Batboard

I have 3 6 rack chargers going on 18 HT600 batteries. The chargers have a charging, complete, and stand by light LED's. After about 20 minutes, the batteries are one by one going into standby - I pull them out and they are VERY Hot. I assume this is a self protection thing for overheating. This shouldnt be overheating like this, should it? Rack unit charger is a NTN4668A. Thanks

My two bits worth:
The Motorola Rapid charger charges at 12X the rated 12 hr current.
Nicads charge at a fixed current, the voltage floats within limit.
The thermistor in the battery pack senses the rapid increase in temperature, and switch to the 12 hour rate.
You are applying so much energy into the battery, eventually the battery becomes charged, so the energy turns to heat.

I do not think that this is very good for long life.
Constant overheating of the cells will cause leaking.
The electrolyte that seeps out of the cell at the seal causes self
discharge, as well as drying out the cell.
Not to mention corrosion of battery contacts.

Remove the battery before it gets hot.
Also bear in mind that a Nicad has about 750 cycles, give ot take.

The nicads are BRAND NEW multiplier batteries.

HI;

If the batteries are getting " to hot to touch" you may have
already damaged the battery.

Also, if the " Contacts " of the charger do not mate properly
with the battery, or if the battery is defective, thare may be
no temp control, and it could mean you are over charging the
batteries.

Best to try one in a Standered Rapid Charger, and see
how it performs there, if it performs OK in a single unit
Raoid Charger, perhaps you may have some Bad Mulit-unit
Chargers.

There is a item you can build to test the slots if you want to
go to all the trouble.


The batteries will get warm to the touch before the Green
LED lamps will light uo.
Monty

Yes it is Normal for the battery to be Hot as Hell in 20 Min.
Especially a Fake Battery.

I have to agree with Bernie and Monty . Your chargers
are probably fine and what you are observing is unfourtunately
a Normal Occurance. 6 Bank Motorola NiCad Chargers are Designed
to be used like on a police force, with 3 shifts, 24 Hours a day, and
the radio is dropped in the charger maybe briefly for 20 min
between each shift. If you do this everyday, In about a year you
will need a new battery. If you leave It cooking in the charger at
the 12 Hour rate, less than a year......

Many Advancements have been made since the Original MX, Saber,
and HT 600 6 Bank Rapid chargers. But If you have one of the
above mentioned classic "oldie but a Goodie" then just be aware
of the overheating the Battery thing. It's a actually Designed that
way, When the Battery gets hot, then it switches over to the lower
charge current. Stupid, but Oh well. Theres a little more to it than
that, but basically thats what happens.

This Little Problem Is more noticable with NON-Factory Batteries.

Also as of late, For Example the Lithium Ion Saber Impress Battery,
the Battery is So smart, It has it's own Charge computer right in
the Battery. So therefor I can leave the Saber in an old Ass 6 Bank
MX Charger w/adapt like Forever. Those Batteries NEVER get Hot
while charging in ANY Charger, Nor are they supposed to.
And I'm sure they make Nicads like that as well. Problem is:
Multiplier Doesn't. At least not that I'm aware of. Factory Motorola
Phone Batteries got Charge Computers in them Also, just for
Reference.

BTW: Will is also aware of this problem, and I believe he has a
solution to it as well. He wants it to start on LO not Hi. It's
a GREAT idea.
I should take mine apart and just put a damn lo-charge , On/Off
switch on it. Since I'm not smart enough to make it start on LO
charge automatically...DOH!! But I could put a switch on it..Hmmmm....

Thanks Matt for reminding me about this.

Yes, we made several mods to the HT600/P200 bank chargers especially those used in the movie industry. Basically changing one resistor and one capacitor per slot. The battery normally gets warm then the charger switches to so-called trickle charge rate but the current is too much and the battery continues to heat up.
Do NOT blame the new Multiplier bats, Stan would get mad!!! it is NOT the batteries' fault.

