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Old 09-18-2022, 01:40 PM   #1
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Charging LiFePO4 rather than AGM

My RV came with 400Ah of AGM batteries that I replaced in April of this year with 400Ah of LiFePO4 batteries.

My house batteries are charged by the OEM Magnum MS2012 inverter/charger. This setup came standard with a simple ME-MR 3-button remote display. This is a very limited remote and doesn't provide much in the way of controlling the charger - or even the Inverter very much. I replaced it with Magnum's most capable remote the ME-ARC50 (a $200 plug and play upgrade). This gives me total control over the charger, it's settings and the same for the inverter. It's a great upgrade. It also permits the installation of Magnum's ME-BMK, a shunt based battery monitor - which I've done.

When I had AGMs I kept my Inverter and Charger ON all the time we were using the RV. This, plus the 300w of solar I have kept the AGMs charged all the time. Which gave me peace of mind.

Now, with Lithiums I continued to operate the same exact way. And when using the RV I've seen those batteries at 100% state of charge (SOC) all of the time. But then I realized that's not such a good thing. Lithium batteries don't like be fully charged all the time and resting at 100% SOC is not recommended.

We're on a month long trip and camping in a National Forest Campground north of Durango. We have 50-amp shore power here and I decided to do some testing.

The batteries were at 100% SOC - and we were on shore power - so I turned off the charger and the inverter. Now all 110v AC appliances were running off the shore power and all 12v appliances on the RV were running off the Lithium batteries.

I kept a close eye on the house batteries and over the past week they've slowly declined in SOC. It's 8300' elevation here so nights are cold (low 40's) so the LP furnace is running some every night keep us no colder than 63 degrees. This is the biggest draw on those house batteries.

After about a week I see my SOC is at 60%. Which is fine and I could keep this up for another week no doubt. The battery monitor says I have 10-days left at my current usage. But I went ahead and turned on the charger.

I saw my AC amps shoot up to 80-amps as the charger quickly recharged the lithium batteries. They really do charge fast and in a couple of hours I was at 100% SOC again. So I turned the charger off again to start the process over. I feel it must be helpful to my house batteries to get exercised this way.

I'm researching my Magnum's settings to change how the charger works when on shore power to automatically stop charging when they reach 90% SOC and then start charging again when they reach 50% SOC. I'm not looking to hit 100% SOC all the time. When driving my DC-DC charger will keep my batteries topped up and there's the solar charger doing some of that work too. I don't think I will need the AC Charger in my inverter/charger very much at all.

I've been RVing since 2003 and I find that understanding 12v house batteries in an RV is kind of a never ending experience. Just when I think I've got things figured out I find there is so much more to learn and apply.

PS. We don't boondock all that much because living in South Texas A/C is always needed until we drive 1000 miles north. When we do dry camp I'll vary my settings as needed.
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Old 09-19-2022, 12:05 PM   #2
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Lithium batteries should not be float-charged as you know. Many brands of Lithium batteries say 90% SOC is fine.

Also drive engine alternators do not hold up well when running at maximum output constantly. There's a guy on irv2.com now complaining about burning up 2 new alternaters on his MH trying to charge Lithium batteries..
That requires a DC to DC charger setup..
There is a lot of information about using/maintaining Lithium batteries on irv2.com, check it out.
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Old 09-19-2022, 02:24 PM   #3
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As I mentioned I have disconnected my Alternator from the house batteries and my Victron DC to DC charger handles charging while driving. I have it set to charge to 13.4v which is just below full charge voltage (13.5v).
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Old 09-25-2022, 05:46 PM   #4
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I saw my AC amps shoot up to 80-amps as the charger quickly recharged the lithium batteries.


