Converting Class A House Batteries to LiFePO4 With an LI-BIM 225

[DonTom]

I have been doing a little research and I am finding that using a DC2DCC to change from lead acid house batteries to Lifep04 may NOT be the correct way to do it in a newer RV such as this 2022 Class A.

If I understand what I am reading, mostly from AI, the correct way is to replace my BIM225 (battery Isolator) with one designed to ONLY be used with lith batteries and still be able to keep the battery boost function.

IOW, simply replace my BIM225 with one of these thingies which are designed for such.

Has anybody else here done such or have any comments on the best way to do this?

I have decided to keep my engine battery as lead acid and only change the house batteries from two 6V Harris, HBDAGMG6-A in series ( 224 AH) to two of these in parallel (400 AH).

No need for a DC2DCC?

I found the stock BIM225 on the left rear of my house batteries, With the LA batteries removed, it should be an easy job.

Before I start this job, I will disconnect all the batteries and kill the solar, which is all easy to do.

-Don- Tonopah, NV

 

[DonTom]

I felt like spending a little of my spare cash so here is what I just now ordered:

These two batteries ( ~$1,500.00 for both)

This (very last one in stock) Lith BIM 225 (~$125.00)

This Lith Converter (~$250.00)

Total=~$1,875.00

But my lead acid house batteries are now five years old, so I assume now is the time, so I can subtract that from the total cost (subtract around $600.00).

I will also replace my engine battery--But with another lead acid.

I do not think I need to worry about it going dead when I can still use the boost switch to tie in the 400 AH of house batteries in another five years or so if it starts to die.

-Don- Tonopah, NV (leaving here in the morning).

 

[DonTom]

The "very last one in stock" just changed from one (the one I just purchased) to 14, just after I bought mine.

-Don- Tonopah, NV

 

[DonTom]

Here are the differences between my stock lead-acid BIM (Battery Isolation Management) module and one designed for the lifep04 batteries. While this is all AI info., I find no reason to question any of it:

"The LI-BIM 225 is a specialized battery isolation manager designed specifically for lithium (LiFePO4) house batteries, whereas a standard lead-acid BIM 225 is tuned for AGM or flooded lead-acid chemistries. The primary differences lie in their voltage thresholds and charging cycling logic to accommodate the distinct electrical characteristics of lithium batteries.

Voltage Sensitivity and Thresholds Lithium batteries have a higher resting voltage than lead-acid batteries. A standard lead-acid BIM often interprets this higher lithium voltage as a "charging" state, failing to disconnect the batteries. This can cause the starting battery to drain significantly when house electronics are used while the engine is off. The LI-BIM 225 adjusts these thresholds to prevent false positives, ensuring the chassis battery is not unnecessarily discharged or overcharged by the house bank.

Alternator Protection via Cycling Lithium batteries have low internal resistance, allowing them to draw high amperage during charging, which can overheat a vehicle's alternator. The LI-BIM 225 manages this by cycling the connection: it connects the house and chassis batteries for 15 minutes while driving, then disconnects for 20 minutes to allow the alternator to cool before re-evaluating voltage. Standard lead-acid BIMs typically remain connected continuously if voltage thresholds are met, posing a risk of alternator overheating when charging large lithium banks.

Charging Logic and Overcharge Prevention The LI-BIM 225 also manages charging from shore power or solar. If it detects a charging voltage on the house side (e.g., from a lithium-compatible converter), it will connect the batteries to charge the chassis battery, but will limit this connection to one hour followed by a two-minute disconnect to re-evaluate voltages. Additionally, it can disconnect the house battery if alternator voltage exceeds 14.4V to protect lithium cells from overvoltage, a safeguard not typically present in basic lead-acid isolators. "

-Don- Tonopah, NV

 

[DonTom]

Here is a diagram of the LI-BIM usage:

It is rated at 225 amps continuous / 1200 amps for 30 seconds.

The three top smaller posts are labeled as (in order left to tight)

IGN - GND-SIG

Bottom Left- "Batt Chassis"

Bottom Right "Batt Coach"

 

[TheBar]

5 posts without anyone replying. Isn't this the same as talking to yourself

 

[Gary RV_Wizard]

It's more a "blog" than a "forum"; a stream of consciousness rather than a community discussion.

But helpful information nonetheless.

 

[DonTom]

5 posts without anyone replying. Isn't this the same as talking to yourself

Yes! It's a good way for me to store some of the info for when I am at home using another computer. At the same time, others may find the info very handy and save them a few hours of research who want to change to Lifepo4 house batteries.

