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Re: Hybrid Lead/Lithium
Scott SV Tengah
I think if you were struck by lightning to the extent that the BMS is killed, the chargers would probably be gone, too. I agree that a weak point, at least in my Victron system, is that a BMS failure would render the Victron chargers useless. To solve this, I bought a backup BMS, which was only $120 USD.
That said, if both my primary and backup BMS die, I could still use the Mastervolt alternator to charge my batteries, just without the cell level over voltage protection. Not a great situation, but as long as you don't charge above say 85% SOC, the likelihood that you'll get a cell over voltage is quite low. If I want to go higher than 85% bank SOC, I can just monitor the individual cells via bluetooth. This is really the "I am in the middle of nowhere and need to charge my batteries" situation that we must think about when we're circumnavigating.
One disadvantage of a lead-heavy hybrid system is that you lose three of the big advantages of lithium: (1) high charge acceptance and charging efficiency (2) stable voltage under heavy load (3) the ability to use all those AH between 10-100% SOC. Do not underestimate the charge acceptance and efficiency gains as it is like getting a 20-35% larger solar array on your boat.
Personally, after over 3 years on this Victron system, I think it works quite well. The BMS tells the charging sources (solar, 230v charger, alternator) to stop charging VS. some other systems which appear to disconnect the batteries from the charging sources, leaving the charging source without a place to send that current and putting that source at risk of damage.
Another thing to think about is the insurance "problem". A non-standard system may raise the eyebrows of insurers more than an integrated system from one manufacturer. I put "problem" in quotes because clearly any insurance companies that have an issue with lithium will clearly need to figure it out and allow it as many of the A50s and I believe all of the A60s have it as standard equipment.
2007 A54 #69