Branched off MS's thread here http://forums.sailboatowners.com/in...-thoughts-musings.137615/page-10#post-1346551
"Primary" is the (much) bigger bank, used for both House loads and cranking the starter in normal circumstances.
The other battery is "Reserve", large enough to run (for a while, a subset of) House Loads if necessary, but top priority is to ensure its capacity is kept preserved to crank the starter, in the event something goes wrong with Primary.
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Maine Sail> This is fine, if that is how you want it, but why do you want it that way?
First of all, why not? Seems overall more logical & consistent with my overall perception of best practices in many other components, sub-systems and design factors.
Given minimized running of engines or gensets, can prioritise immediate smart charging Primary (house), maximizing Bulk high currents getting where it's needed, rather than waiting for a barely depleted starter to be topped up before the more important job starts.
Best scenario for backup reliability, battery health & longevity of the reserve (critical for safety) is maximised by being discharged as little and as infrequently as possible.
Keeps potentially "abusive" cycling patterns, when required, to be isolated to Primary.
Simplifies and gives widest range of choice in isolating/combining technologies, all charge sources directly connected to the one bank, all other batteries/banks clearly subsidiary to Primary. Limits or eliminates relay cycling, or use more intelligent echo/combi charging, enables transitioning to newer more expensive chemistry type.
Possibility exists of building up the "next Primary" bank, over say the first year of service, without a big difference between bank members in number of dis/re-charge cycles, only less critical calendar months "in float on the shelf". When Primary needs to be retired, maybe suddenly when funds are short, if Reserve is large enough can take over as Primary, and a relatively cheap consumer cranking battery can serve as Backup Starter for a while.
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I imagine there may well be other good reasons, as well as counter-arguments.
Those, as well as discussion on some of the less settled ideas above, would be most welcome, from anyone.
Please ignore the original context, any specific switching design or combining tech, let's try to discuss the Primary/Reserve design principle on its own generalized merit, as opposed to the more usual Starter/House dichotomy.
"Primary" is the (much) bigger bank, used for both House loads and cranking the starter in normal circumstances.
The other battery is "Reserve", large enough to run (for a while, a subset of) House Loads if necessary, but top priority is to ensure its capacity is kept preserved to crank the starter, in the event something goes wrong with Primary.
------
Maine Sail> This is fine, if that is how you want it, but why do you want it that way?
First of all, why not? Seems overall more logical & consistent with my overall perception of best practices in many other components, sub-systems and design factors.
Given minimized running of engines or gensets, can prioritise immediate smart charging Primary (house), maximizing Bulk high currents getting where it's needed, rather than waiting for a barely depleted starter to be topped up before the more important job starts.
Best scenario for backup reliability, battery health & longevity of the reserve (critical for safety) is maximised by being discharged as little and as infrequently as possible.
Keeps potentially "abusive" cycling patterns, when required, to be isolated to Primary.
Simplifies and gives widest range of choice in isolating/combining technologies, all charge sources directly connected to the one bank, all other batteries/banks clearly subsidiary to Primary. Limits or eliminates relay cycling, or use more intelligent echo/combi charging, enables transitioning to newer more expensive chemistry type.
Possibility exists of building up the "next Primary" bank, over say the first year of service, without a big difference between bank members in number of dis/re-charge cycles, only less critical calendar months "in float on the shelf". When Primary needs to be retired, maybe suddenly when funds are short, if Reserve is large enough can take over as Primary, and a relatively cheap consumer cranking battery can serve as Backup Starter for a while.
------
I imagine there may well be other good reasons, as well as counter-arguments.
Those, as well as discussion on some of the less settled ideas above, would be most welcome, from anyone.
Please ignore the original context, any specific switching design or combining tech, let's try to discuss the Primary/Reserve design principle on its own generalized merit, as opposed to the more usual Starter/House dichotomy.
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