9V rechargeable batteries and chargers?

[Joerg]

Thanks. Yes, BH is a good place, we've bought from them before. But
LiPoly is only 7.4V nominal for the usual stack of two. That's a tad
marginal for our mikes.

LiPoly: a few% to 100% = [3.6V .. 4.2V]

That's 8.4V fully charged for two cells in series; 50% (nominal) for a
two-stack would be 7.8V.

That could just work. Not a whole lot of margin but maybe enough.
However, we have ordered the 300mAh NiMH batteries already. I had looked
at LiIon solutions but what scares me is that someone could unknowingly
stick this into a regular charger. Probably the same danger with LiPoly.

There is a protection circuit in there, usually, but all this typically
comes from China. And a guy in Germany has seen first hand what can
happen there. A thermistor in a battery pack was economized out of the
design and replaced with ... a 10k resistor.

 

[Joerg]

A though if you have time for the extra work:
2 x 10440 lithiums can be packed in the same space as a 9v. Use one of
those regulated (microchip make them) capacitor voltage doublers +90%
efficiency (plus a bug cap for output surge current), a diode so it can
be charged through the "normal" terminals and a 2.5mm recharge terminal
in the base (plus build your own lithium recharger) and your done - 9v
rock steady 350 - 400 ma hours.

I can already see the headlines "Pastor's trousers caught fire"

They do not have charge terminals and there isn't really any space to
put charge terminals. These are pro-quality metal case units. Wireless
mikes also don't have surge currents. They typically draw a steady
50-60mA because it's FM transmission.

 

[Joerg]

I can already see the headlines "Pastor's trousers caught fire"

[snip]

That could be quite effective if it happened during a sermon on Sodom
and Gomorrah ;-)

Or a genuine fire and brimstone sermon

 

[[email protected]]

David Eather wrote:

ehsjr wrote:
asdf wrote:
On Wed, 11 Jan 2012 10:36:31 -0800, Joerg wrote:


Not these. They are crammed with electronics, all uC controlled with
battery diagnostics and the whole enchilada. If I had a schematic I
could repair them. And I did repair one where somthing in the primary
switcher had blown. But those things don't seem to last and there
comes
a point where repairing gets old. Also, it is absolutely no fun to
find
out Sunday morning at 7:30am that all the batteries are dead and
worship
service begins shortly. This happened three days ago :-(

They might be old NiCd chargers that fail to spot the Delta V on newer
NiMh cells, so that they keep charging forever until you switch them
off or the safety timer, if any, turns them off.

On 9V cells charge is trickier because you have one Delta V point for
cell, which means that if the charger is sensitive it may stop
charging when the first cell reaches the charge, and if it's not
sensitive it could overcharge the battery, frying it in the long time.

For 9V batteries I'd always go with a current limiter (C/10, max C/5)
plus timer.
Don't know about 9V batteries, but for 6 cells NiCd or NiMh I've
had great success with C/10 then taper to ~C/40 when Vset is
reached. I tried some 9V rechargeables way back when and gave
up on them. Maybe they're better these days?

Nowadays all chargers are, unfortunately, fast chargers. Because fast
sells. I wish there was a li'l switch that allowed slow charge which
would be perfectly fine in places such as churches. But there usually
isn't :-(

A though if you have time for the extra work:
2 x 10440 lithiums can be packed in the same space as a 9v. Use one of
those regulated (microchip make them) capacitor voltage doublers +90%
efficiency (plus a bug cap for output surge current), a diode so it can
be charged through the "normal" terminals and a 2.5mm recharge terminal
in the base (plus build your own lithium recharger) and your done - 9v
rock steady 350 - 400 ma hours.

I can already see the headlines "Pastor's trousers caught fire"

[snip]

That could be quite effective if it happened during a sermon on Sodom
and Gomorrah ;-)

Or a genuine fire and brimstone sermon

I didn't think the Lutherans were into hellfire and damnation.

 

[[email protected]]

Then you must have a very rich church

I buy AAs at Lowes for $.20 each. I know times are tough, but there has to be
at least a buck in the collection plate. ;-)

But seriously, then this kind of stuff happens: We open our church to
other groups, mostly for free and to commercial groups for a very modest
fee or donation. Then they use a mike and put it back. Battery still in
there. Now is that still good? Did they use it for a 10min pep talk or a
1-1/2h presentation? Did they turn off the mike during breaks or just
put it under the pulpit?

