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How-to: Building a Lithium House Electrical System | Component Selection

How-to: Building a Lithium House Electrical System | Component Selection

Filed under House Electrical. See all how-to guides.

This guide is a little different than most. Since lithium batteries are still relatively new, less well-known technology, I'll cover break the guide into two parts:

  1. Background on LiFePo4, and an overview of the components that I decided on - which work with any battery technology - in order to build out a kick-ass 12v house electrical system.
  2. Installation of the components, and important considerations when assembling a 12v house electrical system.

Six years ago, when I initially installed my house battery, it allowed me an entirely new sense of calm when I was in camp at night. No longer did I need to worry about my fridge - or the other small electronics I might turn on or charge - draining my starting battery overnight, thus leaving me stranded.

Plus, the whole system of linking the two Northstar AGM 24F using a Blue Sea Systems ML-ACR (automatic charging relay) meant that I could easily - either manually or automatically - link my two batteries for charging or more power, and unlink them to protect the starting battery in camp.

It was fantastic. Mostly.  For the vast majority of my trips - where I'm driving around most of the day - the whole situation worked perfectly. Only when I was camped in a warm place for longer than 24 hours did I still worry that I would completely drain the house battery, unless I fired up the Tacoma for a few hours of charging. And that only happened rarely, mostly when out camping with my Dad.

But batteries don't last forever, and several months ago, I noticed that - when I'd pick up the Tacoma from storage in Las Vegas - the starting battery was having trouble starting the Tacoma. Northstars are no longer sold as such, though they are still available from BatteriesPlus as X2 Power AGM 24F (their house brand), so that would have been the simple solution. However, I think we're all aware that battery technology has improved dramatically over the last six years. It would be crazy for me to ignore those improvements, especially in the Lithium - largely LiFePo4 for this sort of application - space.

Background: Pros and Cons of LiFePo4 (LFP)

With any "new" technology, there are obviously tradeoffs, so I first set about learning just enough about LiFePo4 to feel like I could trade off the major pros and cons of switching over. The biggest drivers - in my mind - seemed to be:

Pros

  • Weight and Capacity - LFP batteries pack energy much more densely than AGM batteries. I don't know all the science behind this, but my 24F AGM battery was rated as 76 Ah (Amp-hours) and weighed in at 59 lbs. An LFP battery of the same weight packs in 280-314 usable Ah, a 3.5-4x improvement, or a huge weight savings, if one should decide to go with a lower Ah LFP battery.
  • Longevity - Where an AGM battery can support several hundred (in the range of 500) charge-discharge cycles, an LFP battery can maintain healthy after 5,000-15,000 cycles. That's an order of magnitude more; if an AGM lasted me 6 years, a LFP might last 60-180 years.
  • Modern Battery Monitoring System (BMS) - All LFP batteries have a built-in (or require an external) BMS. Essentially a computer, it monitors the voltage of the individual cells that make up the logical battery, ensuring that they charge/discharge efficiently, that the current moving through the system is safe for the hardware, and that various parameters are taken into account in order to ensure longevity of the battery. Many BMS also have Bluetooth connectivity so you can monitor everything using an iOS or Android app.
  • Fun and Learning - this isn't really a pro of LFP per-se, but switching over to a new house system would allow me to learn about the new technology and build out a system to support it, improving aspects of my current house electrical system that I knew could use a little love.

Cons

  • Starting Ability - For the most part, today's budget-friendly LFP batteries are not suitable for starting a vehicle. While some (much) higher priced cranking battery options exist, LFP largely excels at providing current in the 100-200A range, not the 800-1000 CCA (Cold Cranking Amps) provided by AGM or traditional automotive batteries.
  • Operating Temperature - LFP is more temperamental when it comes to charging. Charging below 32°F, or discharging below -4°F can harm the battery. While batteries with built-in heaters can help to keep the battery healthy in cold conditions, those heaters draw power, making them a time-limited solution.

Differences / Difficulties

I initially listed these as cons because in today's world - where the starting battery continues to be lead-acid/AGM - these definitely make LFP more of a pain in the butt. However, as LFP becomes more prevalent and is used for the starting battery as well, these differences will go away, hence my breaking them into a different category.

