Trace sw4024 with LifePo4 Battery Bank

I've made the decision to upgrade my FLA batteries to DiY LifePo4. The batteries are are running through two Overkill Solar BMS's and for testing are connected to a secondary charge controller that has two panels on it.

Everything seems good, so I am ready to cut over the big array / charge controller and Trace inverter to the new batteries.

The Trace of course doesn't have a preset for LifePo and that section in the owners manual is annoyingly vague on configuring the charge settings manually.

I don't need to run the generator often, but when I do I would like the settings to be as correct as possible. If anyone else is running a similar setup, would you be willing to share your charge settings for the LifePo's?

Thanks in advance!

Equipment doesn't matter.

3.55V/cell absorption, 28.4V
3.375V/cell float, 27.0V
Disable temperature compensation.
Low voltage disconnect of 24V (9% SoC), but this may be influenced by discharge current. Might need to be lower.

I'm not sure what you mean by "vague", as all the info seems there, but there is quite a bit of it, lots of settings that can be made.

It took me quite a few readings and figuring out the input settings buttons before it started to make sense.

In my user manual -
- read page 42 = Control Panel - Navigating the User Menu (its a bit fiddly)
- read top of page 43 = Accessing the Setup Menu

AC to Battery Charger setting depends on AHrs of your battery bank - see pages 61 and 62
- Press Red and Green - Inverter + Generator buttons to get into settings, then go across to the up down Settings arrows.
- page 61 tells you how to set Bulk and Float voltages, Battery Voltage and Max Charge Amps
- my Trace Generator Charger settings right now, for a 24 Volt System, for low sun or overcast days, are 30 Amp max charge, 28.2 Absorption for 1 Hour and then 27.6 Volts Float, Equalization Voltage is below Float and Time at 00. I tried lower voltages but it meant more generator run time and more fuel. I'm hoping these settings are an okay compromise from charging too fast vs too slow with my Dino fuel generator, which I can need on low or no sun days.

Page 10 tells you about Battery Cable sizing, which is also important and settings will matter if your wire sizing is smaller vs larger. My cables from the inverter to my busbar/battery are 4/0, so
I can maximize any settings without worry of over heating the wiring.

There are no perfect settings, every system and user needs are so different. LiFePO4 charging voltage suggestions and best practices are as already suggested and in MANY other threads here. Do a search. They are also compromises between charging too fast and too full which creates heat, to not enough charging which means lower capacity or longer time and maybe more fuel cost with a motor generator or under charging and drawing down too much. Too Fast, high voltage high amp charging may shorten battery life. But my conditions are also affected by really short days and really cold temperatures which motors don't like starting in. My batteries are in a warm location.

maddslacker said:

I've made the decision to upgrade my FLA batteries to DiY LifePo4. The batteries are are running through two Overkill Solar BMS's and for testing are connected to a secondary charge controller that has two panels on it.

Everything seems good, so I am ready to cut over the big array / charge controller and Trace inverter to the new batteries.

The Trace of course doesn't have a preset for LifePo and that section in the owners manual is annoyingly vague on configuring the charge settings manually.

I don't need to run the generator often, but when I do I would like the settings to be as correct as possible. If anyone else is running a similar setup, would you be willing to share your charge settings for the LifePo's?

Thanks in advance!

Click to expand...

I have a similar problem on my diy Rv. I have 2 Trace SW4024 4400 watt inverters. I want to use two 24V 200Ah LifePO4 batteries. My generator is an Onan Quiet diesel 12.5kw. I have a 50 amp shore power connection. As of now I have one 120v ac panel where it is fed with 120 split 240 so two separate legs of 120. I downloaded from here a diagram for a stacking cable for the inverters. I actually have 3 of the inverters. I was sold 2 when I got the RV and told they worked but one did not. I was lucky enough to find another in practically brand new condition. It is the correct firmware revision so I have a pair that are the same. Right now the inverters are not installed. So I can run the 120V panel off the shore cable with the filter/switch or the generator. Can someone please help? Should I just use one inverter and one battery and run separate one leg panels? I don't need 240. Ore is it better to parallel the batteries into one bank and stack the inverters. I hope I am making sense but even a simple drawing would help. Also some one with 2 inverters please help. Just a roadmap would be great.

The Trace SW inverters also have load shaving capability so make sure you set AC input current limit to avoid overloading generator.

You also need to set charging bulk current appropriate for battery size. On Trace SW inverters bulk current is set via AC input current.
You have to calculate AC input bulk charging current required to get a given DC output charging current to battery.

For 24vdc inverter, battery charging of 100A x 26 vdc = 2600 watts. Divide by 0.92 for inverter efficiency to get AC input power = 2740 watts. Divide AC power by 120vac to get AC bulk charge setting = 2740watts / 120vac = 22.8 amps AC bulk charging input current.

Or you can roughly set battery charging bulk current by dividing desired battery DC current by 4 for AC bulk charge setting.

Since charging is regulated by AC input current there will be slightly higher DC charging amps at low SoC battery voltage and less DC charging current at higher SoC battery voltage.

On generator, as AC output load consumes more of set AC input current limit, the charger bulk current will automatically back down to avoid overloading generator. If AC output loads exceed AC input set limit then inverter will supplement AC input power with battery power.

RCinFLA said:

The Trace SW inverters also have load shaving capability so make sure you set AC input current limit to avoid overloading generator.

You also need to set charging bulk current appropriate for battery size. On Trace SW inverters bulk current is set via AC input current.
You have to calculate AC input bulk charging current required to get a given DC output charging current to battery.

For 24vdc inverter, battery charging of 100A x 26 vdc = 2600 watts. Divide by 0.92 for inverter efficiency to get AC input power = 2740 watts. Divide AC power by 120vac to get AC bulk charge setting = 2740watts / 120vac = 22.8 amps AC bulk charging input current.

Or you can roughly set battery charging bulk current by dividing desired battery DC current by 4 for AC bulk charge setting.

Since charging is regulated by AC input current there will be slightly higher DC charging amps at low SoC battery voltage and less DC charging current at higher SoC battery voltage.

On generator, as AC output load consumes more of set AC input current limit, the charger bulk current will automatically back down to avoid overloading generator. If AC output loads exceed AC input set limit then inverter will supplement AC input power with battery power.

Click to expand...

If I have one battery bank and 2 inverters which one will charge the battery bank. Suppose there is more AC load on one leg as will probably happen? Do I have to have anything other than following a wiring diagram and menu settings. I have of bunch of heavy gauge wire and want to move forward.

EvRv said:

If I have one battery bank and 2 inverters which one will charge the battery bank. Suppose there is more AC load on one leg as will probably happen? Do I have to have anything other than following a wiring diagram and menu settings. I have of bunch of heavy gauge wire and want to move forward.

Click to expand...

Both will charge battery.

It is more important the calibration of charge voltage is the same on both inverters.

During float, you may have a small constant pull from one inverter and push to the other current due to charge voltage calibration being slightly off. Just tweak the float voltage on one inverter to minimize the push-pull current between the two inverters.

Another small issue is the calibration of battery temp sensors between the two inverter. For Lithium-ion batteries you should remove temp sensors from inverter charge compensation. On the inverters, the charge voltage temp compensation is changed at discrete temperature points. At the cross over temperature point, one inverter might be on lower step and other inverter on higher step of float or absorb voltage. This causes a little push-pull imbalance in charge current.

On Trace SW inverters, when they drop from absorb to float voltage they will actively pull down the battery voltage to meet the float voltage setting if there is AC output load to dump the power to. So keep that in mind for lithium ion float voltage setting.