For nearly ten years, I have been giving talks and writing articles about the safe and proper way to replace obsolete RV lead-acid house batteries with the vastly superior lithium-based house batteries. I wrote about this subject five years ago in this article The Advantage of Lithium Batteries for RVs.

In the intervening years, the industry has undergone significant improvements.  The quality of the electronic devices that control the use and recharging of these Lithium (Li) based batteries has improved dramatically.  At the same time, the prices have decreased equally dramatically.  The same is true for the Li batteries themselves.

The best of these products are now produced by Chinese manufacturers that have implemented automation and robotic assembly and testing facilities that rival those of any manufacturer anywhere in the world.  Approximately 98% of all the LiFeP04 battery cells in the world are now made in China, along with the vast majority of assembled Li batteries, no matter how “western” sounding the brand name or what the “engineered in” claims are on the outside of the battery.  The same is true for electronic components, such as inverters, voltage controllers/modifiers, engine alternator charge controllers, and solar charge controllers, among others.

At the same time, major manufacturers and some smaller manufacturers have brought to market home backup power stations that combine 48VDC architecture electronics and, in some cases, 48VDC Li batteries beautifully integrated into one module.  These are sometimes known by the goofy marketing name “solar generators”.  I just call them power stations. These units do not generate "solar", they generate "power".

In the last year or so, the four largest worldwide manufacturers of these devices - Bluetti, EcoFlow, Anker, and Jackery (all four are Chinese companies with Western-sounding names for the North American and European markets) - have been increasing the capacity and functionality of their offerings for the backup power supply market.  Many smaller, lesser-known manufacturers have also entered the market.

To me, these looked like an excellent alternative to the DIY approach of replacing house lead-acid batteries and electronics with Li-based batteries and electronics for the RV and DIY conversion markets. For years, they all fell short in one way or another.  

Well!  Bluetti has just introduced a newly designed unit called the Apex 300 (not to be confused with the existing Bluetti 300 system available before), which includes everything necessary to be a genuine plug-and-play alternative that is better, faster, less expensive, and safer than any DIY conversion approach.  This unit is not yet available for retail distribution (as of spring 2025, when this article is being written), but it is available for pre-order on their website and their Indiegogo crowdfunding platform.  Everything about this unit, including the price, is industry-leading.

They sent me an as-yet-unreleased Apex 300 unit, an expansion battery, an alternator charger module with the wiring harness, and an accessory DC distribution box for a presentation I was preparing to deliver at the FMCA (now FRVA) summer convention in Albany, Oregon, in June 2025. Based on the specs I had seen, I had high hopes for this unit as a new way to recommend to RVers and DIY converters to replace their old lead-acid house electrical system with a state-of-the-art Li-based system, quickly and safely.  When the units arrived, I was impressed by the build quality, industrial design, packaging, modularity, expandability, and features that now make this a no-brainer for anyone building their own RV conversion.  

For starters, the Apex 300 features both a 30-amp and a 50-amp RV receptacle, so all you need to do is plug in your existing 30- or 50-amp shore power cord, and you're done!  Your RV or DIY conversion will behave just exactly as it does when plugged into an RV power post.  So, it makes little difference whether you are at a location with power available or you are boondocking; your RV will work the same.  

The Apex 300 comes standard with two inverter circuits and a slide switch that allows you to select between single-phase 120VAC inverter output or split-phase 240VAC inverter output.  Each inverter outputs approximately 2,000 watts of power.  When the switch is in the single-phase 120VAC position, the two inverters are combined to deliver just under 4,000 watts of pure sine wave AC power—a full 30 amps to the 120VAC 30-amp RV receptacle and approximately 16 amps (just under 2,000 watts) to each leg of the 240VAC 50-amp RV receptacle.  

The Apex 300 units are designed so up to three of them can be connected in parallel via an optional plug and play accessory AC power combiner box to bring the inverter output up to just under 12,000 watts, or nearly 100 amps of 120VAC power (50 amps of split phase power on each leg of a 240VAC circuit).  That is the same as if you had plugged into a 50-amp shore power pole!

