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.
I use two rechargeable nickel metal hydride AA batteries with a wireless mic. They don't last as long as normal batteries, but I only need it run for two hours without recharging so it works well for me.
I've been having a very good experience with Lithium-Polymer 9V rechargeable batteries in my Sennheiser wireless lapel mic. I was able to buy two batteries and a charger for $50.
Had some bad luck with Shure mics. It may of been defective batteries, but the sound quality seemed not as boosted, and mic cut in/out ever 4-5 minutes. I talked to a more professional sound guy (who does some major setups), and he said not to do it. Just use real batteries.
Hopefully this helps!
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.