Bob Thompson1894 wrote:Surely the only advantage of using two batteries is redundancy if one goes faulty? Therefore it is pointless having two batteries without some means of isolation?
A diode would protect against a direct short circuit inside a battery, but not an open circuit (battery comes unsoldered etc.). Having two batteries would protect you against the failure in both cases.
When introducing something to protect against a potential failure, you need to weigh up the likelihood and severity of the feared event against new failures that can be introduced by what you're fitting (in this case the diode itself failing either short or open circuit, or it becoming unsoldered/breaking)
You don't need to do a full failure analysis for your models, but just think about what it is you want to achieve, and try and have an open mind about old wives tales like batteries cross-charging.