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Rebuilding Your Own Battery Packs

South Hills Amateur Radio Club, Inc. (KS3R) on August 24, 2001
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Rebuilding You Own Battery Packs
By Jim - KA3EBX

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A few years back, I bought a used Yaesu FT-727 dual-band HT. The HT was in great shape, and the original FNB-4A battery packs still worked rather well. I really made out on the deal, since it also included a vox headset, wall charger, and rapid desk charger.

I really loved that desk charger. I could drop one of my spare packs into it, and in just an hour, it was fully charged. It wasn't long before I realized the aftermath of what my shiny new desk charger had done to my battery packs. To put it killed them! I should have
used the wall charger. Sure, it would have taken 14 hours to charge a battery, but at least I would have extended their life.

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Well, to make a long story short, I browsed through several popular Ham Radio catalogs, and found that it would have cost around $60.00
to replace my FNB-4A battery pack. What made matters worse was that I needed two of them. Very depressed, I put my handheld up on
the shelf, and there it remained for the next 3 years.

Later, a friend of mine told me about how he sent his battery packs to a lady in California who rebuilt them with nickel metal
hydride cells. Having raised my curiosity, I asked him for her number. It was pretty late at night, when I jotted down the number, so the next day when I got to work, just for the heck of it, I did a
search for her company on the world wide web: The NiCad Lady,

Here I found all kind of information (including pricing) on all of the types of battery packs she rebuilds. She also sells just the inserts (internally assembled battery cells) which you can install
yourself, if you feel brave enough.

I decided to repair the packs myself, so I called and ordered just the inserts. The inserts cost $40.00, so I ordered two of them. My old FNB-4A packs were rated at 12VDC @ 500 mAh. The new ones would be rated at 12VDC @1.0Ah, twice the capacity!

It took about 5 days for the inserts to arrive. They looked almost identical to the old ones. They were already pre-assembled. All I had to do was remove the old ones, and solder in the new ones. It's a pretty easy task but here's some tips you might find helpful if you decide to do it yourself.

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Although this article pertains to Yaesu's FNB-4A battery packs, many of the following tips should also apply when rebuilding another brand of battery pack.

1. On the top of the FNB-4A battery pack, there is a decal which has been applied over the seam between both halves of the battery pack. Cut the decal with an exacto knife, right along the seam.
Don't remove it! It shows which probe is positive (+) and negative (-).

2. Using a very small flat blade screwdriver, carefully pry apart the two halves of the battery case. It should only be tacked together in a few places with glue. Once the halves are apart, lay them side by side. Be careful not to move them around too much, so that you don't break the wire leads.

3. Using a slightly larger flat blade screwdriver, gently pry the battery pack from the case. You will find that they have been glued to one of the halves of the battery case. The glue is pliable, but take care not crack the case.

4. Once the batteries are loose, unsolder the red (positive) wire, and black (negative) wire from the old batteries. You'll notice that there is also a white wire attached. Unsolder this wire at the bottom of the case. This wire tells the rapid charger which battery it is, so that the charger will apply the correct voltage & current. Since we will no longer be using the rapid charger, we won't need this wire. FYI: The temperature sensor will shut off the charging voltage/current
to the battery if it detects overheating in the cells.

5. Remove the old batteries, and install the new batteries, orienting them identically to the way the old ones were installed. Solder the red
and black wires to the batteries. You'll notice I didn't attempt to glue the new batteries to the case. This is to make it easier to replace the batteries in the future. If you can find some packing material (plastic peanuts are great), and wedge pieces of the material between the sides of the batteries and the case. You might also
wish to lay a flat piece of material on top of the batteries before attaching the remaining side of the battery cover. Using some plastic model
cement, apply a small amount of glue (not a lot,
we want to be able to take them apart in the future) along the groove of the case, where the two halves will mesh. Close both halves together, and wrap a rubber band around the case.

6. Plug the wall charger into the bottom of the battery pack. Using a voltmeter, place both leads on the top terminals of the battery (the ones which connect to the HT). You should
see the battery voltage slowly rise toward +12VDC. Don't be surprised if it reaches around +14VDC. This is normal. Let the battery charge overnight, and by that time the glue will have
cured. Unplug the charger, and slide the pack onto the HT. Using the BATT function, the LCD readout should indicate 12.5V. Remove the pack, and continue charging for the recommended time specified by the battery manufacturer.