Take it out and pitch it, no matter how long it might have been used.

Same for our own activities. Often a mike is used for just a few
minutes, for example during the children's message, or announcements, or
stage plays. In a church it is next to impossible to tally up all that
so you end up throwing away lots of good 9V alkalines to the tune of a
buck fifty each. We can't do that.

So don't.

Now if the mfg had been smart and included a wireless batt status
feedback to the audio booth this would be _much_ easier. But they
didn't. Hint to all wireless mike manufacturers: Do that!

The display probably cost too much.

 

[Joerg]

I buy AAs at Lowes for $.20 each. I know times are tough, but there has to be
at least a buck in the collection plate. ;-)

How much do you pay for good quality 9V alkaline batteries? Duracell or
similar.

Take it out and pitch it, no matter how long it might have been used.

That is costly with 9V cells and also not very good environmental
stewardship. God gave us the earth and everything that's on it but he
did not put a spare into the trunk in case we screw up with this one.

So don't.

Hence our need for a good NiMH and charger combination

The display probably cost too much.

Nope, and that is the sad part. The Sennheiser system already has a
fairly luxurious display, backlit, the whole nine yards. It shows the
frequency, the RF level and the audio level, so one alphanumeric string
and two horizontal bar graphs. It would have been a piece of cake to add
a battery alert but ... they didn't :-(

Even on the old Shure Marcad they could have done it. I mean, what's so
difficult about letting the diversity lights blink? Or let the red audio
overdrive LED blink. They are already there, costs nothing.

 

[Joerg]

David Eather wrote:

ehsjr wrote:
asdf wrote:
On Wed, 11 Jan 2012 10:36:31 -0800, Joerg wrote:


Not these. They are crammed with electronics, all uC controlled with
battery diagnostics and the whole enchilada. If I had a schematic I
could repair them. And I did repair one where somthing in the primary
switcher had blown. But those things don't seem to last and there
comes
a point where repairing gets old. Also, it is absolutely no fun to
find
out Sunday morning at 7:30am that all the batteries are dead and
worship
service begins shortly. This happened three days ago :-(
They might be old NiCd chargers that fail to spot the Delta V on newer
NiMh cells, so that they keep charging forever until you switch them
off or the safety timer, if any, turns them off.

On 9V cells charge is trickier because you have one Delta V point for
cell, which means that if the charger is sensitive it may stop
charging when the first cell reaches the charge, and if it's not
sensitive it could overcharge the battery, frying it in the long time.

For 9V batteries I'd always go with a current limiter (C/10, max C/5)
plus timer.
Don't know about 9V batteries, but for 6 cells NiCd or NiMh I've
had great success with C/10 then taper to ~C/40 when Vset is
reached. I tried some 9V rechargeables way back when and gave
up on them. Maybe they're better these days?

Nowadays all chargers are, unfortunately, fast chargers. Because fast
sells. I wish there was a li'l switch that allowed slow charge which
would be perfectly fine in places such as churches. But there usually
isn't :-(

A though if you have time for the extra work:
2 x 10440 lithiums can be packed in the same space as a 9v. Use one of
those regulated (microchip make them) capacitor voltage doublers +90%
efficiency (plus a bug cap for output surge current), a diode so it can
be charged through the "normal" terminals and a 2.5mm recharge terminal
in the base (plus build your own lithium recharger) and your done - 9v
rock steady 350 - 400 ma hours.

I can already see the headlines "Pastor's trousers caught fire"

[snip]

That could be quite effective if it happened during a sermon on Sodom
and Gomorrah ;-)

Or a genuine fire and brimstone sermon

I didn't think the Lutherans were into hellfire and damnation.

True, but some of the sermons can be downright scary yet be an exact
replica of what the bible says.

Some of our family are Catholic. Once we had a longer chat over the
phone and they asked about the difference to us. "Well, for example, we
Lutherans do not believe in purgatory because it's not in the bible" ...
"Oh, ya well, they've long since discontinued that!"

I was almost laughing myself off the chair

 

[josephkk]

Thanks. Yes, BH is a good place, we've bought from them before. But
LiPoly is only 7.4V nominal for the usual stack of two. That's a tad
marginal for our mikes.

Anyhow, we just ordered this:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817355041
http://www.newegg.com/Product/Product.aspx?Item=N82E16817355040

If they really hold the 300mAh minus 20% marketing glitz factor or
whatever we'd be really happy.

