2021 Forest River FR3 30DS Lithium Upgrade

[Gvanorde]

I am replacing two lead acid house batteries with Lithium. I have replaced the Progressive Dynamics 9200 series with a Lithium capable charger/converter. I also purchased a DC2DC 50 amp charger as I am worried about the alternator working too hard and overheating. I want to disable the current battery charging circuit. Does anyone have familiarity with this setup. I need to k ow which head to disconnect to disable the house battery charging circuit.

 

[nvs4602]

Here is the pin out on the 7 pin plug.

 

[Gvanorde]

THanks NVS4602 - This is the inside of the battery bay, and the source of my initial question. I am trying to stop alternator charging so I can rely solely on my DC2DC Charger. Based on the photo, does anyone know which lead to disconnect to stop the factory alternator charging circuit?

 

[Twinboat]

You can try unplugging this plug to disable it but it may effect other things. Try that and see what happens.

In most cases, just removing the ground wire ( circled in red ) would disable it, but not how this BIM225 is installed thru the circuit board.

 

[Twinboat]

The alternator just charges the engine battery. The BIM225 connects the engine battery to the house battery thru the 2 larger cables on it, so actually one battery is charging the other.

If you haven't purchased the DC to DC charger, you may want to pick up a Lithium BIM225 and swap that into the circuit board.

 

[rk06382]

The alternator just charges the engine battery. The BIM225 connects the engine battery to the house battery thru the 2 larger cables on it, so actually one battery is charging the other.

If you haven't purchased the DC to DC charger, you may want to pick up a Lithium BIM225 and swap that into the circuit board.

Ditto on getting a Lithium BIM225. I have been using my alternator to charge my six 100ah Battle Born LiFePO4 batteries for five years without an alternator issue. (Since 2019)

I did have to modify my Battery Control Center SDC-107A for the higher voltage of LiFePO4 in 2019. see: My coach batteries stopped charging from the alternator. (Bad SDC-107A).

 

[NXR]

Call Precision Circuits. They have excellent support and will tell you exactly what you need to do. You're not the first to do this.

See: https://www.precisioncircuitsinc.com/contact-us/

The engine alternator does charge the house batteries directly on our Georgetown with a Precision Circuits BCC. It doesn't matter if the house batteries are connected or not, the alternator charges them. Whether the batteries are paralleled for charging or not is irrelevant; if the alternator is feeding one it's feeding them all.

One person who did that conversion had to disconnect that charging because they did not buy a DC to DC converter. Another Georgetown owner found an issue with the Automatic Generator Start for low house voltage. The touchscreen could not be set to a high enough voltage to trigger the AGS because lithiums hold their terminal voltage a lot longer. Precision Circuits developed a new firmware for them. While an FR3 does not have a touchscreen, if you added an AGS that's another consideration.

Ray

 

[Gvanorde]

Great info gents. This may be a little over my pay grade. I have reached out to Precision Circuits. Let's see what they have to say. I already purchased the DC2DC charger, but I may consider the BIM.

 

[Gvanorde]

This was the response from Precision Circuits:

You will have to remove the buss bar that connects the Batt B terminal of the BIM 160 to the Batt terminal of the BG 160. Move the cable from the Batt B terminal of the BIM 160 to the Batt terminal of the BG 160. The will disable the BIM from connecting the coach and chassis batteries together.

I can see how that will work, but I will lose chassis battery charging from shore power and the Battery Boost switch function (which I can live without). However, I am concerned about losing shore power charging to the chassis.

 

[NXR]

I also would be concerned. If you have a dead chassis battery because there are things connected hot to the chassis battery then the loss of the Battery Boost functionality means you cannot start the engine.

Did they explain why that is needed? I suspect it's due to the constant higher voltage needed to charge lithiums (if you install a lithium-capable converter or charger) and that can boil the chassis battery.

But I thought the Precision Circuits BCC connected and disconnected the chassis battery during charging. I received this from George with Precision Circuits back in 2019:

The BCC charges the Chassis battery anytime the Coach Battery is above 13.2V and the Chassis battery is below 12.6V.

