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  1. #1
    Site Sponsor SolarPoweredRV's Avatar
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    How to Protect Your Lithium Batteries From Cold Weather Charging

    Many of the value priced Lithium batteries (LiFePo4) do not have cold temperature charging protection built into the Battery Management System (BMS).

    Lithium batteries can be used in very cold temperatures, however, they must be protected from charging if the internal temperature of the battery is 32 degrees or below.

    You must protect your batteries from charging from all charging sources...

    Converter
    Inverter/Charger
    Solar panels
    Tow vehicle.

    Some Solar Charge Controllers and Inverter/Chargers have temperature control built in to them, however if you are going to use these devices for temperature protection, it is best if you have a temperature probe inside the battery box. Additionally, you want to set your temperatures so that charging stops before freezing temperatures are reached ( I use 35 degrees) and don't start until after the temps are above freezing (40 degrees, or more). This is because if your internal battery temperature reached freezing, you want to give the batteries plenty of time to warm up internally before charging them.

    If you are using a Converter and don't have an Inverter/Charger that you can turn off the "Charger" portion of the Inverter, you will need to design Cold Temperature Protection into your system design. The way I did this is with a device called a "Battery Protector" from Victron and a thermostatically controlled relay from Amazon (see links below).

    The Battery Protector allows energy to flow (primarily) in one direction and it has an "On/Off" switch on it's face that is simply a loop of wire connecting two posts together electrically, if the loop is broken (i.e.: with a simple switch) the Battery Protector stops electricity from flowing to the battery(ies) preventing them from being charged. Consequently, if we connect the thermostatically controlled relay to the "on/off" switch on the front of the Battery Protect module we can control charging to the batteries based on temperature.

    Warning, this Battery Protector module is designed to handle electricity flow primarily in one direction only! This means that you can't simply connect the Battery Protector module to the positive post on our battery bank and everything will be protected. The Battery Protector is not designed to carry the out going load from your batteries and could cause a fire hazard if you wire your system in this manor.

    Because of the "One Way" directionality of the Battery Protect module, you need to wire it into your system in such a way as to only be connected to the output side of your Converter or Solar Charge Controller (you will also need to prevent charging from the Tow Vehicle). You will need to install a Battery Protect Module on the output side of both the Converter and the Solar Charge Controller (presuming you do not have a temperature prob inside the battery box connected to your Solar Charge Controller) as well as the output from the Tow vehicle.

    To thermostatically control the Battery Protect module (or modules) you will connect the relay (think of the relay as a simple switch) to the two terminals on the front of the Battery Protect where there is a short loop of wire attached. You will configure your thermostat module to open the "Normally Closed" (NC) relay if the temperature drops below your chosen temperature (say 35 degrees). Once the relay is open, the Battery Protect will stop any energy from flowing into the battery. When the temperatures rise above your set point, the relay will close and electricity will begin flowing into your battery. You can control multiple Battery Protect modules by daisy chaining them together into a single relay (essentially you are creating a large loop between all the modules with the relay acting as one switch for all modules).

    If you have an Inverter/Charger instead of a Converter, using a Battery Protect module will not work in that circuit because of bi-directional, high amperage. draw from the batteries and there only being one connection between the batteries and the Inverter. You will need to remember to turn off the Charger portion of the Inverter/Charger until you are comfortable the internal temps of the battery bank is above freezing.

    Alternately, you can install your batteries in a heated space, or build a battery box with warming pads that will keep the battery temperature above freezing. I highly recommend these approaches if you are going to be doing a fair amount of cold weather camping.

    Here are links to the Victron Battery Connect and Thermostatically Controlled relay:

    Victron-Smart-Battery-Protect-Bluetooth

    Amazon.com/gp/product/B076Y5BXD9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


    Notes: the Battery Protect Module works on both 12 volt and 24 volt systems.

    The Thermostatically Controlled Relay is also available for 24 Volt systems and can be purchased for either Fahrenheit or Celsius.

