I am planning on using a SMART RELAY here manf by BLUE SEA called the SI-ACR relay in an upcoming battery project. Another popular smart relay is called a BATTERY SEPARATOR manf by SURE Power Industries. These both pretty much do the same thing.
In todays world of charging deep cycle batteries you cannot use the old days DIODE BASED battery ISOLATORS. These devices uses high current DIODES which will drop your DC VOLTAGE by .7VDC going thru them. In the older days this was not a problem but todays DEEP CYCLE batteries require 14.4VDC to properly re-charge the batteries in a short three hour time period. If you subtract 14.4VDC-,7VDC voltage drop then you only get 13.7VDC to charge your deep cycle batteries, This will take around 12-13 hours to re-charge your deep cycle battery to be able to use it immediate again.
This is why you should install SMART RELAYS verses DIODE BASED ISOLATORs like shown above which will parallel batteries to your normal start battery when charging is needed. This method will keep your down-leg batteries re-charged and never discharge your start battery setup. It does this automatically...
Read up on BLUE SEA SI-ACR charging circuits at their web site - good info there to give you some ideas on what you might need to install.. Same goes for the SURE POWER INDUSTRIES website. Lots of good application info there as well.
Roy Ken
