Isolating a non lithium compatible WFCO converter when upgrading to lithium

qhumberd · July 25

Despite having good success in my recent swap from lead acid to lithium in my 2019 400, and reading the threads on keeping the existing WFCO converter versus an upgrade versus a small separate charger, I went down the rabbit hole and asked AI.

I don't use AI often but here is what it (in summary) told me to do:

Strong Recommendation:

It is highly recommended to isolate the WFCO converter from the lithium battery when you are using your dedicated 10A lithium charger, or when the RV is on shore power in general.

As mentioned in the previous response, you can do this by:

Installing a battery disconnect switch between the WFCO's output and the battery.
Turning off the breaker or pulling the fuse for the WFCO converter's output when on shore power.

This ensures that only your LiFePO4-compatible charger is interacting with the battery when you want it charged, maximizing its performance and lifespan.

So here is my human question:

1. I have the WFCO 8955 PEC (non lithium compatible).

2. I just swapped out my Harris AGMs for a single 230 amp hour LiTime battery. I got a 10 amp Litime charger to bring the battery to full charge when needed.

3. I have a Renogy suitcase 100W solar setup with controller that does have a lithium fe phosphate setting, but when in storage I can't use this.

4. I have a basic shunt installed that can monitor the battery SOC.

Based upon all these recommendations, can I just disconnect the WFCO charging function by disconnecting the wires to the battery at the converter board and not do anything else?

Thanks all

qhumberd · July 25

Well I may have answered my own question. When looking at the WFCO circuit, there are two lugs/ wires that are marked “to battery”.

But disconnecting them seems to block the WFCO from supplying 12V to the trailer circuits when on shore power. So I can seem to figure out how to disable the battery charge part of WFCO without also stopping 12V power to the trailer circuits.
The WFCO manual states it will work with no battery installed, so what did I miss?

qhumberd · July 25

So it requires not forgetting to turn off the battery switch whenever you connect to shore power, but because the WFCO is an integrated circuit it connect on its circuit board disconnect from the battery charging without losing the 12V service to the trailer.

This is how my AI summarized, and it looks reasonable if you don't want to charge your lithium battery with the non lithium WFCO:
>>>>>>>>>>>>>>>>>>>>>>>

Excellent! Having a battery disconnect in place makes this much simpler and safer. You are on the right track.

Let's confirm the steps for using your existing battery disconnect switch to prevent the WFCO-8955PEC from charging your battery, while still allowing the battery to power your RV when off shore power:

Goal:

Prevent WFCO-8955PEC from charging the battery when on shore power.
Allow the battery to power 12V circuits when off shore power.
Allow the WFCO-8955PEC to power 12V circuits when on shore power (even if the battery is disconnected).

Steps:

When connected to Shore Power and you DO NOT want the battery to charge:
- Engage your existing Battery Disconnect Switch to the "OFF" or "DISCONNECT" position.
  - Result: This physically or electrically isolates your RV battery from the rest of the 12V DC system, including the WFCO converter.
  - Outcome 1 (Charging): Since the battery is disconnected, the WFCO converter will not be able to send charging current to the battery.
  - Outcome 2 (12V Power): The WFCO converter, when plugged into shore power, will still continue to supply 12V DC power to all your RV's 12V circuits (lights, fans, etc.). The RV will operate normally on 12V power, but that power will be coming directly from the WFCO converter, not the battery.
  - Outcome 3 (Battery): Your battery's state of charge will not change, as it's isolated. If you have a separate, external battery charger you wish to use, you can connect it directly to the battery terminals when the battery is disconnected from the RV.
When NOT connected to Shore Power and you want the battery to supply 12V power:
- Engage your existing Battery Disconnect Switch to the "ON" or "CONNECT" position.
  - Result: This connects your RV battery to the rest of the 12V DC system.
  - Outcome: Your battery will now be the sole source of 12V DC power for all your RV's 12V circuits. The WFCO converter will be idle (as it has no AC input), and all 12V loads will draw from the battery.

Important Confirmation & Verification:

Understand your specific switch: Some battery disconnect switches cut the positive cable, others the negative. For your purpose, either works as long as it truly isolates the battery from the RV's main DC bus.
Verify Isolation (Optional but Recommended):
- Plug your RV into shore power.
- Turn your battery disconnect switch to "OFF."
- Using a multimeter, carefully measure the voltage directly across your battery terminals. It should show the battery's voltage (e.g., 12.6V).
- Then, measure the voltage on the RV side of the disconnect switch (i.e., the cable coming from the switch towards the WFCO). With the switch off, this cable should not show the converter's output voltage (e.g., 13.6V or higher). If it does, your switch might not be fully isolating the battery.
- Finally, turn on a 12V light inside your RV. It should illuminate, confirming the WFCO is still supplying power to the circuits.

This approach is exactly what a battery disconnect switch is designed for in this kind of scenario. It's safe, effective, and uses existing equipment.

