Switched to Lithium - Change Magnum remote

[CaptainYARRR]

Hey all,

I added 800 AH of Lithium to my coach and so far they have been great. I am using a custom profile for charging that seems to work well.

I'm curious, what does the newer ARC-L offer in its lithium profile that I'm not getting with a custom profile? Can't seem to find a straight answer on it and Magnum hasn't responded.

[Itinerant1]

If the custom settings are working why change the remote. I'm using the me-arc50 with my 500ah lfp bank for 7 years now, working perfectly.

[computerguy]

I agree with itinerant1.
I’ve too used the same remote since 2016. It lets one really customize the point to stop charging. I just with the bmk was as good. It’s useless if you don’t use the magnum solar charger. But thats another story in another thread or two or three.

[Persistent]

Originally Posted by CaptainYARRR

Hey all,

I added 800 AH of Lithium to my coach and so far they have been great. I am using a custom profile for charging that seems to work well.

I'm curious, what does the newer ARC-L offer in its lithium profile that I'm not getting with a custom profile? Can't seem to find a straight answer on it and Magnum hasn't responded.

State of charge monitoring may benefit from a new remote. Monitoring state of charge using lead acid profiles may not be accurate depending on how the monitor is designed.

Measure the battery terminal voltage. If the charger provides 14.4 volts at the end of the charge cycle then it is doing all that is needed.

Meeting the needed lithium charging profile is what is needed. Generally the optimum profile is simple. Different Lithium batteries may have slightly different profiles.

Charge as fast as the charger is capable of up to the battery banks ability to absorb it. Battle Born 100 amp hour Li charge optimally at 50 amps and can take up to 100 amps. So an 800 amp hour bank could optimally absorb up to 400 amps or less.

Charging current drops off naturally as the charge progresses. Charging voltage rises to maximum regulated voltage. Then it holds until charging is finished and balancing has completed. For Battle Born batteries, the optimum is 14.4 volts.

Battle Born batteries tolerate a following float voltage of 13.6, but do not need it. Holding at 14.4 volts is also fine.

Many brands suggest storing them at a little lower than full charge and disconnecting them. Recharge at about 6 months. Battle Born recommends storing them at full charge and disconnected for 6 months.

If your current remote provides what is necessary, then a newer design is unlikely to improve.

[jharrell]

Originally Posted by CaptainYARRR

I'm curious, what does the newer ARC-L offer in its lithium profile that I'm not getting with a custom profile? Can't seem to find a straight answer on it and Magnum hasn't responded.

Having used both with my lithium the are couple things that are helpful that its does compared to custom:

1. Temperature compensation is disabled regardless of whether the temp probe is connected or not, this allows you to continue to monitor battery temperature from the remote, when using custom you must disconnect the temp probe.

2. The re-bulk voltage is set to 12.8 vs 12.1, in custom you will not get it to go into bulk charge unless it sees 12.1v for 10 seconds, LFP's hold voltage above that very well until nearly dead. So what would happen I might run the batteries down to 50% over night, start up generator in morning to recharge and its would just stay in float which more slowly charges the batteries and never gets to absorb voltage, you could manually force a bulk through the menu. With the LFP profile it will hit 12.8 and re-bulk automatically which is more convenient.

You can get around the re-bulk issue on custom by going to the two-stage CC/CV mode which allows adjustment of re-bulk, however that mode has no float so your batteries will constantly cycle between full charge absorption and re-bulk even when connected to shore power. Some prefer this mode. I prefer 3 stage with float so I used custom before and now LFP which is what Magnum thinks is good for LFP's and I agree.

There a few other details as well, like disabling 4 stage with no full charge rest mode by default, this can be done in custom with final charge setting. It also re-bulks as soon as its sees shore power regardless of voltage.

