Lance Truck Camper Lithium Batteries + Alternator Charging

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For our 6-month journey north to Alaska in the Lance 1172 Truck Camper, we decided to try something new: we built a system to generate our RV’s power by charging our lithium batteries with the alternator of the vehicle!

We built out this system in Go North Episode 4: The Journey Begins

Charging Lithium Batteries with Alternator System

​We wanted to do this in order to minimize equipment (no generator or fuel) and maximize quiet operation while still remaining fully powered up.  Our goal was to go a full summer with no generator, no additional fuel to carry, and no additional propane use.

We partnered with Battle Born Batteries to test out this system on our journey.

We partnered with Battle Born Batteries to build out this system and try it out during our remote travels all the way to the Arctic Ocean. ​ 

The following video shares the details of the system and how it performed:

Alternator Charging System Schematic

Before starting, we laid out a schematic of what we planned to install in the truck camper.  Drawing out a schematic for your build is a great way to get a good understanding of how all the components connect. It will act as your map throughout your build.    

​Here is the original schematic as built in the camper:

If you watched the video above you may note a few differences in the schematic.  First the BIM was in the wrong place, on the camper side of the drawing, second there was an additional fuse in the truck charging circuit before the busbars.  This fuse was not installed and not needed because this section of cables was protected from over-current situations by the main battery fuse, and a built in mega fuses in the inverter if it was supplying the power. 

Truck Camper Electrical System Components

Battle Born Lithium Batteries

Battle Born Li-Ion Batteries make up the heart of the system, wired in parallel. 

We had the unique opportunity to assemble these batteries ourselves! Watch these batteries get built in Episode 4 of our Go North series.   

Why Battle Born Batteries?

Battle Born Batteries have made a name for themselves in the RV space. While we had worked on installing them in other instances (like putting in the off-grid RV electrical system in our friends’ Vintage Airstream renovation), we had never used them for ourselves – this was our first time!

​These batteries have an internal BMS (battery management system) that monitors the state of the battery and will automatically shut them down if they get out of spec, i.e. too cold to charge. 

Reasons for Choosing Lithium Batteries

We chose to install 5 lithium batteries for a combination of reasons:  

  1. Weight and Space. We wanted to match weight or be less than the generator and lead acid batteries that would normally be installed.
  2. Power requirements. These batteries hold 1.3KWH of power each so with 5 we would have 6500 watt hours of power available. Through a few calculations we estimated that without charging we could go 5 or 6 days pretty easily on this amount of power.

For most people, this amount of power storage would last even longer, but we are pretty power-hungry. We typically run two computers, charge multiple camera batteries, and running other equipment most of the time. Five or six days would be the max amount of time that we might go without a charge.

Busbars, Inverters, and Electrical Cabling


From the batteries we land the cables on two Blue Seas MaxiBus 250amp BusBars that distribute the DC loads and charging.  From these busbars we connected directly to the RV’s main DC power system. This system powers the lights in the RV, fridge, fans and any other DC appliance.  This connection was easy to make as we installed the batteries in the location of where a built in generator normally is installed and we used the wires that would normally start the generator.  

Also on the DC system is 200W of solar that Lance installed at the factory and will backfeed into the batteries through this system.  

he batteries are a snug fit in this compartment. The busbars are tight as well and its hard to tell where the wires go, but they are laid out like in the schematic.


Connected to the busbar is a Victron 12v/3000/120 pure sine inverter. This inverter converts the 12V DC power to AC power for the general receptacles.  We did not have space in the battery compartment of the RV, so we came up with another plan. We installed this inverter in an adjacent compartment to the batteries. This also worked well because the inverter needs more air to stay cool.

Ideally, you want to keep runs to the inverter as short as possible with a 12V system like this. We kept it just on the other side of the wall about 3 feet from the busbars and ran 4/0 cable to it.   

Electrical Cabling & Inverter Power

We again used wires that would normally be run to the generator to provide the inverter power. The RV also had a transfer switch installed, and we used this to make a permanent junction. This sent all the shore power through the inverter before making it into the RV.  

While this requires the inverter to be on to get power to the RV even when on shore power, it can easily be switched if there was a problem with the inverter. The inverter also serves as a battery charger for when we are plugged in to shore power. It can rapidly recharge the batteries with 120A of charge or around 1600 Watts.

We used a Victron 3000VA pure sine inverter to power the RV. This is the inverter we use in our fifth wheel and it has been great.

Truck Connection

Lastly, the main charging circuit that connects to the charging system of the truck connects to the busbars.  This circuit was made from 1/0 cable and runs out from under the RV to a large 175A Quick Connect plug that connects to the truck side.  On the truck side, the cables run along the frame up to the engine where they connect to the 300A Battery Terminal Fuse.

