[time-nuts] OT Gel Cell question

DaveH info at blackmountainforge.com
Sun Jul 27 21:17:38 EDT 2014


A minor nit

The self-discharge rate is pretty high (20 to 40% per month) and the
charging is not as efficient.

Power density is pretty bad too.

For forklift operation this is not a problem as weight is a good thing, they
are topped off every night and the power used to run a forklift is minimal
given the overall consumption of an average factory.

Wikipedia has a nice comparison

http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery

http://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery

Here is a vendor:

http://ironedison.com/

Dave

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Alex Pummer
> Sent: Sunday, July 27, 2014 15:48
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] OT Gel Cell question
> 
> it is not a high performance battery but extremely robust, see there 
> http://www.nickel-iron-battery.com/
> it is no polluting, it could be shorted out overcharged
> if you are lucky and find one old forklift with Edison 
> Battery -- which 
> was built some fifty years ego....it will out last you too
> you could charge in current mode, C/10, 2C nothing will happen just 
> replace evaporated water in the elctrtrolyt which is KOH
> 73
> Alex
> 
> 
> On 7/27/2014 2:41 PM, Chuck Harris wrote:
> > I too have spent a lot of time charging batteries using different 
> > methods on
> > various chemistries.  Once upon a time, I build a number of 
> suitcase 
> > battery
> > chargers for the US Army that allowed them to charge every portable 
> > secondary
> > battery type that they had in inventory... SLA, AgO, NiCD, NIMH,
> > LiIon...  I proved a concept, and someone else got to make 
> all of the 
> > money
> > off of it when the ARMY shopped my prototypes around... but 
> I digress.
> >
> > When you try to charge a sulfated lead acid cell, you can 
> think of the 
> > cell
> > as being a bunch of little parallel lead acid microcells 
> (uCell). Each 
> > is in
> > some state of charge/discharge.
> >
> > So imagine this:
> >
> > +--+--+--+--+--+--+.....+--+---Plus terminal
> > S..S..S.[B].S..S..S.....S..S
> > +--+--+--+--+--+--+.....+--+---Minus terminal
> >
> > In this case, all of the "S"s represent a microcell (uCell) that is 
> > highly
> > sulfated, and the "[B]" represents a microcell that is in perfect 
> > condition,
> > and is taking a charge normally.
> >
> > If you try to put current into this lead acid cell, the sulfated 
> > uCells will
> > appear as open circuits (due to the sulfate's insulating 
> properties), 
> > and the
> > good uCell will take all of the current, and will keep the voltage 
> > down to a
> > low enough value that the sulfated uCells will not see any 
> significant
> > electrolysis action.
> >
> > So you say, "Pooh, I want the sulfated uCells to charge 
> too!" and up the
> > voltage across the lead acid cell, and poof!  The good 
> uCell dies from 
> > over
> > heating, revealing a new uCell that wants to charge, and 
> poof, it dies,
> > revealing another uCell that wants to take a charge, and poof...
> >
> > You get into a situation where your success causes your failure.
> >
> > If, instead, you apply high voltage pulses to the lead acid 
> cell, you can
> > sometimes beat the system.  The good uCells will take a 
> hit, but it is 
> > short
> > enough that they don't have time to burn up, and the 
> sulfated uCells will
> > get to draw enough current during the pulse that a little 
> electrolysis 
> > will
> > happen, and convert some of their sulfate back into oxide 
> and acid...
> >
> > Sometimes you can win by using a pulse charge system.
> >
> > However, there is a little physical problem that has to be 
> > understood.  Part
> > of the way the lead acid batteries get their high current handling 
> > densities
> > is because the lead plates are made to have high surface area. They 
> > are kind
> > of like sponges on the surface.  And, lead sulfate takes up 
> > significantly more
> > room than lead oxide.  Sorry, that is the way it just is.
> >
> > So, when a cell gets all sulfated up, the lead sulfate that 
> forms in 
> > the deep
> > nooks in the mossy lead electrodes fills the nook up so 
> full that it 
> > breaks
> > it apart, and damages the cell plate.  This happens, albeit slowly, 
> > even when
> > you treat the battery nicely.
> >
> > You can't win. Long term everything heads towards entropy.
> >
> > -Chuck Harris
> >
> >
> > Brooke Clarke wrote:
> >> Hi Robert:
> >>
> >> I've spent a lot of time charging batteries using 
> different methods 
> >> and on various
> >> chemistries.
> >>
> >> When the charge is in the form of a pulse, ideally including a 
> >> reverse polarity
> >> pulse, the charge is more effective.
> >> This is also a way to sometimes, but not always, will recover a 
> >> battery that
> >> otherwise will not take a charge from a DC source.
> >>
> >> I think this works because it takes some time for chemical 
> reactions 
> >> to work and by
> >> using a pulse you can force the reaction to a higher level 
> that you 
> >> can't do using DC
> >> without causing problems such as boiling the electrolyte.  
> For more 
> >> info see Burp
> >> Charging:
> >> http://www.prc68.com/I/BatChg.shtml#Burp
> >>
> >> Have Fun,
> >>
> >> Brooke Clarke
> > _______________________________________________
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