Rechargeable battery question

[~misfit~]

Once upon a time on usenet John-Del wrote:

On Saturday, April 14, 2018 at 9:57:51 PM UTC-4, mike wrote:
On 4/14/2018 1:42 PM, John-Del wrote:
I have this device which uses 14 AA rechageable batteries. It was
originally shipped from the factory with nicds and a charger.

The instructions show it has two recharge modes switchable from the
front panel; recharge and store. The store is a very low trickle
charge. Because it's from the early 80s, I'm assuming it's just a
current limited charger (dumb charge) as it takes 14 hours to
charge the entire group.

I would have like to install eneloops in it, but anecdotal evidence
suggests they don't like this type of charge, so I'm back at
looking at regular nicads for it.

So, is it true that Panasonic eneloop cells need a smart charger
and does anyone know if anyone is making a quality nicad battery
anymore? In the old days, I'd buy Sanyo nicads and although they'd
often advertise less mah per cell than others, they seemed to last
almost forever.

There are a LOT of variables here.
It would be helpful to know what it is.

Trying to avoid that It's a Teknetics 9000 metal detector. Back
when it was new, it was a high end detector. I don't know where I got
it or even when, but there it is in my collection. My brother lost
some keys last fall and has a pretty good idea where they are. He
was going to buy a detector but I told him I have one so that's what
prompted my inquiry.


Are the batteries in series, parallel, separate supplies?

Series, but in two different banks of 8 and 6. If I feed in a dc
supply on the 8 cell bank, the LCD display comes to life and the
controls affect the display. If I put a supply on the 6 cell bank,
it draws current but the LCD doesn't light. No, I haven't powered
both simultaneously. I will before I order any batteries to confirm
it's working.

Is the OFF power drain really zero?

I think so. There is a physical switch for power.


Is it gonna sit for a long time between uses?

Probably, although these are fun toys and I do have several acres of
uncleared woods on my property to explore. One of my best friends
has a house built in 1798 with an original rock wall and outhouse, so
there's that.


The best strategy is to charge the cells externally in a proper
charger and put 'em
back in when you're ready to use it.

I agree, but one of the banks of batteries had a leakage and several
of the very thin battery contacts have disintegrated away. If I
install batteries in it, it would be far more convenient to not have
to physically remove them for charging.

I may have to rebuild the battery box with new contacts and go with
external charging as you suggest. I was just looking for an easier
way out (which is my defining personality trait...)

Thanks everyone.

If it were mine I'd retro-fit a single battery made from lithium Ion cells
with two buck converters to give your two supplies.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[John-Del]

On Thursday, April 19, 2018 at 9:32:41 AM UTC-4, ~misfit~ wrote:

Once upon a time on usenet John-Del wrote:
On Saturday, April 14, 2018 at 9:57:51 PM UTC-4, mike wrote:
On 4/14/2018 1:42 PM, John-Del wrote:
I have this device which uses 14 AA rechageable batteries. It was
originally shipped from the factory with nicds and a charger.

The instructions show it has two recharge modes switchable from the
front panel; recharge and store. The store is a very low trickle
charge. Because it's from the early 80s, I'm assuming it's just a
current limited charger (dumb charge) as it takes 14 hours to
charge the entire group.

I would have like to install eneloops in it, but anecdotal evidence
suggests they don't like this type of charge, so I'm back at
looking at regular nicads for it.

So, is it true that Panasonic eneloop cells need a smart charger
and does anyone know if anyone is making a quality nicad battery
anymore? In the old days, I'd buy Sanyo nicads and although they'd
often advertise less mah per cell than others, they seemed to last
almost forever.

There are a LOT of variables here.
It would be helpful to know what it is.

Trying to avoid that It's a Teknetics 9000 metal detector. Back
when it was new, it was a high end detector. I don't know where I got
it or even when, but there it is in my collection. My brother lost
some keys last fall and has a pretty good idea where they are. He
was going to buy a detector but I told him I have one so that's what
prompted my inquiry.


Are the batteries in series, parallel, separate supplies?

Series, but in two different banks of 8 and 6. If I feed in a dc
supply on the 8 cell bank, the LCD display comes to life and the
controls affect the display. If I put a supply on the 6 cell bank,
it draws current but the LCD doesn't light. No, I haven't powered
both simultaneously. I will before I order any batteries to confirm
it's working.

Is the OFF power drain really zero?

I think so. There is a physical switch for power.


Is it gonna sit for a long time between uses?

