Should the battery isolation manager be replaced when updating to lithium?

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Should the battery isolation manager be replaced when updating to lithium?

January 23, 2021, 03:29:27 am

I have a 1995 LD and upgrading the batteries to lithium. However I am confused as to whether the current setup (from factory) is okay to charge the batteries with the alternator.

In case wondering, I'm upgrading to 12v Battleborns, and planning to leave it as a 12v system so that I can still charge it with the alternator. If anyone knows a way to charge a 24v system with the alternator I would be interested to find out.

Specifically, wondering if this is needed:
LiFePO4 Battery Isolation Manager (BIM) | Battle Born Batteries

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #1 – January 23, 2021, 06:03:15 am

At beginning of our conversion to the 440AH LiFePO4 batteries in 2014, I shared same concern with the engine alternator over charging the house batteries due to the fact of LiFePO4 batteries are very sensitive to over charging. There were no battery isolators on the market (or I could not find one). To cope with this issue, I wired two LED digital voltmeters mounted on the instrument panel of the E450 so I can compare chassis and house battery voltages. What I found the chassis battery may reach 14.2v during driving, the house batteries almost never higher then 13.8v. There is a significant voltage drop (0.5v to0.7v) across the diode isolator of every LD installed by mothership. To prevent alternator over charging house batteries, I also wired a manual switch and a 25amp relay to turn off alternator charging during driving but I almost never used this circuit, there has been no need anyway.

Managing our array of 600w solar panels charging house batteries during long drives on sunny days out west has been another challenge. The solar charge is shut off at 13.79v according to the battery spec and restart when voltage drop back to 13.25 volt. To utilize excess solar energy, I use a 1kw inverter with manual on/off switch mounted the driver seat so I can turn the fridge to a/c mode when there are plenty of solar energy available.

These are my own experiences, others may have different ways to approach these issues.

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #2 – January 23, 2021, 09:31:23 am

All during my BattleBorn battery install I was conferring with Eric Carter at BattleBorn about my setup. He said that the connection to the Ford engine battery system through the solenoid switch will not harm their batteries. I did trade out the Parallax converter for the Progressive Dynamics unit that has a selectable (via jumper pins) lithium charging mode that puts out 14.5VDC to the batteries. Eric conferred that that is good. He says the batteries cannot be over charged as each battery has a battery management system that prevents this. The Blue Sky Energy solar controller that comes with the LD does have to be readjusted for lithium and the tech at Blue Sky walked me through that procedure. Hopefully that is all I will need for keeping the batteries charged.
I am curious as what is the need for a 24VDC charging in your motorhome?

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #3 – January 23, 2021, 09:51:06 am

Quote from: Mike Coachman - January 23, 2021, 09:31:23 am

All during my BattleBorn battery install I was conferring with Eric Carter at BattleBorn about my setup. He said that the connection to the Ford engine battery system through the solenoid switch will not harm their batteries. I did trade out the Parallax converter for the Progressive Dynamics unit that has a selectable (via jumper pins) lithium charging mode that puts out 14.5VDC to the batteries. Eric conferred that that is good. He says the batteries cannot be over charged as each battery has a battery management system that prevents this. The Blue Sky Energy solar controller that comes with the LD does have to be readjusted for lithium and the tech at Blue Sky walked me through that procedure. Hopefully that is all I will need for keeping the batteries charged.
I am curious as what is the need for a 24VDC charging in your motorhome?

Mike,
Your LD has the newer engine ignition controlled solenoid switch to control alternator to house battery charging in the newer LD models. I do not know which model year the Mothership made this change. For older model LDs like our 2004 MB, the charging is through a diode isolator (a one way check valve in the electrical sense) mounted on the engine bay fire wall. In addition, each LiFePO4 battery manufacturers has a specific stop charging voltage that is best for that particular type of battery pack. We select our stop charging voltage of 13.79v (at 90% of capacity) to preserve battery life. All these need to be considered when upgrading from lead acid batteries to lithium

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #4 – January 23, 2021, 12:17:46 pm

The only caveat I know of is that lithium batteries can accept a LOT of charging current. A large enough bank being fed by an alternator with limited output can damage the alternator. You might want to Google for more info about this issue. One hit:
Careful - Alternator Charging Lithium | Victron Energy

Art

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #5 – January 23, 2021, 02:02:27 pm

Hi Tom; Some installers of Li battery systems use the Cyrix-Ct battery combiner   120 Amps, probably more than your alternator can produce. As I understand your system, there shouldn't be a need for any additional controls. The size of the wiring going to the BB batteries should be increased. How many BB batteries are you planning on? If just the two in the slide tray, I would insulate the outside door.
   Some installers use the   Victron Cyrix Battery Combiner
   Amazon has a Cyrix-ct at lower price that might be good for your application: Amazon.com: Victron Energy Cyrix-ct 12/24-Volt 120 amp Intelligent Battery...
It appears this last one will keep your starting battery charged also, if there is extra charge from the solar, or shore power. RonB

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Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #6 – January 23, 2021, 04:04:42 pm

Quote from: RonB - January 23, 2021, 02:02:27 pm

Some installers use the Victron Cyrix Battery Combiner
Amazon has a Cyrix-ct at lower price that might be good for your application: Amazon.com: Victron Energy Cyrix-ct 12/24-Volt 120 amp Intelligent Battery...

