Has anyone had any positive experience using rechargeable batteries with wireless mics?
In particular 9V as they are quite expensive.
I’ve tried metal halide in the past with poor results, but I’m wondering about lithium ion.
The big trick is to find a good battery manufacturer that makes batteries that meet your needs. If you are using them regularly, you will want the highest mAH value you can find and won't actually care about discharge issues (which mostly have to do with having batteries sit unused). I don't have any direct experience with 9 volts unfortunately but have had very good luck with MAHA. We use their AAs in several wireless mics at my church and I use them in all my photography gear with great success.