There are a couple ways in which a practitioner could check if a Sigil was charged. This would allow the practitioner to know if the sigil can be triggered, activated, or that they have efficiently charged it. The following lists are things you can do in order to check for charges in sigils.
This would be like doing a charging method and then just knowing, because you did the charging method it is now charged. This method of checking primarily relies on philosophical deduction to base whether, or not the sigil has been charged. Either the sigil is charged, or not. A charging method was done on the sigil. Therefore the sigil is charged.
Pragmatism, and Induction Method:
In this method you check to see if the sigil is charged by activating it, and seeing if it works. If it works then it was charged. Then you can use simple philosophical induction in order to repeat the results in other forms of sigils. Due to the fact that if it worked in the past it will probably work in the future. This has charged sigils in the past. I have done the same to this sigil. Therefore the sigil is charged.
After you do a charging method to a Sigil, the sigil will be implanted in your conscienceness, and will be heading back into your sub conscience, so that it can be ready to be activated. You will be able to feel that your consciousness is focused upon the sigil, and is ready to be activated. This will probably be a very subtle feeling that you will have in your mind that is there, but is not very noticeable. This feeling will tell you that this sigil is charged at least in your consciousness, or subconsciousness.
You can use any form of divination method in order to ask a yes, or no question in order to check if the sigil is charged. This would be things like drawing a tarot card or rune for it, and asking the question is the sigil charge. You could also take a pendulum, or dowsing rods, and put it over the sigil in order to get a yes or no answer on if it is charged.
Energetic Feeling Method:
You can pass your hand over the sigil in order to feel if there is energy inside it. In order to do this you will need to understand a little bit on how to feel energy probably from previous experiences of energy work. You will feel more intense energy when you get near the sigil, because it is being stored there.
Spiritual Sight Method:
Sigils are charged objects, so you will also be able to see the energy being emitted from the sigil if you have your third eye open. This will usually be perceived much like an aura, and will look like TV static, colorfully light, or heat rising off concrete. You will probably have to of had some third eye experience before seeing it this way.
Spirit work method
Just because you can’t feel the charge doesn’t mean you can’t ask another entity if it is charged or not. This spiritual entity will be a lot more adept at feeling spiritual energy than you and will be able to tell you if it is charged, or not. Then this insight that they provide you with will hopefully be the answer to your question.