recharging a battery with lower current

[PT Wang]

Is there any negative consequences, other than longer time, for recharging a
battery (Li-Ion or NiMH) with current lower than the specification but
similar voltage? For example, to charge with 12V x 100mA while the
specification states 12V x 1A.

 

[soundman]

"PT Wang" <news1003@paultwang.com> wrote in message
news:wXtbc.4519$js.1205@newssvr24.news.prodigy.com...

Is there any negative consequences, other than longer time, for recharging
a
battery (Li-Ion or NiMH) with current lower than the specification but
similar voltage? For example, to charge with 12V x 100mA while the
specification states 12V x 1A.

Battery technology isn't quite that simple. firstly, Li Ion batteries
generally have embedded electronics to protect the cells. That makes it
hard to charge them unless you know what the protection circuit is doing.
Bypassing the circuitry can cause a real risk of damage to the cells and to
you. Most others such as NiMH use current based charging. This means that
you don't charge a battery at a specific voltage but at a specific current.
For example, one pack I have been using recently is an 8.4V NiMH 3.5Ah unit.
This gets charged at 2A and during the cahrge cycle, the voltage at the
battery terminal rises from about 9.3V at the start of the charge to 10.5V
at the end. The current remains at 2A for the complete charge process.
However, a small voltage drop at the end of the charge indicates a full
charge, and at a lower charging current, this won't be detected

Using a fixed voltage will either overcharge batteries, damage the power
supply or perhaps won't ever fully charge the battery. A well designed
charging circuit doesn't have to be complex, but I would suggest you look at
the battery specifications carefully before doing anythig with your own
charger

Peter

 

[happyhobit]

PT Wang <news1003@paultwang.com> wrote:

Is there any negative consequences, other than longer time, for recharging
a battery (Li-Ion or NiMH) with current lower than the specification but
similar voltage? For example, to charge with 12V x 100mA while the
specification states 12V x 1A.

Three Rules for charging a Lithium Ion Battery

1) Current Rate 1C or less. ( Any current LESS then 1C is fine ) ( 1C =
battery current / capacity )

2) Voltage limited to 4.2 volts / cell or less

3) If the battery voltage is below 3 volts / cell, Slow Charge (1/10C) until
voltage greater than 3 volts / cell.


There are several ways to charge NiCad and NiMh batteries.

‘Peak Charging’ is done with a constant current (1C or higher) until drop in
the voltage of the battery is sensed. This voltage drop in the battery occurs
when the battery reaches full charge.

Some charges sense an increase in the temperature of the battery that occurs
after the battery reaches full charge.

‘Trickle Charging’ involves charging at a constant current of C/10 ( .1C) for
12 to 14 hours. A couple more hours at this rate won’t hurt the battery (too
much)

‘Continuous Charging’ involves charging at a constant current of (If my
memory serves me correctly) C/20 (.05C) forever.

Do a Google search for ‘energizer’ and "nickel-metal hydride".

I got;
http://data.energizer.com/batteryinfo/application_manuals/nickel_metal_hydride.htm


Jay
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"I'm pullin' for you; we're all in this together", Red Green
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[Neil Koozer]

PT Wang wrote:

Is there any negative consequences, other than longer time, for recharging
a battery (Li-Ion or NiMH) with current lower than the specification but
similar voltage? For example, to charge with 12V x 100mA while the
specification states 12V x 1A.

Look for "battery university" on the web.

Neil