Battery Isolation Manager (BIM)

Before reaching the engine, however, the cables pass through a Lithium Battery Isolation Manager (BIM) unit. This unit disconnects the batteries when the truck is off and cycles the power 15 minutes on and 20 minutes off. This is toensure that the alternator does not overheat.

Most alternators are not designed to handle the high loads that lithium batteries put on them for extended period of time.  This truck has two alternators, however, and can handle much higher loads, although we are not sure of its limits. It is rated at almost 400A of charging capacity and when on the batteries draw around 100A.

The BIM also has a manual override that we connected to a switch under the dash of the truck. This allows us to force the batteries to come on when we need. The switch helps us get a more rapid charge, leave the batteries on when they are almost topped off (as the current drops), or also help jump start the truck if we accidentally kill its batteries. ​

Connecting to the Truck Batteries

The truck has dual batteries so we connected one of the terminals to one battery and the other to the other battery via a 100A terminal fuse to protect the wires.  We did this because the second alternator only comes on when the loads are exceed on the first and its connected to the second battery.

Connecting our batteries to the second battery drags the voltage down sooner close to the auxiliary alternator and kicks it online to help with the loads sooner.  

​We’re not sure why Ford does not run both alternators at the same time, although I guess to reduce parasitic losses. It is not ideal for this setup, as we still mainly tax the first alternator instead of distributing the load. But at least its there as a spare if we lost the first alternator.

Battery Monitor & Bluetooth

The last part of this system is the monitoring of the batteries and their charging with the alternator.  Between the busbars and the negative battery terminal, we installed a Victron BMV712 monitoring shunt and display.  This device monitors all the current into and out of they system to give us a very accurate state of charge of the batteries.  

This unit has Bluetooth connectivity as well. Because of this we decided not to run the display into the RV and instead opted to just use our phones to read the battery state.  

To control the inverter, we installed a Bluetooth connection to the Victron Multiplus inverter that allows us to monitor the inverter on the phone and turn it on and off remotely.  

These systems have been working great and we feel no need to have a display inside the RV. We have the Victron App on 4 different devices and any of them can check the battery or turn the inverter on and off.  


Alternator Charging System Performance

Since this was our first time designing a system to charge lithium batteries with an alternator, we were curious about how it would perform.

It worked…. that’s the short version.    

It actually worked too well!

We ran calculations to figure out how big of wires we needed to install to maintain 80-100A charge rate when the alternators were sitting at 14-14.2V. 

We didn’t expect that this truck preferred to run at 14.7 or higher voltage almost all the time. 

This higher voltage helped reduce voltage drop and pushed much higher currents than we expected into the battery bank.  When the bank’s voltage was low we saw upwards of 150-180A! 

This is a crazy good charge and would be awesome, except for one thing: the truck couldn’t do it safely. 

Because of the issue we mentioned above, the truck would rarely use its second alternator and thus we could overload the first one.  (We actually didn’t overload it, but it was not designed to sustain the load for extended periods of time and would get way to hot.)

Why the Second Alternator?

As a rule of thumb, alternators can sustain 100 percent duty cycle at about half their peak rated load.  The main alternator was a 225A unit and had a base load of around 50-80A on it, more when running glow plugs, heated seats, or the trucks rapid heat system ( a 1500W cabin heater). 

I think that this cabin heat thing is the main reason for the second alternator, as it was connected directly to it. My belief is the truck was probably programmed to turn the second alternators voltage up when it kicked on.   

Why the Second Alternator Didn’t Work

Let me explain this second alternator not-kicking-in thing. 

Alternators are actually AC power generators then have diode packs on the back to convert it to DC.  They can regulate their voltage by varying the excitation field of the windings and thus create smart charge profiles. 

The field windings are commonly controlled by the vehicles computer system and this truck would keep the main alternator at a very high voltage for a long time, and the secondary alternator at a much lower voltage.  This, in turn, basically disabled it until the main alternator dropped its voltage and they then matched. 

My guess is that under certain conditions like the trucks rapid heat (only used well below freezing) would the trucks computer “turn on” the second alternator.  It would be best if they were synchronized all the time.  I assume a little rewiring could probably make that happen.  

Our Solution

Well, we didn’t charge the lithium batteries with the alternator much in the first week on the road as were plugged in, but realized the issue while we were already on our way north… thus we lived with it. 

I happened to have a IR thermometer with me and took the alternator temps regularly to figure out when they were getting too hot. I assumed anything above 220F was too hot.   

We determined that they would get too hot after about 7-10 minutes of engine running depending on the outside temp.  So, we set alarms on our phones and would manually cycle the alternator every time it went off to charge the RV’s lithium batteries as we drove. If this sounds ridiculous….it was! 

