AGM vs Lithium batteries

General
1

Here is a link for what I think is an unbiased comparison between Lead based batteries and LifePo lithium batteries.

2 Likes
2

Thanks for this Gary. Batteries are on my mind this spring because Soave’s Firefly (carbon mat) batteries are approaching their end-of-life. My general tendency is to use the new technology and I enjoy being part of the process of refining early iterations. However, I’m feeling apprehensive because I see some very smart engineers advocating different approaches for battery management in the lithium camp(s).

My current thinking is that I need to take my time and understand the power requirements on Soave more throughly before trying to select the right battery management approach to use with lithium batteries.

The design that you published last month is a top contender for a boat on a mooring, in my opinion. A boat in a slip with shore power may not realize as much benefit for the investment.

I’m leaning toward sticking with AGM till I settle in on a more clear use pattern for Soave.

Rob…

3

Another good article on the topic, although now a few years old, is: https://www.boatus.com/expert-advice/expert-advice-archive/2023/february/the-latest-on-lithium-batteries

The Ufine article lists the “thermal runaway” problem (the risk of overheating and catching fire) as a downside of Lithium. According to this BOAT/US article, that actually applies only to the older Lithium Ion (L-Ion) batteries. Newer batteries are far more likely to be Lithium Iron Phosphate (LiFePO4), of which the BOAT/US author says:

…the lithium iron phosphate chemistry has risen to the top as the safest of available chemistries at this writing. I’ve heard of no fire-related issues with it.

This doesn’t change the need for knowing and following the appropriate installation standards.

– Bob

4

I have followed the Marine How To suggestions. A T fuse on the LI battery and a DC - DC charger feeding from the 2 golf cart start batteries. All charging sources go to golf cart - start, alternator, shore power and solar.

The 314 amp Watt Cycle has 250 usable amps, vs 100 for the Trojan 105’s at half the weight and .60% of the foot print. AGM’s do not have a long life and the lifetime cost per amp is very high as a result.

5

As I prepare to upgrade my battery storage systems and being asked about the process I’ve come to a semi conclusion that switching to lithium kinda boils down to the old phrase ‘form follows function’.

Basically if you’re a day sailor with occasional overnights and keep the boat at a dock with shore power , lithium is a bit extravagant for your needs. On the other hand if your boat lives on a mooring and you’re cruising for longer periods of time , lithium makes a lot of sense.

One subject keeps coming up is safety . Fact is there are a lot of systems on a boat that require safety concerns and the lack of a track record certainly puts lithium near the top of that list. I have found an interesting option regarding the concern of fire. ( not only for lithium but engineer areas , galley , etc) Its a self activated dry fire extinguisher that works on lithium and other fueled fire sources. I intend to install in the battery box area as well . Cheers , Gary