Probably, although these are fun toys and I do have several acres of
uncleared woods on my property to explore. One of my best friends
has a house built in 1798 with an original rock wall and outhouse, so
there's that.


The best strategy is to charge the cells externally in a proper
charger and put 'em
back in when you're ready to use it.

I agree, but one of the banks of batteries had a leakage and several
of the very thin battery contacts have disintegrated away. If I
install batteries in it, it would be far more convenient to not have
to physically remove them for charging.

I may have to rebuild the battery box with new contacts and go with
external charging as you suggest. I was just looking for an easier
way out (which is my defining personality trait...)

Thanks everyone.

If it were mine I'd retro-fit a single battery made from lithium Ion cells
with two buck converters to give your two supplies.
--

The two supplies don't share a common ground.

 

[Jeff Liebermann]

On Mon, 16 Apr 2018 03:01:35 -0700, mike <ham789@netzero.net> wrote:

Turns out that hobby store brass sheet can be cut into battery tabs.
It welds very easily. I wouldn't use it for anything high current tho.

You might want to try H-type nickel battery strips like this:
<https://www.ebay.com/itm/183182559640>
Ideally, you want mostly nickel strips, not nickel plated steel, but
I've managed to make it work. I couldn't find any H-Type pure nickel
strips on eBay.

With an ordinary strip most of the current goes through the strip,
with less current going through the stainless battery can. With an
H-type strip, the electrodes straddle the slot. This increases the
resistance of the strip as the current now needs to go around the
slot. That results in a larger portion of the current going downward
and through the battery can.

I'm not sure using brass for electrodes is a great idea. I've never
tried it. The resistivity of copper and brass are:
copper 1.7*10^-8 ohm-meters
brass 8.0*10^-8 ohm-meters
making the resistance of identical wires roughly 4.7 times higher for
brass.
<http://www.radio-electronics.com/info/formulae/resistance/resistivity-table.php>
If you look at photos of commercial spot welder electrode tips:
<https://www.google.com/search?q=spot+welder+electrode+tips&tbm=isch>
methinks you'll find that most of them are copper, not brass.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Ron D.]

I've had no issues replacing Ni-Cds with Ni-mH for vTech cordless phones. A pack with 3 AA batteries in series. I have extra connectors and wire now. 5-7 year life.

 

[mike]

On 4/19/2018 9:15 AM, Jeff Liebermann wrote:

On Mon, 16 Apr 2018 03:01:35 -0700, mike <ham789@netzero.net> wrote:

Turns out that hobby store brass sheet can be cut into battery tabs.
It welds very easily. I wouldn't use it for anything high current tho.

You might want to try H-type nickel battery strips like this:
https://www.ebay.com/itm/183182559640
Ideally, you want mostly nickel strips, not nickel plated steel, but
I've managed to make it work. I couldn't find any H-Type pure nickel
strips on eBay.

With an ordinary strip most of the current goes through the strip,
with less current going through the stainless battery can. With an
H-type strip, the electrodes straddle the slot. This increases the
resistance of the strip as the current now needs to go around the
slot. That results in a larger portion of the current going downward
and through the battery can.

I'm not sure using brass for electrodes is a great idea. I've never
tried it. The resistivity of copper and brass are:
copper 1.7*10^-8 ohm-meters
brass 8.0*10^-8 ohm-meters
making the resistance of identical wires roughly 4.7 times higher for
brass.
http://www.radio-electronics.com/info/formulae/resistance/resistivity-table.php
If you look at photos of commercial spot welder electrode tips:
https://www.google.com/search?q=spot+welder+electrode+tips&tbm=isch
methinks you'll find that most of them are copper, not brass.

Perhaps that's what I meant by line two of the quoted part...
"I wouldn't use it for anything high current tho..."
Somebody nitpicked my use of the word, "weld" with brass.
I'll rephrase...

One can use an energy pulse directed through hobby store brass
sheet cut into strips
to effect a connection to a cell very easily, but the resistance
is slightly higher precluding use in applications that require
high current, and may pose corrosion issues in unfavorable
environments, otherwise it is easy to do and works well for
many applications for those who don't have sophisticated spot
welders, a supply of the proper tab media or a desire to
'school' the poor fool who made the suggestion with links to basic
principles and value
a working battery higher than nitpicking the
suggestion that someone
use something imperfect in their eyes.
Methinks thou dost protest too much.
Brass is perfectly adequate for a metal detector.

Stated another way...If I didn't have workable alternatives,
there'd be no reason for me to post.
Scientists like perfection.
Engineers are happy when it gets the job done.