80 amps at 120 vac is gonna burn up your 12vdc cables really fast, like melt the rubber. better check that part.
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Old 09-25-2022, 07:01 PM   #5
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not exactly, you need to rework your math. I am sure the 80 amps was on the 12 VDC side, 80 Amps x 12 VDC = 960 watts, not taking into consideration the inefficiency of his Charger, 960 watts/120 volts = 8 Amps at 120V, not 80
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Old 09-25-2022, 09:49 PM   #6
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creativepart,

We have essentially the same setup -- Magnum MS2000 with ME-ARC50 remote; and two (vs 4) 105aH LiFePO4 batteries.

What I've found is that even though the MS2000 charger has a "custom" setting, and even though I have it set according to what the battery mfr and Magnum recommends (I spent a long time on the phone with a Magnum tech) I still have to manually force the charger into the 'equalize' mode (EQ voltage is the same as absorption voltage) to get it to begin charging.

What we were used to with our Crown GC batteries was the usual situation where the charger would keep the batteries topped off.

Not with the LFP batteries. I haven't been there to witness it, but it seems like the BMS actually has to switch off due to low voltage before the MS2000 charger kicks on.

Initially -- and for quite a while after the installation -- there would be a DC voltage spike when the batteries were charged and the BMS opened up (shut off current flow). I use a Victron Smart Shunt (although Magnum's ME-BMK maybe have been a better choice). The Smart Shunt app showed spikes of about 17Vdc, and the faults in the ME-ARC50 showed the same.

Sometimes the transfer switch (ATS) in the MS2000 would open for about 15 seconds -- my 120V trouble light would turn off -- and then the ATS would reset. Very strange behavior. I take it you never experienced that?

I have to say, I really miss having the batteries topped off all the time. I realize that's not good for LFP batteries, but I have a suspicion that "100%" per the BMS is not truly 100% SOC. Likewise, 0% is not really 0%. The reason I say that is our batteries are warrantied for 3,000 cycles (with at least 80% capacity left) and the mfr says it's no problem to cycle them from 100% > 0% > 100%. They have to assume many people will do that -- as well as storing them at "0%" or "100%" -- so I think what they probably do is use cells that are actually good for (say) 125aH and have the BMS limit them to 105aH.

Just a thought with nothing to back it up.
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Old 09-25-2022, 11:37 PM   #7
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Tim, that was a quote from the OP's original statement.

"I saw my AC amps shoot up to 80-amps as the charger quickly recharged the lithium batteries."
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Old 09-25-2022, 11:58 PM   #8
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I'm gonna agree with you though. My a/c load meter doesn't speak to me if I'm on 50 amp or generator. And it will never tell tell me I'm using 80 amps.
The inverter will tell me if I'm using up to 300 amps.
Don't know what the OP meant.

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Old 09-26-2022, 07:31 AM   #9
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Magnum LiFePO4 settings for on and offline storage.

I have the Magnum ME-RC remote so not quite the same but these values may help. My inverter is a 2800 but that shouldn't matter either. I don't have the magnum BMS I have Blue Sky.

I have blue tooth battery management system so I know my battery SOC directly from the battery management system in the batteries (LifeBlue) . I also have an external (blue sky) battery monitoring system.

Both the internal and external systems will drift off if the batteries are not occasionally fully charged and the monitoring system drifts faster and farther than the internal management system.

Also with out occasionally fully charging on my batteries the cell balancing will also drift off.

We do boon dock a lot, just finished one month dry camping in the Smokies.

I have two setups for my magnum, one offline storage, and one active charge.
Offline storage when we are on grid power. The goal is to keep the batteries at about 50% charge and avoid unnecessary current. Most of the time my batteries are in standby (0 current in or out) and the charger supplies whatever DC is needed.

Active charge is when no grid power is available. The goal of the active storage to get the batteries close to full charge but not spend much time at more than 13.6 volts. Active storage is for generator runs.

