10-20-2022, 02:25 PM
Joe,
Based on your hypothetical/concerns, I'm certain there will be no issue.
(1) For starters -- A good quality marine/RV VSR won't have the flip/flop issue you mention because it will require a _sustained_ period of voltage to make a switch. They also have a low-voltage cutoff, meaning that you'll never have a parasitic drain when one bank suffers a terminal flaw and won't reach nominal voltage.
(2) You'll never drain your chassis-batteries into your house-batteries, or overload your alternator (providing both sets of batteries are SLA/AGM -- if they aren't, there's an alternative solution).
(2)(A) The idea of overloading a quality alternator intended for low-RPM diesel engines is difficult to start with, because they don't suffer the same issue with conventional automobile alternators overheating when running a lower RPM (less cooling).
(2)(B) When you consider that you're dealing with the IRR of SLA/AGM batteries, the issue is further mitigated, even with the large 6x 8D battery bank.
(2)© The output current of the alternator is truly pushing the limit of the wiring and the current the house batteries can accept. Therefore, it's essentially impossible for the VSR to be "on"/connected more than the standard timeout period (typically 2 minutes or less) with the house batteries drawing from the chassis batteries. There are a couple reasons:
(2)©(i) The rate of resistance I mentioned above would indicate that if you were charging a completely dead (or just above the charge-cutoff) battery-bank, the circuit is: Alt > Chassis Bat > VSR (alternator flowing to chassis battery first at high amperage). If for any reason the house batteries could pull more current than the alternator made available, the voltage would have to fall closer to nominal, well under the VSR cutoff. In other words, 2 chassis batteries at 12.86 volts (a full+absorb voltage), with the house-batteries completely discharged at 11 volts (low IRR to accept the highest amperage). Alternator pumps past the high-IRR of the chassis batteries --into-- the house-batteries; no chassis-battery current can flow out. If it were to flow from the chassis battery, the voltage would be well-below the VSR cutoff.
(2)(D) Don't forget that many VSR's have manual override-switches; some are only to manually merge; however, some have a two-way override (merge or no-merge).
I really can't see a scenario where a VSR isn't better for your situation; none of the issues you're concerned with should be an issue with a quality VSR.
If something I explained doesn't make sense, I'm happy to get into more detail, just let me know!
Based on your hypothetical/concerns, I'm certain there will be no issue.
(1) For starters -- A good quality marine/RV VSR won't have the flip/flop issue you mention because it will require a _sustained_ period of voltage to make a switch. They also have a low-voltage cutoff, meaning that you'll never have a parasitic drain when one bank suffers a terminal flaw and won't reach nominal voltage.
(2) You'll never drain your chassis-batteries into your house-batteries, or overload your alternator (providing both sets of batteries are SLA/AGM -- if they aren't, there's an alternative solution).
(2)(A) The idea of overloading a quality alternator intended for low-RPM diesel engines is difficult to start with, because they don't suffer the same issue with conventional automobile alternators overheating when running a lower RPM (less cooling).
(2)(B) When you consider that you're dealing with the IRR of SLA/AGM batteries, the issue is further mitigated, even with the large 6x 8D battery bank.
(2)© The output current of the alternator is truly pushing the limit of the wiring and the current the house batteries can accept. Therefore, it's essentially impossible for the VSR to be "on"/connected more than the standard timeout period (typically 2 minutes or less) with the house batteries drawing from the chassis batteries. There are a couple reasons:
(2)©(i) The rate of resistance I mentioned above would indicate that if you were charging a completely dead (or just above the charge-cutoff) battery-bank, the circuit is: Alt > Chassis Bat > VSR (alternator flowing to chassis battery first at high amperage). If for any reason the house batteries could pull more current than the alternator made available, the voltage would have to fall closer to nominal, well under the VSR cutoff. In other words, 2 chassis batteries at 12.86 volts (a full+absorb voltage), with the house-batteries completely discharged at 11 volts (low IRR to accept the highest amperage). Alternator pumps past the high-IRR of the chassis batteries --into-- the house-batteries; no chassis-battery current can flow out. If it were to flow from the chassis battery, the voltage would be well-below the VSR cutoff.
(2)(D) Don't forget that many VSR's have manual override-switches; some are only to manually merge; however, some have a two-way override (merge or no-merge).
I really can't see a scenario where a VSR isn't better for your situation; none of the issues you're concerned with should be an issue with a quality VSR.
If something I explained doesn't make sense, I'm happy to get into more detail, just let me know!