Replacing new Li-Ion batteries in Class A Motorhome

[mohospinner]

Hello fellow RVers,

I purchased (4) 12V 100aH Li-Ion batteries and want to make sure I don't damage anything.

Here is some information:

Year: 2020
Make: Fleetwood
Model: Pace Arrow LXE 38N (diesel pusher)
Inverter/Charger: Magnum MS2812
Controller: Magnum ME-ARC
Stock Batteries: (4) 6V lead acid batteries wired in series/parallel.
New Batteries: (4) 12V Ampere Time Li-Ion 100AH wired in parallel. (I watched many YouTube videos and read multiple reviews regarding these "Ampere Time" batteries).

My main concern is that I don't want to damage the electrical system, charging system, or alternator. I have read so many threads here and there and need more coherent answers. I have installed the Li-Ion batteries and changed the charging settings with the controller to constant charge/constant voltage (CC/CV) and the Li-Ion charging settings designated by the battery manufacturer. I have a 50A 240V outlet at my house that I plug into when the RV is here. I left it plugged in overnight with the 12V RV porch lights on and noticed before heading to bed that the lights were off and there was no house battery power in the RV (This was after many hours being plugged in to shore power). I disconnected the Li-Ion house batteries that night, re-connected them in the morning and things all looked normal and stable. Do you have any idea what would cause the house system to shut off?

My next question would be the alternator. I've read about DC-DC charging, upgraded alternators, and Battery Isolation Managers (Like this: https://battlebornbatteries.com/prod...ation-manager/) that time cycle the charge current from the alternator to the house batteries so they are not getting charged full time from the alternator. I'm confused with this. Which option is best? What do you use for this? I'm heading on a trip later this week and wondering if I should install a manual disconnect to shut down the charging from the alternator to the batteries before we head out to prevent charging from the alternator until I get this mess sorted out. (Update: I ordered the disconnects and will be installing on this week).

I'm also convinced I should probably install a Victron Battery Monitor to keep a close eye on things...

I appreciate any input and thank you in advance!

[paul65k]

Lots of questions here, I'll start with some of the easy ones first;

YES, you should get the battery monitor. Voltage is a poor way to measure capacity on a LiFePO4 battery as the discharge profile is very flat and then falls off the end of the earth and the Victron SmartShunt or BMS712 would be a great solution.

I think your choice to disconnect the alternator (regardless of what others may tell you) is a very prudent decision until you can figure which solution is best.

I personally believe that the DC-DC is the way to go and I did install dual Victron 30A chargers. The Li-BIM is also a good solution but the charging will be less as it works at 30A for 15 minutes and then is off for 20 minutes so if you do the math you are putting less charge back in the batteries while driving.... but that's not to say this is not a viable solution.

Your decision to wait until you have it completely figured out is wise and whichever solution you choose it should work out well for you.

Good luck and welcome to the next level....... Lithium batteries will change your life!

[757driver]

Your house system shut off because something in the batteries BMS was triggered to shut things down. Could have been over current from charging, cell or battery overvoltage etc. The next morning everything returned to normal so the bank could be reconnected. I would check your charge settings something may be wrong. You mentioned you have set up CC/CV charging. How long is your CV charge cycle? This cycle should be measured in minutes, not hours.

You mentioned getting a lithium BIM or a DC to DC charger. You have more control over a DC to DC charger, but the LI BIM works just fine. What BIM do you have presently? You may not get any alternator charging of your lithium bank in its present form.

[vsheetz]

Options for alternator charging:

Checking to see if the alternator draw is actually excessive and voltage is adequate to charge lithium - act or do nothing accordingly.

The LiBim is just a timed switch. So many minutes off, so many minutes on. The idea is to reduce the duty cycle. Depending on the actual draw and voltage, it may be a solution. I'm not a fan, ymmv.

A DC to DC charger is likely the best if solution needed. Select the proper size unit for the alternator and provides a proper lithium charge profile.

###

My experience with my DP motorhome and 600ah battery bank:

At low SoC the alternator draw is typically 40-45a - not excessive, and reduces as the bank charges. However the voltage is inadequate to bring the bank to a goodly charge level.

So a LiBim would not get the job done.

I've elected to do nothing, as my 1500w of solar typically charges well while traveling. If I do decide to add something, it would likely be a Victron DC to DC charger.

Imho. Ymmv.

[vsheetz]

Using CC/CV. What is the rebulk voltage set to? This is where the charger resumes charging after being silent. Suggest 13.0 bolts with lithium.

If set for lower voltage, as would be used with lead acid batteries, the lithium batteries could have been allowed to go to LVCO.

[vsheetz]

Yes. You need a batteru monitor such as Victron SmartShunt or BMV712. The flat discharge curve of lithium battery negates SoC estimation by voltage.