    Installation Note: the instructions for the relay can be a bit confusing, read them on Amazon before you buy it and make sure you understand the Nomenclature, i.e.: NC, NO, means the relay is Normally Closed and Normally Open, etc.
    Last edited by xrated; 02-20-2023 at 11:43 AM.
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

  2. #2
    Site Team Ynot4me2's Avatar
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    As I'm still designing my install as I'm patiently waiting for cells to arrive, your post gave me an idea. Could a battery disconnect (automotive kill switch) with remote capability be used instead of the Victron Smart battery Protect. These seem to let current flow in each direction as oppose to the Victron. And probably the thermostat that you listed could replace the remote module.
    I'm in Canada and need the heating pads as we often camp early spring and late fall which sometimes have days below 32 but for someone that just needs temporary protection, this might be a better alternative as you would need just 1 of these at the battery that would stop charging from the rig, solar and/or TV.
    https://www.amazon.com/dp/B07DFM2NJ3...tonytrip551-20
    I just might give this a try after my install in completed just as an added protection.
    Steph & Lise
    2019 F150 Lariat 2.7 EB
    2020 Imagine XLS 22MLE

  3. #3
    Site Sponsor SolarPoweredRV's Avatar
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    Quote Originally Posted by Ynot4me2 View Post
    As I'm still designing my install as I'm patiently waiting for cells to arrive, your post gave me an idea. Could a battery disconnect (automotive kill switch) with remote capability be used instead of the Victron Smart battery Protect. These seem to let current flow in each direction as oppose to the Victron. And probably the thermostat that you listed could replace the remote module.
    I'm in Canada and need the heating pads as we often camp early spring and late fall which sometimes have days below 32 but for someone that just needs temporary protection, this might be a better alternative as you would need just 1 of these at the battery that would stop charging from the rig, solar and/or TV.
    https://www.amazon.com/dp/B07DFM2NJ3...tonytrip551-20
    I just might give this a try after my install in completed just as an added protection.

    The problem with this solution is that the kill switch will disconnect your batteries from the coach leaving you in the dark. You could use this type of switch on the output side of the Converter and Solar Charge controller instead of the Battery Protect Module, however, wiring this type of switch not only requires "momentary" energization of the control circuit to disconnect the Converter/Solar controller, it would also require some type of mechanism to "momentarily" energize the control circuit a second time to re-enable the Converter/Solar controller. You could run this type of switch with manual control switches installed inside the coach, however, I would suggest installing red indicator lights that can easily be spotted outside of any control cabinet you may have indicating whenever the circuit is turned off.
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

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    When I upgraded my previous Class A to lithium batteries I did this for cold protection:

    Since lithium batteries don't give off gas, I moved them to an enclosed, heated storage compartment. They came packed completely surrounded in closed-cell form, so I kept them in their packing foam as insulation. Batteries generate heat when they discharge, so insulating them helps keep the heat in.

    I bought an inexpensive 12V Digital Temperature Controller (https://www.amazon.com/gp/product/B019I3YCFS/) and used it to trigger a relay (https://www.amazon.com/gp/product/B019I3YCFS/) that killed power to the converter/charger when the temp dropped below 32 degrees. Including a 20amp circuit breaker (https://www.amazon.com/gp/product/B000WUL6BA/) it cost less than $60.

    The temperature cutoff was mainly in case the RV was in storage with shore power connected. When I was using the RV in the cold, running the furnace would keep the storage compartment well above freezing, so I just needed to protect the batteries if it was cold but I didn't have the heat on. The next batteries I buy will have cold-weather cut-off protection built in to the BMS, so I won't need to add my own cut-off.

    Click image for larger version. 

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    Last edited by RubiconMike; 02-20-2023 at 10:54 AM.