When I was in Public Safety we ran 3 shifts. We painted the batteries and the corresponding chargers (3) different colors. We made up a color for each of the 3 shifts so at least all of the batteries were getting the recommended 16 hrs. I tried to order standard rate gang chargers from
you know who but was told there was no such item. Gee ?? Would be an ideal item for any agency running 3 shifts 24/7.

My two bits worth:
Back in '71 we had a few customers bring in HT220s with the radio, battery and charge pocket all fuzed together.
Seems that Alaxander had a bad run of thermistors.
Was that ever fun to cut apart.
I think Medicom also burnt up a battery box on a PT.
I do not believe that there is a failure in the gang charger that would cause all pockets to over heat.
My experience with Multiplier was good.

My experience with Nicads is that overcharging is the leading cause of failure, and short life. Next is allowing the battery to completely discharge under load. This causes internal shorts. The short can sometimes be repaired by putting a high current thru the battery with the bench supply.
The larger the cell, the better chance of success.

Battery analyzers may give a good capacity reading, but the real test is to put the battery in your desk drawer for a few weeks and see if it still has a charge.
A note about battery conditioners:
Keep in mind that the cell has just so many cicles in a life time. 700 +.

Monty wrote:...Best to try one in a Standered Rapid Charger, and see
how it performs there, if it performs OK in a single unit
Raoid Charger, perhaps you may have some Bad Mulit-unit
Chargers.

There is a item you can build to test the slots if you want to
go to all the trouble...

Hi Monty, can you cast your mind back to 2003? you sent the above reply.
The question I have concerns the last two lines, what is the 'item' ??
Any info appreciated..

Mike

Will wrote:... we made several mods to the HT600/P200 bank chargers especially those used in the movie industry. Basically changing one resistor and one capacitor per slot. The battery normally gets warm then the charger switches to so-called trickle charge rate but the current is too much and the battery continues to heat up...

Can you remember what exactly the mods were Will ??

Mike

Metradio wrote:Hi Monty, can you cast your mind back to 2003? you sent the above reply.

Mike-

Unfortunately, Monty passed away suddenly in September 2004, as a result of a heart attack.
http://batboard.batlabs.com/viewtopic.php?t=38091

I should have looked to see if he had posted recently..

Mike,

I will repost the componet changes in a couple of days. The info is tucked away at the "lab".

And some after market battery makers had used or still use the incorrect thermistor in the battery packs. I'll post the correct value.

My two bits worth:
The rapid charge rate is 12 times the rated 12 hour charge current.
When the cells are sufficently heated the charger reverts to the 12 hour rate. In theory, the battery is at 80% capacity.

If the battery has no thermistor the red lamp will light however you will be in the 12 hour mode.

The 12 hour rate applies when ever the green lamp is on.
A failed or contaminated thermistor will cause the green lamp to come on immediatly.

The battery will get hot if the battery is left in the charger. The instructions indicate that the battery should be removed after 2 hours.

At one time we handed out a "Battery care and feeding" brochure in the parts department. The art work had batteries popping out of a toaster.

Batteries stored in a charger WILL fail very prematurely.
At one time regular chargers had a "trickle mode" The factory issued a SRN stating trickle charge caused damage to the battery, do not use it.

Constant over heating will cause the cells to leak at the terminals, and eventually fail.
Leaking electrolyte (Potassium Hydroxide) can eat holes in the stainles steel battery cell case by electrolysis, causes self discharge, corrosion of contacts, dryed out cells lose capacity.

Leaking cells can cause corrosion of the contacts and metal components of the radio, or charger.

Use a Phosporic acid product to remove corrosion.
Metal prep as used to treat steel before painting.
Any place that sells painting supplies would have it. Be sure to rinse with water to remove the acid.

There is a test set for rapid chargers, if the test set is not available the
rate change circuit may be tested by placing a battery in the charger, with the bottom removed from the charger for access, pull the thermistor contact away from the battery, the charger should revert to 12 hour mode, green lamp illuminate.

A failed lamp could be replaced with a bright LED with limiting resistor.

Thanks very much Will and Bernie, it is most appreciated.

Mike