Switching between isolated and non-isolated supplies?

[zenerbjt]

Hi,
We have a battery powered  circuit as attached. Usually the isolated DCDC SMPS module supplies the load. But every so often one battery is removed for charging etc, and we still need power to the circuit….so we then have the relay (as shown)  which switches between the isolated and non-isolated 5V and Gnds. It “changeover switches” them together.
What worries me is that charge pumping through the isolated SMPS may mean that even with the 1MEG resistor, there may end up being significant potential between the battery ground and the isolated ground?
…especially since there are actually four isolated converters in the real circuit (not just the one as shown).
Do you think there is any chance of this “charge pumping” causing a significant difference in the potentials of  isolated and battery grounds?

[Nusa]

Or, instead of a SMPS, you could plug a spare battery into an external jack and switch over to it with a manual switch. Swap the regular battery with a charged one, then switch it back. Put the old battery on the charger. You never lose isolation.

[Marco]

Just put a multimeter across the 1 Meg resistor and measure it.