Lead acid battery charging phases?

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treez

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We wish to use a lead acid battery for our emergency light product.

We know that there is only one way to charge lead acid, and thats this.

Trickle charge at <C/10 until voltage > 2.1V/cell
Constant current charge till cell voltage = 2.35V/cell
Topping charge which maintains the voltage at 2.35V/cell (the current slowly reduces)
-when the topping charge current has reduced to 0.03C, then go to ...
Float charge which just regulates the cell voltage to 2.25V/cell


..The above must be adhered to if you want any decent lifetime out of the lead acid battery?

My questions are.....
1)...Can the constant current phase be done at any current level?...what ranges of current are allowable?
2)...How much does the 2.35V/cell figure change with temperature?
3)....How much does the 2.25V/cell change with temperature?
4)....Supposing i have a constant current source of C/10 (which can be PWM'd on and off at any duty)...then is it impossible to charge a lead acid battery?
 

1) Battery ratings determine the charge rates, at least C1, some C5 etc.
2)3) depends on battery chemistry.. SLA are more temperature sensitive.. consult with supplier
4) Not impossible, but aggressive charging can put cells out of balance.

Pulse charging is recommended with inductive capacitor discharge to prevent sulfation, a chronic aging factor on emergency light batteries.. We used to make these. the company sold out to an OEM. They work well.
 
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Lead Acid should be charged with voltage and current controlled charger.

There is no constant current for lead acid, this is bad for this type of battery. Use current limiter, and voltage control.

Search EDABoard threads you can find lots of informations.


By the way what happen with NiCd ? :|
 
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Lead-acid type is supposed to get maintenance (checking water level and topping up preferably with distilled or deionized water). The exception is sealed L-A batteries (glass mat), however they cost more, therefore your boss is not unlikely to favor using SLA.

Lead-acid type is best suited for a system that sees regular maintenance, and regular charge-discharge cycles. I believe your customers will want an emergency light that is 'plug-in-and-forget.'

Have you considered gel cells? They are suited to seldom-used, low-maintenance devices. I don't know just how gel-cells compare to nicads, pricewise, etc.

Furthermore L-A have to be kept right side up. If human beings will handle your product, a few will get tipped or spilled or dropped, risking acid spills. (Again sealed L-A is better in this regard.)
 
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By the way what happen with NiCd ?
Click to expand...
NiCad is big and needs constant current trickle charge

With lead acide, there is no trickle charge, but the cell is kept topped up by regulating its voltage....however, the voltage that you should regulate to is determined by temperature....so we'd need tempereture monitoring too.
 

Have you considered gel cells?
Click to expand...
You can be sure that "lead acid" in this thread doesn't mean other batteries than maintenance free lead acid gel cells.
 
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