I have been flying my g20ei for over 10 years. I flew with the original ignition for 3 years before I replaced it because it developed a internal short. There is a lot of info on this ignition here if you care to search.
You would need to give more details to know what vintage ignition you have. Zenoah has more than one over the years.
Here is the ignitions used now (I believe they are RCxel units).
I would just recharge at the field before I went with an RCxel that I modified to the wiring of the original hall sensor.
Yes those Zenoah engineered units were very thirsty. I was happier with the engine after it failed and I replaced it.