Upconverting to group 31 lithium battery

CampHub

@TaG_Im_It Great write up on this, thanks for sharing. Good to know that the stock converter will eventually do the job and solar gets it done.

Michael

Agreed! I'm ordering tomorrow! The only thing I still need to try to decide is which of the two batteries do I want. The gc2 or the grp 31.

I have factory solar also. The older grape solar 100 watt flexable. I did dump the pwm controller and replaced it with a grape solar mppt bluetooth unit that I can set to liFePO4 I think. If not I know it can do custom settings.

Scotty49

Photos edited for resizing.

To answer @CampHub, I ran the battery monitor RJ12 cable from the BMV shunt (installed a cable box for the shunt on the left side of the tub; obtained the box from Whitney at nuCamp parts) out of the back of the tub on the left side through a split corrugated wire conduit to a point beyond the axle and drilled a hole in the floor to accommodate the cable. I used a plastic grommet to pass the cable through and sealed up the underside with a generous amount of silicone caulking.

Then, I ran the cable along the flooring, over the water tank and behind the aft wall of the trailer.

I removed the converter to facilitate the delivery of the wire and to locate the placement of the monitor beneath the 12v / USB outlet. I drilled a 2” hole in the wall, pulled the cable through and attached the monitor. I wrapped up the residual cable with a cable tie and stuffed it behind the wall, put the monitor in place and made sure it worked! Finally finished by replacing the converter back in it’s home.

CampHub

So after @WilliamA commented his RV dealer is seeing people burning up their converters after they put in a lithium battery. I reached out to WFCO tech support about our WF8725 converter and lithium battery's. This was there response: "This is not a lithium style converter. It will charge lithium to about 90 to 95%." There was no mention it would cause the converter to burn up. Like so many of you are already doing use a lithium charger or a solar setup to top off. Time will tell if the converter cannot hold up, then I guess another upgrade

TaG_Im_It

Yah so as I was sitting at 94% today, with converter plugged in, and seeing a negative draw on the amps due to the annoying Jensen products, I realized the same thing. I think the thing waits for the more severe voltage drops of lead acid to decide to start charging. Even with being only able to charge 90 to 95% I still have twice the power capacity, but damn. So yah, i think I can top off with a Battery Tender 1.25 amp, my solar totally works. Tough part is there doesn't seem to be an appropriate LifePo4 compatible converter upgrade in our amp range.

Michael

The closest one I see is a Progressive Dynamics PD4045LIKA

I have not checked physical size yet compared to our wfco unit. I'm going to measure the cutout and depth available probably within the next couple weeks.

The only wiring concern that I would have is the 10 gauge cable to the battery. I would guess it would need to be at least 6 gauge. Maybe 4 gauge.

WilliamA

@Michael said:
The closest one I see is a Progressive Dynamics PD4045LIKA
I have not checked physical size yet compared to our wfco unit. I'm going to measure the cutout and depth available probably within the next couple weeks.
The only wiring concern that I would have is the 10 gauge cable to the battery. I would guess it would need to be at least 6 gauge. Maybe 4 gauge.

In theory......

There are 2 calculations that need to be made: voltage in and voltage out.
For voltage out, as in lights, fans, etc, the wire size need only be as large as the total potential amperage used. If all of the combined devices use 15 amps, then the wire size need only be large enough to carry that, regardless of the battery's amperage rating.
For voltage in, I.E. charging the battery, the wire size need be only as large as the maximum output of the converter/battery charger/solar output. If the charge rate is 10A maximum, then a 10 gauge wire would do nicely. If the charge rate is as much as the rated output of the charger/converter, (as in the potential 45A output of the Progressive Dynamics PD4045LIKA), then for sure you'll need an 8 gauge wire to do that. I strongly suspect that the initial charge rate of any unit charging a single Lithium battery would be more on the order of 20A max initial but quickly dropping to about 10A or so for absorbtion charging. I can't imagine that you'd get 45A of output for a single battery, even a Lithium. If that number is indeed accurate, you could put the thing inside the trailer and use it for a heater. 45Amps? At 13 or so volts? Goodness..... I'm sure all of that information will come in the instruction sheet for the converter.

