Diodes when using parallel RX batteries

[frank killan]

Hi everyone.

 Is it ok to use two RX batteries for redundancy (each having its own switch harness) without blocking diodes. If I have to use diodes is it ok to fit them before the switches as this would not entail ripping my installation apart.

                                                                                          

                                                                                 Thanks in anticipation.

 

                                                                                                    FK

 

[Martin Harris - Moderator]

If you use diodes you'll need 5 cell packs as they will drop @ 0.7 volts. You already seem to appreciate the need for separate charging of the individual packs.

 

I've used parallel packs without any problems after considering the advice on Red  Schofield's website which seems to have disappeared unfortunately  but see here for an archived version (the rest of his battery clinic is also located on the site).

 

Red was the Design and Applications manager of General Electric's battery division (and Gates Energy Products and then Energizer Power Systems) so seems to have pretty good credentials...

 

I favour the fewer components, the greater the reliability approach so "clever" power sharing electronic boxes and regulators don't attract me much. With the parallel battery system you can do a redundancy check before each flight and any single failure but a dead short will result in retaining battery power to the receiver. In fact going to 5 cells and diodes with parallel packs would even guard against this remote possibility.

[frank killan]

Thanks for that Martin I will now proceed with confidence. I also prefer to keep things simple less to go wrong. I prefer to remove batteries for charging.

                                                                                      

                                                                                                        Thanks again

                                                                                                               FK

[Andy Harris]

Schottky Diodes would have a lower drop at @ 0.4V

[Bladerunner]

Posted by Andy Harris on 08/03/2010 20:29:32:
Schottky Diodes would have a lower drop at @ 0.4V

 Agree with this 

Just to add to earlier discussion: Technically the use of diodes is the better option (if you can live with the diode voltage and dissipation losses) as it provides source isolation in the event of a source failure. Semiconductor diodes are exceptionally reliable and robust devices.

 

There are other more complex active solutions but probably beyond the scope of our needs. 

 

Regards