Here is the document from Magnum describing the changes, note you need the L version of the inverter too, not just the remote:

Magnum-Lithium-Program-Review.pdf

[computerguy]

Originally Posted by jharrell

...
2. The re-bulk voltage is set to 12.8 vs 12.1, in custom you will not get it to go into bulk charge unless it sees 12.1v for 10 seconds, LFP's hold voltage above that very well until nearly dead. So what would happen I might run the batteries down to 50% over night, start up generator in morning to recharge and its would just stay in float which more slowly charges the batteries and never gets to absorb voltage, you could manually force a bulk through the menu. With the LFP profile it will hit 12.8 and re-bulk automatically which is more convenient.

You can get around the re-bulk issue on custom by going to the two-stage CC/CV mode which allows adjustment of re-bulk, however that mode has no float so your batteries will constantly cycle between full charge absorption and re-bulk even when connected to shore power. Some prefer this mode. I prefer 3 stage with float so I used custom before and now LFP which is what Magnum thinks is good for LFP's and I agree.
...

Hmmm, not sure what firmware revision this is in reference to. My ME-ARC (purchased in Dec 2016) allows me to change the re-bulk voltage to whatever I want. I did it recently for the reason you mentioned. If my bank goes down a certain amount and I want it to charge via the genset it was not doing it. Setting the re-bulk lower and it does. Screenshot of the manual attached.

[jharrell]

Originally Posted by computerguy

Hmmm, not sure what firmware revision this is in reference to. My ME-ARC (purchased in Dec 2016) allows me to change the re-bulk voltage to whatever I want. I did it recently for the reason you mentioned. If my bank goes down a certain amount and I want it to charge via the genset it was not doing it. Setting the re-bulk lower and it does. Screenshot of the manual attached.

Looks closer, its only allows re-bulk setting if final charge is silent, which is no float, this is very similar to CC/CV in fact I don't really see a difference. In CC/CV this is called re-charge volts instead of re-bulk.

Again if you want to float your batteries and not cycle them while plugged in and also having a reasonable re-bulk voltage then you must use the LFP setting:

[757driver]

Originally Posted by CaptainYARRR

Hey all,

I added 800 AH of Lithium to my coach and so far they have been great. I am using a custom profile for charging that seems to work well.

I'm curious, what does the newer ARC-L offer in its lithium profile that I'm not getting with a custom profile? Can't seem to find a straight answer on it and Magnum hasn't responded.

Now that you have a lithium bank here is some in-depth reading on the proper care and feeding of those batteries.

https://marinehowto.com/lifepo4-batteries-on-boats/

https://marinehowto.com/drop-in-life...ated-consumer/

Your 2016 Magnum inverters may not be capable of using a remote with the lithium setting, it depends on the revision status of your inverters.

Unless your battery manufacturer specifically requires a float charge I would not use it. A lithium battery continuously floated at 13.6v or greater will be held at a full charge which is not good for lithium. Float charging is a leftover from lead acid days and should have no place in lithium charging. Your custom profile also has an absorb time period which if left at a high value can damage your lithium bank.

Switching to a CC/CV charge profile or final charge of silent will allow you to set your charging voltage as well as the rebulk voltage. Once the bank is charged up charging stops until the rebulk voltage is reached.

Many seem to be worried about cycling a lithium battery thus the float setting. In 5 years of full time use I have put on 350 cycles on my lithium bank. Your cycle count would be higher due to the smaller bank but you get the picture. For lithium which should last for several thousand cycles (if properly looked after) I don’t see why adding a few extra cycles is so concerning.

[jharrell]

Originally Posted by 757driver

Unless your battery manufacturer specifically requires a float charge I would not use it. A lithium battery continuously floated at 13.6v or greater will be held at a full charge which is not good for lithium.

Define not good? LFP batteries have a lower cell voltage at 100% SOC than other lithium chemistries and are much more chemically stable, therefore the have very little voltage driven aging. The idea that holding a lithium battery at 100% ages them more quickly comes from higher voltage chemistries.

LFP do not need a float like lead acid because of their slow self discharge, they however are not damaged by a float either.

Almost all LFP charge profiles use float including Magnum and Victron, even Tesla recommends holding at 100% SOC on their LFP cars rather than 80% SOC on their NCA cars.

