Originally Posted by
JohnMac
A little bit of knowledge can be a dangerous thing.
However, I would caution you against using two batteries in the way you have suggested. If you use one for the Rx and a different battery for the servos, you are now relying on two batteries, switches and harnesses to be good. That is a worse situation than having a single battery. Better to have 2 batteries in parrallel, either through some propietery power distribution hub, or through two diodes, one in each switch lead. In this way you have double the capacity of battery on tap, and double the current availibility too. Best of all should one system fail, you have second. Bigger capacity and better suited batteries are they way to go, and always two of them IMO.
Finally, NiMh are for TV remotes!
John
John Mac (another John M
)
The idea of using two separate batteries, one for the servos, and one for the receiver is not for redundancy protection... its to get the current hungry hi-voltage, digital / coreless servos off the receiver's pin connector buss... putting the servos on their own high current buss, and powering the receiver with its own battery, done properly is just as reliable as a single battery arrangement... actually its more reliable in the terms of protecting the receiver from a brown-out... and with the batteries we have today that were designed for repeated hi-discharge / re-charge cycles, used to power these minimally current hungry devices in retrospect, the batteries will never see their maximum designed thermal / discharge rates in these two particular locations (receiver and servo power), which further reduces the chance of a battery failure.
A properly assembled battery pack (one each for the receiver & servo buss), with a high quality soft switch, or even mechanical switch; properly isolated from vibration, has proven to be extremely reliable... in over the 50 years I've been in this hobby, since I was a young kid, and especially in the last 25 years, I have never seen a battery pack, short out internally or go open from a bad cell... all the failures I seen related to batteries, are caused by the operator; poor installation, poor assembly of the battery pack / cold solder joints... broken battery or servo wires from allowing them to dangle and not properly restrained.. using damage batteries recovered from crashes, etc.... granted mechanical switches can fail under vibration, but this is preventable with proper installation and maintenance... and as previously mentioned, the use of good quality components.
John M,