Or perhaps the range that you could experience with different manufacturers
of 9v batteries...
Thanks
Lewis
co...@ee.unb.ca
I've seen new batteries go above 10 amps (on a Beckman DVM
w/20A full scale range).
--
((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
William Beaty bbe...@microscan.com
Software Engineer http://www.microscan.com
Microscan Inc., Renton, WA 425-226-5700 x1135
Sent via Deja.com http://www.deja.com/
Before you buy.
I find that value very difficult to accept.
Sadly, I have no 9-Volt transistor batteries on hand to run a test,
but I'll get some and post a follow-up.
My measurement of short-circuit current from 1-1/2 Volt AA and C cells
ran between 800-ma. (AA) and 1.0 Amp (C).
Based on this, I'd estimate the peak current output of a 9-Volt transistor
batter (alkaline type) to be at best 500-600 ma., but I'll get a fresh one
tomorrow and post the measurement result. (Actually, I'm going to buy
6 of them anyway, because my smoke detector batteries are due for
replacement.)
Harry C.
> Based on this, I'd estimate the peak current output of a 9-Volt transistor
> batter (alkaline type) to be at best 500-600 ma., but I'll get a fresh one
> tomorrow and post the measurement result. (Actually, I'm going to buy
> 6 of them anyway, because my smoke detector batteries are due for
> replacement.)
FYI, 9V Duracell (fresh from Costco, 2003 "best-before" date) gave
(briefly) over 5A output, before polarization began to take its toll.
1 or 2 "Kirkland" AA cells in series gave ~4.7A, it decreased less
quickly.
Interesting info. I put a 1N4004 across a fresh 9V battery for 30 seconds
and it smoked a bit but survived (no heatsinking). If you want
bullet-proof reverse polarity protection, a 3A shunt diode would be a
better bet.
--
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany "The Journey is the reward"
sp...@interlog.com
Fax:(905) 271-9838 (small micro system devt hw/sw + mfg)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>The renowned Harry H Conover <con...@tiac.net> wrote:
>
>> Based on this, I'd estimate the peak current output of a 9-Volt transistor
>> batter (alkaline type) to be at best 500-600 ma., but I'll get a fresh one
>> tomorrow and post the measurement result. (Actually, I'm going to buy
>> 6 of them anyway, because my smoke detector batteries are due for
>> replacement.)
>
>FYI, 9V Duracell (fresh from Costco, 2003 "best-before" date) gave
>(briefly) over 5A output, before polarization began to take its toll.
>
>1 or 2 "Kirkland" AA cells in series gave ~4.7A, it decreased less
>quickly.
>
>Interesting info. I put a 1N4004 across a fresh 9V battery for 30 seconds
>and it smoked a bit but survived (no heatsinking). If you want
>bullet-proof reverse polarity protection, a 3A shunt diode would be a
>better bet.
Until someone puts in a NiCad :)
-- John Devereux
> Interesting info. I put a 1N4004 across a fresh 9V battery for 30 seconds
> and it smoked a bit but survived (no heatsinking). If you want
> bullet-proof reverse polarity protection, a 3A shunt diode would be a
> better bet.
Umm... no Spehro. I really got bitten by that.
Used a (large, IN4000-size) diode to protect
against reverse polarity from a 9v battery in
a handheld instrument. I tested it here many
times with ordinary PP9 zinc-carbon batteries.
Shipped 50 pieces. Customer returned about 15
or 20 as 'not working on receipt' and I had
to bear the cost of replacing the 7106 chips.
Turned out he was using rechargeable batteries
and I suppose that if there is enough current
then there is sufficent volts across the diode
to divert some into the chips. :-((
And note this.....
1. Those 9v battery connectors are so damned obvious.
2. Our enclosed leaflet said 'switch OFF when
replacing batteries'.
3. I used a 3-pin connector for the thermocouple
input, so that the power was OFF when the T/C
was not plugged in.
And STILL that customer managed to blow up chips.
--
Tony Williams.
> Tony Williams.
Hi Tony,
Forcing a short circuit is a lousy way of protecting a user-accessible
device. I laugh when a fail-safe method has the potential of generating
arbitrarily large currents. What if the user decided to hook up a car
battery to get longer battry life?
Can you put the diode in series with the load? It would drop the voltage
slightly, but a battery-operated device needs a wide supply tolerance
anyway.
Best Regards,
Michael R. Monett
mailto:mkmo...@hotmail.com
Previously, Tony Williams wrote in sci.electronics.design:
{ In article <Na1v4.30221$c7.8...@news1.rdc1.on.wave.home.com>,
{
{ --
{ Tony Williams.
{
--
Pat Ford email: pf...@qnx.com
QNX Software Systems, Ltd. WWW: http://www.qnx.com
(613) 591-0931 (voice) mail: 175 Terence Matthews
(613) 591-3579 (fax) Kanata, Ontario, Canada K2M 1W8
> Hi Tony,
> Forcing a short circuit is a lousy way of protecting a user-accessible
> device. I laugh when a fail-safe method has the potential of generating
> arbitrarily large currents. What if the user decided to hook up a car
> battery to get longer battry life?
> Can you put the diode in series with the load? It would drop the voltage
> slightly, but a battery-operated device needs a wide supply tolerance
> anyway.
This was 20-odd? years ago Mike.... One of the
(many) lumps that some of have to make in order
to 'make our bones' in this job.
I originally did a parallel diode to extend the
life of a zinc-carbon battery as long as possible.
And yes, it was later changed to a series-diode.
The only problem there was deciding on how many
Kv to rate the piv of the diode for. :)
--
Tony Williams.
[snip]
A Polyfuse might work well here.
Cheers
--
Keith Wootten
>Based on this, I'd estimate the peak current output of a 9-Volt transistor
>batter (alkaline type) to be at best 500-600 ma., but I'll get a fresh one
>tomorrow and post the measurement result.
