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?

Bill, I have a background in risk of technical system. I have a diesel generator on the boat and I understand the technology, probably better than most. The issue for me is all and simply about risk. It is not about the technology, although technology probably has an answer to the risk problem. I'm hoping someone can point me at it??

I want to reduce the risk of running out of power on a string of cloudy days on long passages to keep critical systems going. Any configuration (including anything derived from Victron's information) has risk. Any differential risk analysis tells us that introducing LFP, with any of the current system topologies or commercially available devices significantly increases risk. In my particular case the risk differential is exacerbated as if push comes to shove I can turn the generator on.

In technology terms a system that allows an EXISTING LA bank and a new LFP bank to be charged appropriately and is able to run loads from either bank is needed. There are diagrams that suggest this can be done, but some of the critical components are marginal at best in these configurations.

+x

 

Andy.Todd - 27 Aug 2022

Bill, I have a background in risk of technical system. I have a diesel generator on the boat and I understand the technology, probably better than most. The issue for me is all and simply about risk. It is not about the technology, although technology probably has an answer to the risk problem. I'm hoping someone can point me at it??

I want to reduce the risk of running out of power on a string of cloudy days on long passages to keep critical systems going. Any configuration (including anything derived from Victron's information) has risk. Any differential risk analysis tells us that introducing LFP, with any of the current system topologies or commercially available devices significantly increases risk. In my particular case the risk differential is exacerbated as if push comes to shove I can turn the generator on.

In technology terms a system that allows an EXISTING LA bank and a new LFP bank to be charged appropriately and is able to run loads from either bank is needed. There are diagrams that suggest this can be done, but some of the critical components are marginal at best in these configurations.

Andy,

I don’t have a degree in risk management, but have enough electrical maintenance and repair experience to know a dangerous situation when I see one. We all have a different tolerance for risk. Ours is pretty low since we are full time cruising overseas and one mistake could have dire consequences. There are by now probably thousands of experienced cruisers that have installed LFP batteries in their boats, and evidently feel that the significant advantages are worth the risk. Reading general/cruiser social media forums and reports about undetermined cause fires on boats with lithium batteries will not help you assess the risk in doing a proper LFP install.

I’m curious where did this statement come from?
“Any differential risk analysis tells us that introducing LFP, with any of the current system topologies or commercially available devices significantly increases risk”.

In all the extensive research I have done on lithium batteries I have never seen anything like that. In fact properly installing and using LFP batteries is, according to most electrical experts with significant LA AND LFP battery experience, less dangerous/risky than using LA batteries, especially as they age. “Properly” is the key word here. This opinion comes from the trusted websites (add Battery University to those) I mentioned in earlier posts, not from cruising social media sites with a mixed bag of accurate opinions. Of course there are several options for installing a LFP system, some, especially drop in installs and those done with inexpensive and inappropriate equipment, have more chance of having a problem than others.

The required BMS for all LFP installation adds another level of safety not present in a LA install. And the cells themselves rarely fail after the first 6 months of use and never due to anything like spontaneous combustion. Additional security for overseas cruisers like us from a failure can easily be mitigated by carrying an additional BMS, a extra cell or two and a few other inexpensive components. Cruising overseas we believe you can never have too many spares.

Installing a dual chemical LFP/LA system only complicates your electrical system and will not solve your running out of amps problem long term. But it does increase the risk of a failure. If you are worried about that see my comments above about system design that ensures you will have sufficient holdover house bank capacity for at least 3 days. Beyond that just use your alternators if underway or portable generator if in port. Simple. If you want to discuss how to easily charge both a LFP house bank and LA start battery we can do that.

We believe that anyone that has not actually done a proper DIY LFP install is hardly experienced enough to render a trusted opinion regarding any LFP vs LA battery risk. I don’t know where the Morgan’s Cloud forum falls. We all have to make our own decisions about what to put on our boats. But relying on cruiser social media will get you good and bad opinions, and unless you have sufficient knowledge from prior research, it will be hard to separate the two.

Dave McCampbell
SV Soggy Paws