Magnum MS2012 and LiFePO4 Settings

[creativepart]

This is a topic that previously came up often, but I haven't seen it for a while. I contacted Magnum asking for specific help and their response was "Watch our Videos" But those videos are zero help with this.

I've gone through and written out all of my settings from the ME-ARC50 remote and hope that someone can help critique the settings I've chosen.

First, I have two 200Ah Renogy LiFePO4 house batteries for a total of 400Ah. Fully charged voltage is 13.5v. The max charging voltage is 14.4v. Max charging amps is 100A.

Here are the charger settings in my MS-2012 Inverter/Charger.

NOTE: I do have the ME-BMK Battery Monitor Kit installed.

System Settings
01D - Max Charge =100A

Inverter Settings
02A - Search =5w
02B - LBCO - 12.0v
02C - AC in Time - N/A
02D - AC in VDC - N/A
O2E - AC in SOC - 80% - 95%
02F - Powerup - Always Off

Charger Settings
03A - AC Input: 30-amp/50-amp depending on shore power
03B - VAC Dropout - 80VDC
03C - Battery Type - Custom
03D - Absorb Done - SOC 90%
03E - Max Charge Rate - 100%
03F - Max Charge Time - 6hrs
03G - Final Charge State - Float
03H - EQ Reminder - OFF

BMK Settings
05A - Charge Efficiency - 99%
05B - Amp Hour Size =400

Thanks for any help you can provide on these settings.

[Persistent]

These are the charging instructions.

Charging Battery

• DO NOT exceed the maximum continuous charge current of the battery.
• Only charge the battery with a battery charger or charge controller that is compatible with the lithium iron phosphate battery.
• Depending on the length of time between manufacturing and shipping, the battery may be received at a partial state of charge (SOC). Please fully charge the battery prior to the initial use.

During the standard charging process the battery is charged at 60 amps (120 amps max for two batteries in parallel) until the battery voltage reaches 14.4V.

Then, the battery is charged at a constant voltage of 14.4V while tapering the charge current. (Battery tapers the current. Charger maintains 14.4 volts.)

The standard charging process is considered complete when charging current is less than 10 amps (20 amps for two in parallel).

However, leaving the battery on float (14.4 volts) will continue to balance the battery cells and will not damage the battery. The standard charging process normally takes 5.5 hours.

32 degrees F to 131°F (0°C and 55°C).

https://www.renogy.com/content/RBT20...anual_V1.0.pdf
See page 9.


System Settings
01D - Max Charge =100A

Charger Settings
03A - AC Input: 30-amp/50-amp depending on shore power
03B - VAC Dropout - 80VDC
03C - Battery Type - Custom
03D - Absorb Done - SOC 90%
03E - Max Charge Rate - 100%

This must result in current limiting to 120 amps maximum.

03F - Max Charge Time - 6hrs

This may be a little short at 100 amps maximum. Charging current should be less than 20 amps when switching to float. However, if float is 14.4 volts, then it does not matter. It will continue to charge as long as it needs it.

03G - Final Charge State - Float

This must result in 14.4 volts maximum. Lower voltage is OK if batteries have reached full charge (20 amps or less at 14.4 volts). The instructions are not clear on this. 13.6 volts may continue to balance the cells. I can't tell.

03H - EQ Reminder - OFF

[computerguy]

Hmmm, First thought. The Magnum BMK IMO is worthless in my setup.
I have solar and with solar the BMK thinks its full EVERY morning as the sun rises and starts to charge my system. I had conversations with the engineers over at Magnum and they know this is a problem. Their solution is to use the Magnum solar charge controller. If you use that it may work better.
For you without solar it may or may not be a problem. Keep tabs on your system daily. I have the MagWeb so my data is kept online.
I'd be VERY leery of the SOC from the Magnum. I use voltage as this is what my manufacturer said. 14.1 for 6 mins is all they recommend.
The 03G - Final Charge State I would make silent. I don't have Renogy though. I have GBS cells for 5+ years now and they are still have over 100% capacity. Keeping lithium at 100% charge is not good over the lifetime of the battery.
05A - Charge Efficiency I would leave at Auto but again for me this is not good because of the solar problem listed above.

[creativepart]

Computer guy... I do have a small amount of solar, 300w on the roof.

By the way, I have two Battery monitor's - the Magnum and the Victron Smart Shunt. They both use the same shunt but each is wired into it's own controller. Add to that that my Renogy batteries have built in Bluetooth so I get their SOC directly from the batteries via the Renogy app.

So, far, all my BMK numbers are very close to each other. The batteries may say 98% and the Victron may say 97% and the Magnum usually agrees with the batteries.

