Lithium MS2812 Conversion from Lead Acid

[WinePress]

I have successfully converted from lead to lithium. I used information from this forum (Thanks Richpatty) and others to arrive at the settings for the non existent lithium profile of the Magnum MS2812. I am trying to now fine tune the settings. I have no issues with bringing the batteries to 100%, My issue is trying to maintain the resting levels at less than 100%. When set up on shore power I would like to have the batteries set at about 80%. My understanding is that will allow the batteries to have a longer life. This seems to be elusive with my current settings. Once the bank is fully charged I bring down the voltage and the bank will begin to discharge down to about 80%, then a couple of hours later it back will be back at 100% then slowly begin to discharge down. So it is this constant back and forth that I can’t figure out.
I am unfamiliar with the Magnum feature CC/CV and was wondering if anyone has used this setting to manage their Li bank. It seems like this may be a possibility but I’m not sure what the settings should be.
The Chinese manufacturer, Chin is of no help. They only offer to say charge to 100% and don’t worry about it as the internal BM will keep the cells from overcharging.

Here is my settings currently-
Batteries- Two 12 v 280 amp LiFePO4 batteries Mfg. Chin
Charge profile for Full Charge-
Absorb- 14.2
Float- 13.6
EQ- 14.2
EQ Time- .1
Absorb done- 5.0 hrs
Charge rate- 100%
Max charge time- 8.0 hrs
Final Charge- Silent
Re-bulk Voltage- 13.2

Charge profile for 70- 80 %Charge- (Will not stay at 80, creeps back and forth from 70 to 100)
Absorb- 13.0
Float- 12.9
EQ- 13.0
EQ Time- .1
Absorb done- 5.0 hrs
Charge rate- 100%
Max charge time- 8.0 hrs
Final Charge- Silent
Re-bulk Voltage- 13.0

Any help and experience is greatly appreciated.

 

[Richpatty]

This is a great point... I believe there is a way to do this... This is from page 13 from the ME-ARC remote (which is an upgrade from the one that comes with the MH.).
I have NOT tested this.

SOC Connect – Incoming AC only connects when the battery bank State of Charge (SOC) falls below the Connect SOC setting in the SETUP menu’s 02E AC In - SOC menu item. Disconnects from incoming AC when the battery bank SOC rises above the Disconnect SOC setting, also from the 02E AC In - SOC menu. This feature requires the optional ME-BMK (battery monitor) to be installed. See SETUP menu 02E for more information on the Set Connect SOC menu settings.

You do need to make sure you get to 100% at least monthly to ensure all the cells in the batteries get balanced.

Also there is some good videos on this topic from Will Prowse.




I don't travel as much right now and my RV is covered when stored, so I shut down as much as I can and let the batteries drift down in charge, They take a full month to get low...and by then it is time for either a trip or the RV's 30 day "exercise" where I get the batteries back to 100%.

I hope this helps ...

 

[WinePress]

Thanks Rich,
I will make these changes and see how the system reacts.

 

[newmarokie]

Wine,
You might consider adjusting the rebulk voltage and let the batteries cycle up and down

 

[WinePress]

I’ve done quite a bit of testing to get the Magnum to respond correctly to the Lithium’s. My aim is to be able to be on shore power and have the batteries holding at about 80% charge. I’ve learned that trying to vary the charging voltage isn’t the way to go as Lithium’s hold the voltage throughout the discharge curve. I made changes setting 2E. This setting is suppose to limit charging based on SOC of the the batteries. I found this did not work. I was hoping that the SOC connect % would be the answer.
Newmaroakie suggested above to look into the rebulk voltage. This is working. By going to the silent charge setting you can vary the voltage to when it will bring the batteries back up. For my application 12.9 to 13.0 works. Not perfect, but they are not sitting at 100% charge 24/7.

That said, my perfect scenario would be for the inverter / charger to bring the batteries up to 80 or 90% and then disconnect them until needed. Instead what happens is that even on shore power the batteries are in a constant state of flux, sometimes charging, sometimes discharging, never just idle.
Current settings:
Absorb- 14.2
Float- 13.8
EQ- 14.2
EQ Time- .1
Absorb done- 90% SOC
Charge rate- 70%
Max charge time- 8.0 hrs
Final Charge- Silent
Re-bulkVoltage- 13.0



The answer is of course to replace the Magnum with a more up to date replacement.



Any suggestions welcome.

 

[Richpatty]

Interesting. I am glad you got the rebuke option to work…at least mostly. And I agree that the magnum interface and functionality sometimes leaves me wanting more. If mine ever dies, I will be happy to get a Victron.

Keep us posted.

 

[newmarokie]

In thinking about where you are trying to get, the easiest solution is to put disconnects on the house batteries. Most coaches (and I think all Newmars) have a constant parasitic drain. Changing inverters will not solve that. We can come up with setting to get the magnum to charge to 80%, but then the parasites start working on that charge. Lithiums will sit at a charge for months if they are diconnected from all drains.

 

[WinePress]

Finally got the MS2812 inverter to play well with my Lithiums. I’ve learned more about this technology than I planned on. A .01 volt is a big change. Unlike lead acid, these retain their output voltage near constant throughout the discharge cycle. My goal was to be able to maintain the batteries at a 70 to 80% charge when I’m at home on shore power and not have to upgrade the inverter to Victron with a true lithium profile. There is a wealth on info on the Cruisers forum, a marine forum and lots of YouTube videos. Cruisers is where I stumbled on the proper profile setup.

