Our batteries are reaching a stage where replacement will be needed shortly. Consequently we are thinking about LiFePO4 batteries which are lighter, smaller, don't require same capacity, can be discharged further and last longer but are a bit more costly.  Does anyone have any experience or advice re these batteries?

Dave, just a correction. You say 'Your desire to significantly increase usable battery capacity with a much lighter and physically smaller house bank,,,etc'. I was quoting Philip's desires and making the point that these may not be good reasons to take some level of risk of changing to all LFP if he has a LA topology that worked for him. Plus the considerable time and effort required to research the subject.... as you and every sensible advisor attests to.

I have a background is in Risk. My assertions are based on this knowledge. In which case just changing from something that has worked for a long time to something new and different has a significant comparative risk. While most users will never suffer the consequence of failure of a LFP system, depending on the situation the consequences of LFP failure are more severe than with LA. That risk can be quantified and for my situation the risk-weighted cost of LFP failure is too high. An answer to this might be a dual chemical approach. The technical challenge is how to do this without increasing risk.

The best argument for 'dual chemical' is on Morganscloud. This means a dual redundant LA / LFP systems. It is not connecting LA and LFP, as there a lot of conflicting advice about on social media. This implies very significant risk such that you would never consider for a boat. RAN sailing on YouTube have the type of dual chemical system I'm referring to, but they use it in a different way than I want. When their LFP goes down they completely disconnects the LFP and switch on an independent LA back up bank.

Because my LA system works fine (logically and operationally) for the most part I want to keep it. I would like a little back up to run critical systems for cloudy days on long off shore passages. The other benefits for amp hungry appliances would be a bonus but not a reason. Commonly this is done by charging the LFP through the LA, but that negates the efficient charging capability of the LFP. An answer could be a charging bus going to an either/or switch normally set to the LFP bank. The LFP charged the LA through a DC/DC converter. The LA is connected to the critical loads, the LFP to the rest. If the LFP goes down you can switch the charging sources to the LA.... except any DC/DC converters on the market seem very marginal for this configuration.

Any insight would be appreciated?

Andy, it sounds like you might be best served by simply adding a portable generator to your existing LA system with which you are familiar and comfortable.

If you want a good resource for understanding what’s out there (LFP), along with numerous (nearly) applicable schematics, the Victron website is an excellent place to start - though even that gets rather confusing when you’re drilling down to the nitty gritty details.

I’m no longer a participant on Morgan’s Cloud, but agree it’s a reasonable (if opinionated) resource. My problem with the site was that Harries is so risk averse that to follow many of his recommendations would require more finance than I have at my disposal! Dual electrical systems seems to be following that general pattern!

Hope you find the right solution for your requirements!


Bill Balme