Switching the House Battery Bank to LiFePO4

[tpenfield]

I switched my house battery bank from 5 AGM batteries over to 2-3 LiFePO4 batteries. One of the motivators for the change was a weight savings ( 5 x 72 lbs. vs. 3 x 28 lbs) as well as extended runtime away from shore power.

Each engine has its own battery bank consisting of a single lead-acid battery.

The boat already had solar charging of the 3 banks of lead-acid batteries. In converting to LiFePO4 for the house bank, I upgraded the solar controller and added a DC-DC charger to buffer the alternators for charging the House (LiFePo4) bank. The house bank also supplies a 2,000 watt inverter for AC loads. Each battery bank has 3 sources of charging . . .

Solar Power
Alternator Power
Shore Power

The system took a little bit of tweaking, based on experience, but now it is in a final form.

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The boat sits on a mooring when not in use, so the solar charging comes in handy as it keeps the batteries fully charged. I found that the DC-DC charger needed a bit of tweaking as it was trying to bulk charge the LPF (House) bank at lower RPM and it could not support the amperage. I put a SPST switch in the ignition sense wire so the alternator charging could be activated manually when the boat is underway (at higher RPMs)

Sharing this for others who may be planning a similar system.

 

[fallguy]

My boat is similar. I am running 90hp Yamahas and two Orion chargers. …Very nervous about smoking the alternators. They are only 33amps each. I put the Orions on two minutes maximum time on bulk and I think 120 seconds off or something like that, but really want to current limit way down. I have 535w solar panel that will provide 2kwh a day or about 70Ah if my math is close. Heat is diesel and stovetop is propane, so demands are low.

Someone told me I could current limit my alternators with a device and someone else with #10 wire before the step up Orion.

Battery is 200Ah redodo 24v, nom 25.6, charging to 27v.

Any advice welcome. I would be glad to get maybe just 5 amps from each engine. I bought a Sterling charger that will limit to 6-7a. 5 amps for 8 hours running on twins is like 80Ah; that and the solar and I will probably stay ahead. Add a shore power day now n then, etc.

 

[tpenfield]

Yes, 33 amps as an alternator rating is fairly limited. I went with a 30 amp Orion, given that the alternator that is designated to charge the house bank is 65 amp rated. I tried using the voltage parameters on the Orion, set fairly high (like 14.5 volts), but found that it would go into bulk charging once the engine had brought up the starting battery. The alternator(s) are really not ready to produce decent current until they get into the high idle or even cruising RPM range.

To complicate matters, my boat has electric steering and shift, so with the alternator trying to do bulk charging at idle speeds was causing low voltage issues while in the harbor and around docks. At one point the engine shut down, because the voltage was too low. So, I put the SPST switch in place that you see in the diagram and I can selectively do the DC-DC charging once the boat is underway at cruising speed.

It would be nice if the Orion series had a current limiting function, but I did not see any such thing. I know the a new series of chargers came out from Victron in the past couple of years. When I was buying components for the system, the new ones were not readily available.

I also, got a copy of the ABYC E-13 standard, which covers lithium batteries. Not sure if you consulted the ABYC standards in your design. One interesting and controversial thing in the E-13 standard is that the system "should" provide warning to the operator of the vessel, if (and before) one (or more) of the lithium batteries is going into protection mode (or otherwise going off-line). Well, if a couple of milliseconds suffices as being 'before', then OK. But it seems to me that aspect of the standard is not done with a good knowledge of the battery management systems (BMS) that most batteries have internally.

I also learned that the low temperature charging protection (LTCP) feature on my (LiTime) batteries is logically flawed in that charging is shut-off at 32˚F (0˚C), but discharging does not shut off until about 0˚F. So, as winter temperatures approached, the batteries stopped charging from the solar, but would continue to discharge to a point of going into low-voltage protection. One of my batteries did not recover from the low voltage come spring time, but it was replaced under warranty.

 

[tpenfield]

. . .

Someone told me I could current limit my alternators with a device and someone else with #10 wire before the step up Orion.

Any advice welcome. . . .

"Balmar APM" is a commonly used device to protect alternators from over current into LiFePO4 banks.