Simple LiFePo4 Battery Installation

[Milou]

I am the proud new owner of a 1983 Beneteau First 38.

I’m upgrading my batteries to a LiFiPo4 dual bank. This season I will not have shore power (I have a Xantrex Truecharge 40, if I run into shore power somewhere) and the solar will not go in until spring of ’15. So, we will be weekend cruising and charging off of the alternator only. Well, I might get a small solar panel to top things of for the week or two between uses. The goal is to use the boat and refit over the next two years then depart for extended cruising spring of ’16.

House Bank: 4 of 400 Ah Winston cell connected in series
Start Battery: 1 of 12v 40Ah Winston

Charging: Existing 90 amp internally regulated alternator and adding a Sterling Power Pro-Reg D. I am going with the Sterling so that I can get temperature sensing at the alternator. I also want to be able to upgrade the alternator (may get sick of running the engine 1-2 hours a day) and use the same regulator in the future. This season energy use will be very low only lighting (mostly LED), VHF, speed and depth instruments and anchor windlass. No refrigeration, no autopilot, no chartplotter, no radar, no watermaker.

I dislike the 1/off/2/all switch. I am going to replace it with an on/off for the house and an on/off/parallel for the start battery, with a Blue Sea ACR charge relay.

Monitoring: Xantrex Linklite battery monitor and a Junsi cell logger for the house bank, and 2 Blue Sea LVD low voltage disconnects. Everything will be over current protected.

BMS or no? A better way than the ACR to integrate? Thoughts or suggestions?

[GILow]

I will be watching the responses here with interest as you describe similar setup to that I am considering, with the difference that we will have around 300 watts of solar plus our Aerogen 6.

My concern with what you describe is that I can't see how you will get adequate charge TIME but I don't yet really understand this battery chemistry so I will be keen to see what those that do have to say.

Matt

[CharlieJ]

It is my design philosophy to:
1. Use the organic controls in the various charging sources to limit and control charging of an LFP bank.
2. Use a BMS with cell voltage as well as bank voltage as a back up and to ensure that an HVC and LVC are managed should they occur.
3. There is no doubt that, at some time, cell (parallel string) balancing will be required. At that time having a BMS installed makes this operation very straight forward.
4. The cost of a BMS is so small, that it makes no sense, to me, to not install one.