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sdowney717 · 24-04-2012, 05:51

Took out the old larger Ni-cad batteries.
There were 7 of them and they are wired in series. Two of these were internally shorted.
Two breakers are in this battery pack.
One breaker goes to the negative bottom pin and is used when pack is put in a charger, this one is slightly smaller.
Other breaker is wired in series with the batteries for a dead short protection.

I used 8 NIMH 2100MAH batteries which I tested and they held power after charging for a week.
You can get 8 AA into this pack as they have a smaller diameter than the original Ni-cad's.
I tore the original tabs from the Ni-cads and I soldered them onto the new NIMH AA. I used a two trigger Weller solder gun on high heat. It needs to be powerful enough to put enough heat into the solder. The negative side takes more heat as the metal case is bigger than the smaller positive post.

I tapped the batteries in 2 groups of 4 side to side and allowed them to offset each other, two layers of NIMH. The breakers sit in the offset hollow ends, one on one end, the other on the other end with the smaller breaker pointing down when looking at it with one side removed. that removed side is the side that has the charge indicator light. Doing it that way allows the 8 batteries and breakers to fit and not interfere with the circuit board. I had to snap off one inner plastic battery spacer on the side as the soldered tab makes the battery pack a little wider.

I also had to lengthen some of the inner wires to make it all fit properly.
The left negative screw terminal on the bottom of the pack needs an insulator or one of the batteries will touch it. I used masking tape of about 5 layers.
Two Red wires are positive and both go to the positive battery post of the last battery in the battery string.

One black and one white wire are negative. The white wire comes from the smaller breaker and the black wire comes from the circuit board. Both get soldered to the lower negative metal post on the bottom of the pack. Negative circuit completes back threw the small breaker to the last battery negative post in the battery string.

So far it is charging and working. I was thinking 8 NIMH instead of 7 would make it work longer. I had read in the technical service manual not to exceed 16 volts and the pack reads 10.5 volts fully charged.

So It can be done and cost me nothing as I had these batteries left over from several years past when they were used in some digital cameras.

senormechanico · 24-04-2012, 07:43

I did a similar thing several years ago with my Icom VHF using old 3v. laptop cells.
The battery pack is ever so slightly fatter, but it still fits into the charger/holder.
Radio works great and has more battery life by a mile.

SoonerSailor · 24-04-2012, 16:47

You are only charging each cell up to 1.31 volts. Good Nimh chargers will typically take a cell up to a bit over 1.4 volts, so you may be undercharging them a bit using that 7 cell charger. How much, I dont know.

Another potential problem relates to the voltage at which the radio stops drawing current from the battery. With 8 cells you are somewhat more likely to reverse charge one of the weakest cells as pack voltage falls. This is will accelerate the failure of that cell, and is even more likely to happen if each cell isnt getting fully charged, as it seems is the case.

Finally, NimH cells tolerate ling term trickle charging more poorly than NiCd.

After all that, everything may be just fine anyway. Good luck with it!

Chip

Lake-Effect · 25-04-2012, 10:04

I just replaced the NiCd cells in an Apelco 510 VHF handheld. After carefully cracking open the battery pack, I saw they were 6 AA-sized, but with tabs. There are lots of AA-sized surplus NiCds around; I found some for $1 each... and it all worked.

Since I replaced NiCds with same, I know that the charger will work fine.

If you're replacing NiCd with a different chemistry cell, the charging may not be ideal, and in rare cases might be dangerous. One option is to just buy a cheap NiMH charger and adapt it to your charging station.

Anyways, a working radio is miles better than a dead one.

hellosailor · 25-04-2012, 13:05

sd, replacing cells and battery packs isn't all that hard but you may have missed a few points and as a result may have issues.

Replacing 7 cells with 8 means the new pack will never be properly charged with the old charger. In addition the radio may be getting too high a voltage and be damaged. Generally, a bad idea to change the voltage of the assembled pack.

The two devices you found may not have been fuses. Typically there is at least one fuse, yes, but also one or two diodes to prevent the battery pack and the charger from conflicting. If you omitted one or both of those, you may find problems charging as well.

Swapping NiCd and NiMh can also cause problems as the voltages and charge routines can be different, and if the new cells have 2x or 3x the capacity of the typical 600mA commercial NiCds that were used (for a reason, they're cheap AND rugged) it may need 24 hours now to get a full charge. That you can usually get away with, if you don't mind the longer charging times that will be required.

But there are more gotchas. The cells with solder tabs have the tabs welded onto them with explosive welding. When you solder to a "button top" conventional battery, at either end, there is a very good chance you have partly melted the rolled-up material inside with some damage and premature failure to come. It is not a good idea to cheap out this way, you really want to buy solder-tab batteries if you want them to work and last.

And there's all sorts of quality in batteries. Some will self-discharge within 30 days, others will hold power for most of a year. Rated capacity doesn't tell you how long it will hold on the shelf.

I rebuilt the pack in my SH VHF mainly because they had discontinued them and I had no time to wait for a commercial rebuild. But The Nicad Lady and Bulldog Battery are two of the places that will do rebuilds for you. Properly, with solder tab premium batteries, and all fuses and diodes kept in place. And very often they are about the same price that new batteries alone would be.

Kudos on the DIY spirit, but if one of those soldered batteries now overheats due to the internal damage from soldering--you might not want to leave them charging while you are out or asleep. I've seen NiCd packs blow up, and it ain't pretty.

**noelex 77** · 25-04-2012, 13:23

These batteries are charged with constant current not voltage, so it's likely that the charging voltage will be unchanged.
The old batteries are likely to be 700mHr so the charging time will increase considerably.
Icom suppled a lot of their early radios with packs of different voltages so the pack voltage is likely to OK as well, but do check they made a 9.6 v or higher pack for this radio.
High capacity no name batteries do not have a long life and are much more fussy about their charging parameters than the old Ni cads so don't leave the radio on charge indefiantly.

sdowney717 · 04-05-2012, 11:43

Radio still working, holds a charge. So far successful.
the rebuilt pack reads 10.3 volts today.
This battery pack has a small circuit board which must function to regulate something?
Before attempting the rebuild, I did put 12 volts directly to the radio portion and it worked. And a google search located a preview of the service manual which said not to put more than 16 volts to the radio.

It would make some sense to allow the radio to work from a 12 volt boat battery in case of extreme distress I think.

the batteries were NIMH of Kodak and Rayovac Energizer brands.
I had 2 Duracells which I could not use as they wont hold charge along with all the blue Chinese ones which are duds. All these batteries are at least 5 years old. The bad batts charge but after a day are drained just sitting.

Anicky · 08-02-2014, 09:35

Message to Lake-Effect from Toronto,

Hi, I must replace the batterie pack from my Apelco 510 vhf. I'm really interested to know how did you "carefully cracked open" the pack. Interesting too, your mention about the charger performance with different batteries. I would put 6 NiMh 1650mAh 1.2V in replacement. Could you please giving me your opinion.
Many thanks!
Anicky (CS36T now in the Açores)

senormechanico · 08-02-2014, 09:48

As an electronic hobbyist, nearly every week I "carefully crack open" battery cases, and all manner of "sealed" cases.
I use a plastic hammer and a sharp chisel along the seams.
Don't hit it hard, just a sharp tap, then move along a bit and you'll see it begin to open up.
BTW, that handheld VHF I mentioned in a previous post in this thread is still working wonderfully.