Battery Upgrade - Concern for alternator & Mixing Chemistries

This is my first post. We bought a 2021 Tag XL Boondock last year. We took about a half dozen trips last summer around MI, IL and WI. The longest was 2 weeks. Loved them all and our new teardrop. All of them were at sites with no power. As a result, we decided to upgrade the battery system. I bought a Renogy 100W solar suitcase with a 20amp charger controller with a lithium setting because although we have a solar panel on our camper, it’s always in the shade. I also bought a Renogy 100AH 12 V lifepho battery along with a Victron charger with a lithium setting. Charging the new battery with the new charger seems pretty straightforward. I also understand with shore power, the battery will only charge to about 80% due to the WFCO power converter not having a lithium setting.
My concern is my 2018 Jeep Grand Cherokee’s alternator and the health of both my Jeep’s and my camper’s batteries. I have read many posts here as well as on other sites and there seem to be a lot of opinions out there. One post I read the person cut their 12V aux wire on their trailer plug. This makes some sense to me given I have the charger and solar, but I’m not sure if there are circuits on my camper that use this other than for charging the battery. I have read a lot of posts about not mixing battery chemistries…using isolators and DC to DC chargers. I’ve also read about using the battery disconnect switch to isolate the camper battery, but this approach also will mitigate the break away circuit to the brakes on my camper.
I want to protect my investment and vehicles while not over-engineering the right set up. I am looking for input on risk to my Jeep’s alternator as well as the risk to both my batteries and the most straightforward mitigation steps I need to take if at all.


  • Sharon_is_SAMSharon_is_SAM Administrator Posts: 544

    @Suskat9 - lots of discussions over on the TaB forum for more info.

    Sharon | Westlake, Ohio | 2017 TaB CSS

  • JamesDowJamesDow Member Posts: 504
    edited May 7

    I have esentially the same Renogy setup with a 2012 Rav4 as tow vehicle (TV). No problems. Get about 11% increase in scope of charge per 200 highway miles. No issues with alternator, but I am aware not to over tax charging a bunch of usb things when driving at night.

    I added a simple switch on the TV to cut 12 volt to trailer. Don't worry about cutting TV power unless sitting connected, not running for say a few hours. Why? Don't want to loose trailer battery power charging the TV. No need in my mind for DC/DC adapter or other converter or isolator. ( could easily just unplug for same result)

    I have found the [email protected] converter will charge my lithium battery to around 84% just plugged in parker driveway.... but if plugged into shore power with battery switch on and refrigerator running, the lithium will charge to over 96%. Why? - the [email protected] converter has three charge status that it will cycle through. One of the three is over 14 volts, which charges the lithium battery.

    Don't know what your power draw is while camping. Mine mainly is Norcold refrigerator, some recharging of phones & GoPro and seldom use of Fantastic Vent fan. (Use 9" usb battery fans instead) The trip I am currently on started with lithium battery around 98%. Use my 100 watt Renogy suitcase and after two full days I am at 86.5% state of charge. Even full desert sun 99+ degrees the 100 watt solar panel is not keeping up. This is in-part of daytime temps along with setting refrigerator to daytime temp of 31 degrees and then 38 at night. Just planning on three more days, so I will be fine. I also just got a 50 watt pannel (for a 300 watt Renogy power Station) so I may try and hook up in parallel just to see what it will add.

    Bottom line is you should be fine with your setup. Do a few trips and see if any needs arise.



  • Suskat9Suskat9 Member Posts: 2

    Thank you for your feedback and sharing your experiences. I am reassured that what I have is sufficient to go out this year and see how my new stuff works. Thanks again, Dan,

  • Hwy395_bumHwy395_bum Member Posts: 8

    Best article I have read:

    My story:
    Like most people I first started having trouble with the Norcold right from the start. I added a second battery - still no worky. Many people added a wire from the battery straight to the Norcold so my suspicion was the WFCO-25 is totally under rated. I was an early adopter of the PD4135. After cleaning up some of the wiring - no more issues.

    When I bought it, they said I could get a free upgrade to their Lithium motherboard. I had a chugged up lithium setup at the time and was really happy when they told me it was available. Took 1 hour to swap the board as their design has all the wiring on a separate plug in connector.

    Swapped the Zamp controller in the 80watt portable for a Renogy (added bonus of two USB ports). Zamp said it was compatible with lithium but as the article mentions - not so. The only thing I was worried about was the truck charging.

    My solution, since the truck has an inverter built in and a 110vac socket in the bed was to use an auxiliary charger that came with my original lithium battery. I cut the wire going to the trailer connection, spliced 2 wires and ran them to the bed and connected them to the charger, mounted it and plugged it in. All I need to remember is to hit the inverter switch on the dash after I start the truck.

    If you think this was a lot of work, well that is one expensive battery, we off grid almost exclusively.

    The article above validates everything I did. Not one issue with power ever since.

  • MrGGBrownMrGGBrown Member Posts: 37

    While the built-in WFCO 8725 charge controller won't charge a LiFePo battery correctly, at least it doesn't seem to have the lead-acid charging modes that can be damaging to a LiFePo battery, per the linked article. According to the WFCO specs, "Nominal voltage output modes are a 13.2 VDC range “float” mode, 13.6 VDC range “absorption” charge mode, and a 14.4 VDC range “bulk” charge mode." Despite what many people report with other LiFePo batteries, I can regularly get my Lion Energy LiFePo battery to 100% using the standard WFCO 8725 charge controller. Must be differences in the BMS.

    Greg Brown
    Bellevue, WA
    2016 PVTT [email protected]

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