I depends on the charging circuit. Most ni-cad circuits are designed to trickle charge at 0.1C where C is the mAh rating of the battery. You can do this indefinitely without harming the battery.
If you try and charge a ni-mh battery at that rate, once it is fully charged, you will damage it. Safe trickle charge rates are on the order of 0.004C so it would be impractical to unconditionally charge at such a low rate. Typically, ni-mh battery chargers terminate their charging using a delta V/t or a delta T/t (where V is voltage, t is time and T is temperature).
Benchmarq (by Texas Instruments) makes a whole series of charge ICs like the bq2002t that I have used in the past but the simple thing would be to simply replace the battery with a similar one.
Steve
--- In Simmons_Drums@yahoogroups.com, vout@... wrote:
>
> Hi,
>
> I've recently had to repair several bits of Simmons kit including SDS6 and SDS7 units - these had both suffered from battery leaks, luckily not too severe.
>
> I think the original batteries were ni-cad and I am wondering what would be a suitable substitute type that does not leak. There are ni-mh, also li-ion types available, I think some other type as well.
>
> My knowledge of battery technology is practically zero, so looking for some informed opinion here. I was intending to use ni-mh batteries, would that be ok?
>
> Cheers, vout
>