When Kent had his electrical upgraded, AM Solar installed a Victron Cyrix to use the engine's alternator.
Extra solar panel option

There are several Vicron Cyrix combiners, for various applications and amperage ratings.
https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-120-A-EN.pdf
For owners of older rigs, with diode isolators, one of these combiners would be a good replacement.
They are available for both AGM and Lithium batteries.

Larry

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Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #7 – January 24, 2021, 06:43:49 am

Quote from: Older_Fossil - January 23, 2021, 12:17:46 pm

The only caveat I know of is that lithium batteries can accept a LOT of charging current. A large enough bank being fed by an alternator with limited output can damage the alternator. You might want to Google for more info about this issue. One hit:
Careful - Alternator Charging Lithium | Victron Energy

Art

You are right Art. A large pack of lithium battery could draw a large charge current but if an in series 30amp circuit breaker or fuse is wired in, it will protect the alternator. In addition, due to the presence of diode isolator and the higher battery voltage range, the alternator could drive a smaller charging current to the lithium batteries than that of flooded batteries. For example, the charging voltage of our CALB LiFePO4 battery at 50% capacity is 13.2v, compare to that of flooded battery at 12.2v at 50%. Say the alternator voltage regulator is set at 14.3v, the diode isolator takes out 0.5v, than there is only 13.8v charging voltage available to the batteries.

From my own experience, the actual charging current by alternator never exceeded 20 amps if I kept the battery pack above 50% capacity in order to prolong the battery life.

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #8 – January 24, 2021, 01:02:13 pm

Quote from: cli288 - January 24, 2021, 06:43:49 am

From my own experience, the actual charging current by alternator never exceeded 20 amps if I kept the battery pack above 50% capacity in order to prolong the battery life.

When our coach's 440-amp battery needs charging, I have seen over 60-amps from the alternator and up to 65-amps from the PD 9270 converter.
By replacing the diode (Pre-2007 LDs) with a battery combining relay, such as the Cyrx, the diode's voltage drop will be eliminated, delivering full voltage to the coach battery.

For those lucky enough to own a 2021 LD, the new V8 offers a dual alternator option, a 240/157-amp combo.
The 240-amp alternator can be dedicated to just charging the lithiums. The marine world has aftermarket regulators available for charging lithium batteries. This would be a great setup for lithium batteries and winter boondocking.
Example.
https://oceanplanetenergy.com/wp-content/uploads/sites/86/old/genasun-ar2-altregmanual-2011-01.pdf

Larry

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #9 – January 24, 2021, 01:30:19 pm

Thanks for the update Larry, it is amazing automotive technologies have progressed, now duo alternators with one dedicated to charge lithium batteries! My concern will be the large current fast charging generate a lot of internal heat which will cause permanent damage to the batteries itself. I placed thermocouples on each of the 4 batteries placed in the space underneath the fridge and always observed higher cell temperatures in the two batteries in the middle, especially during large current charging when we use the Magnum 2kva inverter charger. Our TriStat MPPT solar charger could also deliver high current from the 600w solar panels tilted up but we ran the fridge in these situations to divert some of the current away from batteries to reduce charging heat to prolong the battery life.

If I ever need to revise the battery pack for some additional reason, I would place a thick aluminum sheet between each of the batteries sandwiched together to conduct charging/discharging heat out. High capacity LiFePO4 batteries are still very expensive, I want to get as much of their useful life as I can.

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #10 – January 24, 2021, 01:52:45 pm

Quote from: cli288 - January 24, 2021, 01:30:19 pm

My concern will be the large current fast charging generate a lot of internal heat which will cause permanent damage to the batteries itself. I placed thermocouples on each of the 4 batteries placed in the space underneath the fridge and always observed higher cell temperatures in the two batteries in the middle,.

It's my understanding that a lithium BMS monitors each cell's temperature and will cut off charging if the temperature is too high or low, as well as monitoring voltage.
Additional cooling isn't a bad idea, as well as leaving an air gap between batteries if the room is available.

Larry

Re: Should the battery isolation manager be replaced when updating to lithium?

Reply #11 – January 24, 2021, 02:47:01 pm

When I started to work on our battery pack in 2014, I could not find those more sophisticated BMS capable of handling the 440 AH batteries to individually charge each cell, the simple ones just bleed charges to achieve balance while reporting temperatures of each cell. There was no mention of air gap. In fact, the connecting bars require each cell to be tightly packed together and the corner fastening hardware builds the cells tightly to achieve mechanical integrity to cope with shakes and vibrations in the vehicle.

A lot of "lessons learned" over the years bonedocking on the lithium batteries. So far, I have not seen much of capacity deterioration of the pack since we "babied" it. Keep my fingers crossed...

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