Saved by the Voltage Drop

Now, the good part is we did’t have to do this forever, because the truck would eventually drop the alternator voltage and we could just leave the system on to charge more slowly. But, that meant monitoring the voltage of the truck each day, too.

Once it dropped, which happened anytime from 1 hour run time to never,  we would just switch the system on and let it go. This usually charged around 50-80A depending on the Battle Born Batteries state of charge. 

Is there a fix?


I would have liked to implement a fix for it but we were traveling the north having a grand old time.  Trying to line up a package delivery and do the work was tough with a tight schedule and being in the middle of nowhere. So we just lived with it. 

Ideally, I would have put a DC-DC converter in between the truck and camper. 

The image below is a DC-DC charger unit that would have solved all of these problems.  These do as the name suggests: they charge.  They take one input source and modulate it so that it matches the required output charging characteristics.  Usually, they are fully programmable for your requirements. 

This is one DC-DC option. Sterling Power has a whole line of DC-DC converters for different options. Battle Born Batteries carries them for sale.  

A DC-DC unit would not only have helped during our truck’s absurd bulk charge sky-high voltage, but also when the voltage dropped.  It can keep the output voltage constant regardless of what the alternators are doing, and you can set limits so you don’t overload your vehicle.  The result: a nice even charge of the lithium batteries from the alternator.

This would add cost to the system but would take away lots of headaches and make it just work.   

This is a redesigned schematic that I would recommend. A DC-DC converter would allow you to run smaller wire and you would not need the LI BIM disconnect switch as it takes care of that.

So, would you do alternator charging of lithium batteries again?

Totally.  We loved not having a generator, not messing with fuel, etc. Between the Battle Born Lithium Batteries power storage capacity and the ease of charging them off the alternators as we drove, the system worked as we hoped!

Even with our hiccup, the system did what it was supposed to do and helped us create Go North.  For future projects, I would happily build the same system but with the DC-DC converter. I’d also use smaller charge wires from the truck. 

I might also modify a truck with dual alternators to run both of them all the time so I could get a better charge.  

Overall, we were very happy with system and love having quiet power whenever we needed it!

​Learn more about Battle  Born Batteries here!

Read more about our Go North Adventure and Series here!

*Note: This article contains affiliate links.

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Mortons on the Move

We are Tom & Caitlin Morton. We gave up the stationary life for one where we are constantly on the move. We live in a fifth wheel RV and travel with our two pups, Mocha and Bella. We enjoy hiking, biking, boondocking, videography, and upgrading our RV to suit our off-grid mobile lifestyle. Our goal is to share educational, entertaining, and inspiring content with our readers and viewers.

View Comments

  • What’s the model number if the Bluetooth adapter for the Multiplus so that it can talk to the victron phone app?

  • Did you create a spreadsheet that had a list of all devices that consume electricity, along with their amps, volts, watts, and average daily hours used? I did that for my upcoming, first RV later this year and it was quite informative about anticipated battery usage. I'm curious since you are anticipating 4-5 days off of about 6000 watt hours. Do you plan to drive most days or boondock for several days w/o driving (and its associated battery charging) ?

  • I like the idea of using a 12v inverter (maybe 1500 watt) and going in as AC to the Victron and let the Vicron charge the batteries according to the charging profile you already have loaded. If the inverter is in the cab of the truck, that's less 1/0 wiring. You can use AC wiring back to the camper. I know it's inverting then converting back but it seems easier.

  • Question about the 7 pin connector in relation to the lithium bank being at a higher voltage than the truck lead acid battery.
    Can you please explain what prevents the power flowing from the lithium house bank back through the 7 pin connector into the truck battery when left plugged in while not running? If not isolated some how are you concerned that the small wire size in the 7 pin connector is undersized for the possible high amperage flowing back into the truck battery, especially if the truck battery is low and the house bank is fully charged?
    I look forward to your response...
    Cheers, Colin

    • I'm a retired mechanical engineer, custom truck camper DIY'er with a 2004 F350/Lance 1130. MY situation is that the truck has a factory-installed relay on the trailer connector power lead that goes on and off with the ignition. This will prevent any back feeding. I can only presume other years and truck manufacturers do the same thing.

      On the issue of the ampacity of the trailer connector; This is a real issue. I believe the standard trailer cable has a 12ga wire but think it more likely the coupling is more limiting. I would suggest that if you have any situation OTHER THAN a single stock alternators and lead-acid house batteries, that you will need a dedicated power cable coupling the vehicle to the camper. In my case, I have 2 alternators with the second modified specifically to charge my (24V/17.5 kWh Nissan leaf battery) camper battery. I use a 2ga cable and 175A Anderson plug. I also have a current/voltage display in my center console and a thermostat sensing my alternator temperature (120C cut out/110C cut in) that cycles the excitation power to my external voltage regulator to deal with the issue of alternator overheating (and it does well). FYI, I melted the 175A Anderson connector once because I failed to ensure all contacts were fully locked into the connector and one backed out, leaving a poor connection that heated.

