/diy/ - Do It Yourself

Hi /ohm/, /g/ here. I bought an old laptop from the early 90s and it takes seven C-type 1.2V battery cells connected in series to get 8.4V voltage total. The cell technology is specified as NiCd, but I don't think those are sold any more. The laptop also takes a 4-pin power supply with two different voltages: 12V and 9.5V. I have no idea which voltage goes on which pin and how many pluses and minuses there are (there is a chance I could find this out by disassembling the laptop, but I'm not very good with electronics so idk), and sourcing an original power supply for this model is pretty much impossible nowadays. Nevertheless, if I somehow happened to come into possession of a working charger, I would like to be able to charge the batteries inside the laptop and not have to use an external charger. My first thought was lithium-ion rechargeable batteries, but those don't seem to be sold in this form factor and voltage specification. The only stuff that matches the specification is nickel-metal hydrate batteries. I can get type Cs with 1.2V and they are rechargeable. The only problem is that I've read that NiMH batteries can only be used in place of NiCd batteries if they will not be charged inside the device. Different charging characteristics will make NiMh cells quickly deteriorate. At least that's what I've read, so I came here looking for confirmation and asking for better ideas if anyone has any. Going with NiMh would necessitate using an external charger, but chances of finding or making a working power supply for this thing are very slim as it is, so it's not a deal-breaker.