560Ah LiFePo4 Battery

[AllenC57]

The latest addition to my boat was this 560 Ah LiFePo4 (Lithium Iron Phosphate ) battery build. It consists of 8 280Ah EVE prismatic cells in a 2P4S configuration. It has a 200A BMS, meaning it can deliver that much from the batteries if needed. This battery takes up the space of 2 group 31 batteries. You can see a group 31 battery beside the grey LiFePo4 box for size comparisons. The group 31 AGM is only used for starting the engine. The lithium battery is thermally monitored by 3 probes to the BMS and is programmed to disconnect if any parameters are exceeded. There is a 250A ANL fuse directly off the positive post followed by the positive buss bar. The great thing about this battery is that it has more usable power than 8 of those group 31 AGMs! For example with a 100Ah AGM, only about 50Ah are usable. You can use 100% of the LiFePo4, but using only 80% will increase its life.

One of the main considerations when installing a LiFePo4 battery is burning up your alternator. I handled this by installing a Victron DC-DC charger between the AGM battery and the LiFePo4 bank. There are other considerations as well, that I won't go into now, but of course safety is the main consideration. I believe that a properly installed LiFePo4 battery system is as safe as any AGM. Last spring we spent about 3 months cruising from NW FL down to the Keys and back and the battery worked flawlessly (we only carried two 170W SunPower solar panels). We ran the built-in fridge along with a portable 12v freezer, microwave, ice-maker, coffee maker, induction cooktop as well as all of the boat's other electronics. We have a 2200W pure sine wave inverter that can be seen in one of the photos.

FYI. The cost to build the battery was about $1500 for the 8 cells and the 200A JBD BMS.

 

[Ralph Johnstone]

One of the main considerations when installing a LiFePo4 battery is burning up your alternator.

Why not use a external alternator regulator to limit the output of the alternator ?

 

[AllenC57]

Why not use a external alternator regulator to limit the output of the alternator ?

For sure, an alternator w/ external regulator is the way to go... just went for the quickest, cheapest solution for now. The alternator that is standard with my boat is just a 51A and has no capability for external regulation. I'd surely like a nice high output Balmar with external regulation one day.

 

[Ralph Johnstone]

The alternator that is standard with my boat is just a 51A and has no capability for external regulation.

Sounds like you 're in the same boat ( I know, lousy pun) as I was in back in 2010.

The engine is a Yanmar 2GM 20F and the alternator is a :
HITACHI ALTERNATOR, LR155-20B 129772-7720, 12V - 55A.
I paid about $50.00 for a five minute job at a auto electrical shop to have it wired for external control.

The most output I had seen before the external controller was 12A to a 50% SOC battery bank. After the external controller :

I found I had no need for a larger alt. as the Hitachi wasn't putting out squat at it's 14.2V maximum voltage. The Balmar has 14.7V at bulk charge to a 50% SOC battery bank.

The alternator was doing so well, I installed an exhaust fan to cool the engine compartment as the alt. output was cutting back due to the high temperature inside the the Nike shoe box.

I quickly rejected the idea of a bigger alternator once I fully understood why an alternator without an external regulator won't deliver squat.

 

[AllenC57]

Sounds like you 're in the same boat ( I know, lousy pun) as I was in back in 2010.

Interesting... but unless you've got a LFP battery bank, I'd say we're not quite in the same boat
The LFP battery can handle up to 200A of charge current... putting any more money into regulating my existing alternator wouldn't do me any good, because I'm already regulating to 30A using the Victron DC to DC charger. It would only be an advantage for me to move up to say a 170A alternator to charge up quickly. I've looked into it and the cost would be around $1700 with alternator, regulator and replacement pulleys for the engine. Since I had plenty of power on my last cruise, I just don't see it as a high priority item now... just a nice-to-have.

 

[mermike]

I suggest you replace the ANL fuse with a Class T. The ANL does not have sufficient interrupt capacity to handle a bank of that size.

 

[Ralph Johnstone]

I've looked into it and the cost would be around $1700 with alternator, regulator and replacement pulleys for the engine.

Yipes . More money than I've got laying around just to charge my batteries in a couple of hours. Mind you, I'm sure you've got a lot more wind than we do and spend your time actually sailing. Any movement here is accomplished with an easy 75% motoring. I've found we can exist electrically for about 3.5 days getting down to 50% SOC at its lowest. That's with fridge, stereo, LED lights and anything else I'm too lazy to do by hand.

What do you have on board to require that much power ?

 

[Hayden Watson]

I have my 108Ah Ample Power alternator setup so that it outputs 60A max and on my two 10-days cruises this summer, my 560Ah LFP pack never dropped below 50% SOC with just the normal motoring that I did.