  • How did you find technical information about how Ford sets up its dual alternators? I have looked everywhere and have not been able to get reliable complete info for my 2019 F250 diesel. The truck has a 157A and 175A alternator (but that info I found myself by tracking the model numbers on the alternators). Other than that, Ford has been no help. Also, I really dislike the Lithium BIM charging "schedule" (15 minutes on and 20 minutes off) that Battleborn designed into the Precision Dynamics device. I believe they did that as a wild guess to cover as protect as many alternator types as possible at the expense of killing charging efficiency. I am planning to use the Victron buck boost DC DC converter. Would you do the same if you did it over again?

    • Justin,
      I have a 2004 F350 with dual alternators (but a custom setup). My investigation of my truck's factory setup may be helpful but I can't guarantee it. On my factory setup, Ford set up the primary alternator to be energized by the 'ignition on' of the key. The second alternator was controlled by the ECU. It was only allowed to come on if the system voltage sagged considerably (cut in voltage escapes me). This may be how your 2019 is controlled. The reason is fuel economy. Ford is incentivized to seek a higher fuel economy, not more utility. I believe this is a poor system for our purposes. I have considerably altered my system but what I did could be useful to you. I run my second alternator dedicated to charge my 24V lithium camper battery directly so have replaced the internal regulator with an external (Transpo Voyager set at 29.4V) bypassing the ECU control. I have implemented multiple controls of my own to interrupt the 24V excitation to the regulator to manage charging. Power has to flow through all these to energize the alternator regulator; 1) Ignition relay to only operate 'key on', 2) BMS 'charging allowed' relay, 3) manual 'enable' switch in cab, 4) thermostat on alternator (120C cut-out, 110C cut-in). It does a very good job of maximizing the alternator output (based on actual temperature), not on a timed cycle. I think this is a good solution to maximize the charge rate much higher than a DC-DC charger could do (usually maxing out at ~40A). I can run at 87A before the 120A alternator starts to cycle on and off by the thermostat. At low SOC, I have seen over 150A. I have not had to charge often enough at low SOC to figure out what the duty cycle of the alternator is to arrive at an average charge rate but guess that its probably over 100A which could be improved with a 220A alternator (higher duty cycle). Balmar makes a 'charging regulator' that can do all of this (for $400) but my system only cost about $40.

      • That makes a lot of sense, From my testing that is exactly how this truck operated, only using the second alternator under extreme situations.... which I think could cause the first to fail sooner. I love the idea of a completly new regulator external to the trucks control.... Your cost is great too!

  • Whats up Tom! I just stumbled upon your videos this week as i was trying to figure out how to use a salvaged Tesla battery with a solar setup!
    One thing i'm trying to do is setup the alternator to charge the battery for emergency situations (and general charging when driving). Iv come across some ways to use victron products with victron batteries, but I don't know the chemistry of batteries enough to figure out if the LiFePO batteries can easily be exchanged with the NCA Tesla.
    from my understanding the dangers are overcharging the battery, and overworking the alternator. so i figure that the battery makeup is redundant if i can set up a relay to prevent overcharging, and another to keep the alternator from exploding (which may not be an issue, its a 160 amp 14v alternator on an international 4700 ex-ambulance).
    if we took your diagram for the battleborn batteries, what other (if any) systems would need to be in place to make it tesla compatible?
    I look forward to your reply!

    • So sorry I missed this comment, did you see our latest video. With a proper BMS setup for Teslas to disconnect if high voltage you can use a DC-DC 12-24V converter and set your own charge profile. But like with other charging means, have a voltage monitor and secondary battery disconnect.

      • Hi, I purchased two Model S batteries and the 24/3000 inverter but I have decided to switch to a more conventional Battle Born 12V setup. I think it will be easier to sleep at night on top of them. I think the BB batteries will be more set-and-forget.

    • Apples and Oranges really. BB is great for ease of installation and guaranteed safety. Not great for cost and weight. Teslas or other re-used systems are cheap and typically lightweight. Great for packing tons of power in small spaces but more complicated to install and safety is up to you as if they get out of spec they will catch fire. Gotta be confident you know what you are doing with them!

  • I have heard of other alternator charging setups that functioned more like a trickle charger and taking hours of driving to charge to batteries part way. Do your modifications and the BIM over-ride allow for a more rapid charge?

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