The other thing one has to keep in mind at non-techie places such as
churches is the occasional mishap. Like when someone sticks a LiPoly
battery or LiIon into a regular charger and *POOF*

Come back around with a status report after you have used them for a few
months.

?-)

 

[Joerg]

Come back around with a status report after you have used them for a few
months.

Yep, I shall try not to forget to do that

Probably more than 1/2 year though because you can't tell a premature
battery capacity drop before that. I neither believe nor expect the 1000
cycles most marketeers claim. If we get 100-200 out of them I'll be
happy. Capacity and the reliability to accumulate a true full charge is
much more important to us.

 

[Jasen Betts]

Martin Riddle wrote:

LiPoly: a few% to 100% = [3.6V .. 4.2V]

That's 8.4V fully charged for two cells in series; 50% (nominal) for a
two-stack would be 7.8V.

That could just work. Not a whole lot of margin but maybe enough.
However, we have ordered the 300mAh NiMH batteries already. I had looked
at LiIon solutions but what scares me is that someone could unknowingly
stick this into a regular charger. Probably the same danger with LiPoly.

A typical 9V-shaped NiMH rechagable outputs a nominal 7.2V

there may be some brands constructed with 7 pancake cells in them,
but AIUI mut use 6 AAA cells.

eg: http://ecx.images-amazon.com/images/I/51JD362JMPL._SS500_.jpg
(fine print lower left corner)

If they will run off those rechargables Li-poly will be an improvemenr.

 

[Joerg]

Martin Riddle wrote:
LiPoly: a few% to 100% = [3.6V .. 4.2V]

That's 8.4V fully charged for two cells in series; 50% (nominal) for a
two-stack would be 7.8V.

That could just work. Not a whole lot of margin but maybe enough.
However, we have ordered the 300mAh NiMH batteries already. I had looked
at LiIon solutions but what scares me is that someone could unknowingly
stick this into a regular charger. Probably the same danger with LiPoly.

A typical 9V-shaped NiMH rechagable outputs a nominal 7.2V

Nowadays they are pretty much all 8.4V except for some Maha/Powerex and
maybe other brands with 9.6V.

there may be some brands constructed with 7 pancake cells in them,
but AIUI mut use 6 AAA cells.

eg: http://ecx.images-amazon.com/images/I/51JD362JMPL._SS500_.jpg
(fine print lower left corner)

If they will run off those rechargables Li-poly will be an improvemenr.

Those are really sub-par these days and our mikes do not run on 7.2V
NiMH batteries. Must be at least 8.4V. There are some 9.6V versions as well.

I'd love LiPoly because of the mAh but afraid someone will screw up with
those but putting them in a standard charger. We even had people throw
NiMH away because they thought they were primary cells.

 

[Mike]

Joerg,

It seems many of the problems are caused by the manufacturer's choice of
battery style. He needs ~8 volts to operate the mike, but the required
current will quickly drain the battery. So you are faced with an
expensive battery that has a short operating life and minimal number of
recharges before it has to be discarded.

How about using a clip-on microphone with the cable going to a belt-
mounted transmitter. The battery could be an external package mounted on
the belt with an extension cord to the transmitter.

That way you could enlarge the battery pack to whatever is needed, and
use whatever battery type gave the best performance for the money. This
would allow you to use much less expensive batteries that will stand up
to the heavy use.

Perhaps you could use a battery that has a simple method of monitoring
the state of charge. For example, I believe that a sealed lead-acid shows
the state of charge by simply measuring the voltage at the terminals. But
I don't know if SLA is available in the small size needed.

I went to a recent LTspice seminar by Mike Engelhardt. He used a similar
arrangement with a belt transmitter, but I didn't think to enquire what
kind of microphone he used. His speaking tours cover a lot of countries
in a very short time, so he doesn't have much chance to keep the
batteries charged. Maybe you could ask him what kind of setup he uses and
see if that would help fit your needs.

Mike

 

[Joerg]

Joerg,

It seems many of the problems are caused by the manufacturer's choice of
battery style. He needs ~8 volts to operate the mike, but the required
current will quickly drain the battery. So you are faced with an
expensive battery that has a short operating life and minimal number of
recharges before it has to be discarded.

How about using a clip-on microphone with the cable going to a belt-
mounted transmitter. The battery could be an external package mounted on
the belt with an extension cord to the transmitter.

That's what we have. Shure and Sennheiser belt packs plus lapel
microphones. Also two handhelds of same technology.

