diy solar

diy solar

Wondering about charging a LiFe from existing RV power distribution center.

CalvinUtrex

New Member
Joined
Jul 15, 2021
Messages
3
Location
Winona, MN
Background: I recently purchased a Chins 100Ahr LiFePo4 based on Will’s “teardown youtube”. I have a small RV (RPod) and replaced the old 100Ahr AGM with the Li. My RV system uses the standard WFCO power center to charge the battery when on shore power. For solar charging I utilize three roof mounted 100W flexible panels (in parallel) with a Prostar 30 (gen3) PWM controller. Morningstar will help me set up the solar controller to work with the battery (so I think I’m okay there). The flex panels were only putting out about half their rated power when new, but after 4 years they’re about worthless so those are going to be swapped for rigid. Now my question for you saged experts:

What problems would I encounter using the existing trailer power distribution center to charge my Li battey (WFCO 8900 series, if that helps) when on shore power? It seems to “float” at 13.6V. Not sure what other battery charging functions it employs.

additional info: when not in use, I do not keep the trailer connected to shore power. For long term storage (up to 4 months) I disconnect the battery. When in use, we typically travel for 6 weeks, of which maybe 6 nights total connected to shore power. I use a small inverter lp generator when the solar panels can’t keep up with our use. I route its power directly through the WFCO for charging the battery.
 
P.S. Looked at specs on my WFCO charging modes. 13.2V for float, 13.6V for absorb, 14.4V bulk (max 4 hours at bulk). It puts out 55A. Is this too high charging current for a 100Ahr Li?
 
My trailer is only 5 years old and I have never seen the WFCO do any of the steps except for float, I gave up on it and installed a Renogy DC-DC charger at the output of the WFCO. It performs perfectly. Here is my wiring diagram.
 

Attachments

  • Renogy DC-DC Charger wiring diagram.pdf
    380.6 KB · Views: 30
P.S. Looked at specs on my WFCO charging modes. 13.2V for float, 13.6V for absorb, 14.4V bulk (max 4 hours at bulk). It puts out 55A. Is this too high charging current for a 100Ahr Li?
Most don't like more than a 0.5C charge, that would be 50 amps.
Most cells will take a full C charge, but the BMS probably won't.
Higher charge rates cause temperature increases and can shorten cell life.
 
Thank you all for your replies. Other than my converter being a little bit high on charging amperage, I didn’t hear other problems. Since I will be using the converter on both shore power and generator, I’ll look into dropping to 35 amps. As far as the WFCO never moving out of “float” (Jasgeer), that hasn’t been a problem. I often took my DOD on the AGM down in voltage to trigger the bulk and absorption stages. But I can see that with the voltages of the lithium battery, the WFCO would not function well as it does with lead-acid cells. Your DC-DC setup also has temperature sensing, and that could be useful as the chins battery doesn’t have a low temp cut out.
 
The temp. sensor for the Renolgy DC to DC is used on the FLA settings not the LFP settings. (You can not use it for low temp disconnect)
 
I replaced my 210 ah lead acid batteries with 200ah lithium battery and use my WFCO 8900 to charge and then use the solar panels to top off. According to WFCO the 8900 will charge lithium but to charge 100% you need to replace their 8900 lithium series.
 
Background: I recently purchased a Chins 100Ahr LiFePo4 based on Will’s “teardown youtube”. I have a small RV (RPod) and replaced the old 100Ahr AGM with the Li. My RV system uses the standard WFCO power center to charge the battery when on shore power. For solar charging I utilize three roof mounted 100W flexible panels (in parallel) with a Prostar 30 (gen3) PWM controller. Morningstar will help me set up the solar controller to work with the battery (so I think I’m okay there). The flex panels were only putting out about half their rated power when new, but after 4 years they’re about worthless so those are going to be swapped for rigid. Now my question for you saged experts:

What problems would I encounter using the existing trailer power distribution center to charge my Li battey (WFCO 8900 series, if that helps) when on shore power? It seems to “float” at 13.6V. Not sure what other battery charging functions it employs.

additional info: when not in use, I do not keep the trailer connected to shore power. For long term storage (up to 4 months) I disconnect the battery. When in use, we typically travel for 6 weeks, of which maybe 6 nights total connected to shore power. I use a small inverter lp generator when the solar panels can’t keep up with our use. I route its power directly through the WFCO for charging the battery.

WFCO makes a retrofit AC to DC converter that has lithium compatible charge voltages. That is probably the easiest and simplest way forward. $200 on Amazon or so depending on exact model.

Or put that $200 towards a Victron Multiplus which will solve the charging problem and also get you a decent inverter and other functionality.
 
Back
Top