Can I run the same EA on the same time frame with 2 different charts of the same pair?
To make this question even simpler I have EA #1
I open EUR/USD Attached to 15min Chart EA #1
Open Another EUR/USD
attach it to that 15min chart also?
Will it not open 2 postions?
If you run the EA with the same settings it will [B]most probably[/B] open 2 (same) positions as it is [B]most probably[/B] based on the chart on which it is running. However, there are a lot of “if” here so why don’t you just test how it works on a demo account so we don’t make blind guesses. And please come back with a feedback 
The thing is I cant run two EA’s at the sametime on Mt4 during a backtest. lol
The important part isn’t if your EA will open a trade on each chart, it probably will - If your EA however engaged a trail, or some other variable close, that is the problem. If it opens a trade and sets a SL and TP, then you should be fine - however, from my little bit of experience, setting a fixed TP instead of a auto engaging trail is leaving money on the table. And if your EA can differentiate between which trade it initiated, and you have different trail settings for each timeframe, then you can run into issues.
I agree with eyedfondue, to be totally sure that your EA is working correctly you need to set it to run on a demo account for a few weeks and then run a real account for at least a month. I would use a very small lot size and a very small account sise first so that you are not rising too much if the EA goes crazy!
Oh well in this case I believe you expect too much from MT4, lol. However, if you are using the strategy tester why don’t you just run a test with your EA and then simply double the result you get, if the settings of the EA remain unchanged during the both tests. It should give you the result you need if my logic is correct. After all you are running the same EA on the same chart. So even if you run the second test with different EA settings you could add the result to the first one. I got lost 