  • Charging - Each battery chemistry (lead-acid, AGM, LFP, etc.) charges most efficiently/completely with a different charging profile. That is to say, at any point in the charge cycle, a different amount of voltage and current are required for optimal charging. Alternators in most vehicles (today) are designed to charge AGM/lead-acid batteries, not LFP. As such, a dedicated DC-DC charger - that takes the output of the alternator and modifies it slightly to accommodate the charging profile of LFP - is needed in order to achieve efficient and optimal charging.
    Note: This isn't new. Many alternators in older vehicles were optimized for lead-acid batteries only, so even installing an AGM-based house battery would benefit from a DC-DC charger, in order to accommodate the slightly different charging profile of AGM vs. lead-acid.
  • Battery Linking - Similarly to charging, it's not a great idea to combine - connect directly - batteries of different chemistries. This is because they charge/discharge/rest at different rates and with slightly different voltages. By connecting them, there is risk that these imbalances will cause strain on one or both batteries, significantly reducing their lifespan; in extreme cases, doing so could even cause one battery to explode. Thus, unlike an all-AGM system where two batteries can be combined for more power when winching, for other high-current operations, or even just for charging, using an LFP battery for the house system really means that the two electrical systems must be isolated from each other, with the exception of a common ground.

My Thoughts (aka Why LiFePo4 and not AGM?)

As I mentioned, the easiest thing I could have done would be to just drop a couple new AGM batteries into the Tacoma and call it a day. Plus, the "Cons" + "Differences / Difficulties" lists are longer than the "Pros," so why would I ever choose LFP?

In the end, the only difference that had me seriously considering AGM was the ability to link batteries - via a switch in the cab - and fully combine them into a single battery bank connected via thick, 1/0 copper cable. I've used this ability a few times to jump start my starting battery with the house battery, and it's extremely reassuring to know that I'm unlikely to get stuck in the middle of nowhere with a truck that won't start due to a dead battery.

My solution to that problem is twofold:

  1. I purchased a highly rated - and reviewed by Project Farm - lithium jump pack. While not as convenient as flipping a switch, it should allow me to jump myself quickly if my starting battery dies.
  2. It is possible to reverse the wiring on a DC-DC charger so that I can use the house battery to recharge the starting battery. Again, not as convenient as flipping a switch, but essentially like plugging in a battery charger to a receptacle in the garage in order to keep the starting battery charged up.

Otherwise, the ability to have a lighter weight, higher capacity battery that will last longer than I have left on this earth seems like a pretty cool idea. Plus, I love learning new stuff like this.

House Electrical System Components

Note: While this isn't the only system that would work with any individual battery chemistry - AGM, lead-acid, LFP, etc. - it does work perfectly well with any battery chemistry by simply replacing the battery.

Putting together a house electrical system for the first time can be intimidating. Besides identifying all of the functional bits that enable various features, there are the mundane questions like what wire size to use, where to add fuses and breakers, and how to mount everything robustly in order to survive thousands of bumpy trails.

What I'm describing.

I'll list what I chose below and a brief reason for each. In many cases, there are certainly other good choices out there, so feel free to ask questions or suggest alternatives if you think I'm missing something. Below, I'll cover the following:

  1. Battery and BMS
  2. Master On-Off Switch
  3. Battery Shunt
  4. Master Distributor / Fused Bus Bar
  5. DC-DC Charger
  6. Solar Charger
  7. Constant-Power 12v Accessory Fuse Block
  8. Ignition-Switched 12v Accessory Fuse Block
  9. 120v Inverter

Before getting into details on the components, I also want to touch on the following important aspects of the overall system:

  • Brand Considerations
  • Wire and Connector/Lug Considerations
  • Fuses and Breakers

The diagram above, installed.

Brand Considerations

I want to say a few things about the importance of component brands.

First, it is important to purchase quality components when building a house electrical system. Spending a little more money to ensure that a component works both well and correctly, has been subjected to the appropriate certifications, and has a reputation for reliability is worth it. Having to replace a component that has failed, or having the failure cause a vehicle fire are not worth saving a few dollars here and there.

Top tier brands: RedArc, Victron, Blue Sea Systems, Bussmann
Mid-tier brands: Renogy
Lower-tier brands: Ever-changing list of names that are found on amazon.

Second, if there are quality products from a single brand, they likely work well together and provide a more cohesive ecosystem. For example, components from Victron - a reputable brand that I chose to use - all communicate via Bluetooth to a single VictronConnect app, so the entire system can be monitored in one place, and critical information for every component is available at a glance, rather than having to open - and dig through - several different apps.

Everything in one place; the Victron Connect app ecosystem.