It implies that the chassis battery voltage is monitored somehow and only charged when the voltage drops below 12.6 volts DC, but maybe I'm reading too much into that.


I'd ask them for the specifics of the reason and also if there is a workaround to keep the chassis battery charging from shore power or generator power.

I know a few people who had alternator failures and they worked around it by running the generator to power the converter to supply 12 volt DC power to the chassis battery to keep it charged up and the electrical circuits need to run the engine powered up. That let them avoid being stuck somewhere or needing a tow. They could drive to a place where the alternator could be replaced.

Ray

 

[cub22908]

This was the response from Precision Circuits:

You will have to remove the buss bar that connects the Batt B terminal of the BIM 160 to the Batt terminal of the BG 160. Move the cable from the Batt B terminal of the BIM 160 to the Batt terminal of the BG 160. The will disable the BIM from connecting the coach and chassis batteries together.

I can see how that will work, but I will lose chassis battery charging from shore power and the Battery Boost switch function (which I can live without). However, I am concerned about losing shore power charging to the chassis.

This is exactly how I did the separation for my lithium upgrade. I also moved the solar from house to chassis to keep the chassis battery charged. Since I only have one solar panel and lithiums aren't supposed to be kept full in storage and one 115w panel will do little to nothing for you when boondocking that is what I've done. I also put in a disconnect at the lithiums so there is no draw when in storage. So far works for me.

 

[Reverse_snowbird]

I am replacing two lead acid house batteries with Lithium. I have replaced the Progressive Dynamics 9200 series with a Lithium capable charger/converter. I also purchased a DC2DC 50 amp charger as I am worried about the alternator working too hard and overheating. I want to disable the current battery charging circuit. Does anyone have familiarity with this setup. I need to k ow which head to disconnect to disable the house battery charging circuit.

My knowedge of this subject is limited.
However the dc-dc charger should solve your problem without having to change the BIM and it will also address the overheating.
Is it possible to mount that dc-dc charger near the positive terminal of your house batteries? You should probably disable the chassis batteries first.

 

[NXR]

I also moved the solar from house to chassis to keep the chassis battery charged.

Great idea. A friend with an old Winnebago put a small solar panel on his dash and plugged it into a 12 volt power outlet. That power outlet was wired to the chassis battery so his little solar panel kept the chassis battery from going dead in storage.

Ray

 

[Twinboat]

Since to BIM only charges the chassis battery when there is shore or generator power, install a small battery maintainer and wire it to the chassis battery.

For those using an inverter/chager, The 120 volt end of it will need to be wired before the inverter/charger but after the auto transfer switch.

 

[Twinboat]

My knowedge of this subject is limited.
However the dc-dc charger should solve your problem without having to change the BIM and it will also address the overheating.
Is it possible to mount that dc-dc charger near the positive terminal of your house batteries? You should probably disable the chassis batteries first.

Leaving the BIM in service will make the DC to DC charger unless in protecting the alternator, one of its features.
As it boosts the voltage, that higher voltage is going to circle around thru the BIM and back to the chassis battery and alternator. That will tell the alternator to stop charging.

 

[Aussieguy]

chassis battery should not drain if you disconnect the cables
the alternator will keep it charged just like it does in any truck
you just have to drive some days to fully charge it
or use one of the many other simple solutions once a month or so

generator ... plug in a battery charger to the chassis battery to a 120v outlet




If you got near full house bank ... you can even just use jumper cables to allow the chassis some charge.... 20 minutes or so.

Original post is that the OP has purchased a dc-dc 50amp
disconnect the BIM as they said and use the dc-dc
since you are (hopefully) driving the chassis battery will get charged

50 amps is NOT a huge draw on the alternator .
make sure you wire it with correct size wires to make best use of the driving time you have

if you camp for MONTHS in one spot work out a schedule to keep things charged
BUT remember... you get the most bang for your $$ by investing in good HOUSE solar if you intend to boondock a lot.

moving power from house to chassis is easy enough
manaully connect the batteries together in one of many ways that you feel the most comfortable with.

do NOT leave the BIM connected if you install the dc-dc you can only use one of them at a time