Rebuilding your own battery packs is fun, easy & considerably less expensive than purchasing new ones or having them rebuilt for you. They should give you years of trouble-free service. I have received quite a number of emails from fellow hams who have rebuilt their battery packs using this procedure and who have told me they have been extremely pleased with the new performance. Should you have any further questions regarding this article, please feel free to contact me by email at Additional information is available on our club's web site, SHARC-NET, at

NOTE: A word of caution about charging nickel metal hydride batteries: It is strongly recommended that you use a slow method of charging, generally 10% of rated capacity of the cell (ie: a 1200mAh cell should have a charger output of 120mAh), unless you have a "conditioner charger system". Also, due to the increased capacity of the cells, you will have to charge your packs for a longer length of time.
To calculate the appropriate charge time for your battery, use the following equations:

Slow Charge: (cell capacity in mAh/Charger output in mAh) x1.4
Fast Charge: (cell capacity in mAh/Charger output in mAh) x1.5

Member Comments:
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Rebuilding Your Own Battery Packs  
by KV4BL on August 25, 2001 Mail this to a friend!
Hi Jim, and thanks for this interesting and informative article. I have two left thumbs and as such, will probably use the services of the No-Cad Lady or similar company, at least with my current radio (Kenwood TH-79 AD) and batery packs. I have been averaging about 2 years of life with the PB-34's that I commonly use in my radio. I use the Kenwood KSC-14 rapid charger as I use this radio almost daily and frequently don't have time to wait on a 14-18 hour charge. I usually completely discharge the batteries prior to recharging by locking the backlight in the "on" position and tuning to the local NWS channel on VHF and a local (always busy) police channel on the UHF side. This expedites the discharge somewhat. This year funds were short so I went to a local "Interstate" battery dealer who carries all types of batteries and had him repack one of my PB-34's. This was $45 as opposed to the usual $80 for a new PB-34. He was only abe to repack with Ni-Cads and my power availability is the same as before but they do work just fine. The PB-34 is a very challenging design but he was able to do a great job of taking it apart and putting back together. I have two old PB-32's (6v 600mah) batteries which sadly, kenwood no longer makes. These little batteries were great for situations when I didn't need the full 5 watts and portability was a plus. Think I'll send them to the N-Cad Lady and let her do a repack on them. As using the wall charger for the TH-79 ties up the battery AND the radio, would I be ok just charging the NiMH cells in the rapid charger but in the "slow" charge mode? 73, Ray KV4BL
Thanks for the battery rebuilding story.  
by WD8MGO on August 25, 2001 Mail this to a friend!
Thanks for the well written story on battery pack rebuilding. My old but reliable ICOM-32AT battery packs need to be rebuilt and placed back into service.
The only problem is finding the time. I would like to try the newer type of cells described in the article considering I own a MAHA charger.
RE: Thanks for the battery rebuilding story.  
by N3TBK on August 26, 2001 Mail this to a friend!
Jim, great article! I fine that by putting the battery pack in a vice and applying controled pressure on the seams reduces the amount of prying needed with the screw drivers. With repeated rotations of the battery pack and being slow and careful many times the case pops open with no prying. God Bless! N3 The Big Kahuna
Rebuilding Your Own Battery Packs  
by W5DCT on August 26, 2001 Mail this to a friend!
Thanks for the great info Jim. I'm glad to have found a place where you can acctually get people to share information.The article was well written,I learned a good deal from it. 73's Dean'o/KD5JZN
Rebuilding Your Own Battery Packs  
by K9MRK on August 26, 2001 Mail this to a friend!

Hi Jim,

I've been doing this with my old HT's for awhile now
and it's a great idea especially when battery packs
become unavailable for a particular unit. Also have
done it on older cellphones and calculators.

Like to add a couple of comments.

I hear that there are "differences" (though no one
seems to be able to tell me what) in charging metal
hydride cells vs. ni-cads. So if you are rebuilding
an older unit that came with ni-cads, you might want
to stick with them. Same for hydride cells. If anyone
know what those difference are (rate/voltage?) please
drop me a note.

