Batt-Bridge questions

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Batt-Bridge questions

Electric Vehicle Discussion List mailing list
 Thanks, for the information
I have been researching & looking at a lot of different Reed Relays.
I understand, a 12V Reed relay coil is needed to be able, to be operated, by the ignition of an automobile's electrical system & that the switched current is only going to be like 20ma.
but, there are so many of different voltages, capacities etc. 
I also, noticed that many even have different ohm rating's listed.
Could you recommend or point me toward a specific relay for this situation or at least what details to look for?

It may be a dumb question but, could a (12V - 1.5Kohm) Reed Relay be used as, or in place of, the 1.5Kohm resistor & as a switch?
Thanks,            Kevin

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Re: Batt-Bridge questions

Electric Vehicle Discussion List mailing list
Kevin Trombley via EV wrote:
> Thanks, for the information. I have been researching & looking at a
> lot of different Reed Relays.

Hi Kevin,

A reed relay is just a small relay. Their contacts are sealed inside
glass, and good because the contacts can never get corroded or dirty.
This makes them especially good for "dry circuit" applications, where
the current or voltage are so low that normal relays can suffer
from contact corrosion problems.

> I understand, a 12V Reed relay coil is needed to be able to be
> operated, by the ignition of an automobile's electrical system & that
> the switched current is only going to be like 20ma. But, there are so
> many of different voltages, capacities etc. I also, noticed that many
> even have different ohm rating's listed. Could you recommend or point
> me toward a specific relay for this situation or at least what
> details to look for?

An easy way is to go to digikey.com and search for "reed relay". It will
be the 2nd item in the "Relays" list. Click "in stock", "12vdc" coil
voltage, and "DPST 2 form A" contact form. That will cut it down to
"only" 15 to choose from. :-)

All of them are rated to switch 100vdc or more. You will have two
contacts in series, so each one will only see half your pack voltage.
Thus a 100vdc part is still good for switching up to a 200vdc pack. Any
will work, but you might as well use the cheapest one (HE108-ND, $2.21 each)

> It may be a dumb question but, could a (12V - 1.5Kohm) Reed Relay be
> used as, or in place of, the 1.5Kohm resistor & as a switch?

No. The relay's contacts go in series with the resistors. The relay's
coil get connected to some point in your 12vdc circuit that will be on
when you want the Batt-Bridge to work.

--
Whether we or our politicians know it or not, Nature is party to all
our deals and decisions, and she has more votes, a longer memory,
and a sterner sense of justice than we do. -- Wendell Berry
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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