Not a sailor, but John may be referring to my "opportunity circuit
" experiments on CRVL. Mods please delete if this is inappropriate for your forum.
When designing the electrical system
for my campervan I installed a redundant 12v circuit alongside the normal house power 12v runs. This second circuit is only energized when there is more power available than needed for critical loads. In my application:
: FLA charging
, ventilation, LED lighting
devices, running laptop
, donating power to others, dehumidifier, etc
My first thought was that anytime the charger
was in Float we are good to power the circuit. Another time we have excess power is later in Absorption. The most elegant way to do this is probably to poll
the controller through its interface (with a pi or arduino?). I'll do this in the future in my Copious Free Time. I think some higher end controllers will also energize the LOAD output when Float is active but I cannot recall
For now I am using ~Vfloat (a little less) as the indicator for excess power. Unfortunately this causes a false positive in Bulk when Vbattery is more than Vfloat but not yet Vabs. I mitigate this issue by chaining a 12v timer to the LVD. I am somewhat overpaneled so a delay of less than an hour is enough to ensure I am far enough into Absorption that falling acceptance means power is available for opportunity loads. The timer is not intended to run loads directly, so it triggers a relay.
LVD --> delay --> relay == opportunity circuit energized
reconnect: 13.7v (just under my Vfloat == 13.8)
It has worked well for me. Before dawn my bank is usually 80-100% SoC because the opportunity circuit/loads were shut off when the sun went down.