rgleason wrote (at post #52) :
“There are many approaches to this system, some having more disadvantages than others. My comments are interleaved.” RG
Well said but it is possible to arrive at a design that does not have disadvantages.
My comments are also interleaved.
1. The 12BO switch left in the BOTH position and house loads can discharge both the start battery as well as the house bank.
--This can happen any way it it is wired. It hasn't happened to us yet.
---->It cannot happen if you remove the offending component. (ie: get rid of the 12BO switch)
---->Emergency (ie: fire) shutdown switch at both house bank and starter batteries.
---->Charge the start battery from the house bank with a DC/DC charger
. (keep a spare DC/DC)
---->Charge and maintain the starter battery fully charged whether the engine is running or not.
---->Buy a jumper cable for emergencies if you must.
3. Most alternators
do not have built in overcurrent protection and the output current is limited by the resistance of the wiring
--I think it is important to charge safely and efficiently, treating your batteries to power within specs but more quickly than built in regulators, protecting the alternator, without running the engine more than necessary. Therefore it is reasonable to use a good external regulator
properly programmed for your battery type with battery and alternator temperature sensors.
---->External or internal regulator, needs to sense and limit the output current
---->An alternator charging a large house bank must meet this requirement to be reliable.
---->Waiting until the alternator overheats is not good enough, although it is better than nothing.
---->What can we do? Stop promoting products as "proper" just because the label contains the word “marine”.
---->Ask the salesman “Does this product actively limit the charging current at the rated Amps?”
---->Let us know if you find a product.