[time-nuts] OT Gel Cell question
alex at pcscons.com
Sun Jul 27 18:47:58 EDT 2014
it is not a high performance battery but extremely robust, see there
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
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
> chargers for the US Army that allowed them to charge every portable
> 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
> 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
> as being a bunch of little parallel lead acid microcells (uCell). Each
> is in
> some state of charge/discharge.
> So imagine this:
> +--+--+--+--+--+--+.....+--+---Plus terminal
> +--+--+--+--+--+--+.....+--+---Minus terminal
> In this case, all of the "S"s represent a microcell (uCell) that is
> sulfated, and the "[B]" represents a microcell that is in perfect
> 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
> 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
> 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
> 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
> 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
> 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
>> 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
>> Have Fun,
>> Brooke Clarke
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