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From: Raveninghorde on 25 Jun 2010 19:11
I am used to charging NiCd or NiMH cells however I haven't done it
from a solar panel before. I'm happy I can hold the solar panel near
the point of peak efficiency but I am concerned about charge
termination due to the variable power available from solar panels.

Normally for NiCd I would use negative delta V for termination with a
back up timer. For NiMH I would use a thermistor for delta T
termination. However I can see potential problems with solar as the
power source.

In principle I could lay out a 60W panel in Arizona and charge the
batteries without problems - until someone parks a truck and shades
the panel dropping the charge current.

So what is the best way to terminate charge on nickel based batteries
with a variable power source?
From: Martin Riddle on 25 Jun 2010 19:27


"Raveninghorde" <raveninghorde(a)invalid> wrote in message
news:16da261ntm8hp49umugnu0lvmq54rlmgrv(a)4ax.com...
> I am used to charging NiCd or NiMH cells however I haven't done it
> from a solar panel before. I'm happy I can hold the solar panel near
> the point of peak efficiency but I am concerned about charge
> termination due to the variable power available from solar panels.
>
> Normally for NiCd I would use negative delta V for termination with a
> back up timer. For NiMH I would use a thermistor for delta T
> termination. However I can see potential problems with solar as the
> power source.
>
> In principle I could lay out a 60W panel in Arizona and charge the
> batteries without problems - until someone parks a truck and shades
> the panel dropping the charge current.
>
> So what is the best way to terminate charge on nickel based batteries
> with a variable power source?

Terminate at 40c , if the batteries get that hot in the sun, you may
damage them during charging.

Cheers


From: Bill Sloman on 25 Jun 2010 19:48
On Jun 26, 1:11 am, Raveninghorde <raveninghorde(a)invalid> wrote:
> I am used to charging NiCd or NiMH cells however I haven't done it
> from a solar panel before. I'm happy I can hold the solar panel near
> the point of peak efficiency but I am concerned about charge
> termination due to the variable power available from solar panels.
>
> Normally  for NiCd I would use negative delta V for termination with a
> back up timer. For NiMH I would use a thermistor for delta T
> termination. However I can see potential problems with solar as the
> power source.
>
> In principle I could lay out a 60W panel in Arizona and charge the
> batteries without problems - until someone parks a truck and shades
> the panel dropping the charge current.
>
> So what is the best way to terminate charge on nickel based batteries
> with a variable power source?

http://www.edn.com/file/25378-Solar_panel_powers_two_stage_lead_acid_battery_charger_pdf.pdf

--
Bill Sloman, Nijmegen

From: Kevin McMurtrie on 26 Jun 2010 01:03
In article <16da261ntm8hp49umugnu0lvmq54rlmgrv(a)4ax.com>,
Raveninghorde <raveninghorde(a)invalid> wrote:

> I am used to charging NiCd or NiMH cells however I haven't done it
> from a solar panel before. I'm happy I can hold the solar panel near
> the point of peak efficiency but I am concerned about charge
> termination due to the variable power available from solar panels.
>
> Normally for NiCd I would use negative delta V for termination with a
> back up timer. For NiMH I would use a thermistor for delta T
> termination. However I can see potential problems with solar as the
> power source.
>
> In principle I could lay out a 60W panel in Arizona and charge the
> batteries without problems - until someone parks a truck and shades
> the panel dropping the charge current.
>
> So what is the best way to terminate charge on nickel based batteries
> with a variable power source?

Keep a device on the battery that measures all current in and out. It
can estimate the charge power well enough to prevent wear.

LiFePO4 and Li-Po are other options. They'll give you the same power
rate, much better density, less self-discharge in AZ heat, and simpler
charging.
--
I won't see Google Groups replies because I must filter them as spam
From: Robert Baer on 26 Jun 2010 02:03
Raveninghorde wrote:
> I am used to charging NiCd or NiMH cells however I haven't done it
> from a solar panel before. I'm happy I can hold the solar panel near
> the point of peak efficiency but I am concerned about charge
> termination due to the variable power available from solar panels.
>
> Normally for NiCd I would use negative delta V for termination with a
> back up timer. For NiMH I would use a thermistor for delta T
> termination. However I can see potential problems with solar as the
> power source.
>
> In principle I could lay out a 60W panel in Arizona and charge the
> batteries without problems - until someone parks a truck and shades
> the panel dropping the charge current.
>
> So what is the best way to terminate charge on nickel based batteries
> with a variable power source?
I do not know about charge termination, but a diode in series with
the panel prevents the battery from discharging back into a
non-illuminated (or poorly illuminated) panel.
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