  5. #5
    Site Team Ynot4me2's Avatar
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    Quote Originally Posted by SolarPoweredRV View Post
    The problem with this solution is that the kill switch will disconnect your batteries from the coach leaving you in the dark. You could use this type of switch on the output side of the Converter and Solar Charge controller instead of the Battery Protect Module, however, wiring this type of switch not only requires "momentary" energization of the control circuit to disconnect the Converter/Solar controller, it would also require some type of mechanism to "momentarily" energize the control circuit a second time to re-enable the Converter/Solar controller. You could run this type of switch with manual control switches installed inside the coach, however, I would suggest installing red indicator lights that can easily be spotted outside of any control cabinet you may have indicating whenever the circuit is turned off.
    Your absolutely right, my mind was just going all over the place. I guess one could run all charging wires (charger, solar, tv) back to a buss bar of some sort then to either a Victron Battery protect or kill switch with thermostats then to battery.
    In my situation the kill switch for the charging under 32 will be my BMS if my heating pads cant keep up. So need for it. I love your post, they always get me thinking (and spending) LOL
    Steph & Lise
    2019 F150 Lariat 2.7 EB
    2020 Imagine XLS 22MLE

  6. #6
    Site Sponsor SolarPoweredRV's Avatar
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    Quote Originally Posted by Ynot4me2 View Post
    Your absolutely right, my mind was just going all over the place. I guess one could run all charging wires (charger, solar, tv) back to a buss bar of some sort then to either a Victron Battery protect or kill switch with thermostats then to battery.
    In my situation the kill switch for the charging under 32 will be my BMS if my heating pads cant keep up. So need for it. I love your post, they always get me thinking (and spending) LOL
    I understand how things can seem "Too Big" to wrap your head around the whole system. One of the things that help me is to look at each device and look at how that piece fits into the system as a whole and how that device would react if I change something in another part of the system.

    I seriously considered the idea of sending all of the charging outputs to a single Buss Bar (except for the Inverter/Charger output) however, I ran into the issue of the combined amperage from all the devices being to high for the Battery Protect module to control (especially if those devices are capable of producing "Surge Power" to start electric motors).

    In your case where you have the warming mats and a BMS capable of sensing the cold temperature and stopping any charging from taking place below 32 degrees, the BMS acts as a safety/fail-safe mechanism to protect your batteries.

    When it comes to protecting your batteries from charging by the Tow Vehicle, I would suggest having a switch inside the Tow Vehicle which can stop the TV from charging the batteries. Alternatively, you could run the charging wire from the Tow Vehicle to the same Battery Protect module you are using for the Converter, because, your Converter would not be active while you are towing, so one device can perform two functions. If you are using a DC to DC Converter in your Tow Vehicle to charge your batteries you should already have a switch controlling the DC output to the batteries.

    One thing I think I should mention: in your case, where you have warming mats for your batteries and a BMS that is capable of stopping the batteries from being charged if the internal temperature is below 32 degrees, you don't really need to add any of the Battery Protect modules because you already have two methods of protecting your batteries from charging in cold temperatures. This post was primarily for those who purchased batteries without BMS cold temperature protection.
    Last edited by SolarPoweredRV; 02-20-2023 at 02:09 PM.
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

  7. #7
    Site Sponsor SolarPoweredRV's Avatar
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    Quote Originally Posted by Ynot4me2 View Post
    Your absolutely right, my mind was just going all over the place. I guess one could run all charging wires (charger, solar, tv) back to a buss bar of some sort then to either a Victron Battery protect or kill switch with thermostats then to battery.
    In my situation the kill switch for the charging under 32 will be my BMS if my heating pads cant keep up. So need for it. I love your post, they always get me thinking (and spending) LOL
    I understand how things can seem "Too Big" to wrap your head around the whole system. One of the things that help me is to look at each section or part and look at how that piece fits into the system as a whole and how that part will react if i change something in another part.

    I seriously considered the idea of sending all of the charging outputs to a single Buss Bar (except for the Inverter/Charger output) however, I ran into the issue of the combined amperage from all the devices being to high for the Battery Protect module to control (especially if those devices are capable of producing "Surge Power" to start electric motors).