BTW, a DC2DCC can still be used after the LI-BIM 225 to the house batteries, but that will break the path for the boost switch. But that would make it extra easy on the alternator yet then can charge to 100% SOC from the alternator. But my 180 watts of solar should get me to 100% SOC anyway after a long drive, besides not needing 100% SOC with 400 AH worth of house batteries.

I am thinking is is best to NOT use a DC2DCC in this, but I am not crazy about the high loads on the alternator even if only for 15 minutes at a time with 20 minutes off time.

-Don- Tonopah, NV

 

[DonTom]

I wonder why this guy will not mention the path for the boost starter switch is broken with the DC2DCC.

But I do wonder how the duty cycle of 15 min on/20 minutes off (not 15 minutes off like he claims) at how many amps on & off compares to how many amps continuous or even if it can be compared.

Did Victron hire this guy or what?

-Don- Auburn, CA

 

[DonTom]

Here it shows what is really in the simple "switch", as mentioned above. While there is a 225 amp (1,200 amps for 30 seconds) switch in there for the final output, there is also a lot of junk besides the timer. Such as the stuff to monitor voltages, etc. to tell the switch what to do.

BTW, the Li-Bim is made by Battleborn. Can we trust them to make these correctly, unlike their batteries?

-Don- Auburn, CA

 

[John From Detroit]

There are many ways to limit current and some do not bother voltage all that much.
I had one circuit I had to wire bypass power to and since I was concerned the original path might self-restore I used a self resetting thermal current limiter/indicator instead of a fuse This device has very low resistance at no or very current so it does not seriously affect voltage but pass enough through it it heats up and limits the current.. To Well the one I used was about 1/2 amp. And it indicates when it's doin that too.

Oh the common name for that device: Incandescent light bulb.

 

[DonTom]

Oh the common name for that device: Incandescent light bulb.

The first message there by Kevin, just below the video, explains how the Li-BIM really works and what it does.

I don't think your Incandescent light bulb will do all that quite as well.

-Don- Auburn, CA

 

[John From Detroit]

The first message there by Kevin, just below the video, explains how the Li-BIM really works and what it does.

I don't think your Incandescent light bulb will do all that quite as well.

-Don- Auburn, CA

Not sure... It limits current. though to do a proper job of it you'd need a rather large bulb for that job.
I was limiting to about 1/2 amp or less.
You'd' need what. 300 watts of bulb well perhaps 1200 or more watt since they never get to full brilliance in that kind of situation .. The filament of an incandescent light is what is called a positive temperature coefficient resistor. That is when cold it's low resistance but as it heats up the resistance goes up.. big time.
But since any resistance will reduce charge current you need a lot of lamp to charge the battery and limit the current.. For what I was doing (running a small motor) I did not need that much current.

 

[DonTom]

Not sure... It limits current. though to do a proper job of it you'd need a rather large bulb for that job.
I was limiting to about 1/2 amp or less.
You'd' need what. 300 watts of bulb well perhaps 1200 or more watt since they never get to full brilliance in that kind of situation .. The filament of an incandescent light is what is called a positive temperature coefficient resistor. That is when cold it's low resistance but as it heats up the resistance goes up.. big time.
But since any resistance will reduce charge current you need a lot of lamp to charge the battery and limit the current.. For what I was doing (running a small motor) I did not need that much current.

Perhaps new RVs will start using the JFD method soon.

-Don- Reno, NV

 

[DonTom]

And here is the guy for BBB to talk about their Li-Bim.

 

[DonTom]

I just now discovered a small disadvantage with this BIM system.

It does the same with my solar, on for 15 minutes then off for 20 minutes, which has no advantage, just reduces the charge time by more than half.

My solar charges everything in this vehicle. It is designed if anything is charging it all is. The engine starting battery, my 400 AH of LifeP04 house batteries as well as my 300 AH added battery for my ham radio and high current stuff (but this works with a DC2DCC--but from the 400 AH batts,, so 400 AH batts need to be charging first).

I am now trying to decide if I want to redesign the entire solar thing or just leave it this way. I will probably get enough charge even this way by the end of the day anyway, with my added solar panels (470 watts worth, max, a couple of smaller panels are in series with the stock 200 W roof one). The genny works direct to the house batteries, via the converter, unlike the solar, so it doe not charge of and on and will stay on. The only thing now that will charge the batteries full time.