Wire and Connector/Lug Considerations

The wire and connectors used in an electrical system are often an afterthought, but are critical to proper functioning of the system. I (almost) always like to overbuild - use larger wire than necessary - from this perspective, since running wire through the confines of a vehicle is difficult. I only want to do it once, even if I want to increase the size of the system later.

Obviously, larger wire can carry higher amperages over longer distances. The trade-off is ease of installation and weight. Always use a reputable wire sizing guide to determine minimum / recommended / overkill wire sizes.

Be sure to only use pure copper wire (aka oxygen free copper). I learned this the hard way, and now recommend the following reputable wire options. I've limited myself to the following sizes, just so I don't have so many different wire sizes hanging around:

I rarely use the following sizes, opting instead for an adjacent size in the list above, but I'll provide links to reputable options for completeness:

For lugs and connectors, be sure to go with pure copper or tinned copper, sized appropriately for the wire. I like to crimp+heatshrink anything 8 gauge or larger, and crimp+solder+heatshrink anything 10 gauge or smaller.

The most important thing when picking wire and terminals is that they are pure copper. Optionally tinned for corrosion resistance.

And while we're talking about wire and connectors, there are a few tools and supplies for cutting, crimping, and protecting the connectors from their surroundings.

Useful tools.

Fuses and Breakers

Every positive wire in the system should be protected by a fuse or circuit breaker that will blow (fuse) or trip (breaker) before the wire can get so hot that it melts and/or catches on fire. The fuse/breaker should be mounted as close to the power source as possible so that if it should blow, any wire between the power source and fuse/breaker is minimized (since it will remain energized).

If the fuse/breaker is far from the power source (battery), and a short circuit occurs between the power source and the fuse/breaker, the fuse/breaker will not trip, and you are at serious risk of fire.

I like to use several classes of fuses and circuit breakers:

  • Blue Sea Terminal Fuse - (holder) (fuses) - connected to the battery terminal to cut all power if a critical short circuit occurs in the system.
  • MEGA Fuse - (60A) (100A) (125A) (200A) (250A) (300A) - used on the primary positive bus bar to provide protection of circuits in the 60-300A range. Be sure to only purchase official Victron/Littelfuse branded fuses; other brands do not blow reliably, subjecting the system to both false alarms and risk of fire.
  • Blade-type fuses - (assortment) - Used in fuse blocks for 12v accessories.
  • Bussman Circuit Breakers - (30A) (50A) (60A) (80A) (100A) - used in places where the ability to quickly switch the breaker on/off in order to isolate a part of the system (e.g. the DC-DC charger or the entire 12v accessory fuse block) is beneficial.

And with that, it's into the "fun" stuff.

Battery and BMS

Product: Wattcycle 280Ah Smart Mini LiFePo4 Battery

This is a no-name brand, meaning it is relatively inexpensive, but received good reviews on build quality, customer service, and performance from Will Prowse who knows this stuff like the back of his hand. I also liked that it was half the size (7.64"D x 15.12"W x 10.04"H) of other similar-capacity LFP batteries, weighed the same amount (57 lbs) as my Northstar AGM, and that it included a Bluetooth-accessible BMS.

"More power than I'll ever need."

The app doesn't do much, but it does work.

Battery technology is always improving - and quickly - so look around for the best battery that fits your needs. Wattcycle has already replaced the 280Ah battery I purchased with the 314Ah Smart Mini LiFePo4 Battery, and it's cheaper than what I paid. More battery for less cost!

If you don't need quite as much capacity, the 100Ah version of the battery is a great choice. The fact that it is "almost free" and "tiny" (5.4"D x 9"W x 8.2"H) make it incredible. Seriously, I probably should have gotten this battery.

Master On-Off Switch

Product: Blue Sea Systems 6006 m-Series Battery Switch (ON-OFF)
How is it connected: Connected to the positive bus bar of the Lynx Distributor and the via 2 feet of 1/0 cable to the Terminal Fuse on the positive terminal of the LFP battery.

Although the Wattcycle BMS allowed me to connect to it with Bluetooth in order to turn it off and remove power from the rest of the house electrical system, I still liked the idea of having a physical switch in place in order to de-energize and physically isolate the battery from everything else when I'm messing with the system. I think of it like a main breaker in a household panel.

I needed a switch that could handle high currents - at least the 210A that the BMS would allow - and that would be reliable over time. The Blue Sea Systems 6006 Battery On-Off Switch fit the bill perfectly in that it was from a reputable company and was rated for a continuous 300A.

Master On-Off.

I also discovered that this switch could be bolted directly to the positive bus bar of the main distributor, eliminating the need for a small cable running between the two components, and allowing for a very compact installation.