I've found most of these batteries are just normal
AA or AAA cells with tabs. You can get these real
cheap (Ni-cads at least) from model airplane places
like Tower hobby for $10-$15. Often at higher
capacity than the origionals.

I've found one of the best investments you can make
with an HT you intend on keeping for awhile is to get
the accessory alkaline battery pack when available.
No reason you can't put chargable batteries in them
and it makes it real easy to replace cells when they
begin to fail. Also you can always fall back on
regular batteries if you forget your charger at

Mark K9MRK

RE: Rebuilding Your Own Battery Packs  
by KC0JBJ on August 27, 2001 Mail this to a friend!
"...get the accessory alkaline battery pack when available. No reason you can't put chargable batteries in them..."

I beg to differ.

For some HT's there is a big difference. My Alinco DJ-V5 has an accessory alkaline pack. It holds 4 AA cells. At 1.2 volts, nominally, per cell, this gives 4.8 Volts, which is half what the standard Ni-Cad battery pack puts out. Remember Ohm's Law? P=V**2/R, so power out is reduced to 1/4 of what the 9.6V pack can produce.

On the other hand, ICOM did it right with the T2H, supplying the standard Ni-Cad pack as a non-sealed pack, just like an alkaline shell. So not only can you replace the cells easily when they wear out, but individual cells which go bad can also easily be replaced. Good job ICOM.

Another drawback of some alkaline shells if you want to use rechargeable cells is there is no provision for recharging them in the pack. You must take them out and recharge them in a separate charger, then remove them again and replace them in the shell. What a hassle! Again, not so with the T2H, and in an emergency you could remove the depleted Ni-Cads and replace them with Alkalines. My solution with the Alinco was to buy an aftermarket 9.6V Ni-MH pack and switch off.

So before you jump to buying the accessory alkaline shell just to put Ni-Cad or Ni-MH cells in it, check the capacity and whether it is wired to charge cells in it. Some are, some are not. Of course you can always use the alkaline shell for its intended use, emergency backup power.
RE: Rebuilding Your Own Battery Packs  
by N9EYL on August 27, 2001 Mail this to a friend!
I had an old Azden 2M HT just gave to me recently because replacing the battery pack would probably cost more than this old HT was worth.

I priced the loose solder tab nicads at radio shack for 5.99 for two batterys. The HT needed 8 total. So that was about 24 dollars for just the batteries. And then I would have to solder it all together and not have it look like a piece of junk. Anybody try soldering these things together without the right tools?

Anyway, I went to "Batteries Plus" to get a house battery replaced on my RV and got to talking to the guy about my HT. Inside of a half hour he tack welded together a nicad pack for me with my original connector with the correct two voltages of 4.8 and 9.6 volts. He epoxyed it all together for me and shrinked wrap it in nice original looking blue shrink wrapping for get this about 23 dollars including the tax.

These DC tack welders that look like a small drill press are the right tool for soldering these things together not a soldering iron. Unless of course you have the solder tab nicads but then they don't look as professional as these did.

Anyway, I was impressed.

Rebuilding Your Own Battery Packs  
by WB2WIK on August 28, 2001 Mail this to a friend!
Very nicely done article! Thanks for writing it, and sharing this information so well.

One comment, though: The article makes it sound like you're convinced "rapid charging" destroyed your cells. While that may be true, that isn't the norm. Possibly they were too old to take the strain of rapid charging, or the charger itself had some defect.

I use a SIMA (brand) "intelligent rapid charger/conditioner" purchased for the purpose of rapidly charging the NiCd pack on my Sony 8mm camcorder, and it works beautifully. I recharge the Sony NiCd packs in <40 minutes, and have done so literally hundreds of times (typically 2-3 times each week, for about two years), and the Sony packs still work exactly as new. So, I started using it for my Kenwood HT NiCd packs, from a TH28A and a TH315 (these are older units, but just examples), and enjoy the same results. I have not used "slow charging" in a very long time, and my Kenwood packs are showing no signs of wear or degradation.

Although the SIMA product is not an amateur radio accessory, I see something similar is offered by MAHA <> as their model MH-C204F.

