Adding House Battery

[acdiii]

I'm repowering a 24 Cape Horn CC with DF 175s. The boat currently has 2 batteries with Perko switch for house and starting located near the transom. I would like to add a house battery under the console and leave the existing batteries in place for starting. I've ordered the aux charging cable to charge the house battery which will pull off one of the engines and run to the console. My intent was to keep the house battery and starting batteries totally separate. Will this work? Is the length of the aux charging cable an issue?

Thanks
Andy