Here is some third party information about two batteries/one receiver including some discussion on the topic of do you need a diode or not. I'm no battery expert but this fellow is from the battery industry.

http://www.rcbatteryclinic.com/

click on "Parallel Operation = Reliability and Flight Time" on the left hand side.


Also, on the NO BS Batteries webpage (my understanding is this fellow used to work for SR Batteries before breaking out on his own), there is a frequently asked questions section. Here is the link with some good info and I have cut and pasted the specific recommendations he makes about not needing a diode.

http://www.hangtimes.com/rcbattery_faq.html

Here's the quote:

"Q: Ok, that’s pretty kewl.. but my instructor sez I need diode protection or the packs will cross-talk or try to charge each other.

A: Sorry.. your instructor has been gaffed by Under-Informed Magazine Columists or the Battery Mis-Information Committee of your local fields Wives Tale Tag Team. There is NO need for diodes or a 'backup' circuit board (something else that adds weight, complexity and another possible failure point) and in fact there's no flight-safety significant energy transfer between packs at different charge levels.

You can test this yourself.. just plug a discharged pack and a fully charged pack together in a Y-Harness and check the two packs the next day.. You’ll find the system will pass a load test if checked through the ‘Y’, and you’ll also find that less than 20% of the charged packs energy has been ‘used’ by the discharged pack when you separately cycle-test the two of them. Next, consider that your average flight is 10-12 minutes, not 24 hours! The mythical "Energy Transfer Between Packs" scenario is simply NOT a flight safety issue and checking both packs before flight with a loaded ESV will certainly 'pick up' a weak pack before you fly it anyway!"


Hope this is helpful to you.

Dave Michael