Hi Ed,
You were kind enough to reply to my post re -Racal RA 6790 info. You
mentioned the batteries are available as replacements. Do you know the
source for them? Your anti-spam id does not allow me to contact you
directly.

Thanks,
Keith, ve3ts

Keith Densmore wrote:

You were kind enough to reply to my post re -Racal RA 6790 info. You
mentioned the batteries are available as replacements. Do you know the
source for them? Your anti-spam id does not allow me to contact you
directly.

I got mine from Battery Outlet in Hampton, VA, since they are a five-minute
drive from my office. Any good battery supplier should have them in stock.
Just take the old one in and ask them to match it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Hi Keith,

I didn't like the idea of exposing my cpu card to another
leaky nicad, so using a couple of wires, I mounted a pair
of AA cells off board. The AA cells hold the memory longer
than the original battery, and the trickle charge is more
in line with what a AA cell can safely handle.

-Chuck Harris

Keith Densmore wrote:
Hi Ed,
You were kind enough to reply to my post re -Racal RA 6790 info. You
mentioned the batteries are available as replacements. Do you know the
source for them? Your anti-spam id does not allow me to contact you
directly.

Thanks,
Keith, ve3ts

Keith Densmore wrote:
Hi Ed,
You were kind enough to reply to my post re -Racal RA 6790 info. You
mentioned the batteries are available as replacements. Do you know the
source for them? Your anti-spam id does not allow me to contact you
directly.

Thanks,
Keith, ve3ts


Hi, Keith -

The Varta batteries for the RA6790/GM are available at www.mouser.com
Mouser part number 672-55615702
Price $6.10

This is a Nickel Metal Hydride cell.
I don't know if it will have less of a leak risk
than the original Ni-Cad used by Racal.

73,
Ed Knobloch

Edward Knobloch wrote:

Hi, Keith -

The Varta batteries for the RA6790/GM are available at www.mouser.com
Mouser part number 672-55615702
Price $6.10

This is a Nickel Metal Hydride cell.
I don't know if it will have less of a leak risk
than the original Ni-Cad used by Racal.

73,
Ed Knobloch

Hi Ed,

I cannot recommend this at all!

NiMH cells don't like being trickle charged. If you want to
charge them at a "trickle" charge rate you need to use a smart
charger that will cut off the current after they have reached
full charge.


-Chuck Harris

Chuck Harris wrote:

NiMH cells don't like being trickle charged. If you want to
charge them at a "trickle" charge rate you need to use a smart
charger that will cut off the current after they have reached
full charge.


Hi, Chuck -
Yes, I agree that one must be careful about using a NiCad charger
with a NiMH battery, the NiMH can be in danger of overcharging.

In the Racal receiver memory protect circuit,
there is a silicon diode in series with a 270 Ohm resistor
from the 5V supply to the 2.4V battery, which means about 7 mA
trickle charge rate. I looked at the Varta site, for a 110 mA-H
button cell (2/3 capacity of the 150 mA-H Racal battery suggestion),
they say either 11 mA continuous trickle or 22mA for 1 year
would be overcharging. So, there should be no problem in the Racal.

73,
Ed Knobloch

Edward Knobloch wrote:


Chuck Harris wrote:


NiMH cells don't like being trickle charged. If you want to
charge them at a "trickle" charge rate you need to use a smart
charger that will cut off the current after they have reached
full charge.


Hi, Chuck -
Yes, I agree that one must be careful about using a NiCad charger
with a NiMH battery, the NiMH can be in danger of overcharging.

In the Racal receiver memory protect circuit,
there is a silicon diode in series with a 270 Ohm resistor
from the 5V supply to the 2.4V battery, which means about 7 mA
trickle charge rate. I looked at the Varta site, for a 110 mA-H
button cell (2/3 capacity of the 150 mA-H Racal battery suggestion),
they say either 11 mA continuous trickle or 22mA for 1 year
would be overcharging. So, there should be no problem in the Racal.

73,
Ed Knobloch

Hi Ed,

There is alot of pressure on the NiMH battery makers to pretend the
NiMH cells are direct replacements for NiCD cells. If you are willing
to accept drastically shortened cell life (compared to NiCD), they are.

What I have found to happen (during my research phase for a series of
rapid chargers I designed for the US Army) is NiMH cells, once they
achieve full charge, will outgas if continued on even a 1/20th C
charge rate. Pressure builds, and the safety valve spits... Soon,
the cell is bone dry, and has no capacity. I found that you could keep
the cells on a 1/100th C rate indefinitely, and it did a good job of
keeping the cells from self discharging... well new cells anyway.

So, a good compromise for a trickle charger is to charge at 1/10th C
for 14 hours, and switch over to 1/100th C. The Racal cannot do this.

-Chuck Harris