AnOldUR · July 25

We rarely have shore power while camping, but when we do I'll simply turn the battery disconnect off. In our case, rooftop solar will keep the battery topped off, but with the switch off there is very little discharge on the LiFePO4's. I have mounted a 30amp charger near the battery. It's wired directly to the battery and bypasses the battery disconnect. When there's a need to charge from shore power while the battery switch is off I'll use that, but it seldom happens.

qhumberd · July 25

Great, that sounds like it will work for me as well.

thanks for your help

deepsea5 · July 25

When I put the Converter in my Tab 320 on its own breaker, I also mounted a 120 Volt receptacle next to the WFCO panel. The receptacle is powered from the Converter breaker, using 14/2 Romex. I cut off the female end of a 15 Amp (14 AWG stranded wire) extension cord and permanently wired it to the Converter. The Converter now draws its power from the newly installed 120V receptacle. The receptacle allows me to also plug in our Ecoflow Delta 3 Plus for charging, or plug in our 60A LiTime charger when I eventually install the 300AH Newtipower lithium battery. It also makes it easy to disconnect the Converter-just unplug it from the receptacle.

Image: https://us.v-cdn.net/5021717/uploads/editor/4e/5cy98spyp1pw.jpg

Horigan · July 25

If connecting an Li charger “directly” to the battery, be sure to connect the negative charging wire to the Load side of the shunt.

When I added a solar charger and an Li charger, I replaced the one stud terminal block with a multi-stud bus bar so as not to stack terminals on a stud.

qhumberd · July 25

Yep thanks. As usual I forgot a step. Now it all works for my setup. Travel with battery on, powering frig and emergency brakes. The small charge fro TV alternator not an issue.

Camp ⛺️ on battery as required, and then when at a site with shore power or back home make sue battery disconnected, then plug in small charger. Shunt tracks use and recharge.

We are ready.

best to all

bjn2 · July 28

You don't need to disconnect the converter to use a stand alone charger. Your solar is connected directly to the battery and charges whether or not you have the WFCO on shore power.

Your non-Lithium modified WFCO won't output high enough voltage to fully charge your new battery. Your solar can when there's enough sun, and your smart stand alone charger can. The battery management system in your battery cuts off charging once it reaches capacity no matter how many charge sources you have coming in.

Note that even when you turn off the battery disconnect switch, the solar input goes directly to the battery. The solar controller and smart shunt both will consume power from the battery to run their bluetooth radios. I also have a TPMS amplifier that's connected directly to our battery. The disconnect just isolates the battery from the converter and the DC circuits that are fused at your converter.

dsfdogs · July 28

@qhumberd I'm not sure how you are connecting your LiTime battery charger to charge your batteries, but an easy way is to plug it into the solar port. I've done with this my Noco 10amp charger. You'll need to get adapters for the correct polarity. The WFCO in my '23 400 wasn't charging the lithium correctly so just as you said above, if at camp with hook-ups, I could use the 20amp outlet at the pedestal for the charger while the trailer is plugged into the 30 amp, turn off the battery and plug into the solar port. I've also done this at home during winter storage, and, I've done this while camping without hookups and plugging into my Goal Zero 1000watt battery bank.

qhumberd · July 28

Thanks @bjn2 and @dsfdogs for that feedback. I perhaps was being overly cautious with this new and relatively expensive battery. Not having extensive electrical experience I was not sure that keeping the lithium battery on the non lithium WFCO while also on my smaller 10 am lithium charger was safe for the battery. But I guess that electrons are electrons no matter where they are generated, and the BMS on the new battery is there to protect it.

I have room and a 120 V plug in my cargo bay set up for the small charger, so I should not need to use the solar port, but it is great to know that is an option. I just tried this out by discharging the new battery off shore power to around 50 % then disconnecting the battery and plugging the trailer to shore power and plugging in the small 10 amp charger. It was slow, but it worked fine. Running both together would be a lot faster, as long as it is safe for the battery.

dsfdogs · July 28

I've never charged with the Noco battery charger and the WFCO at the same time. I guess I'm cautious too.

SLJ · July 28

If I'm plugged into shore power the batteries are off. I just put a disconnect switch right after the battery shunt and have a Victron Smart charger that plugs into shore power wired in after the shunt to charge the batteries. The Victron smart charger supplies 30 amps so the batteries charge quickly. I wouldn't depend on a WFCO auto sensing converter for charging any lithium.

qhumberd · July 28

dsfdogs said:

I've never charged with the Noco battery charger and the WFCO at the same time. I guess I'm cautious too.

If there is no hurry, then charging with converter isolated just seems reasonable.

And @SLJ I put my charger on the load side of my shunt so I could keep up with charge going to the battery and time left to 100%. Otherwise my process is just like yours. Likely your shunt is able to figure out your battery SOC; mine has to be reset unless it goes thru the shunt

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Isolating a non lithium compatible WFCO converter when upgrading to lithium

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2019 T@B400 Boondock Lite "Todd"

2019 T@B400 Boondock Lite "Todd"

2019 T@B400 Boondock Lite "Todd"

2019 T@B400 Boondock Lite "Todd"

2019 T@B400 Boondock Lite "Todd"

2019 T@B400 Boondock Lite "Todd"