12 volt lead acid

[degarb]

At radio shack they sell a 5 amp hour 12 volt lead acid battery that doesn't weigh too much for a tool belt mount. 60 amp hour, not too bad! You could run over 4 watts of power and have a practical work light ( I worked 15 hours straight yesterday with my lights on all day.)

Is it possible to resistor run this to a direct drive high powered head lamp? What would be the down side?

 

[MrAl]

Hi there,

I use Lead Acid batteries for lights and i find that they work well. For
example, i use one 6v LA to drive a light that normally takes 4 AA cells,
and it runs much longer than with the AA cells.

Using a resistor for this app 'might' not be the best idea, unless the
voltage of the battery is matched pretty well to the light itself (several
LEDs in series perhaps). Otherwise, a 'down' converter would be better
and get you more run time out of one charge.

The down side to using LA is that they die out after a certain number of
recharges, worse than NiMH. This means if you can use NiMH you would
be better off in the long run, as long as you get good NiMH cells to
begin with. They make pretty hefty NiMH cells these days too, and you
could use battery holders to make a battery pack perhaps.

 

[Norm]

Hi there,
The down side to using LA is that they die out after a certain number of
recharges,

The biggest killer of SLA batteries is running them too flat like any lead acid battery the don't like deep discharge.
Norm

 

[SilverFox]

Hello Norm,

However, if your application revolves around running them flat, you can still improve the cycle life by using a different charge algorithm.

Most lead acid batteries are only good for around 150 - 200 full discharge cycles, but changing the charge algorithm results in getting 700 or more full discharge cycles.

A couple of questions come up...

Are we discharging them to death?

Or, are we charging them to death?

Tom

 

[Kremer]

Hello Norm,
However, if your application revolves around running them flat, you can still improve the cycle life by using a different charge algorithm.

Most lead acid batteries are only good for around 150 - 200 full discharge cycles, but changing the charge algorithm results in getting 700 or more full discharge cycles.

Eh, so pulse charging for LA's now ?

 

[TigerhawkT3]

A nice DD from a 12V SLA is four XR-Es (or Seouls, or whatever). With four Q2s, I get about 200mA.

 

[Phaserburn]

Eh, so pulse charging for LA's now ?

Interesting. Any wallwart chargers available for this?

 

[MrAl]

Hello Norm,

However, if your application revolves around running them flat, you can still improve the cycle life by using a different charge algorithm.

Most lead acid batteries are only good for around 150 - 200 full discharge cycles, but changing the charge algorithm results in getting 700 or more full discharge cycles.

A couple of questions come up...

Are we discharging them to death?

Or, are we charging them to death?

Tom

Hi Tom,

That little paper (link) is a bit of an oversimplification however.
There are a number of steps involved in that procedure and i dont
know if that would be practical for most people to do.
Do you know of any link with a more direct algorithm written out?

Here's a link if anyone can get this paper, i'd be glad to read it over
and see if i can come up with a circuit and/or algorithm to do this
if none other can be found on the web somewhere...

http://ieeexplore.ieee.org/Xplore/l...85/00838406.pdf?tp=&isnumber=&arnumber=838406

 

[SilverFox]

Hello Al,

I knew someone was going to ask more about this...

Here is the paper that got it all started. I was looking for it earlier and couldn't find it.

I have played with this a little and it is pretty interesting. I use the NiCd setting on my charger and go for -dV termination. I believe I had to use a lower current than they used to control venting.

Tom

 

[MrAl]

Hi Tom,


Great, so do we get a relatively simple algorithm out of this or something
that is going to be extremely hard to apply?

I wouldnt mind looking into this further as i have personal interest in
the possible life extension of LA batteries too.

 

[degarb]

A nice DD from a 12V SLA is four XR-Es (or Seouls, or whatever). With four Q2s, I get about 200mA.

you mean in series, i take it. How would a duel head on hat and one wrist light plus variable 2 ohm pot? Almost would need special made jacket.

This would be a 9 volt requirement. ALso wouldn't drain down to zero often. How would cycle life be?

What down converter does one envision?

I suppose a tri head would work too, but fearful might add unneeded mass.