Changing to LiFePo Batteries

[tiltrider1]

CatTom, if your HC alternator uses an external regulator, I would invest in a regulator like the wakespeed that allows you to safely connect to an LFP bank. The other alternator can continue to charge the start bank.

Running the alternators through a FLA or AGM start bank is a simpler, cheaper way of converting to LFP. Trying to put 600 amps back into a bank using a 60 amp DC to DC charger while motoring is not practical. In my case I my hops are short and my stays are long so I just run the generator while I am motoring.

 

[Iggy]

I've seen this solution a lot, and it makes sense, but I usually see it in the context of a single engine, hence single alternator, configuration.

I've got two engines. One has a higher-capacity, externally-regulated alternator to charge the house bank, while the other has a stock alternator and charges the starting bank. It's not really clear to me if a DC-DC charger would benefit me at all.

Each engine has one wire from the battery selector switch to both the starter and alternator. And since I can (usually) start fine off the house bank, there's no need to flip switches when starting or stopping the engines.

My current thought is that my first step toward a LFP migration would be to run separate wires for charging and starting. I'm going to have to draw those circuits out and figure out the best way to accomplish that.

Thoughts?

If I had two engines, I would wire it basically the same way. If one engine was to break down. I would want both/all banks be able to receive a charge from the good engine.

In other words, you want to be able to use your VHF, GPS and start your engine knowing your batteries are good.

 

[rslifkin]

If I had two engines, I would wire it basically the same way. If one engine was to break down. I would want both/all banks be able to receive a charge from the good engine.

In other words, you want to be able to use your VHF, GPS and start your engine knowing your batteries are good.

Agreed. With twins both engines should ideally charge the house bank. Each one charging only its own start bank is fine though, as if one engine is shut down then nothing should be drawing from that engine's start bank.

 

[CaptTom]

If I had two engines, I would wire it basically the same way. If one engine was to break down. I would want both/all banks be able to receive a charge from the good engine.

The same way as I have now, or the same as I suggested, separating charging and starter cables?

As it is, I can start either engine and/or run my house loads from either bank. I can charge to either bank from either alternator. Since one alternator is higher capacity, I generally point that one at the house bank, and leave the other in reserve and to keep the starting bank topped off. For FLA batteries this seems like a very reasonable, simple and robust solution. It's only when I start looking at LFP that I see complications.

 

[SteveK]

I have one engine charging start batteries which in turn DC2DC charge the house bank, the other engine charging the GEN start battery which in turn DC2DC charges the house bank. Then I have a crossover from engine start to house bank which in theory will put max available through the DC2DC chargers to the house. Have not used as such, had it there to be able to charge all off one engine.

 

[tiltrider1]

I see no issues with sending both alternators to the same bank or sending them to different banks. In the case of a mandatory engine shut down you still have the generator as a source of electrical power.

 

[Bob Cofer]

Update on the installation: The system is working great and a significant upgrade over the AGM's. One of the unintended consequences though is the fact that 300lbs of batteries were removed from the starboard side of Puffin and replaced with 60lbs of batteries. This produced a noticeable list to port.

Initially I planned on adding ballast to correct the issue but after some research and digging around I discovered 250lbs of lead ballast behind the stove and cabinets on the port side. Lucky for me it was bolted in and bedded in something like 5200. After much prying it was finally removed and my list was gone.

Just something else to consider if you make the change to these lighter batteries.

 

[z1nonlyone]

Bob, if your set up was FLA I would say you wired your batteries incorrectly. If it was FLA I would recommend you move your house positive to the opposite end of the bank.

I am not sure if it is as big an issue with LFP. Just curious what others think.

I look forward to hearing about your experience with this new arrangement.

I agree. I think the main reason is to make sure the batteries are all getting charged at the same rate.

 

[Bob Cofer]

They are wired per the battery manufacturers schematic. We will see if this works or if I end up changing to the corner to corner scheme.