73 de Steve WB2WIK/6
Rebuilding Your Own Battery Packs  
by W5ZIP on August 30, 2001 Mail this to a friend!
Good article, and one that is needed by most ops over a period of time. I have replaced all of my nicad packs over the years. "Experts" tell us that nicads don't develop a memory. I have flown R/C for 40 years and I can testify that they do! That is why I now use the NIMAH batteries (nickel-metal-hydride). If you use nicads for a short period of time then consistantly recharge them fully you are asking for problems. As a rule, discharge them completely once per month then recharge. With NIMAH you do not have that problem! You normally just have to extend the charging time if you are using your old 50mah charger.
In one response, alkaline holders were mentioned... keep in mind that alkaline batteries (new) carry a voltage of 1.5 VDC. Nicads and NIMAHs carry 1.2 VDC.
As an added glue will hold your packs together, both the batteries and the case. It also comes off fairly easy the next time you replace.
For those of you who want to save money visit
I was amazed to find the 1600mah AA with tabs for $2.00 plus shipping.
Works for me!
Rebuilding Your Own Battery Packs  
by W8TIF on August 30, 2001 Mail this to a friend!
Great article, Jim! If your desk charger was to be "smart" enough to sense just what battery pack you had inserted for re-charging, why did it "kill" your battery packs? It sure shouldn't have, unless your battery packs were already on (or near) their last legs.

I've used an iCOM BC-35 desk charger for years and years and it has never caused a battery pack failure due to over-charging or under-charging. My NiCads, however, are getting pretty old and some of them are a little wobbly.... I'll take your advice and get some "refills" from the NiCadLady!

Karl K - W8TIF
McKinney, Texas
RE: Rebuilding Your Own Battery Packs  
by KH7EY on October 2, 2001 Mail this to a friend!
Good topic! Anybody have any details on opening a Kenwood PB-39 battery pack?
thanks, bob KH7EY
Rebuilding Your Own Battery Packs  
by VE7BOV on February 20, 2004 Mail this to a friend!
Hi Jim
I have read on several occasions that the charger for your Yaesu and also the FT-209r kill batteries.
I feel there is a disign flaw in your charger and it overcharges your batteries and causes them to vent.
Once the seal has been broken nicads dry out and the owner decides the drop-in charger is at fault and killed the battery. Why not get in there and change things to make the charger charge at a Rate the batteries like. Sounds like a wall charger is the best thing for your battery. I worked for 19 years at a place that had Motarola handhelds and a 4 bay charger, I got the batteries after they failed if I wanted them. I must have taken a dozen of them home over the years. Guess what they left them in to long, the cells vented and by the time I got them you could see white fuzz at the posative lead. in all those years I think I got perhaps 3 usable cells. WATCH YOUR CHARGE TIME AND CURRENT.

The FNB-17 yaesu battery is not easy to open. Batteries are hotglued in on both sides. It takes patients and extremely slow prying to get them open.
I have done 2 of them now holding NIMH 2/3A cells.
From I rebuilt a Kenwood 12 Volt
PB-12 using AA nicads 7 cellsl from Surplus Cell Phone batteries, lower voltage but I can use the Wall charger and it works great. I had to saw 3 of the edges of the kenwood battery packs and then pry them apart. Used a Doller Store fine hacksaw about 6" blade, took time but was worth it. On the PB-12 leave the internal resister in other wise you will over charge the battery.

Does any one know how to open Icom BP-83 batteries I believe they can be rebuilt with AAA nicads.

Looking for surplus nicads try THE ELECTRONICS GOLD MINE. IN Arizona. They have 4 AA nicads in a pack for less than a $1 a piece. cheeper in quantity.

another thing if you are trying to solder tabs do your self a favour and get batteries and solder them together with Very wide SolderWick, I forget the number I used. The Tabs on individual nicads when you solder the tab to the other battery will not allow some cases to close properly. not a good Idea for FNB-17 It takes more of a blob of solder to do the job.

I have had problems with second source Nicad Packs from Batteries America they do not hold a charge very long. both ICOM BP-83 equivalent and Yaesu FNB-10. I will be rebuilding the FNB-10 but need help on how to open the Icom BP-83. I have been told to slam the bottom of it against a concreat floor a few times. any other Ideas. I do not have any AAA rechargables yet so hopefully someone will have other Ideas.

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