Upgrading NiCad to NiMH with ∆V charger

[ericmark]

I have some old Icom radios which have battery packs of NiCad cells which are charged in an old delta voltage battery charger. These chargers detect the drop in voltage as the battery becomes fully charged then reduce charge rate to trickle for next half hour then turn off. The charger does 6 batteries at a time. At the moment 3 cells are set to discharge first and 3 cells to just top up charge. There is a link to select mode.

Now all these batteries are getting old and now really need the cells changing. However the old NiCad cells are now only for military and medical use and we need to upgrade to NiMH cells. However the point where the voltage drops once the battery is fully charged with NiMH cells is not as defined as with the old NiCad cells. So although with new cells likely the charger will work as before as the battery becomes older the cells may not trigger the change to trickle charge.

So once upgraded there are two questions.
1) Should I disable the discharge before re-charge as the NiMH cells don’t have the chemical memory problems associated with NiCad cells?
2) Should I enable the discharge before re-charge as the delta Voltage device may not work and so it will rely on the time out after so many hours so should start from scratch?
3) Find out the circuit diagram and modify charger to trickle charge only and not use delta voltage detection method. (Not sure if I could anyway)
4) Leave as it is not worth the hassle of changing.

The charger is an Icon CM60 and is used with a U16 radio converter to ham band.

Sorry about the odd title seems this site does not know what delta sign is?

 

[flameport]

Leave it as it is - but replace the cells while the NiCd type are still available.

 

[ban-all-sheds]

Icom are still in business - why not ask them?

Alternatively you can find people selling NiCd batteries and packs for them.

 

[ericmark]

My local rally has been and gone so will have to look around for another one. There is a guy from Midlands who sells the cells so will need to find his contact details.

I have same problem with FT290R but at least with that one I can remove the cells and charge with a standard C cell charger. I had not until another post on this forum even thought about the different voltage curve. So need a supply for 2/3 lenght AA cells to fit in original cases. I have one case only that will take AA cells. I also have same problem with other radios.