That way you could enlarge the battery pack to whatever is needed, and
use whatever battery type gave the best performance for the money. This
would allow you to use much less expensive batteries that will stand up
to the heavy use.

Perhaps you could use a battery that has a simple method of monitoring
the state of charge. For example, I believe that a sealed lead-acid shows
the state of charge by simply measuring the voltage at the terminals. But
I don't know if SLA is available in the small size needed.

Under a pastor's robe that would be a major bulge. Unless the pastor is
a heavy-set guy (ours isn't) people could think he's got a
concealed-carry gun

I went to a recent LTspice seminar by Mike Engelhardt. He used a similar
arrangement with a belt transmitter, but I didn't think to enquire what
kind of microphone he used. His speaking tours cover a lot of countries
in a very short time, so he doesn't have much chance to keep the
batteries charged. Maybe you could ask him what kind of setup he uses and
see if that would help fit your needs.

Usually speakers like him use the setup provided by the hotel or other
event venue. For example, you cannot legally use most US systems in
Europe and vice versa.

The new Sennheiser belt packs are much better because they (finally!)
figured out that AA cells are much more efficient. The new series can
offers over 6h or uptime. However, those things are expensive and we
can't just toss >$2k worth of gear. The new charger is only $40, much
better deal. If that together with 8.4V/300mAh batteries still won't be
good enough we'll try the LiPoly variety that Martin suggested. But only
after major training so nobody ever plugs these into a regular NiMH charger.

 

[Mike]

Joerg,

[...]

That's what we have. Shure and Sennheiser belt packs plus lapel
microphones. Also two handhelds of same technology.

Then just get a 9V battery clip and bring it out to your own battery
pack, mounted on the same belt. Your choice of AA, C, D, etc.

[...]

Usually speakers like him use the setup provided by the hotel or other
event venue. For example, you cannot legally use most US systems in
Europe and vice versa.

No, he has his own system, including a Class D amplifier and speaker. I
asked if he had any problems going through airport security. I believe he
said the only problem was when he used his own amplifer, they always
questioned it. But that stopped when he got a small commercial unit.

The seminars last from about 8:00 am until I think 3:00 pm or so. Then he
has to catch a plane to go to the next city. He arrives late, so he
barely has time to check in and get some sleep, then back at it again the
next morning. A terrible, grueling schedule. I asked him how on earth
does he manage to keep his energy up. His answer was medical grade
caffein!

The new Sennheiser belt packs are much better because they (finally!)
figured out that AA cells are much more efficient. The new series can
offers over 6h or uptime. However, those things are expensive and we
can't just toss >$2k worth of gear. The new charger is only $40, much
better deal. If that together with 8.4V/300mAh batteries still won't
be good enough we'll try the LiPoly variety that Martin suggested. But
only after major training so nobody ever plugs these into a regular
NiMH charger.

A 9V battery clip with a sold shell cost very little on eBay. I got some
- they are very good quality. You can hook them up to anything you like.

I would recommend coating the contacts with a light film of petroleum
jelly (Vaseline). This removes any surface oxidation and leaves a thin
film that lubricates the contact and prevents grime and oxidation from
forming. It reduces the contact resistance by a factor of ten and
stabilizes it. I have measured the results and can confirm it works. It's
an old radio engineer's trick from the 1930's, taught to me by the
engineers at radio station CFRB in Toronto, Canada. Works great on all
kinds of electrical connections - SATA, memory, flashlights, toys, etc.

Mike

 

[Mike]

[...]

Usually speakers like him use the setup provided by the hotel or
other event venue. For example, you cannot legally use most US
systems in Europe and vice versa.

No, he has his own system, including a Class D amplifier and speaker.
I asked if he had any problems going through airport security. I
believe he said the only problem was when he used his own amplifer,
they always questioned it. But that stopped when he got a small
commercial unit.

Just for confirmation, here is a picture I took while he was setting up
for a seminar. You can see the overhead projector is turned on, and I
think he is extending the legs on a stand for the notes. As you might
imagine, he has done this many times, so it is very smooth and there is
no wasted motion. He can do it in his sleep.

http://static.panoramio.com/photos/original/64983445.jpg

I only wish I had taken more pictures. He is a fantastic individual, and
he has done an incredible job getting SPICE to new users. Along with
Helmut, these two are my vote for the most influential engineers of the
century.

