Battery pack and charger question

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Chris W - 29 Mar 2006 07:55 GMT

I have a Kenwood PB-39 9.6V NiCd battery for my Kenwood TH-G71. It has
5 contacts on it. On the side that is in contact with the radio, there
are 2 contacts labeled + and - so I will call them R+ and R-. On the
back of the pack there are 3 contacts labeled, -, T and + I will call
them B-, BT, and B+. I have a universal smart charger that will charge
anything from a 1 to 30 cell NiCd or NiMH or similar voltage lithium and
lead acid battery packs.. If I connect that charger to the B- and B+,
it does nothing. Same if I hook it to any combination of the 3 contacts
on the back. It has a way to sense if it is hooked to a battery and if
the polarity is correct before it will start charging. If I hook the
charger to R+ and R- it will charge, to do that I have to take the
battery off the radio. BTW the charger is an Orbit Microlader made in
Germany, marketed to the RC airplane industry. There is something that
won't let the charger work right between the battery and those contacts
on the back. I want to know what. So here is the experimenting I have
done. With the battery in a stable state (two days since it was charged
and no load has been applied).
Voltage measurements.
R+ and R- = 10.562V
B+ and B- = 10.526V
B+ and BT = 10.517V
B- and BT = 0.000V

R+ and B- = 10.560V
R+ and BT = 10.551V
R+ and B+ = 0V
R- and B- = 0V
R- and BT = 0V
R- and B+ = 10.527

All of these measurements were repeatable with in +/- 0.001V

Resistance measurements.
resistance between leads on DMM 0.30 ohms

R- and B- = 0.30 ohms so really zero.
R- and BT = 8.9K ohms
R+ and B+ = meter display flashes 0L and the auto ranging graph at the
bottom bounces back and forth.( not sure what that means)

Other than the resistor between the negative side of the battery and the
BT terminal what does this all tell me if anything? And more
importantly is there anyway to trick my charger to work with the
contacts on the back of the battery?

Signature

Chris W
KE5GIX

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Mike Y - 29 Mar 2006 17:53 GMT

Sounds like your battery has temperature detected charging. That's really
the
best way to go. I have a pulse charger for NiCads and it has a temp sensor
that you lay against the side of the pack. You pack appears to have it
built in
to work in the unit. There might also be some 'protections' on the external
contacts.

It sounds like your RC charger is a generic pulse charger. Or even less,
just a current limited charger. Some of the chargers I've seen like that
use
high current pulses when they start up, then fall back to a constant current
trickle charge. But if you don't know how your charger works...

Just hook up the charger across the main battery terminals that feed power
to the radio. Do NOT hook up to the 'other' ground on the 'T' side. I
suspect
that .3ohm reading is NOT essentially zero!

Yep, sounds like you're going to have to take the battery out of the
radio...

Or buy the 'real' manufacturers charger that the radio 'drops into'.

Mike

> I have a Kenwood PB-39 9.6V NiCd battery for my Kenwood TH-G71. It has
> 5 contacts on it. On the side that is in contact with the radio, there
[quoted text clipped - 40 lines]
> importantly is there anyway to trick my charger to work with the
> contacts on the back of the battery?

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Chris W - 29 Mar 2006 17:48 GMT

>Sounds like your battery has temperature detected charging. That's really
>the
[quoted text clipped - 6 lines]
>It sounds like your RC charger is a generic pulse charger. Or even less,
>just a current limited charger.

Nothing generic about this charger. You can hook it to you computer to
chart the charge curve. It has 4 different charge programs for NiCd and
NiMH batteries, it will charge every battery type I have ever heard of
and one I have never heard of (Lithium Tadiran)

>But if you don't know how your charger works...
>

I do know how each charge mode works. None of them will do anything
with this battery on the back terminals.

>Just hook up the charger across the main battery terminals that feed power
>to the radio. Do NOT hook up to the 'other' ground on the 'T' side. I
>suspect
>that .3ohm reading is NOT essentially zero!
>

Well if I put the 2 meter leads on a clean copper plate about 1/8"
apart, I get a reading of .25 ohms which is a difference of .05 ohms a
dirty contact could make up for more than that. so I am willing to get
that there is nothing between the negative side of the battery and that
terminal. Whatever is there seems to be between the positive terminal
of the battery and the positive contact on the back of the radio since I
can't get the meter to give me a reading of resistance between the 2
positive terminals, not a reading of zero, it just flashes the screen
and won't give any reading at all. I also couldn't get my meter to give
a capacitance reading between any pair of terminals, I didn't try to
test capacitance on any terminal pairs that had a voltage though.

>Yep, sounds like you're going to have to take the battery out of the
>radio...
>
>Or buy the 'real' manufacturers charger that the radio 'drops into'.
>

Since the battery is an almost worthless 600mah, I'm not going to waste
money on a fast charger dedicated to that battery. I have a battery
pack on the way that I think I will use as an external battery, and rig
up a set of powerpole contacts in the alkaline battery pack for that
radio to connect the external battery to..

Signature

Chris W
KE5GIX

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give the gifts they want
One stop wish list for any gift,
from anywhere, for any occasion!
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CWO4 Dave Mann - 29 Mar 2006 18:16 GMT

>>Sounds like your battery has temperature detected charging. That's really
>>the
[quoted text clipped - 48 lines]
> up a set of powerpole contacts in the alkaline battery pack for that
> radio to connect the external battery to..

Here are a couple of thoughts, perhaps there is a limiting resistor inside
the battery pack. I found one in an Alinco pack that I took apart.

You can still use the individual cells -- I am sure you know that already --
I make it a habit to buy battery packs of all sizes, etc at yard sales. I
disassemble them in my shop and see what is inside. Most of the time the
AA size NiCad cells go directly to a charger and then into the kitchen
drawer where they are used for everything from TV remotes to the answering
machine.

The only problem with some of the battery packs is that the terminals are
not soldered by spot welded. I solve this problem by using a solder drop
on top of the cut off terminal attachment and then file it so the batter
top and bottom look like a regular AA or D or C or what ever.

Sure this is all a bit of labor, but I now have enough batteries to power
the city of Nashville, TN, if only I can find a way to hook it up and
charge for it HI HI

73's

Dave
N4CVX

~~~~~~~~~~~~~~~~~~~~~~~~
Study History - Know the Future

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Mike Y - 29 Mar 2006 22:06 GMT

Well, if it's a 2-terminal interface to your charger, there's only so many
ways
it can work. I'm not putting down your charger. I'm just saying that you
have
to meet the criteria the charger requires to charge effectively. And since
the
charger doesn't have a thermal sensor...

If you really don't care about the battery pack, and the terminals on the
rear
don't HAVE to stay the way they came from the factory, but are easy to
access, consider breaking open the pack and making the two rear terminals
hardwire to power and ground so that you CAN easily attach to your charger.

But keep in mind that the pack may not stay as cool 'in' the radio as it
would
outside the radio...

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Electronics Forum / Basics / March 2006

Battery pack and charger question