[Persistent]

Each Li drop in battery design has its own requirements. So different brands require different charge profiles. The differences may small, but significant. It depends on the built in BMS.

The Magnum was designed for lead acid charging profile. Adapting it to Li charging requires knowledge of the Renology requirements and knowledge of the Magnum controls.

The Renology profile appears to want 14.4 volts continuously. The Renology BMS will accept a maximum of 60 amps for each 200 amp hour battery when deeply discharged. If the charger cannot supply that much, the battery terminal voltage may drop. That is OK.

Voltage will rise as the Renology charge progresses because the Li battery limits current more and more as it charges. Eventually the terminal voltage will reach 14.4 volts if the charger allows.

The Magnum must be set to provide 14.4 as long as the Renology is accepting current. Lead acid batteries that the Magnum was designed to charge require that voltage be dropped to 13.6 or so after a few hours. Possibly 4 hours. 4 hours is not enough for the Renology.

Instructions for the Renology say the 200 amp hour battery is "considered charged" when voltage is 14.4 and current is less than 10 amps. Once charged, charging at 14.4 needs to continue to provide cell balancing and balancing between the two batteries. How long is hard to say. It depends on each individual cell and each battery.

Battle Born batteries will disconnect when they are fully charged. Possibly the Renology batteries will do the same. Charging current will then be zero amps.

The Magnum and the Victron must be capable of regulating voltage when the Li battery disconnects. Battle Born's will stay disconnected until terminal voltage drops below a certain voltage. Reconnect voltage may be 13.2 volts or so. Possibly the Renology will do something similar.

This means that dropping to a float voltage of 13.6 is fine after the Li battery has disconnected. Dropping to 13.6 sooner may limit battery capacity until balance has been restored.

These are the optimum profiles for use while RV is occupied. There are storage profiles to consider.

Not all drop-in Li batteries work the same. Certainly Li cells have other requirements. An external BMS is required to keep cells and RV systems safe.

[hclarkx]

I'd say the proof is in the pudding. Since the charger is not ideal for LiFePO4, I would keep an eye on it through a few charge-discharge cycles to be sure the results are appropriate for LiFePO4 (or close enough). So knowing what LiFePO4 needs in the way of charging is important.

Every manufacturer has a different charge profile specification, but with few exceptions (Battleborn mostly) the cells being charged are prismatic and are virtually identical in chemistry from manufacturer to manufacturer. As such the different charge profile specifications you see are simply manufacturer's preference and vary largely with the manufacturer's focus. This might be on longer life or it might be on customer ease-of-use or it might be on extra balancing to ensure balance is maintained.

The bottom line is that if your cells are prismatic (not cylindrical, not pouch) then you want to see the following voltages during normal day-to-day usage (not storage).

Battery discharged to some extent and needing to be charged. Voltage is between 13.0 and 13.3 when the battery load is near zero and the battery has been sitting for a while.

The charger cuts in and begins charging the battery. Voltage rises, hitting about 13.8V at around 90% SOC and rises more rapidly after that and very rapidly as voltage rises above 14.0V. Voltage stops rising at 14.4V. ((NOTE: chargers designed

Battery voltage sits at 14.4V for a while. Since the battery is at about 99% when voltage hits 14.4V, more time at 14.4 adds very little to the SOC. Spending some time at 14.4V is suggested by some manufacturers to get that last percent or for added balancing. Better BMS designs get the balancing done without this time at 14.4V though cells that are less uniform may need extra balancing even with good balancing as voltage rises up toward 14.4V.

Battery is ready for float voltage. The charger voltage drops to around 13.6 volts internally. The battery voltage drops over time from 14.4V to 13.6V. Faster if there is load on the 12V system (minutes) or more slowly with little or no load. Voltage stops dropping at 13.6V as the converter cuts in to take load off of the battery.

Voltage holds steady at 13.6V as the converter/charger picks up 12V system load (within it's capability) to maintain voltage. If higher load pulls voltage down lower for some time, but not low enough to re-start the charge cycle, the charger will bring voltage back to 13.6V.

With the above in mind, and a good voltmeter reading voltage at the battery terminals (or a good monitoring system), you can confirm that the charger is doing a reasonable job and not taking life out of the batteries with excessive time at 14.4V or letting voltage drop too low. ((NOTE: Some converters designed for lead-acid batteries do not kick into bulk mode (the initial charge up to 14.4V) until voltage drops to or below 12.6 or 12.7V. LiFePO4 battery voltage may never drop this low even under heavy load. As such, these chargers may require a re-boot each time LiFePO4 charging is needed.))

Even with a proper LiFePO4 charger (converter) I would suggest tracking a few charge/discharge cycles to be sure all is copacetic.