Electrical Engineering - To Ed from OP: Re: NiMH Battery Re-Charging

Author

To Ed from OP: Re: NiMH Battery Re-Charging

Robert11

2008-01-03, 5:25 pm

Hi Ed,

Thanks for reply.

Any potential danger like overheating, fire, etc. if "overcharged" for many
hours ?

Thanks again,
Bob

------------------
"ehsjr" <ehsjr@bellatlantic.net> wrote in message
news:5c9fj.18329$oh5.4777@trndny08...
> Robert11 wrote:
>
> You'll get less than optimum life from the batteries, but
> so what?
>
> It is probably a "non-issue". 16 hour charging is not the best
> approach, but it is not horrible, either. It's actually a pretty
> good compromise. Eventually, your batteries will fail due to age,
> overcharging, undercharging, whatever. You can put time, energy
> and money into getting the absolute maximum life from them, or
> accept the fact that less than optimum charging and use will give
> you less than optimum life. In most cases, the delta between
> optimum life and a somewhat shortened life is not worth the cost
> and effort needed to get the optimum.
>
> We don't know the specifics of the radio's charger, but as long as
> you charge using it you are "stuck" with whatever it does. You can
> manage the situation to some extent, if you wish. If you are
> concerned about "10 minute per day" (or whatever) operation, you
> can use the radio that way, and estimate how many days to wait
> between charges. Or you can pull the batteries out of the radio and
> charge them with an external charger that has the features you want.
>
> Ed
>

Dave Martindale

2008-01-04, 5:25 pm

"Robert11" <rgsros@notme.com> writes:

>Any potential danger like overheating, fire, etc. if "overcharged" for many
>hours ?

Not at 150 mA. The batteries are likely rated at 1500 mAh or more,
probably above 2000 mAh if they were purchased recently. So you're
charging them at what is called the C/10 rate or even less. The cells
can withstand that charge rate indefinitely, only getting a little warm
if they are already fully charged.

This will reduce their life compared to a good fast charger, but NiMH
cells aren't that expensive to replace when they eventually fail.

Dave

Stuart

2008-01-04, 5:25 pm

In article <uvGdncoVTLIM9eDanZ2dnUVZ_rmjnZ2d@comcast.com>,
Robert11 <rgsros@notme.com> wrote:
> Hi Ed,

> Thanks for reply.

> Any potential danger like overheating, fire, etc. if "overcharged" for
> many hours ?

Always possible.

My advice would be a proper external charger - one of the "clever" ones.

I have one here, it charges only until the cell is fully charged. It has
four channels, to allow four cells to be charged simultaneously, each
monitored independently. Each channel has an LED. When the LED goes out
the cell is charged. It is not unusual, even with a set of four always
used together to see the LEDs go out a different times.

--
Stuart Winsor

From is valid but subject to change without notice if it gets spammed.

For Barn dances and folk evenings in the Coventry and Warwickshire area
See: http://www.barndance.org.uk

ehsjr

2008-01-04, 5:25 pm

Robert11 wrote:
> Hi Ed,
>
> Thanks for reply.
>
> Any potential danger like overheating, fire, etc. if "overcharged" for many
> hours ?
>
> Thanks again,
> Bob
>

No. Provided the charger in the radio doesn't become
defective and is used per directions, you could leave
the batteries charging in there for years and not have
a fire. The batteries might be ruined by that, but
that's the extent of the likely problem.

Ed

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