[creativepart]

I'm wondering about your description of your home shore power connection. You said "50amp 240v". But a 50 amp RV shore power connection is two 120v 50 amp legs. So, it's similar but certainly not the same thing at all.

Have you been using this home shore power set up from before you made this battery switch? Is it possible that the home shore power setup has damaged or tripped your on board charger?

[vsheetz]

Here's a pretty good article on the care and feeding of Lithium batteries.

https://www.solacity.com/how-to-keep...tteries-happy/

[mohospinner]

Originally Posted by paul65k

Lots of questions here, I'll start with some of the easy ones first;

YES, you should get the battery monitor. Voltage is a poor way to measure capacity on a LiFePO4 battery as the discharge profile is very flat and then falls off the end of the earth and the Victron SmartShunt or BMS712 would be a great solution.

I think your choice to disconnect the alternator (regardless of what others may tell you) is a very prudent decision until you can figure which solution is best.

I personally believe that the DC-DC is the way to go and I did install dual Victron 30A chargers. The Li-BIM is also a good solution but the charging will be less as it works at 30A for 15 minutes and then is off for 20 minutes so if you do the math you are putting less charge back in the batteries while driving.... but that's not to say this is not a viable solution.

Your decision to wait until you have it completely figured out is wise and whichever solution you choose it should work out well for you.

Good luck and welcome to the next level....... Lithium batteries will change your life!

Thanks Paul65K,

Ok on the battery monitor. It seems like the logical thing to do and I have heard nothing but praise for Victron products.

I think I will disconnect the alternator until I go with the Victron DC-DC charger like you mentioned. You mentioned "Dual", can a single charger have enough power to charge my 400aH battery bank or do I need (2) DC-DC chargers?

I will submit a summary when I get this all sorted out.

Thanks again!

[mohospinner]

Originally Posted by 757driver

Your house system shut off because something in the batteries BMS was triggered to shut things down. Could have been over current from charging, cell or battery overvoltage etc. The next morning everything returned to normal so the bank could be reconnected. I would check your charge settings something may be wrong. You mentioned you have set up CC/CV charging. How long is your CV charge cycle? This cycle should be measured in minutes, not hours.

You mentioned getting a lithium BIM or a DC to DC charger. You have more control over a DC to DC charger, but the LI BIM works just fine. What BIM do you have presently? You may not get any alternator charging of your lithium bank in its present form.

Thanks 757, I will check the CC/CV settings today or tomorrow. I currently have a stock BIM that was installed new in the coach and have no idea where it might be, but probably not going down the aftermarket BIM route as I would rather deal with the more effective DC-DC charging method. Thanks again.

[mohospinner]

Originally Posted by vsheetz

Options for alternator charging:

Checking to see if the alternator draw is actually excessive and voltage is adequate to charge lithium - act or do nothing accordingly.

The LiBim is just a timed switch. So many minutes off, so many minutes on. The idea is to reduce the duty cycle. Depending on the actual draw and voltage, it may be a solution. I'm not a fan, ymmv.

A DC to DC charger is likely the best if solution needed. Select the proper size unit for the alternator and provides a proper lithium charge profile.

###

My experience with my DP motorhome and 600ah battery bank:

At low SoC the alternator draw is typically 40-45a - not excessive, and reduces as the bank charges. However the voltage is inadequate to bring the bank to a goodly charge level.

So a LiBim would not get the job done.

I've elected to do nothing, as my 1500w of solar typically charges well while traveling. If I do decide to add something, it would likely be a Victron DC to DC charger.

Imho. Ymmv.

Helpful info. Thank you Vince.

[mohospinner]

Originally Posted by vsheetz

Using CC/CV. What is the rebulk voltage set to? This is where the charger resumes charging after being silent. Suggest 13.0 bolts with lithium.

If set for lower voltage, as would be used with lead acid batteries, the lithium batteries could have been allowed to go to LVCO.

I will check this later today or tomorrow and see what the settings are and modify if needed.

[mohospinner]

Originally Posted by creativepart

I'm wondering about your description of your home shore power connection. You said "50amp 240v". But a 50 amp RV shore power connection is two 120v 50 amp legs. So, it's similar but certainly not the same thing at all.

Have you been using this home shore power set up from before you made this battery switch? Is it possible that the home shore power setup has damaged or tripped your on board charger?

It's the same 240V 14-50 outlet you would use with any larger coach or 5th wheel. (4 wires), 2 hots, 1 neutral, and 1 ground (240V between hots, 120V between hot/neutral or hot/ground). It's exactly the same.Thanks

[mohospinner]

Originally Posted by vsheetz

Here's a pretty good article on the care and feeding of Lithium batteries.

https://www.solacity.com/how-to-keep...tteries-happy/