Paralleling 9V batteries?

T

T. Ryan

Guest
I need longer battery life than a single 9V provides.

What is the conventional wisdom on wiring two or more in parallel,
particularly since any two could not be expected to have exactly the
same charge?

Advisable or not? If not, any way around it by adding certain passive
components.

Thank you,

Tom Ryan
 
A 9V battery is essentially six watch batteries stacked in a metal can.
It is more efficient and easier to move to six 'AAA' cells than to use
two 9V batteries.
 
"T. Ryan" <ryanelec@transpoint.com> wrote in message
news:irjfs0dtoik0nggv8rqoij3fdn06c1bhfn@4ax.com...
I need longer battery life than a single 9V provides.

What is the conventional wisdom on wiring two or more in parallel,
particularly since any two could not be expected to have exactly the
same charge?

Advisable or not?
Click to expand...
Not! I second the six standard elements approach =)

If not, any way around it by adding certain passive
components.
Click to expand...
Two diodes will do the trick. But you'll loose voltage
(=>power=>efficiency)...

/Anders

Thank you,

Tom Ryan
Click to expand...
 
On Tue, 21 Dec 2004 18:27:51 +1100, T. Ryan <ryanelec@transpoint.com> wroth:

I need longer battery life than a single 9V provides.

What is the conventional wisdom on wiring two or more in parallel,
particularly since any two could not be expected to have exactly the
same charge?

Advisable or not? If not, any way around it by adding certain passive
components.

Thank you,

Tom Ryan
Click to expand...
If the batteries are ordinary alkaline or carbon/zinc types, then
paralleling with no extra circuitry is perfectly all right with no potential
problems regardless of their state of charge.

If the batteries are rechargable, NiCad or Lithium, they can be
paralleled with no extra circuitry if both batteries are new and both are
charged to the same state before being paralleled.

Jim
 
On Tue, 21 Dec 2004 18:27:51 +1100, T. Ryan <ryanelec@transpoint.com>
wrote:

I need longer battery life than a single 9V provides.

What is the conventional wisdom on wiring two or more in parallel,
particularly since any two could not be expected to have exactly the
same charge?

Advisable or not? If not, any way around it by adding certain passive
components.
Click to expand...
A 'good' way is to add a a diode (or "rectifier" depending on
current used) in series with each battery, so the higher voltage (and
more fully charged) battery will provide the most current, and no
current (other than a little reversed-bias diode leakage,
insignificant) will flow from one battery to the other.
If near-full battery voltage or high efficiency is important, the
0.6V drop of regular silicon diodes can be reduced to about 0.2V by
using Schottky diodes.

If this is a one-off project, the above should be fine, but if it's
a production product I would think the solution is a bigger single
battery (I have never ever seen a product that had two batteries in
parallel) or string of cells in series, such as six AAA or AA 1.5V
cells.

Thank you,

Tom Ryan
Click to expand...
-----
http://mindspring.com/~benbradley
 
Mark Jones wrote:
If near-full battery voltage or high efficiency is important, the
0.6V drop of regular silicon diodes can be reduced to about 0.2V by
using Schottky diodes.


I'd like to add that Schottky diodes have significantly higher reverse
leakage current. No such thing as a free lunch. :)
Click to expand...

They can also have more voltage drop than 0.2V when large currents pass.
For ex., an SR304 rated 40V 3A drops about 0.43V with 3A of current.

--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov -- NOTE: Remove "BOGUS" from email address to reply.
 
larwe@larwe.com wrote:
A 9V battery is essentially six watch batteries stacked in a metal can.
It is more efficient and easier to move to six 'AAA' cells than to use
two 9V batteries.
Click to expand...
Hardly easier to change.
 
Batteries connected in series last longer though you're getting less
Ah. The parallel connection drives current through each other when not
operating and this tends to destroy them earlier. You though need to
take into account though the costs of the 6 AAs against the 2 9V's.
 
In article <irjfs0dtoik0nggv8rqoij3fdn06c1bhfn@4ax.com>,
T. Ryan <ryanelec@transpoint.com> wrote:
I need longer battery life than a single 9V provides.

What is the conventional wisdom on wiring two or more in parallel,
particularly since any two could not be expected to have exactly the
same charge?

Advisable or not? If not, any way around it by adding certain passive
components.
Click to expand...
You can get battery holders that hold 6 AA cells and use the same
snap connector as a 9 volt cell.

Philmore BH3634, $1.19 at Frys
(or cheaper at All Electronics).

Radio Shack, for some reason, only sell ones that have 4 or 8 cells.

Mark Zenier mzenier@eskimo.com Washington State resident
 
Ever take apart a nine volt battery? It is six little cells wired in
series.
Nine volt batteries are costlier by the watt-hour than buying cells and
putting them
together in series yourself.
Any cells from AAA to D offer better power to the dollar than the
nine-volt package.
 
in article 1104031707.258059.280280@f14g2000cwb.googlegroups.com,
kellrobinson@yahoo.com at kellrobinson@yahoo.com wrote on 12/25/04 10:28 PM:

Ever take apart a nine volt battery? It is six little cells wired in
series.
Nine volt batteries are costlier by the watt-hour than buying cells and
putting them
together in series yourself.
Any cells from AAA to D offer better power to the dollar than the
nine-volt package.
Click to expand...

Yeah, but the cost of the sockets detract from the savings.
 
Ian Stirling wrote:
larwe@larwe.com wrote:
A 9V battery is essentially six watch batteries stacked in a metal
can.
It is more efficient and easier to move to six 'AAA' cells than to
use
two 9V batteries.

Hardly easier to change.
Click to expand...
 
I read in sci.electronics.design that kellrobinson@yahoo.com wrote (in
<1104031707.258059.280280@f14g2000cwb.googlegroups.com>) about
'Paralleling 9V batteries?', on Sat, 25 Dec 2004:

Ever take apart a nine volt battery? It is six little cells wired in
series.
Click to expand...
NiCd batteries have seven cells. 7 x 1.2 = 8.4, which is considered near
enough to 9 V for marketing.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
John Woodgate wrote:
I read in sci.electronics.design that kellrobinson@yahoo.com wrote (in
1104031707.258059.280280@f14g2000cwb.googlegroups.com>) about
'Paralleling 9V batteries?', on Sat, 25 Dec 2004:

Ever take apart a nine volt battery? It is six little cells wired in
series.

NiCd batteries have seven cells. 7 x 1.2 = 8.4, which is considered near
enough to 9 V for marketing.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
Click to expand...
And the reason that 9 volt batteries are not being used in new designs
is that AA cells offer significantly better power density.
--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
I've seen 7.2 and 8.4V versions, but the 7.2, made from six slim cylindrical
cells is more common.
The 8.4 is seven button cells.

It's pretty much a waste though, to power a 5V system from 9V, especially if
it draws any significant current. Switchers help, but there are low current
ranges where the linears are more efficient than the switchers.
 
On Sat, 25 Dec 2004 23:37:11 -0500, Jon Yaeger <jono_1@bellsouth.net> wrote:

in article 1104031707.258059.280280@f14g2000cwb.googlegroups.com,
kellrobinson@yahoo.com at kellrobinson@yahoo.com wrote on 12/25/04 10:28 PM:

Ever take apart a nine volt battery? It is six little cells wired in
series.
Nine volt batteries are costlier by the watt-hour than buying cells and
putting them
together in series yourself.
Any cells from AAA to D offer better power to the dollar than the
nine-volt package.



Yeah, but the cost of the sockets detract from the savings.
Click to expand...
Only once.
 
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