Testing 2 year old Victron LiFePO4 batteries?

[MerMike]

I've been working on a redesign of my electrical system. I was planning on going with a pair of the Firefly G31s, but I found a pair of 90 AH Victron LiFePO4 batteries (p/n BAT512900400) @ $500 ea. I have been going back and forth on LiFePO4 for many reasons, but if these were healthy, it would tip the balance.

They are at least 2 years old. I say at least, because a slightly newer part number was discontinued a year ago. The seller says they've never been used. They have been stored partially charged. The seller "takes them out periodically to charge them". I don't have any more detail than that at the moment.

Is there a simple way to evaluate their health? I have the means to run a reasonably accurate 20 hour capacity test if the seller is willing, but need to research its applicability to LiFePO4. Is there a better way?

Thanks,

Mike

[MerMike]

Well dumb me, there's no need to do a 20 hour test on LiFePO4. With zero to minimal Peukert effect, I should be able to to put a load on the bank and count the amps.

[ttex]

I would buy them.

[MerMike]

Why would you buy them?

[smac999]

You still need to buy the bms, hv and lv cut off relays. And make sure your chargers and alternator are programable and can limit current once hot. Ie external regulator.

If you are comparing $1000 For 2 fireflys to $1000 For 2 victons You are still missing $$. To make the victrons work correctly. So it’s not a fair money comparison.

The 20h test will not work. Because the voltage does not slowly drop to 10.5v at 0%. (At which point you manually stop the test) I have no idea how to test them. I guess you could do a similar test until the bms shut off.

[MerMike]

Yes, I understand there are more components required. The Ample Power charging system is working, but is no longer supported. Neither is the Freedom 10 inverter/charger. The charger doesn't support carbon foam or lithium. The Bank Manager II battery monitor croaked and the wiring is a mess. It all needs updating.

I already own one Firefly new in the box, but the battery compartment is over 10 feet away from the main bus, requiring $500 of 4/0 cable. I could install the smaller, lighter lithium batteries much closer and free up some space. As I mentioned in the original post, if the batteries were healthy it would tip the balance.

I was originally thinking about using 260 AH Winston cells with a REC-BMS, Venus GX, and a Victron Compact Multiplus 12/2000. Remote monitoring is also highly desirable, and the Victron gear has it. The Victron batteries, while smaller, would work and the Victron BMS costs less as well.

[MerMike]

Found the answer in this post from Maine Sail:

https://marinehowto.com/lifepo4-batteries-on-boats/