Re: Sheer's Fuel Cell Rant

["Jon \"Sheer\" Pullen" <sheer@brassrat.net>]

> > My batteries are 97% efficient, power in to power out.
>
> Are you sure?  As an example, with PbA, when you discharge at say 20A,
> the voltage under load will be between 2.0Vpc and 1.75Vpc.  When you
> recharge this same battery at 20A, the cell voltage will be between
> 2.2Vpc and 2.4Vpc (or more) at 20C.  This >10% difference in charge vs
> discharge voltage represents a >10% inefficiency, and your NiZn sag more
> than PbA under discharge.

No, of course I'm not sure. I'm using the figures evercel has given me, but,
as lee hart says, there are liars, darn liars, and battery salesmen.

At some later date I hope to perform some experiments to confirm these
figures - until then, as far as I can tell, I'm putting _approximately_ as
much energy in as I'm taking out.

I know they're 90%+. beyond that, I can't say with any certainty.

> I think this is really the argument for fuel cells in a nutshell.  As
> long as the fuel is plentiful and the exhaust clean, the only concern
> with efficiency is to the extent that it impacts how far one can drive
> before refueling.  And the emphasis (predictably) is on providing
> greater energy storage capacity instead of improved efficiency, not
> unlike battery electrics as it happens.

Fair enough.

> I don't think this is quite fair.  It is my understanding that SAFT will
> sell directly to hobbiests and that the only stipulation is that they
> will not warranty the batteries unless you use a charger that satisfies
> their charging requirements and your battery box design is approved by
> them (to ensure the modules will receive adequate cooling).  Yes, there

I found it very difficult to get batteries out of SAFT. I was just speaking
from my own experience.

> is a lead time, but there is also product, and it IS available to
> hobbiests.  Let's appreciate what we've got.

I appriciate that they are making a product. I also appriciate that some of
their high pricing is because they have gotten screwed by GM (anyone else
know that story?).  But I still find their attitude frustrating. When I
talked to SAFT, it wasn't just a matter of warentee - they flat out would
not sell me the batteries. 6 month lead time, and you gotta use our $3500
charger or it's not a deal. It may be that the person who I spoke to was not
fully informed - I later talked to someone there who was quite helpful, and
quite willing to sell me batteries [it sounded like] no matter what charger
I used. But that was after I had already sent the check to evercel.. ;-)

S.