95% of the time I actually use the equalize function for active charge but monitor the batteries closely. I find that the equalize mode provide more current after the batteries get close to 13.6, 20 or 30 amps more, and thus shorten my generator run time. In equalize I charge to between 60% to 90% depending upon my ability to run the generator the next day and the anticipated solar. Don't let the 14.4 volts scare you. The charger never gets to that if you stop short of 100% SOC and even if you were to forget occasionally it won't shave much life off of your batteries.

I have offline and active for my solar as well.



My settings.


Magnum Inverter Charger
Offline Storage
These settings seem to hold the batteries at about 50% SOC in a standby state.
Absorb
13.2
Float
13.2
Equalize
14.2
Final Charge
Float
Charge Rate
100%
Absorb time
1/10 Hour


Active Charge
These setting exceed 90% but do not reach 100%

Absorb
14.2
Float
13.6
Equalize
14.4
Final Charge
Float
Charge Rate
100%
Absorb time
.1 Hour
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Old 09-28-2022, 01:41 PM   #10
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When I read this, “ Lithium batteries don't like be fully charged all the time and resting at 100% SOC is not recommended.”

I knew the answer, but in order for people to have trust in my response, I contacted Battleborn. Here’s their response… Hope this helps, at least if you have Battle Born batteries…
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Old 09-28-2022, 02:03 PM   #11
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Quote:
Originally Posted by Wyatt View Post
When I read this, “ Lithium batteries don't like be fully charged all the time and resting at 100% SOC is not recommended.”

I knew the answer, but in order for people to have trust in my response, I contacted Battleborn. Here’s their response… Hope this helps, at least if you have Battle Born batteries…
So, can that be interpreted to mean that it may not be a good idea to leave your LFP at 100% SOC while connected to a solar array? Since the charge controller is looking for a 5v delta between input voltage and battery voltage, if you’ve got more than 18.5v coming from the array, (let’s say 36v) and battery voltage is 13.5v @ 100%, would the constant charge from the controller harm the battery, or would it be protected by the bms?

Would like to know so I’ll know if it’s necessary to disconnect the array.
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Old 09-28-2022, 04:07 PM   #12
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The solar “disconnects“ automatically every night. I not only never disconnect my solar panels, I don’t even have a way to do so. The charge controller is a configurable smart charger. I have mine set to stop charging at 13.4v. Fully charged is 13.5v.

BY the way, I don’t have Battleborn batteries. But I think you’ll find plenty of confirmation for holding LiFePO4 batteries in a slightly under charged state.

I’ve been keeping my inverter/charger’s charger off throughout this month long trip. I find this exercises my batteries a little each day. I use about 7% SOC overnight and my solar panels recharges them slowly all day. Previously, my inverter kept the batteries at 100% SOC day and night more or less continuously.
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Old 09-28-2022, 08:42 PM   #13
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I’m sure I could find plenty of online confirmation which is why I contacted battle born directly. Everyone has an opinion some are just better than others and what I find online is a lot of people are just repeating what they heard someone else say rather than what the facts are.
I would be curious if other lithium battery manufactures state in their manuals not to keep them at 100% state of charge.
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Old 09-29-2022, 07:56 AM   #14
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Quote:
Originally Posted by Wyatt View Post
....
I would be curious if other lithium battery manufactures state in their manuals not to keep them at 100% state of charge.
LifeBlue has no problem leaving the batteries at 100% SOC. If you take your batteries to the 100% SOC charge as specified by the manufacture you are very likely to get warranty service and the stated service life.

However it is also understood that running current through a LiFePO4 battery after it is fully charged will reduce its life. Fully charged is somewhat difficult to determine with a LiFePO4 battery because it requires rather precise and accurate voltage and current measurements. Unless you use a highly integrated system like Victron you probably don't have accurate and sufficiently precise measurements to optimize battery charging for maximum cell life.

Therefore to be safe and get the most out of the batteries some people choose to investigate ways to optimize battery life by compensating for component inadequacies. This is especially true if you have drop in replacement batteries that provide no BMS telemetry and you must guess the state of the battery charge, current, balance, and even temperature.

