Looking for a special selector switch...

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Externet
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Looking for a special selector switch...

Post by Externet » Sun May 20, 2012 4:04 pm

Hi all.
Would like to find an industrial selector switch that will hook to four 12V batteries and provide connections

- all in parallel 12 V
- two series/two parallel for 24 V
- all in series for 48 V

No off position needed. There is many rare items out there, perhaps someone knows/suggests one. ~15 Amperes or more would be great.
- Abolish the deciBel ! -

sghioto
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Re: Looking for a special selector switch...

Post by sghioto » Wed May 23, 2012 10:25 am

Externet I would be :o and in :shock: if someone can find that special switch. However it can be produced using a couple of relays. I must have too much time on my hands because I drew up this schematic after thinking about it for awhile. Would have uploaded sooner but my internet was down.
BTW is this for a solar project?

Steve

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haklesup
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Re: Looking for a special selector switch...

Post by haklesup » Wed May 23, 2012 1:55 pm

If you plan to switch a hot 15A load, you either need quite heavy duty relays or don't expect them to last very long.

This should be possible with some creative wiring of a rotary switch, I think at least 3 position 3 pole but I don't have time to work it all out right now. Digikey lists 66 rotary switches in the 10A to 50A contact range with a good selection of 12A switches. all are non shorting but you might actually want a shorting type to avoid dropouts when you switch. If your load is a motor, I wouldn't worry, angular momentum will carry it through any glitches.

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Re: Looking for a special selector switch...

Post by k7elp60 » Wed May 23, 2012 4:44 pm

I would add a fuse in each + lead of the batteries, and every connection to that terminal is after the fuse.
The reason is that the short current current can be many times the load current and it can make connecting wires red hot.
I speak from experience. I once did a circuit that connected two 6V batteries in series for the load and in parallel for charging. I didn't have a fuse on either battery. An error was made will testing and the connecting wires became red hot and my shop was filled with smoke. The batteries were 6V 10Ah sealed lead acid batteries.

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haklesup
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Re: Looking for a special selector switch...

Post by haklesup » Tue May 29, 2012 4:19 pm

I'll also never forget the mini mushroom cloud I made while instantly vaporizing all the insulation on 12 feet of wire connecting a bank of batteries. DC Breakers, Fuses or fusable links are essentially mandatory on high power and even low power battery powered projects.

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Lenp
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Re: Looking for a special selector switch...

Post by Lenp » Wed May 30, 2012 9:05 am

sghioto!

Holy Moley.... Relay Logic !
Hey, I thought I was the only one who still thinks in relays instead of processors. (I really do both)
I still have some vintage rotary steppers and books from Automatic Electric on relay switching fundamentals.
A lost art indeed!

Len
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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Externet
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Re: Looking for a special selector switch...

Post by Externet » Wed May 30, 2012 12:22 pm

Great, Steve. Shows a great amount of involvement and time; it can be a mind twister to come up with the schematic.
It is more for like a 3 speed electric motorcycle. The 'switches/relays' on the market are only for 2 batteries:

http://www.texasindustrialelectric.com/ ... switch.asp

And unable to find one for four batteries.

I have a doubt on your schematic. I understand the drawing as is yields 48V;
----> To energize RL2 coil; RL1 would have to be energized too.
- Abolish the deciBel ! -

sghioto
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Re: Looking for a special selector switch...

Post by sghioto » Wed May 30, 2012 4:37 pm

To energize RL2 coil; RL1 would have to be energized too
That's correct!
With just RL2 energized you would have the top and bottom battery in parallel at 12 volts, in parallel with the middle two which are in series at 24 volts which is NO GOOD. :yuck:

Steve G

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