Is There a Lithium Converter Replacement for the WFCO WF-8735P

Updated 04/25/2025 | Published 04/17/2020

Question:

Do you have a Lithium power converter replacement that will fit the WFCO WF-8735P power panel?

asked by: Larry B

Expert Reply:

I spoke with Progressive Dynamics and they informed me that you cannot replace just the converter section and you would need a new panel, the Progressive Dynamics Mighty Mini AC/DC Panel and Converter/Smart Charger part # PD4045KA.

The Progressive Dynamics Mighty Mini AC/DC Panel and Converter/Smart Charger now comes with a lithium switch.

expert reply by: Conner L

Matt R.

11/15/2021

You’re suggesting replacing a 35 amp panel with a 45 amp panel. Why? Wouldn’t Progressive Dynamics panel # PD 4135k be a better replacement? Replacing a 35 amp for a 35 amp. It can be used with lithium ion batteries and lead acid batteries with a flip of a switch built into the panel.

Les D.

11/22/2021

According to Progressive Dynamics website the PD4135 Power Center is the direct replacement for the WFCO 8735 and includes Lithium charging. However, if you had multiple high amp-hour batteries you may want the 45-amp model to charge those batteries in typical time.

Kurt L.

2/24/2022

I'm considering making the same change. If the existing converter is 35 amp, will upgrading to a 45 amp converter require potential changes to the wiring?

Les D.

2/24/2022

I spoke with my contact at Progressive Dynamics about your inquiry and he said that if you upgraded from 35 amp to 45 amp, then your 45 amp (charging amperage to batteries) charger would need 8 to 6 gauge wire especially if Lithium charge levels. Your trailer may already be wired for with sufficient wires. This also depends on the distance from the charger to the batteries. Shorter distances may only require lighter gauge wire.

Rocky P.

4/22/2025

@LesD I'm considering the same kind of upgrade from a WFCO WF-8735-P (35-amp converter, lead-acid only) to a LiFePO4 battery compatible converter like your suggestion of the Progressive Dynamics # PD4045KA (45-amp converter, with LiFePO4 option via a manual switch). I have been considering the WFCO WF-8735-AD direct upgrade with "auto detect" (AD) technology. But lots of RVers have had trouble with it NOT detecting a LiFePO4 battery, probably because their wire run is greater than WFCO's 10-foot max specification. I have a 16-foot wire run, so am considering a converter with a manual switch for LiFePO4. I also have a 280Ah LiFePO4 battery with bluetooth BMS that I haven't installed yet to better handle boondocking.....why I would like a higher amp converter. BUT I'm not thrilled about having to upgrade to a heavier gauge wire run under the RV. You say "... your 45 amp (charging amperage to batteries) charger would need 8 to 6 gauge wire especially if Lithium charge levels. Your trailer may already be wired for with sufficient wires. This also depends on the distance from the charger to the batteries. Shorter distances may only require lighter gauge wire." So wire gauge vs. length of wire run is critical to be able to handle the amperage safely. As I mentioned, my wire run under the RV is 16 feet of 8 AWG from battery to converter and has worked flawlessly for the WFCO 35 amp converter. Will that 16-foot run of 8 AWG wire be ok for the PD4045KA 45-amp converter as well? Or would I have to upgrade the wiring to 6 AWG for that 16-foot run if switching to the PD4045KA? What do you think?

Kate F.

4/25/2025

@RockyP I want to apologize that we did not see this sooner. I got your question that you wrote in with the link to this comment, so thanks for writing that in. You're asking all the right questions, wire size and run length make a big difference, especially when you're moving to a higher amp converter and switching over to LiFePO4 batteries. Since you’ve got 16 feet of 8 AWG wire running from your battery to the converter, and it’s worked fine with your current 35-amp WFCO unit, it makes sense to wonder if that same wiring will hold up with a 45-amp converter like the Progressive Dynamics # PD4045KA. Technically speaking, 8 AWG wire can handle 45 amps, especially in RV chassis wiring where it’s in open air and not bundled. So yes, it should be safe. The main issue isn’t safety, though, it’s voltage drop. LiFePO4 batteries have a fairly tight charging voltage range (around 14.2 to 14.6 volts), and even a small drop can keep them from reaching a full charge. With 45 amps running through 16 feet of 8 AWG wire (32 feet round trip), you could see around a 0.36-volt drop, not terrible, but enough to impact charging performance over time. Upgrading to 6 AWG wire would bring that voltage drop down to about 0.2 volts, which is a much better place to be. That means faster, more efficient charging and helps ensure your 280Ah LiFePO4 battery gets a full charge every time. It also gives you more breathing room if you ever upgrade to a larger converter or use your system heavily for boondocking. If pulling new wire sounds like a pain (understandably), there are a couple of workarounds. You could run a second 8 AWG wire in parallel with the existing one to effectively double up and reduce the drop. Or, you could look into adding a DC-to-DC charger closer to the battery, that lets your converter send power over the existing wiring more efficiently, and the DC charger handles the precise charging profile for the lithium battery. In short, your current setup can technically work, but if you want to get the most out of that big lithium battery (especially for off-grid use) upgrading the wire would be a smart move. Let me know how the install goes, if you have any questions along the way, you know where to find us =)

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