Not charging to 100% is one way to approach this problem. You may not know exactly where you are on the charge profile but if you maintain adequate capacity and try to stay short of unnecessary current you definitely have a better chance of maintaining battery life than if you hammer them with unnecessary current for an unnecessary period even though they can probably take it.

That and I personally just like learning and experimenting.
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Old 09-30-2022, 02:45 PM   #15
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Dick,

My bad, I looked right past what he said and never gave it a second thought, but you are correct he said AC, my apologies, hey, where in Whidbey have some family and a couple friends that live on Whidbey.
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Old 10-01-2022, 06:00 AM   #16
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It is my understanding Lithium batteries should never be "float" maintained, only bulk and absorption charge modes should be used for the charger.
reference: .https://battlebornbatteries.com/char...es-the-basics/
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Old 10-01-2022, 09:00 AM   #17
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I want to repeat that my comments about my batteries are about sitting on shore power with my inverter/charger constantly applying a float current to keep my LiFePO4 batteries at 100% SOC 100% of the time. I don’t think that’s healthy for them. When I had AGMs I thought that was a good plan.

On travel days my batteries are topped up via solar power and my DC2DC charger. When sitting for days in a campsite my solar ends up being enough to do the job for the little 12v loads I’m seeing each day to reach 100% SOC just about everyday.

After I return home I plan to work on the Magnum’s configuration setting to achieve the same thing automatically. Currently I’m going to keep the charger in my inverter set to OFF.
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Old 12-04-2022, 06:20 PM   #18
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I have basically the same setup with the Magnum remote which is capable of resolving your issue. You need to set final charge to "silent". Then it will keep it on float for a couple of hours and then remove all charge voltage. The SOC will slowly drop over time until the voltage hits a certain level. By changing your settings to "custom", you can have it "Re-bulk" at 13.2. You can set your bulk voltage time for perhaps 4 hours and set it to 14.4 or 14.5. If it hits that top end, it will immediately go to "silent" mode and begin the slow decline over several days. That is a better way to treat your lithium batteries. If, by chance, 4 hours goes by and you did not fully reach 100%, you can hold the on/off button for 10 seconds and put it on equalize. Be sure your equalize voltage is no higher then 14.4 (set in the custom settings). The equalize will time out in 4 hours and the charger will revert to "silent" mode (no voltage applied. Try to read and understand the Magnum remote. I know it is not for everybody, but once you start playing with it, it starts making sense.
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Old 12-05-2022, 09:16 AM   #19
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With all this talk about settings on the Magnum 2012, I was wondering if anyone was running the newer remote WITH the Lithium option for batteries? I recently started this project (changing to LifePO4) and ordered the required remote head. My model had a "-L" on the box (ME-RC50-L) and had a sticker which read "Lithium ready" . The guy I spoke with at Magnum support said they were having LOTS of callbacks when trying to advice customers of the "custom" settings. So apparently added the LFE option to the firmware.
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Old 12-05-2022, 10:14 AM   #20
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The lithium version wasn't available when I got my new remote. Magnum is so behind the times when it comes to Bluetooth and Wifi, etc. You'd think it would be so easy to download an update for the remote to add the Lithium profile. But no you have to buy a new remote.

I used to get great advice from Magnum on specific settings every time I contacted them via email. But after I installed my new batteries I sent a detailed email telling them all the settings I needed and the specs of my batteries.

The response - which came 5-days later was, "We have a number of videos on YouTube about how to set up the MS2012 for Lithium. Please review those videos on the topic."

Not one of the videos addressed any of the settings I inquired about.

You'd think in 2022 Magnum would have not only updates for download for Lithium batteries, but also remotes that contain Bluetooth output and smartphone Apps for their products. But even if you buy a new Magnum MS2012 today you have none of those features. (They do make a $400 WiFi add-on but it only applies to larger power systems with multiple inverters.)
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