I need to connect two same high current batteries in parallel. We are toking about two 20A batteries. What kind of connector would do the job?
Coat hanger wire, FTW!
Can you give us more specs for the battery - or a battery datasheet?
You have to be careful that one battery doesn't start to charge the other. To prevent this you should connect them together with diodes. However you do get a voltage drop across them and they will get hot at high currents, so to minimise the voltage drop use Shockley diodes.
These are batteries for RC plane models. They work on 11.1V and can supply up to 20A each.
Are you sure that if I connect them black to black, and red to red they can start charging each other? Even if they are same battery model, size, spec etc.?
Are you sure that if I connect them black to black, and red to red they can start charging each other?
100% yes, you will never get the same voltage on the batteries even if they are identical, the one with the highest voltage will charge the other. A series resistor on each battery can also help in spreading the load evenly between the batteries.