dual cell controller
 

I just bought 2 150maH batteries and I am planning to do a dual cell mod. My only question on the subject really is if you have to mod the controller. Most people who have done the dual-cell mod, modified their controller to like givemore voltage when it charged. (I am hooking the batteries up in serial). Is it absolutely necessary to mod the controller,or can i just charge it like twice?

You will need to up the voltage in your controller to charge the 2 cells! Have the batteries for the controller in an external pack or make up a standalone charger. Remember you can't just add the extra batteries to your controller. You will have to modify the circuitry otherwise you are likely to bugger something up. My controller stops working at 4.5V, after that you need to add some voltage regulation to the circuitry. It is by far easier to make a standalone charger with 3 or 4 AA batteries which will be plenty for a dual cell.

There is a thread which might help you out here

Or the most basic charger is connecting 3 or 4 cells straight to your charge pad (after disconecting from the controller).

But there are many different ways depending on what you want. If you are building anysort of charger make sure you have a multimeter so as to test the current you are pushing into the car batt. And never let your car batt get too hot to touch.

I've just got to suggest the "Oval Bullet Clone" remotes here.

Box stock it comes with a 3x AA battery holder, charge base, and transmittter that might already be on your frequency, and you get a parts car. It can also double as a car carry case, modify it to match your car and it'll look trick enough you might be able to get past it being CLONE parts.

A little bit of creative wiring, and you should be all set. You could even be able to redo the charge circuit and have the timer & light still work at the higher voltage.