LiFePO4 RV Battery - Use Renogy Dual Input DC-DC charger instead of upgrading Converter?

[wlemst88]

Hello,

Trying to replace my Lead Acid battery with a DIY LiFePO4 battery on my Travel Trailer. I'm cost conscious but cost prudent too.

When camping I'm 50% of the time boondocking and 50% full electric hookups.

I had an idea I wanted to run by y'all. I want to get a Renogy 50A DC-DC On-Board Battery Charger with MPPT. SKU: RBC50D1S-CA so that I can safely charge with my vehicle and also get an MPPT charger for some solar. I've also been thinking that I have to upgrade my WFCO WF-9855 converter to something Lithium capable.

But then I got thinking - Why can't I just run the output of my non-lithium WFCO 9855 into the solar/vehicle input of the Renogy DC-DC charger which is Lithium capable? Wouldn't that work? Save me the cost on upgrading the converter?

Thanks in advacnce!

 

[shortyjacobs]

I’m bumping this because I have the same question, (also bumped a different thread in a different group with a similar subject, forgive me regulars!). Did you try this wlemst88?

 

[rickst29]

I don't know how the standard WFCO would react to a pure load, with no "battery" being present (to test whether it should be in Boost, Bulk, or Float mode). I am hoping that other converters (I have a PD) which do have a "Lithium charge" constant-voltage output would be willing to maintain that voltage into a pure load (being battery warmer pads) with no connection into the LFP batteries - but I haven't tested it yet.

My own Trailer is a fold-up model, and I haven't yet opened it to put that circuit in place (with a recently built warming-pad-equipped LFP battery).

 

[shortyjacobs]

I don't know how the standard WFCO would react to a pure load, with no "battery" being present (to test whether it should be in Boost, Bulk, or Float mode). I am hoping that other converters (I have a PD) which do have a "Lithium charge" constant-voltage output would be willing to maintain that voltage into a pure load (being battery warmer pads) with no connection into the LFP batteries - but I haven't tested it yet.

My own Trailer is a fold-up model, and I haven't yet opened it to put that circuit in place (with a recently built warming-pad-equipped LFP battery).

For what it’s worth, the WFCO 8955 I have says in the manual that it doesn’t need a battery to run. In fact, it recommends disconnecting the battery as a troubleshooting method. Supposedly, it should push in boost at 14.6V without a battery connected, (but it also will drop to 13.6 or something for bulk after 4 hrs: not clear if that would still happen without battery?). If the voltage drops to 13.6 or 13.2, a Dc-Dc charger like a kinsae 1250 or Orion should still boost it up, right?

 

[wlemst88]

My LiFePo4 cells arrived last week but my power supply for top balancing isn't due until Thursday. I hope to test the converter wired to the alternator input of the Renogy DC-DC charger this coming weekend. It should work though. I relocated my converter away from my fuse panel to where I'll have the battery, charger, and inverter

 

[shortyjacobs]

I’m excited to hear your results!

My LiFePo4 cells arrived last week but my power supply for top balancing isn't due until Thursday. I hope to test the converter wired to the alternator input of the Renogy DC-DC charger this coming weekend. It should work though. I relocated my converter away from my fuse panel to where I'll have the battery, charger, and inverter

I’m excited to hear your results!

 

[Jasgeer]

I have my Renogy DC-DC wired to the output of the WFCO or the output of the power from the truck so that it properly charges the trailer batteries either way. I incorporated a dual battery switch to make the connections. If anyone wants to know how to connect it I can provide more information.

 

[time2roll]

I would give the existing WFCO a try. Seems like a solution looking for a problem.

 

[teederb]

Just ordered the Renogy 40amp DC to DC charger and will give intalling it between my WF-9855 and LiFePO4 batteries. I will update with my results.

 

[shortyjacobs]

I've got a test setup with a 200AH LiFePO4 battery ready to test with my WFCO on my next trip (this coming weekend). This was me checking out the Kisae DMT1250 doing a 50 amp charge from the alternator, (tow vehicle alternator stayed cool....good news there).

 

[shortyjacobs]

Update, installed the battery and DMT1250 in my trailer last night. DMT1250 takes the output of the WFCO8955 (FLA only) on the alternator port. Even though the WFCO8955 is rated at 55 amps, seems I was only getting around 45 amps out of it, but good enough for me (~5ft of 4 gauge wire between WFCO and DMT1250). Had it charging for an hour or two, no issues. Gonna call it good!

 

[John Frum]

@shortyjacobs did you try the wfco direct to your battery bank?

 

[shortyjacobs]

@shortyjacobs did you try the wfco direct to your battery bank?

Nope. It wouldn't have hurt anything, but the WFCO charge profile is meant for flooded lead acid, and will only get the lithium to 75-80% charge.