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Battery pack and charger question

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?

--
Chris W
KE5GIX

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Reply to
Chris W
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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)

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

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.

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..

--
Chris W
KE5GIX

Gift Giving Made Easy
Get the gifts you want & 
give the gifts they want
One stop wish list for any gift, 
from anywhere, for any occasion!
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Reply to
Chris W

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

Reply to
Mike Y

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

Reply to
CWO4 Dave Mann

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...

Reply to
Mike Y

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