Battleborn recommended storing their batteries at 100% SOC as it does not effect cycle life and allows much longer storage before self-discharge effects the battery life.

Here is Battleborns CEO Dr. Denis Phares explaining why float is not bad and that holding LFP's at 13.6v is "perfect" for months at a time, the whole video is extremely informative on what actual causes short life spans and why LFP are so stable:

https://youtu.be/ywn-vBjKblI?t=858

I would not claim that cycling an LFP is any worse or better than floating, as I said I prefer floating for various reasons not related to longevity and it seems most LFP charger presets agree with me. I would suggest not providing inaccurate information trying to scare people away from using their LFP charge profiles that include float.

[Itinerant1]

When "float" is mentioned it can mean many different things to users.

When I mention float it's in a daily use system being daily charged by solar.

It's important when mentioning "float" how exactly you mean it. In a daily use system or an rv resort park queen with the occasional more often than not being plugged in.

Me personally for the occasional 184 times I was in an rv park since installing my system with lfp I would turn off the charger on the Magnum hybrid inverter/ charger and set the incoming power to either 50a or 30a depending on the pedestal power. Solar would top off the little use from 12v items during the night and the next day would top off and float at 13.6v till the sun went down again.

Other than that as a full-time continuous boondocker with 2,307 days of the past 2,491 days. 1,017 days was the longest strech between power poles hookups, right now 11/5/21 was our last power pole hookup. Maybe in a year the Honda eu2200i or eu2000i will be used a dozen times for a hold over charge of 2 hour run time or 200ah put back into the batteries.

It would be safe to say that my batteries have been at float atleast 90% of the time for a couple hour to 5 hours at times off of solar while it was powering other item in the 5th wheel. If harm is being done I'm not seeing yet or noticing it while using any of the 120v appliances in the 5th wheel. Daily draw is 175-225 ah +/- or 35-45% DOD. We're somewhere around 700 +/- full cycles on the batteries.

So is floating causing detrimental harm? I don’t believe in my use pattern.

I hope everyone that switches over to lfp has as good experience that we're having with them and the system.

[computerguy]

Originally Posted by jharrell

Looks closer, its only allows re-bulk setting if final charge is silent, which is no float, this is very similar to CC/CV in fact I don't really see a difference. In CC/CV this is called re-charge volts instead of re-bulk.

Again if you want to float your batteries and not cycle them while plugged in and also having a reasonable re-bulk voltage then you must use the LFP setting:

Attachment 385954

Attachment 385955

Attachment 385956

Ah, ok, I see what you are saying. I don't use float as my batt manufacturer says it is not good to leave these at float. I will get more life out of them letting it discharge and then recharge. As said, one should always check with their specific battery manufacturer and model.
I am now 7 years in on my install living full time and I still have over 100% capacity of my lithium battery bank.

[jharrell]

Originally Posted by computerguy

AI don't use float as my batt manufacturer says it is not good to leave these at float.

Interesting, are you still using the Elite Power Solutions pack using GBS Cells?

Because the chargers that EPS sells for their packs seem to have a 3 stage with float at least according to their website:

[computerguy]

Originally Posted by jharrell

Interesting, are you still using the Elite Power Solutions pack using GBS Cells?

Because the chargers that EPS sells for their packs seem to have a 3 stage with float at least according to their website:

Attachment 386022

I am still using them. No idea about their chargers and there can be so many configurations with different products and BMSes. I am going by what I was told back in 2016/17 when I installed mine with the Magnum and the BMS I was sold at the time. Certainly possible that float or not float can be ok.

[Itinerant1]

Originally Posted by computerguy

I am still using them. No idea about their chargers and there can be so many configurations with different products and BMSes. I am going by what I was told back in 2016/17 when I installed mine with the Magnum and the BMS I was sold at the time. Certainly possible that float or not float can be ok.

I'm using their (GBS) senseboards and EMS/ CPU. It seems either way we're both doing ok.