I've actually be going slower and with less range for some time now.

48 volts and 18Ah overall should make for a little fun this summer... we will see... (and I'll be sure to brag if I set some new top speeds )

If the remaining cells are "spent" I'm going to order four more 18Ah cells and have all fresh cells... these cells cost about $36 each delivered...

 

[EMF]

The point I am trying to make is there is no right answer. It's what do you want. Safe is happy with lead. I'm not. Neither is right or wrong it's simply a preference. All this in depth diagnosis is leaving out an important factor, and that is what does the person want? You cannot make a case for any one power source as "the best".

If you get right down to it, you could REALLY save money and simply use a bike as intended with no motor at all. Or- you could put a freaking sail on it or lash it to an unsuspecting motorists car.

The fact of the matter is there are more factors than cost. Many many factors when we make something ourselves. I guess this is what makes this ebike building more hobby like, as you can get creative, you can go for whatever parameters you like. Thank goodness or this would be quite a boring endeavor. With all the choices out there we are seeing constant innovation which is interesting to see here and read about.