Mike

 

[Joerg]

Joerg,

[...]

That's what we have. Shure and Sennheiser belt packs plus lapel
microphones. Also two handhelds of same technology.

Then just get a 9V battery clip and bring it out to your own battery
pack, mounted on the same belt. Your choice of AA, C, D, etc.

Oh, our pastor and others would hate that. Plus it'll wreck the whip
antenna on the belt pack in no time. They have to wear the pack inside a
pocket. Also, there are no battery clips, it's a nifty slide-in bay with
a sturdy metal latch.

[...]

Usually speakers like him use the setup provided by the hotel or other
event venue. For example, you cannot legally use most US systems in
Europe and vice versa.

No, he has his own system, including a Class D amplifier and speaker. I
asked if he had any problems going through airport security. I believe he
said the only problem was when he used his own amplifer, they always
questioned it. But that stopped when he got a small commercial unit.

Well, I guess where there is no plaintiff there will be no judge. Don't
let the French equivalent of the FCC hear that

The seminars last from about 8:00 am until I think 3:00 pm or so. Then he
has to catch a plane to go to the next city. He arrives late, so he
barely has time to check in and get some sleep, then back at it again the
next morning. A terrible, grueling schedule. I asked him how on earth
does he manage to keep his energy up. His answer was medical grade
caffein!

Yikes! That's an almost perfect recipe to work yourself up towards a
heart attack. And at Mike young age those are often fatal.

And I agree, Mike ought to be given a Nobel prize or something. He has
done more for electronics engineering than nearly anyone else.

A 9V battery clip with a sold shell cost very little on eBay. I got some
- they are very good quality. You can hook them up to anything you like.

I would recommend coating the contacts with a light film of petroleum
jelly (Vaseline). This removes any surface oxidation and leaves a thin
film that lubricates the contact and prevents grime and oxidation from
forming. It reduces the contact resistance by a factor of ten and
stabilizes it. I have measured the results and can confirm it works. It's
an old radio engineer's trick from the 1930's, taught to me by the
engineers at radio station CFRB in Toronto, Canada. Works great on all
kinds of electrical connections - SATA, memory, flashlights, toys, etc.

Even the Chinese know. The cheap meters I got for the road all had that
on the wiper contacts. Probably Confucius told them

 

[Mike]

Mike wrote:

Yikes! That's an almost perfect recipe to work yourself up towards a
heart attack. And at Mike young age those are often fatal.

I'm sure he was joking. I used to travel a great deal on business, and the
adrenaline can keep you going for a while. But his tours are unbelievable.

And I agree, Mike ought to be given a Nobel prize or something. He has
done more for electronics engineering than nearly anyone else.

Amen

Mike

 

[Joerg]

[...]

The new Sennheiser belt packs are much better because they (finally!)
figured out that AA cells are much more efficient. The new series can
offers over 6h or uptime. However, those things are expensive and we
can't just toss >$2k worth of gear. The new charger is only $40, much
better deal. If that together with 8.4V/300mAh batteries still won't be
good enough we'll try the LiPoly variety that Martin suggested. But only
after major training so nobody ever plugs these into a regular NiMH
charger.

One way to deal with that is to throw out every NiMH charger

Of course we'd do that. However, you know how it goes. Someone swaps a
battery during a bible study and puts the other in his shirt pocket.
Drives home, darn, should have stuck this into the church charger. When
the family gets there next Sunday it'll be too late. Oh wait, the
teenagers have some sort of charger up there and that has those 9V
battery contacts ... *POOF*

 

[josephkk]

Usually speakers like him use the setup provided by the hotel or other
event venue. For example, you cannot legally use most US systems in
Europe and vice versa.

The new Sennheiser belt packs are much better because they (finally!)
figured out that AA cells are much more efficient. The new series can
offers over 6h or uptime. However, those things are expensive and we
can't just toss >$2k worth of gear. The new charger is only $40, much
better deal. If that together with 8.4V/300mAh batteries still won't be
good enough we'll try the LiPoly variety that Martin suggested. But only
after major training so nobody ever plugs these into a regular NiMH charger.

If you add LiPoly to the mix, please be sure to use a very different
connector. It will help reduce oopsies.

?-)

 

[Joerg]

If you add LiPoly to the mix, please be sure to use a very different
connector. It will help reduce oopsies.

And that's the problem, it is impossible to do so. It must be the
regular 9V battery contacts or they won't fit the mikes.