If you can open-up the battery pack, you will find a number of (probably) AA sized batteries within. It is most likely that one - and it only needs to be one - of the batteries has gone down. By down, I mean that it has gassed out all its liquid, and has either gone dry or crystallised inside the cell. If you can find out which cell or cells it is, you can replace them.
In last months PBO, it was stated that you cannot/shouldnot solder onto Nicads or NiMH batteries. You can - if you do it properly and carefully. First get yourself some Low Melting Point solder, clean the top and bottom of the batteries with fine wet and dry. The solder will take very quickly with very little heat transfer to the battery. I have just done this with my Braun shaver using NiMH batteries - and its working better than before. I use a gas soldering iron. Another of the good things to come out of Ireland, along with the beer!!
I have similar problem with an Icom IC-M1 Euro, currently being checked out by techies. This does not use pencil batteries. Apparently Icom now use Lithium/Iron batteries with much better charge life, but still awaiting verdict on whether such unit available to fit mine.
It was a brand new pack that's discharging. However I've just discovered that the mains adaptor is putting out 18v instead of 12. Suspect its damaged the pack. and a very expensive pack it is to. I did try to get the old one open but its a Navico Axis 200 radio and the pack is sealed plus theres a clip device that holds it in the radio which as far as I can see can only be removed by breaking it.
If you fully discharge lithium Ion batteries they go pop and thats the end of one of the cells. Discovered that with a portable pc. So best thing to do with them is to keep charging them unlike Nicads which have to be discharged before charging.
Had a discusssion with Simrads technical support dept this morning, very helpful and knowledgeable. recommended discharging battery with a light bulb 12V and then recharging. The new batteries need this complete discharge/recharge cycle to get up to full capacity.
I've had an Apelco VXL 501 hand held for about 5 years now and the battery pack wasn't holding its charge. I carefully split the casing with a penknife and found 9 AAA sized NiCd cells inseries. I bought another nine NiMH from my local Maplins shop (about £30) and soldered them together as the originals were. I then superglued the case back together and Bingo! Works a treat. The battery life is MUCH longer than it ever was (like about 36 hours on receive mode, squelched) and I don't have to completely discharge it before re-charging (no memory effect with NiMH). As a proper replacement pack was over £70, I'd recommend this to anyone!
As previously reported, my Icom was losing charge after few hours.
Took it into 'The Shortwave Shop' Christchurch Dorset (01202 490099) & they checked it out. It now apparently will operate for 12 hours+ on transmit.
They continuously discharged & charged it over a week & suggested that I fully discharge & fully charge on a regular basis to keep charge level in memory up.
In Model shops and Maplins etc. the batterys are supplied with tags specially for soldering ..... you shouldn't solder standard NiCds or NiMh that do NOT have tags ... it causes gassing of the electrolyte and also can block the 'vent' in the positive 'button', plus its difficult to get silver soft solder to 'stick' to the plain cell.
Go for the NiMh tagged cells and save a packet on replacement packs.
For those interested there are speciality discharge / charge packs from Model Shops that were designed for Model Radio Control sets etc. You can get something like in a Maplins etc.
On ships we used to do the lightbulb trick with the Walkie Talkies .... BUT you must NOT take the pack down till the light goes out ! If you do that you risk 'overdischarging' the pack and then not charging it back again.
An old trick that works ..... if you find a cell is not charging, take a full charged cell and quickly connect across the duff one for a split second .... it sounds horrendous, but battery factory told me that one. REMEMBER ONLY A SINGLE CELL - not a pack !!!! It apparently breaks the crystal structure that forms inside NiCds and restores charge ability. You then repeatedly charge and discharge and you should bring it back to near full working capacity......