Re: (ET) When did they start making car batteries out of gold??

["David Roden (Akron OH USA)" <etpost drmm net>]

On 18 Aug 2013 at 16:33, Robert Troll wrote:

>  If there is indeed a 4x improvement in life-cycle between the two
> batteries that would mean one battery CALB should last 32 years in
> standard ET use? 

LiFePO4 batteries haven't been around long enough for anyone to know for 
sure.  We really don't know how long they will last.  At best it's 
extrapolation; at worst it's marketing.  

In addition to a definable cycle life, lithium batteries have a calendar 
life - that is, they degrade with time even when they're not used.  A123 
System project a 23% loss of capacity at 15 years.  I say "projects" 
because 
they really don't know for sure.  They say they're extrapolating.  From 
what 
I can tell, that estimate is based on a test only 100 days long.  Will 
their 
data hold up?  We don't know yet.

LiFePO4's proponents claim a cycle life in the range of 2000-3000.  This 
claim comes from the manufacturers, too.  Are they offering a warranty?  
Will the manfacturer you choose still be around when you need to collect 
on 
that warranty?  If they are, will they honor the warranty?  This isn't a 
trivial question, as we'll see in a moment.

I have yet to see any independent verification of these cycle life claims, 
but if it's true, you can bet that it's going to be a lot like lead 
batteries - you MAY get this cycle life IF you charge and discharge under 
proper control.  Again, IMO, this means you need an automatic battery 
management system. 

But even if you DO get 2000 cycles in an ET, suppose you use your ET on 
average once a week for mowing or moving snow.  Two thousand cycles would 
be 
38 years of use!  More likely calendar life will be the limiting factor in 
this case. 

A123's calendar life estimate applies to their cells, of course.  We don't 
know how or whether it will apply to the larger and cheaper Chinese cells. 
But AFAIK we don't have another, so let's use it for now.  

In 15 years you'll lose 15% capacity to calendar aging, and (also from 
their 
estimates) another 5% to 20% to cycle life.  Whether the battery is then 
still usable for your needs will depend on how much you've oversized it.  
And whether the battery manufacturer will still be around to honor their 
2000 cycle warranty (if they gave you one) is another question.

As I said before, I'm already getting 15 years of real world use out of my 
East Penn Deka gel batteries.  OTOH, we don't yet have any 15 year, real 
world experience with LiFePO4.  Given that, I can't see any benefit for me 
from LiFePO4 in my ET.

On 18 Aug 2013 at 12:47, Kim Petty wrote:

> It is my understanding that LiFePO4 can be damaged if they are charged
> below 32 F. An electrak in an unheated garage should  probably have a
> battery heater of some sort if it is going to be used  for snow
> removal. 

I've read that too.  Again, we don't have enough real world experience to 
know how this will play out.  But it underscores the fact that charging 
lithium batteries properly isn't the simple, straightforward process it is 
with lead batteries.

Don't get me wrong, LiFePO4 is good stuff - where its strengths are 
needed.  
That's mostly in cases where you need a lot of energy storage in a 
relatively light (compared to lead and even NiMH) and relatively stable 
(compared to other lithium types) battery.

Of course someone who's selling a battery is going to emphasize its 
positives and gloss over its negatives.  I'm not selling LiFePO4, nor in 
fact am I selling ANY battery, so I don't have a horse in this race.   

However, I've used LiFePO4 in a scooter, where it was the right choice for 
its specific energy.  So far it's performing well, though I've only used 
it 
for about a year and a half and maybe 50 cycles.   Based on what I see so 
far, I'd use it again for a scooter or e-bike, and probably for a 4-wheel 
road EV.  

I'll probably use LiFEPO4 for my push mower too.  Weight matters there.  
Alas, you're unlikely to see many such critters from the big 
manufacturers, 
because a lithium battery would drive the cost too high.  They have to 
stay 
at least somewhat competitive with gas push mowers.

Would I use LiFePO4 in my ETs?  Probably never in my E15.  Even with dead 
lead batteries as ballast, it would still be lighter, and I don't want 
that.

If the gel batteries in my R36 rider gave up tomorrow, which isn't likely, 
I 
might consider LiFEPO4 for it.  There lighter would be OK, maybe even 
good.  
But I'd probably do it mostly for the experience, sort of as a further 
warmup to using LiFePO4 in a road EV.  If not for that - probably not.