question aboutMotorola batteries for JT or HT1000s

Hi...I am a park ranger with a standard police/fire JT1000 Motorola VHF radio. My radio had Motorola NTN7143C and NTN7144A Ni-Cd batteries. They charged happily in a Motorola NTN1174A charger.

I purchased Motorola replacement WPNN4013A Ni-MH batteries. They come with warnings not to use the NTN1174A charger. Their labeling lists using only the NTN1168A charger.

Would a cross pollination (instead of buying a new $140 charger):
A) over-charge the batteries eliciting an explosion if left unattended for more than a month.
B) under-charge the batteries, never allowing them to pass into the fully charged state of adulthood.
C) send the charger into core meltdown all over the table.
D) wicked reduce the long life expectancy of these fine cells.
E) all/none of the above.
F) and more (please explain your answer).

Thank you for your prompt response,
Jerimoth (NH park ranger)

A) is the main problem. I'm really not familiar with that particular battery and charger but the following is true for the general case of charging NiMH with a NiCad charger. The voltage change that the smart chargers use to detect the fully charged condition is much smaller for NiMH than for NiCads. This means that most Ni-Cad chargers can miss the fact that NiMH batteries are charged and continue to charge them at the high rate until the batteries are damaged by heat (could burst or leak). AFAIK, any NiMH charger can charge NiCads without problems.
There are a number of possible solutions. For one thing, most overnight (not rapid or 1 hour) chargers charge at a low enough rate that they will not overheat the batteries. This is normally less than 5-10% of the batteries nominal capacity, or 50-100ma. I've used standard 120ma NiCad chargers to recharge NiMH AAs many times without problems. It is best to have plenty of cooling air flow (put it near a fan or breeze). For $25-30 you can buy a smart NiMH charger - you will have to find one that can mate (or be modified to mate) with the connectors for your battery pack. There have been a number of suitable chargers mentioned in this forum - search for battery charger over about the last 2-3 months. This is listed as an oddball 7.5v 2700ma battery - my guess is its 6 sub C or maybe 6 A size batteries. I believe it was MaHa (see Thomasdistributing.com) that had a nearly universal connector battery charger , I just don't recall the model no. HTH, -RussH

All good info above, and A) is the main problem, yes. Seeing as how RussH did a good job explaining why, I won't rehash it, bout I would recommend that if you are looking for a cheap Moto charger, you could most likely pick one up off of eBay, they have Moto gear by the truckload! I don't know the part number offhand (I'm at work), but the charger I use has a pocket on the front angled rearword at about 45 degrees, and the rest of it looks remarkably like a brick. It works just fine with my ni-cd and ni-mh packs, but it won't do li-ion. You'd need one of the Impres units to do that, and not many of the Moto's use li-ion packs, anyway. Mostly just the new (expensive!) XTS series.

I have seen this charger go for between $30-75, and I believe it retails for about $120.

Chris

Dear Tweek and RussH:
I will look into MaHa chargers and also on Ebay. It's funny, because I've been using one NiMH battery (I also have 2 other Ni-Cds) in my regular charger for a year now, without any problems- it's just that the latest batch came with this particular warning from Motorola. Thanks very much for your help on this. Jerimoth

Ranger J,

If memmory is any good at all, these smart chargers for NMiH are rather involved.

They do an annalysis of the cell or cell pack then select the correct charge current value. The chips calculate the charge state based upon internal cell impedence.

Where I used to work me made exotic radios for the NBC community (Nuclear, Biological and chemical weapons). Some of our clients wanted rechargable batts. I would suggest looking up W&W Assc. in Bethpage New York. They make and market consumer chargers for NMiH LMR (land mobile radio) batts.

Another idea is to look at licence plates that visit your park. Find ones with ham radio call signs. Make pals with these people. Ask those guys what the story is. About 1 in 30 truly knows his stuff and will give you spot on answers like the above dudes. Many of the people in the two way business are hams, and might send you a charger as long as you don't mind if it's scratched or dented.

It's always good to make contact with law enforcment.

Judging by the tone of your letter, you have to buy your own commo gear and the Ranger office is not supplying you with support there. I know that's standard pratice for some small police departments.

Wish I was home to help.

Guys like you are the backbone of public safety and rapid rescue.

For the moment this is the best I can offer.

Good luck
Jack Crow in Iraq.

Ok, while I'm home and looking at it, my charger is a NTN1709A, if you are interested in the model number. Here's a few eBay examples:

One for $50

Currently $38

$79, expensive, but really good pic of the charger...

I've had no problems with this unit, and if you watch eBay, it's likely you could grab one for $50 or so.

As far as using universal chargers to charge the packs, I will mention that hooking up to those little pad contacts can be a pain in the arse. I needed to use my charger/discharger on some to check their performance, and wound up making a betal bracket rig that used the underside contacts (can't discharge through the 4-group for the drop-in chargers) for my needs. Works ok, but it's a pain for anything other than occasional use. I would definately recommend a regular Moto charger, just to avoid that kind of hassle, especially when I'm charging every day! /ubbthreads/images/graemlins/smile.gif

Chris

Re: question aboutMotorola batteries for JT or HT1

Jack...thanks very much for the vote of confidence....even those of us who are paid often volunteer hundreds of hours on SAR in New Hampshire above and beyond, and we basically buy all our own gear. Chris- thanks for the tips, I'll start looking at Ebay for a charger and look at the other sources referenced above. Thanks again, Jerimoth

Re: question aboutMotorola batteries for JT or HT1

Hey Jerrimoth, this is the FAQ page on the charger I was thinking of. It can be reconfigured to adapt to most battery packs.
http://www.thomas-distributing.com/mh-c777plus-faq.htm You can link back to other pages (lots more info) on it from there.

Re: question aboutMotorola batteries for JT or HT1

Hey RussH. Thanks!! Greatly appreciated advice from you and everybody in the forum.