Battery Shunt

Product: Victron SmartShunt IP65 500A
How is it connected: Connected to the negative bus bar of the Lynx Distributor and the via 2 feet of 1/0 cable to the negative terminal of the LFP battery.

A shunt allows a high-level view of system status.

As with the Master On-Off Switch, the Victron SmartShunt isn't entirely necessary since the Wattcycle BMS technically allows me to check the system's state of charge (SOC) as well as the current rate at which the battery was being charged/discharged. However, the SmartShunt enables three additional features which I find valuable:

  1. It exposes the system SOC and current rates in the Victron app, alongside data from all other Victron devices installed in the system. Having everything in one central hub - rather than a separate app for every device - is a huge convenience.
  2. In addition to monitoring the SOC and current rates for the hosue electrical system, it also monitors the voltage of the starter battery, exposing it in the Victron hub.
  3. It monitors the entire battery bank. With only one battery, this is duplicative as mentioned above, but if another battery is ever added to the system, the SOC and other parameters can be monitored in a single place instead of checking each battery separately.

Just like the Master On-Off Switch, the SmartShunt can be directly connected to the main distributor, eliminating the need for a small cable running between the two components, and allowing for a very compact installation.

Main Distributor / Fused Bus Bar

Product: Victron 1000A Lynx Distributor
How is it connected: Positive bus bar connected to Master On-Off Switch. Negative Bus bar connected to Victron SmartShunt and vehicle ground via 15-foot 1/0 cable.

There are a couple of routes to go for a main distributor / fused bus bar. The first is to build positive and negative bus bars yourself from individual components. The second is to purchase a Victron Lynx Distributor, which combines everything into a single device.

Seems large. Is large. Turns out to be very space-efficient.

The Lynx Distributor may initially seem like an expensive luxury, but it turns out to have a couple big benefits over a component-built system:

  1. It is extremely compact. While it's still the largest component of my build, it contains two 1000A bus bars, four MEGA fuses along with LEDs that show the condition of each fuse, a system ground post, and a cable-routing system to keep everything tidy. Likely, it is half the size of a home-brew fused bus bar.
  2. It is reasonably priced. When compared to the cost of bus bars, fuse holders, nuts, bolts, and the cables necessary to build an equivalent power distribution system, the Lynx Distributor is actually cheaper than the individual components.

When assembled with the Master On-Off Switch and Battery Shunt, the result is a lot of functionality with zero cables.

DC-DC Charger

Product: Victron Orion XS Smart DC-DC Battery Charger 12 | 12 50A
How is it connected: Input from the positive battery terminal in the engine bay via 15-foot 1/0 cable, with a 60A circuit breaker to allow isolation. Output to the Lynx Distributor with 1 foot of 4-gauge cable.

The last time I'd looked at DC-DC chargers was several years ago when I ended up deciding on a Victron Solar Charge Controller (see below). At the time, RedArc was the leading name in the space, and all things being equal, I'd probably have gone with RedArc even today if I hadn't experienced the Victron ecosystem since using their solar charger.

Appreciating what I'd seen from Victron, I set about researching their DC-DC chargers. For years, they've offered several options - all with Bluetooth and ranging in charging speed from 5A to 30A - all under the Orion Tr Smart line of chargers. Recently (in January 2025), Victron released the first of a new line of Orion XS Smart DC-DC chargers which completely redefined the bar in terms of:

  • Size - smaller than half the size of an Orion Tr
  • Efficiency - up to 98% vs. the more standard 80%
  • Cooler operating temperature - 110°F vs. 155°F
  • Charging ability - 50A vs. 30A

These improvements - and the fact that it integrates with the same Victron app - made my decision on a DC-DC charger easy.

One of the best chargers currently on the market.

The older Orion Tr (left) next to the new Orion XS (right).

Solar Charger

Product: Victron SmartSolar MPPT 100/20 Solar Charge Controller
How is it connected: Connected to the Lynx Distributor with 1 foot of 12-gauge wire, with a 30A circuit breaker on the positive wire to allow isolation.

I picked up the Victron SmartSolar MPPT Solar Chage Controller several years ago when I added Infinite Free Power to the Tacoma. While "infinite" has been a bit of a stretch - in total it has generated a total of only 859Ah, enough to charge my new 280Ah LFP battery a whopping 3 times - it introduced me to the Victron ecosystem, and enabled me to see firsthand how reliable and polished their products behave.