I'd like to think that it would be possible to simply hook a Lithium-specific 110v charger into the trailer 110v system and leave it hardwired so when on shore power it runs, but if the 12V input from the charger is also in parallel to the 12V input from the converter, there may be some issues with that. In addition, leaving a charger connected when NOT hooked to 110V on the other end may lead to reverse current discharging through the charger. Modern battery chargers have reverse-circuit disconnect to prevent that and I can't imagine that a smart charger isn't built in that way, but it's only prudent to make sure.

For the near-term, this is all a bit of a sticky-wicket. I'm sure that the converter industry will quickly get up to speed on higher voltage output converters but in the meantime, it's up to we, the huddled users to work the problem. I will be watching the research both here and on the T@B forum to see what folks are coming up with.

By the way.....
For those of us who haven't yet given up on the old-tech deep cycle battery, many of the issues are the same. If we ditch the dinky group 24 jobs in lieu of a larger 12V or dual 6V batteries, the converter will still need to be up to the job of monitoring and charging the increased amperage capacity of those too. In my case, just going up from a group 24 to a group 27 seems to have my converter scrambling to deal with the increased capacity. The first time I charged it, the charge time was much longer and once it dropped down to trickle, was still .4 volts lower than the group 24. I'm just letting it work for now and will see if is just a case of taking a few charge cycles to bring the Duracell group 27 battery up to 100% or if the WFCO simply isn't up to the job of cycling the larger amperage capacity. If so, it's still a simple matter of swapping the converter for a larger one. I'll just monitor for now. As the experts say: "As yet, the observations support no conclusions...." But then again, Psychiatrists say that too. Maybe we all need a bit of both? lol....

WilliamA

TaG_Im_It

Hey I think this is actually closer to the stock wfco. Its 30 amp. https://battlebornbatteries.com/shop/progressive-dynamics-30-amp-lifepo4-battery-charger/

CampHub

@TaG_Im_It Instead of adding back 4lbs you might want to look at a solution similar to this. This is a 40ah charger so up sizing the charge wires would be required. https://www.progressivedyn.com/specialty/pd4000l-series-lithium-power-centers/

Michael

https://teardrop-trailers.vanillacommunity.com/discussion/comment/4658#Comment_4658

This is the one that I listed above. It basically would replace the entire converter. I'm just not sure about the mounting depth. My last two weeks have been pretty busy and I haven't been able to measure the existing wfco unit but I hope to next weekend.

TaG_Im_It

Ok, for now, I'm satisfied with a 94% "shore charge"; given IF I'm boon docking and power is crucial I have solar hooked up (mid level 100w) and it runs the fridge with a surplus and charges the battery completely. I ran the trailer to Joshua Tree this weekend and for the first time measured the Acura Mdx charging power. In between the wfco and the solar. Usually like a 2 or 3 amp surplus.

CampHub

Truly amazing how much energy is in the LiFePO4 energy system. First weekend out was worry free. A battery monitor is a must IMO or you will have no way to know how much energy you have in the box-o-wonder. The battery box I had laying around is adjustable to different battery sizes so I was able to put the shunt inside the box with the battery. I put some closed cell foam at the bottom of the battery box to keep the battery from sliding into the shunt. 10# propane on the left. To top off the battery at home we are using a battery tender plugged into an Anderson power plug we use for ham radio and solar.
Piece of mind electron storage mod complete!

Misterbee

After being on the road for seven weeks in my brand new T@g XL, I am about ready to dump my lead acid battery in favor of the Battle Born, or maybe the new Trojan Trillum.

Slightly off topic: where is the WFCO charger/converter located, and how does one access it?

CampHub

@Misterbee it is the unit that holds your fuses and circuit breakers. https://wfcoelectronics.com/product/wf-8725-25-amp-power-center/

TomD

Mister bee..my experience has been that every adventure out with these trailers highlights something else you need to add as regards modifications. That’s good fun and a challenge. The outcome eventually is a camper that is closely tied to your camping world. Happy camping.