You have all got me now wondering whether there is a better option than a VSR for a single out board?
what's the optimal step up?
A DC/DC charger WITH solar adaptability teamed with a victron smart battery protect?
I have learned to hate VSR's now I have a boat with 2 outboards. Have always promised I will design a smart relay that uses current sensing as well as voltage, but alas I have not had time to date. I have even bought the parts to start the prototype. The ultimate goal would be to integrate a smart relay with the Victron solar charger so I could direct charge to the right battery bank with set priority. I am about to run out of work in about 2 months, so maybe then, maybe?
You have all got me now wondering whether there is a better option than a VSR for a single out board?
what's the optimal step up?
A DC/DC charger WITH solar adaptability teamed with a victron smart battery protect?
I had a redarc solenoid housed in a weather proof box in the old boat for a decade. Still working when I sold it. I've done exactly the same in the new boat. Usual 1, 2, both, off switch. Batt 1 to solenoid then to batt 2. Use position 1, prioritise charge to batt 1 and keep batt 2 charged as well. Switch to batt 2 when all else fails.
It's pretty normal for a large capacity outboard to pull enough power to cause enough voltage drop to make a VSR drop out with a standard lead acid battery. While cranking mine drops low enough to trigger the low voltage alarm on my dual voltage gauge which triggers at 11 volts. The differences in your system I suspect are as a direct result of using lithiums which have a higher terminal voltage.
Nothing wrong with Victron gear Brett. I have used plenty of Victron chargers, voltage reducers and solar regulators on various jobs over the years. Hadn't really considered it for my own application though as I'm not looking for any sort of monitoring and space constraints realistically limit me to a single 100 amp battery so the Enerdrive eLite suits perfectly. I will stick with their charger as it then avoids any issues with warranty should a problem occur. I also drive past the end of the street where their head office is every day which doesn't hurt either.
I'm not sure whether they incorporate any sort of arc suppression into VSR's - never pulled one apart but Ranmar is spot on here. Contacts opening under load is the most likely suspect for contact erosion and subsequent failure in a relay. Have you checked to see if the VSR is staying engaged under the use of the pot hauler and anchor winch as well? Would be interesting to do a postmortem on one to see whether it is a contact failure or otherwise causing the issue. Potentially using the ignition sense if the version you are using may make them last longer if it is dropping out under starting that is causing the dramas.
I use a Victron Argofet. Nice solid state device for charging and isolating 2 or 3 batteries from a single alternator. Bit more expensive than a VSR at around $140 for 100A two battery version. Also, the most current directed to the battery with the lowest charge which may not always be what you want, but works for me.
https://www.victronenergy.com/batter...tery-isolators
After having the standard 1+2 switch looking a bit second hand, I fitted one of the Redarc VSR (same as in OP's picture), had a couple laying around from our 4WD days. It's mounted up under the rear same place where the factory switch was. It's been there for a number of years now, never had an issue. I do always listen for the click as it activates after starting the outboard (115 ProXS) and I hear it disconnect not long after shutting down the outboard when using the fridge and/or elec motor.
When using the bimini I lay the solar blanket over the top and plug in to the primary, then it's not long before it engages from the primary being full.
Best thing I've done, no more mucking around with the manual switch, and I always know the primary is ready for when it's needed. I do carry a bridging wire (been meaning to fit the switch to the dash) in case the primary fails though, but never had to use it. Obviously don't have the twin motor issues.
Cheers
Corry