    In your case where you have the warming mats and a BMS capable of sensing the cold temperature and stopping any charging from taking place below 32 degrees, the BMS acts as a safety/fail-safe mechanism to protect your batteries.

    When it comes to protecting your batteries from charging by the Tow Vehicle, I would suggest having a switch inside the Tow Vehicle which can stop the TV from charging the batteries. Alternatively, you could run the charging wire from the Tow Vehicle to the same Battery Protect module you are using for the Converter, because, your Converter would not be active while you are towing so one device can perform two functions. If you are using a DC to DC Converter in your Tow Vehicle to charge your batteries you should already have a switch controlling the DC output to the batteries.
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

  8. #8
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    Quote Originally Posted by SolarPoweredRV View Post
    Many of the value priced Lithium batteries (LiFePo4) do not have cold temperature charging protection built into the Battery Management System (BMS).
    We just replaced a set of F.L.A. batteries with LP04 (LifeP04) units - they do not have built in cold weather protection. I also upgraded the factory WFCO converter to a Lithium charging capable unit. While I appreciate what the Lithium units are buying us for our one/two days of boondocking we do while traveling, I had no idea the LP04 batteries were going to create such a problem traveling in the cold. I've figured out how to disable charging from the tow vehicle side, on a Ford you just pull the charging fuse, but I'm struggling with RV side. Wouldn't I be fine to simply turn off the converter at the fuse box/power center? If so, I'm ok with doing this for now. If not, I'm not sure I understand how to wire in the Victron protection unit and still maintain "normal" battery operation for the RV (as I only have one wire that connects to the battery)?. I'm assuming there is a separate wire, somewhere in the mess that is the RV wiring, that controls just the charging side of things? If so, I'll have to drop the underbelly insulation and go fishing.

  9. #9
    Site Sponsor SolarPoweredRV's Avatar
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    Quote Originally Posted by wam6187 View Post
    We just replaced a set of F.L.A. batteries with LP04 (LifeP04) units - they do not have built in cold weather protection. I also upgraded the factory WFCO converter to a Lithium charging capable unit. While I appreciate what the Lithium units are buying us for our one/two days of boondocking we do while traveling, I had no idea the LP04 batteries were going to create such a problem traveling in the cold. I've figured out how to disable charging from the tow vehicle side, on a Ford you just pull the charging fuse, but I'm struggling with RV side. Wouldn't I be fine to simply turn off the converter at the fuse box/power center? If so, I'm ok with doing this for now. If not, I'm not sure I understand how to wire in the Victron protection unit and still maintain "normal" battery operation for the RV (as I only have one wire that connects to the battery)?. I'm assuming there is a separate wire, somewhere in the mess that is the RV wiring, that controls just the charging side of things? If so, I'll have to drop the underbelly insulation and go fishing.
    There are several solutions to "cold weather" charging. The easiest is to install the batteries inside the coach, or in a heated hold where the temps will not get below freezing.

    Additionally, do you camp when the Temps are below 32 degrees? If not, you probably don't need to do anything special to avoid charging your batteries in cold Temps. However, most of us will need to protect our battery investment against cold temp charging.

    You are correct in looking at both your Converter and Tow Vehicle charging to ensure you don't charge in the cold, others will also need to ensure their Solar system can't charge as well.

    If your cold weather camping is infrequent, simply pulling the Tow Vehicle fuse and switching off the breaker that controls the Converter will be sufficient (note: be sure to switch off the Converter before the temps reach freezing). If you are boondocking and will not be running a Generator, (and do not have Solar) you would only need to remove the fuse from the TV if you intend to travel.

    Another solution is to place a heater in the battery box that will prevent the batteries from getting too cold.

    The final solution would be to design an automatic, thermostatically controlled, solution using something like a Victron battery protect module and a relay type thermostat.
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

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