One problem that I ran into is the the BMK is not as accurate as I thought. When the batteries are brought up to 14.4 for a full charge the BMK reads 100% SOC. This is fine, but I do not want to store at 100% for a long period of time. To reduce the charge you will need to bring down the absorb and float voltages. This confuses the BMK and it will not be accurate as far as SOC % goes. However, the BMK is very accurate with voltage and that is where it is useful in my application. I learned to go by volts not SOC for monitoring the charge.

In settings 03G there are three options. Multi, Float and Silent. Most everything I’ve read says to use Silent with a setting voltage to initiate a rebulk of the bank. This is where I had my issue as when the batteries hit the rebulk threshold the charger would bring the batteries back up to full charge. No matter what I would set the voltage the BMK would indicate 100% charge. This is not accurate as the voltage was lower that a 100% charge.

The answer was to not go with silent but rather go with float. The float setting will keep the batteries at a certain voltage once it reaches the float stage.

I have two profiles
Travel day or prepare for dry camping. Aim is to have battery bank at or near 100%
03 Charger Setup
03C- Custom
Absorb volts 14.4
Float 14.2
Set EQ 14.4
Time 0.1 hrs
03D Absorb done 100% SOC
03E 100% for fastest charge, but I set 50% not in a hurry
03F 8 hrs
03G Final Charge
Set to Float



At home or on Shore for extended time
03 Charger Setup
03C- Custom
Absorb volts 13.3
Float 13.2
Set EQ 13.3
Time 0.1 hrs
03D Absorb done 100% SOC
03E I set 50% not in a hurry
03F 8 hrs
03G Final Charge
Set to Float

Your battery profile may require slightly different voltages. At rest with 100% charge, voltage reading should be 13.6 at the battery terminals. I noted that I lost 0.1 volts from the battery terminals to the BMK. This is due to Cable resistance.

We did some dry camping on this years road trip. I was able to go 24 hrs with minimal compromises to our usual usage. This includes microwave usage. Still had 20% left. Did learn that Starlink can be a real power hog.

Safe travels

 

[Richpatty]

Good info. Thanks for reporting back.

 

[MikeyG]

Great info Winepress. Thank you. Question on your two rpofiles. Is there a way to put them into two different "favorites" so all you do is switch from one to the other or do you have to go into the Magnum settings and change the profile each time?

 

[Neal]

I'd like to hear more info on why people believe the 80% SOC is your target for a RV battery in use, even in storage. In my opinion, if you have any type of load draining the battery and a charger charging the battery, this doesn't apply. Or does it? If you're going to remove the batteries for long term storage, then yes, I understand the 80% SOC for that scenario IF the Apple iPhone battery scenario applies (which is NOT LiFePO4 chemistry). But not for an "active" battery. Prove me wrong.

Started a new thread for this discussion:

Thread 'Storing your RV - with LiFePO4 batteries'

Saturday at 12:12 PM

I'm creating a separate thread I started in another discussion so we can discuss this topic and focus on this specific theory. I'm seeing some believe that 80% SOC is where you should store your "active" LiFePO4 batteries, which is probably coming from the Apple world of iPhone battery management (which are NOT LiFePO4 batteries). This may be true if you physically remove and store your battery in a controlled environment. I'm not sure it's true for a battery that remains connected in a RV and is under any load, parasitic or not, and connected to a charger which may only float charge over...

• Neal
• Replies: 3
• Forum: Electrical, Generators, Solar, Batteries

 

[lostinfla]

I'd like to hear more info on why people believe the 80% SOC is your target for a RV battery in use, even in storage. In my opinion, if you have any type of load draining the battery and a charger charging the battery, this doesn't apply. Or does it? If you're going to remove the batteries for long term storage, then yes, I understand the 80% SOC for that scenario IF the Apple iPhone battery scenario applies (which is NOT LiFePO4 chemistry). But not for an "active" battery. Prove me wrong.

Started a new thread for this discussion:

Thread 'Storing your RV - with LiFePO4 batteries'

Saturday at 12:12 PM

I'm creating a separate thread I started in another discussion so we can discuss this topic and focus on this specific theory. I'm seeing some believe that 80% SOC is where you should store your "active" LiFePO4 batteries, which is probably coming from the Apple world of iPhone battery management (which are NOT LiFePO4 batteries). This may be true if you physically remove and store your battery in a controlled environment. I'm not sure it's true for a battery that remains connected in a RV and is under any load, parasitic or not, and connected to a charger which may only float charge over...

• Neal
• Replies: 3
• Forum: Electrical, Generators, Solar, Batteries

When I changed to lithium, the battery manufacturer (Epoch) said lithium batteries love to be in a state of constant charge/discharge. When plugged in at the house, there's a constant draw of between 2 and 5 amps which brings the bank down to around 50% before charging kicks in bringing them to 100% SOC. As I remember, my rebulk point is set at 13.0v. If the battery(s) are completely disconnected from the system for storage, they said to put them at around 60 -80%. Since ours is plugged in to 50a when in "storage", I leave the charging system as is. Seems to be working great so far.

 

[WinePress]

I leave the coach powered 24/7. Need the 12 volt side to run the AC system. If you disconnect the battery bank the Magnum will not provide 12 volts. Have to keep telling myself that it is a charger not a converter. I could throw a couple of lead acid batteries to satisfy the Magnum but would rather not be switching batteries around.
Everything I’ve read so far indicates that this technology does not like to sit at 100%, so I’m just trying to limit that to about 80 and float there. Once the 80% float has been achieved the batteries go back and forth 4 to 8 amps back and forth. This is where the solar geeks say that they live the best.
I don’t think I can store the two different profiles but it would be nice if I could.
I think there are several ways here to skin the cat, this method works for me. I will keep tweaking for improvement, however, that said this technology is awesome. Brings a whole new meaning to “Get the lead out”.