Re: drop LiFePo4 batteries vs LiFePo4 cells in a bundled pack #solution


Mark Erdos
 


 

We are obviously not all wired the same (pun intended). I see discussions regarding Lithium technology on many forums and while I agree it's a step in the right direction, it is still not for me, yet.

Alan, I 100% agree with your BMS shutdown concern. For those who recall having rotary switches for multiple battery banks, you probably remember the warning printed in bold type on the switch: Do not turn off with engine running. If a high output alternator is suddenly disconnected from the battery bank with the engine running, that electric energy has to go somewhere. Watch how quickly a fire ensues. I would imagine, if one is using the bow thruster the engine is most certainly running.

Speaking of rotary and regarding Scott's phone analogy, I am older enough to remember the days when phones were for calling people and were as such crystal clear. Anyone else remember AT&T's pin drop campaign? The phrase "can you hear me now" was never uttered. While phones have now advanced into pocket computers, I, for one, miss the days of a clear voice at the other end. Perhaps the next generation of phones will fix this. And, perhaps the next generation of batteries will fix the issues with lithium today.

 

With best regards,

 

Mark

 

Skipper

Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising - French Polynesia

www.creampuff.us


On 5/2/2022 10:05 PM, Alan Leslie wrote:
Thanks Scott...great post....

Everyone has different requirements (and ability to pay!) ... so everything relevant needs to be considered....those Victron batteries are VERY expensive !
n=1 studies are often not useful ...on my previous boat I had AGMs that lasted 10 years, I have an Amel friend who has his set of AGMs now for 9 years, Ours are 6 years and still performing.....because they have been well managed.
But I don't think that's the point.

My concerns, still, are around this sudden disconnect business, and now, about how you deal with periods away from the boat.

I can see now that it is possible to have very high short duration discharges from LiFePO4 batteries, as needed for the bowthruster, but we had better be sure we have enough peak A availability so that the battery BMS doesn't suddenly decide its had enough and disconnect at the worst possible moment.

When Covid struck, we had left the boat in a marina connected to shore power with a battery charger on and the frig and freezer running, fully expecting to be back in a few weeks.
A year later I came back and everything was OK.

How would that work with Lithium?

I understand they don't like to be kept charged and actually prefer to be disconnected -  so would it make sense then to have say one or two AGM batteries (with their own charger) just to keep the boat going and disconnect the Lithium when parked for an indeterminate time? 

Another option might be, for us, we have a 100A Victron Skylla battery charger which has a Power Supply mode - maybe disconnect the battery bank and put the Skylla in Power Supply mode when leaving the boat??

I really like the potential that LiFePO4 batteries offer but my concerns, as everyone now knows, are wide ranging....and developing daily....but not necessarily in the negative!

Cheers
Alan
Elyse SM437

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