Extra Battery Bank

You can never have too many amps on a boat.  With today's gadgets and instruments they seem to eat up amps right before your eyes.  Three years ago I install a second bank of batteries.  That was in addition the the main house bank of 600 amp hours.  The second one was of the same type but only four 6 volt 200ah which gave me an additional 400 amp hours.  Unfortunately in installing this bank I decided to remove the engine start battery believing that the I had enough amps and the charging regime of a starter battery was different from the two house deep cycle gel batteries.  One seasons experience I found that after a few days the two banks had dropped on voltage and it was not save to rely on them to start the engine.  It always started but the draw of the starter was just too great.
While in Oz I purchased a new 1,2 both battery switch, went to my store a took off a role of battery wire.  It is heavy being pure copper.  I thought I would have to make it into a belt to wear on the plane to keep the hold luggage within limits but Emirates gives you 30Kg and this time I was just under the limit.

I set about analyzing the current situation.  I thought I knew the circuits and had then drawn in my electrical diagram but like everything on a boat things change and one forgets what changes you make.

The next challenge is to draw the schematic of what the circuits should be and then to see if you can implement it within the confines of the switch box.  Again having a store of wire, crimps and clampers on board helps to make the job easy.  I had luckely left the engine battery wire on the board so connecting the new switch was only a question of running the new wires to the right places and getting the connections right.  After a few minutes the dead was done and the the time was right to throw the switch. 

Engine started first go and went into charge mode for the engine battery bank. Great.  Move the switch from 1 to both and the second house bank receives a charge.  You can now use the windlass and the alternator will take the load.  Then when that is completed either leave the switch to both on move to 2 to dedicate the current to the second bank.  I f the first bank need charging just change the main battery switches to both and the both get the amps.  Hopefully giving me more amps than I will need.