>
> Harry C.
>
A new Radio Shack 9 Volt rectangular battery, part # 23-875, measured
with a Fluke model 73 multimeter shows a peak short circuit current of over 6
Amps for a second or two and over 5 Amps for several seconds after that.
Jim
> Umm... no Spehro. I really got bitten by that.
> Used a (large, IN4000-size) diode to protect
> against reverse polarity from a 9v battery in
> a handheld instrument. I tested it here many
> times with ordinary PP9 zinc-carbon batteries.
> Shipped 50 pieces. Customer returned about 15
Ouch!!
> or 20 as 'not working on receipt' and I had
> to bear the cost of replacing the 7106 chips.
> Turned out he was using rechargeable batteries
> and I suppose that if there is enough current
> then there is sufficent volts across the diode
> to divert some into the chips. :-((
Ok, it *might* have worked had there been a small
resistor in series with the chip power supply. At 5A
there will be >1V across a 1N400x... that's
the SC current for an alkaline cell, not a NiCd. A
51R resistor would drop only 50mV at the 1mA a 7106
draws, but limit the reverse current to about 10mA.
It's 20-20 hindsight, I know. 8-(
> And note this.....
> 1. Those 9v battery connectors are so damned obvious.
> 2. Our enclosed leaflet said 'switch OFF when
> replacing batteries'.
> 3. I used a 3-pin connector for the thermocouple
> input, so that the power was OFF when the T/C
> was not plugged in.
> And STILL that customer managed to blow up chips.
8-( Probably did other things too, they sound like what we refer to as
"blacksmiths" (no offense intended to actual skilled blacksmiths..).
I've been burned by variations on this in the past... with
thermocouple inputs, I finally had to accept that a certain percentage of
them will meet an untimely end with 240VAC connected across them, there is
really no practical way to protect them at a reasonable cost. Best you can
do is a series fuse or fusible resistor and back-to-back diodes, and that
still has to come back to the factory to be repaired, so it it's scarcely
better than nothing (but with lots of extra parts to fail etc.).
I'm writing up a somewhat related protection scheme for a magazine, I'll
post the URL (months from now) when it shows up in print, if anyone's
interested.
> Forcing a short circuit is a lousy way of protecting a user-accessible
> device. I laugh when a fail-safe method has the potential of generating
> arbitrarily large currents. What if the user decided to hook up a car
> battery to get longer battry life?
I think this method is OK if you can guarantee it doesn't cause any secondary
problems. For a car there should be a line fuse, so hopefully the user learns to
plug things in the correct way because otherwise he has to fork out for a fuse
each time (aluminium foil fuse users can get what they get). Even with a fuse
I've seen PCB tracks taken out because the undersized tracks can't cope with the
fault condition.
> Can you put the diode in series with the load? It would drop the voltage
> slightly, but a battery-operated device needs a wide supply tolerance
> anyway.
The drop of the series diode is a bit of a bummer, especially if you have
regulators on board, the effective battery life starts to diminish
unnecessarily. For devices that have a fairly low run current, you can put a low
value resistor in series with the battery and keep the reverse diode at the
circuit side. Here, the voltage drop across the resistor is low during normal
operation and the fault current is kept to a safe level.
Regards
Rob
[...]
> This was 20-odd? years ago Mike.... One of the
> (many) lumps that some of have to make in order
> to 'make our bones' in this job.
>
> I originally did a parallel diode to extend the
> life of a zinc-carbon battery as long as possible.
> And yes, it was later changed to a series-diode.
> The only problem there was deciding on how many
> Kv to rate the piv of the diode for. :)
> Tony Williams.
Heh heh!
Lewis Cobb <co...@ee.unb.ca> wrote in message
news:89hrth$iv5$1...@malakbel.unb.ca...
> Hi and thanks for reading this posting. I'm wondering if anyone has some
> data on what the short circuit current is for a typical 9v alkaline
battery?
>
I've noted in my Psion that the internal resistance of a charged alkaline
PP3 = 3 ohms.
This was from H&H, I think.
9V / 3R = 3A
Paul.
Hi gang,
Some nicads are capable of supplying a lot more current.
Has anyone posted the story about the World Model Train Racing
Championship in Germany? A drag race to see who can send a toy train
down a track the fastest.
The winner got almost 5 hp each from two 1.5-inch diameter motors
running 3,682W, or 94A at 60V using 40 Panasonic P 180 SCR-Z Nicads.
You can see their ultimate toy at:
http://www.manufacturing.net/magazine/dn/archives/2000/dn0207.00/dn0207.00/03ult.htm
>"Lewis Cobb" <co...@ee.unb.ca> wrote in message
>news:89hrth$iv5$1...@malakbel.unb.ca...
>> Hi and thanks for reading this posting. I'm wondering if anyone has some
>> data on what the short circuit current is for a typical 9v alkaline
>battery?
It must be a lot more than I used to think. Dropped a used one from
the smoke detector at home into my pants pocket while installing a
replacement.. Something felt awfully hot in there after a while,
apparently the 'old' battery had been shorted by some keys and still
had enough in it to heat the battery.
You might try connecting a 10A meter across a known good battery
for a short time. It will cook the battery but at least you will
have your data.
Roy Schmaus
http://www.ee.ualberta.ca/~schmaus/
If you have money to burn than take two 9V batteries and plug them into each
other. Talk about emergency hand warmers!
Regards,
Boris Mohar
Viatrack Printed Circuit Designs
>>You might try connecting a 10A meter across a known good battery
>>for a short time. It will cook the battery but at least you will
>>have your data.
You may even blow out the meter's 10+ A fuse! I've even seen miniature button cells that have more than
10A short circuit current.
Al