And I often use the genny anyway to charge up the bike in places like this. The easy way is just for me to leave it all as is.

-Don- Big Creek Camp, NV

 

[Mark_K5LXP]

Double your panel size to make up the difference.

The house battery is the primary bucket to (re)fill, any other charging can be indirectly done from those. I have powerpole (175A) pigtails on my batteries for dynamic source/load connections as needed. I use them mostly for testing but handy for 'just in case'.

Ham operators are good at one-way communications...

Mark B.
Albuquerque, NM

 

[bigbAZ]

Why can't you just go to a standard isolation solenoid and a DC-DC charger and connect a small switch to either the + or - side of the solenoid coil that you can engage if you ever need the boost function? I actually put a plug in connector on the - side of mine, if I ever need the boost function for the chassis battery I will just plug the connectors together. The more likely scenario is that my chassis battery bank may get too low to start the generator, in that case I'll start the RV, then start the generator.

A good DC-DC charger like a Victron will monitor your house bank just like your BIM does and charge appropriately.

 

[DonTom]

Double your panel size to make up the difference.

The house battery is the primary bucket to (re)fill, any other charging can be indirectly done from those. I have powerpole (175A) pigtails on my batteries for dynamic source/load connections as needed. I use them mostly for testing but handy for 'just in case'.

Ham operators are good at one-way communications...

Mark B.
Albuquerque, NM

Cannot be done as I am already too close to the 100 VDC limit of solar for my Go-Power MPPT controller. I have two solar panels on the ground in series with the stock 200 W on the roof for a total of 470 watts (as rated) or often around 75 volts of solar. Should not go over around 80% of the solar controller rating as sometimes they will put out more than spec., which happened to me in AZ when I used three external panels and it shut off the controller (otherwise no harm done). My solar voltage then was around 90VDC until that one extra sunny day when I got no charging at all when it went above 100 VDC--when I was not there! I had no solar charging, which happened while I was out on a long day hike.

For here now, I had no choice but to fix the issue and I just got done doing such. The issue was that the disconnect from the battery would often cause the Go-Power MPPT to crash and stop drawing any solar current, during the 15 minutes it should. I had to keep on doing hard resets because of it. And then still was 20 minutes off for 15 minutes on and again needed a hard reset! That got old fast!

Anyway, it was an easy fix because it is a 6-wire solar controller. I left the house battery (batt 2) connected as is. But I disconnected BOTH wires for Batt 1 (house battery) and wired the neg wire to my Victron SmartShunt (so it will read correctly) and the hot wire direct to my 400-AH worth of lith batteries.

It is all in the next compartment over, and I already had the holes drilled for other wires. As you know, I started modifying the electrical stuff in this rig about I week after I purchased it new.

The wired in Go-Power as well as my Smartshunt for the house batteries is now showing around 244 watts of solar charging. I now have 52 volts @ 4.7 amps of solar (244 watts).

9.76 amps to the house battery at 13.45 VDC @ 94% SOC, 131 watts, low only because I am now at 96% SOC with my 400AH lith house batteries.

And now will be as steady as it should be for the battery SOC% and changes in sunlight. Some of this is used for keeping the engine battery charged up (13.1 VDC, current shows as zero (is not measured)

So it's all fixed. I am glad it gave me MORE trouble so I then I had no choice but to fix it!

I always carry wire, tools, etc, with me for these type of fixes for when I am out in the middle of nowhere. Often gives me something to do.

Again, I am the only person here. All those who came in last night already left.

-Don- Big Creek Camp, NV

 

[DonTom]

Why can't you just go to a standard isolation solenoid and a DC-DC charger and connect a small switch to either the + or - side of the solenoid coil that you can engage if you ever need the boost function? I actually put a plug in connector on the - side of mine, if I ever need the boost function for the chassis battery I will just plug the connectors together. The more likely scenario is that my chassis battery bank may get too low to start the generator, in that case I'll start the RV, then start the generator.

A good DC-DC charger like a Victron will monitor your house bank just like your BIM does and charge appropriately.

Yes, and that is what I use for the 300AH lith battery that I added for my toys (ham radio and I also use it for the MW over and Keurig, to prevent house battery draining). The 300 AH Lifepo4 charges from the 400 AH LifePo4 house batteries, with a Victron DC2DCC between them.

Anyway, see the above message I just typed while you were also typing. I am all fixed. It was a very easy simple easy fix and I am now at 97% SOC from my solar with the new 400 AH lith house batteries.

-Don- Big Creek Camp, AZ