At the time, I was trying to decide between a RedArc, a Renogy, and the Victron, and ended up choosing the Victron because it sat between Renogy (at the lower end) and RedArc (at the higher end). Plus, in my research, I discovered that there were two types of solar charge controllers:

  1. Pulse Width Modulation (PWM) - in essence a switch that connects a solar array to a battery. The controller sends out a series of short charging pulses to the battery - a very rapid “on-off” switch. Between pulses, the controller constantly checks the state of the battery to determine how fast, and how long the pulses will be. This is a proven technology, but one that requires the panel to be matched to the battery, and does not optimize the current/voltage for the most efficient charging.
  2. Maximum Power Point Tracking (MPPT) -  more sophisticated than PWM, the controller will run the solar panel at a voltage/current combination that generates the optimal power, and then convert that to the optimal power/current combination to charge a battery. This optimization can result in 10-40% more efficient charging, and also allows the controller to change the power sent to the battery at different times - in essence, allowing for fast charging when necessary before switching to trickle charging once the batteries are near capacity.

Clearly, I wanted an MPPT controller. The Redarc fit that bill nicely, except for the price, so I set out to find other brands. Ultimately, two brands kept popping up - Renogy and Victron. Both seemed to have their followers, but reading between the lines on reviews, it became clear that Renogy was a leader due to (low) cost, and Victron was a leader due to (high) quality. Not only that, but the Victron SmartSolar line allowed for configuration and monitoring of the controller via Bluetooth from a smartphone - a very nice touch. And, since the Victron focused on being a solar controller only, its price was significantly less than the Redarc.

So, while I stumbled into the Victron SmartSolar MPPT charge controller a few years ago, doing so made my decision selecting components now, much easier!

My introduction to an amazing product line.

Constant-Power 12v Accessory Fuse Block

Product: Blue Sea 12-Circuit Fuse Block
How is it connected: Connected to the Lynx Distributor with 1 foot of 6-gauge cable, with an 80A circuit breaker on the positive cable to allow isolation.

There's nothing all that sexy about a fuse block. The idea is to go with a trusted brand so that the positive and negative bus bars in the block can handle the loads placed on them, and in that regard Blue Sea Systems is a reputable supplier of high-quality fuse blocks.

Tried and true.

I'm reusing the circuit block from my first house electrical system, which supports 100A across 12 circuits. While I might be able to overload it by turning on all eight accessory circuits I currently have wired in, it's rare that I use all eight at the same time, and unheard of to be using them all at full power.

I've also installed an 80A Bussman Circuit breaker so I can easily isolate the Accessory Fuse Block from the rest of the system when I am performing maintenance on the circuits connected to it.

Currently, the following accessories run off of the constant-power fuse block:

Ignition-Switched 12v Accessory Fuse Block

Product: Blue Sea 6-Circuit Fuse Box powered via a quality 4-pin 12v 40A relay (ARB 180905SP, Viair 93944, Bosch, etc.)
How is it connected: 40A relay input is connected to the constant power accessory fuse block with 1 foot of 10-gauge wire; switched via ignition power. 6-circuit fuse block is connected to relay output with 6-inches of 10-gauge wire.

I chose this Blue Sea Fuse Block for the same reasons as the constant-power version: a reputation of reliability.

This fuse block powers the following accessories, ensuring that they are only drawing power from the house battery when the key is in the ACC or ON positions; alleviating the risk of inadvertently draining the battery when the engine is not running.

By installing a relay, anything powered by this fuse block will only work when the key is un the ACC/ON positions.

120v Inverter

Product: Cheap, no-name, 175W Inverter
How is it connected: Connected to the constant power accessory fuse block with 1 foot of 12-gauge wire.

I decided on a different inverter setup that will be common for most people. Most house electrical systems will wire a powerful (1000-3000W) pure sine wave inverter directly to the Lynx Distributor, with a dedicated circuit breaker on the positive line. However, I've found that I don't use much A/C power when I'm on trips, so a low-power, fanless inverter is the perfect solution. 175W is plenty to charge batteries for various electronics (camera, laptop, toothbrush, handheld radios, etc.) and being fanless means that it is also noiseless if we happen to be sitting in the cab at 4:00pm on a winter afternoon, waiting to go to bed.

Putting it All Together

With all the components selected, it was time to get started putting it all together. I'd base my new LFP House Electrical system on the AGM system I'd built several years earlier, taking into account a few optimizations and improvements that I'd realized in that time.

This was going to be a fun project.

 

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