LiFePo4 batteries tested.

[The Glassman]

Following-on from an earlier post, have now installed these Lithium Iron Phosphate batteries (LFP's) and had a four day trip to see how they perform.
They have been very, very impressive!
I fitted 2 x 120Ah units from Sterling to replace 4 of the (v good) Numax C120 lead-acids. Along with a battery-to-battery charger, a new ac-to-dc regular charger (both Sterling), new Victron isolator switches and battery monitoring system, a complete rewire and new fuses. Once all set up, it works beautifully. There are two 100A alternators feeding the system. Yesterday morning after a fairly normal evening/nights use, we were showing just under 50Ah (c.20%) used. I then ran the (1600w) inverter to make my morning Nespresso and the inverter voltage read-out showed 13.2v! After only 25 minutes cruising (at 1300rpm), the batteries were 100% full.
Rather an expensive exercise, but at 40 years old this year, the wiring was starting to look like that in one of those pictures one sees of towns in India?. Should have rewired her years ago!
Some other benefits I hadn't forseen...both 'fridges are suddenly behaving perfectly - ditto the TV and most of all, the Eberspacher.
I've yet to take the system down below 50% charge, but have no reason to believe that the system voltage won't still be <13.2v. That test is next trip, where we'll have 3 days moored at Henley without shore power. Looking forward to that very much.
Ben Sterling was most helpful and responsive to my frequent queries, and their delivery service is exemplary - as were Victron's too.
The bad news.... batteries 2 x £600, dc-dc unit £720, ac-dc unit £450 Victron kit £200, fuses, cabling etc £200. Best part of 2 weeks work at 3-4 hrs/day. So not much change from £3k. BUT - a rejuvenated old boat (and skipper!) Also worth bearing in mind the long life of these batteries (10-15 yrs+) and that they are best winter-stored without a charger, and they're happy to go down to 90% discharged without damage. Plus a bit of dosh back for the (excellent)old Sterling alternator booster/controller and the digital, 4-step ac-dc charger.
One happy boater!

 

[oldgit]

Thanks for that.....food for thought.

 

[Richard10002]

Is there something to stop them charging, or reduce the voltage to float, when they are fully charged?

 

[The Glassman]

Yes, firstly the (Sterling) batteries themselves each have a BMS - a battery management system fitted and secondly, the dc-dc (battery to battery) charger/controller oversees and manages the process. With the excellent little Victron monitor on the dash (about £125 or so), you can watch the process going on as you cruise. Better than the telly!?
I certainly wouldn't go ahead with a fairly complex installation such as this without components and advice from reputable Suppliers.

 

[Outinthedinghy]

Interesting to see how long they do last. Sterling put a 5 year warranty on these batteries. As there is a BMS on there it is techncally impossible to "abuse" the batteries in the way that people do with Lead Acid.

Hopefully it does do ten years but I am intrigued by the warranty time. The BMS does allow the battery to go out of it's chemical "comfort zone" in order to be charged by an ordinary alternator so this could be why the warranty is not ten years.

Worth being aware that the BMS is capable of discharging the batteries over time when not in use. Keep an eye on the voltage.

I've got several different types of Lithium batteries including Lithium Titanate, LiFePO4 (these were heavily discounted small mastervolt batteries) and normal NMC lithium ion batteries. Several different uses and mainly solar charged.

Only had them for a short time so don't know how long they will last but in voltage terms they are amazing compared with the old lead bricks.

I do have an AGM for engine (diesel) start battery on one of the boats.