Battery power---Does this "lashup" scare you?

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ken60

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Location
Maine
This series setup of 9 volt batteries was given to me by a niece with the request that I make her a new one as it is dead. It is used to power a control board which runs a number of light bulbs switched on by switches (some type of spring loaded thing that is placed on a chair) that is used to determine who jumps to their feet first in a school quizzing meet.

I have not yet seen (but will before I do anything) the switches/control board. I just wonder how this has never been shorted out and what the result would be if it was. 90 volts DC is pretty potent.



 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Are you sure that is not to cause the students to jump up.:thumbsup: a little jult never hurt anyone. :happysad:
 

rlundsrud

Senior Member
Location
chicago, il, USA
I wouldn't solder the new setup the way this one was done. The heat could cause a battery to explode. I would connect it together using 9v snap on leads, then wire them together in series, this would also simply battery replacement.

I am a little troubled by this being a 90v setup that students will be playing with. I am primarily concerned about injuries sustained from falling or flailing when shocked. You should really check out what they are doing with it before you proceed.
 

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
There is a you tube video showing the arcs and sparks you can make when you put a couple of hundred 9 volt batteries in series.
 

DTLight

Member
Location
Mesa AZ
I'd also be a little concerned about using a 9v battery snap connector as the disconnect for the whole string. It would be really easy to get zapped. Maybe you could the pair of snap connectors with a fluorescent ballast quick disconnect?
 

GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
As long as neither end of the battery bank (or the switches and lights) is grounded, the setup should be pretty safe except for whatever is used for a disconnect. And it should not be disconnected under load.
You would definitely feel 100V DC (although it will probably end up closer to 75 volts as the battery voltage drops with use.)

It is possible that the high voltage is needed to fire a neon lamp rather than to light a domestic 120V bulb, but who knows....

There definitely needs to be a box or at least a cover for the battery stack.
If you end up soldering, if you do it quickly not much heat will end up being conducted along the internal foil to the end battery in the stack. Do not hold heat on it for long (don't use too small a soldering iron so it takes too long to heat up.) Tin the wire ahead of soldering it to the battery.
 

Barbqranch

Senior Member
Location
Arcata, CA
Occupation
Plant maintenance electrician Semi-retired
You don't need to solder the batteries together, you can just snap them into a double row. I knew of some people in physics departments that got all the old wireless microphone batteries from theater arts that were half dead and used them to make low current 450 volt supplies (for demos).
 

n1ist

Senior Member
Location
Massachusetts
Occupation
Principal Electrical Engineer
Maybe they are using neon bulbs? Latches made from dual triodes? It will be interesting to see what the rest looks like.

/mike
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150622-1958 EDT

Some Internet reports indicate that the short circuit current of a 9 V battery may be in the range of 5 A for several seconds. Not a safe choice for a classroom setup.

Consider changing the bulbs to LEDs and a low voltage battery. Possibly a 6 V battery with binding posts. Also could use an electronic current limiter.

What is the exact logic of this circuit?

.

.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I had a 9V battery in my pocket once with some coins. Caught my pant leg on fire and burned the crap out of my thigh. 10 of them in series is very dangerous.
 

Tony S

Senior Member
I had a 9V battery in my pocket once with some coins. Caught my pant leg on fire and burned the crap out of my thigh. 10 of them in series is very dangerous.

Same happened while I was talking to a colleague. The battery pack for his radio was damaged and in the same pocket as his bunch of keys. I noticed the smell of burning before he did.

I quite enjoyed chucking water down his trousers.
 

mgookin

Senior Member
Location
Fort Myers, FL
This series setup of 9 volt batteries was given to me by a niece with the request that I make her a new one as it is dead. It is used to power a control board which runs a number of light bulbs switched on by switches (some type of spring loaded thing that is placed on a chair) that is used to determine who jumps to their feet first in a school quizzing meet.

....

If that is a correct statement, nobody is getting shocked. Pressure sensitive switches are on the seats, kid jumps to their feet, lights come on.

No shocking of kids involved.

This does not need to be done with 90 vdc.

The best service you could provide them is doing it with flashlight light bulbs at 3vdc and teaching them a safer way than having a 90vdc supply around a bunch of kids.
 
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