Battery capacity can be expanded in the same plug-and-play way.  Each Apex 300 unit comes with just under 3000-watt hours of 52VDC Li battery capacity built in (about 250-amp hours of nominal 12VDC).  The add-on battery modules also have the same capacity, and you can plug in up to six additional battery modules to each of the up to three Apex 300 units for a whopping 56KWH of output - enough to run a whole house for several days.  

The way Bluetti designed these units, the included interconnect cable also contains the communication lines, so that integration as you expand is automatic.  There are no settings to adjust, no dip switches to toggle, and no phone app settings to modify. Simply plug in and play; you can start drawing power to run your RV's lights and appliances.

This allows you to start with the inverter output and battery capacity you need, and have room and budget for now. You can then expand it later to fit your needs as they change over time.  For example, if you have been traveling alone and then decide to partner up with someone, thereby requiring more power throughout the day, you can then add another expansion battery to meet your new needs.

The Bluetti expansion batteries are aggressively priced at around $0.30 per watt-hour, which is about the same price as high-quality bare Li batteries these days, so there is little in the way of savings from trying to create capacity expansion on your own.  And, all those automatic integration features and compact interconnect cables are hard to pass up.  

I was surprised to find that even the built-in cable locking feature played a safety role.  The add-on battery will not automatically charge from the central unit unless the interconnect cables' locks are on.  So, you can’t have a cable coming loose with a lot of charge current flowing through it, even in high-vibration environments like your RV or DIY conversion experiences.  Nice!

While there is limited solar panel space on the roof of a bus, van, truck, or other RV, Bluetti also offers an optional accessory box that can accommodate even massive solar arrays wired together in hundreds of volt strings to minimize interconnect wire sizes and losses from partial shading.  Again, nice!

I appreciate the way they designed everything around optional expansion modules and controls, allowing users to pay only for the features they actually use.  Speaking of that, the introductory prices are really aggressive.  The Apex 300 unit by itself is $1,200 with their “super early bird” pricing and $1,400 with their “early bird” pricing.  My guess is that the “early bird” price point will be about the standard sale price going forward.  

All four of these big suppliers - Bluetti, EcoFlow, Anker, and Jackery - tend to have their products frequently on sale, so the actual price you see can fluctuate over time quite a bit.  As I write this, the $1,200 price for the Apex 300 is more than price competitive, even with the small, lesser-known manufacturers, especially when you factor in the five-year warranty from a large, worldwide company that will almost certainly be around to honor that warranty going forward.  

If your objective is to be able to overnight for a day or two at a Harvest Host site, or a commercial establishment that allows overnighting, or at a friend or relative’s house without plugging in, I recommend starting with the following configurations depending on the size of your RV and whether it has an absorption or a compressor-based refrigerator.  

For vans, trucks, short buses, mid-size and smaller RVs with absorption refrigerators, start with one main unit and one expansion battery as shown below.  That will give you just under 4,000 watts of inverter power and just under 6,000 watt-hours of battery capacity.  For larger buses and RVs with residential-style compressor refrigerators, I recommend starting with one Apex 300 main unit and two or three expansion batteries.  That will provide you with just under 4,000 watts of inverter power and 9,000 to 12,000 watt-hours of battery capacity.  

The one downside to this plug-and-play approach is that if any of the internal components fail, this unit is not user-repairable. You would have to send it to Bluetti or some authorized service center. Therefore, you could use two Apex 300 main units and just one or two expansion batteries to provide just under 8,000 watts of inverter power, along with the same 9,000 to 12,000 watt-hours of battery capacity.  

Having two Apex 300 main units provides you with running redundancy in case something happens to one of them while you are traveling.  You would still be able to function, just at a bit lower capacity, until you can get that one failed unit fixed or replaced.  Also, if you decided to carry one of your units out to work on your cabin in the woods, you would still have one unit in your RV to power your appliances. 

The advanced LiFeP04 cells in this Apex 300 and the expansion batteries are rated for between 4,000 and 6,000 charge/discharge cycles before they reach 80% of capacity, which is the factory-designated “end of life” point.  That is 15 to 20 years of fully discharging them every day and fully recharging them every day, which no RV owner would ever do.  Even after reaching that point, they still work just fine, but they only have 80% of the capacity they had when new.  

Another way of looking at this capacity is that if each expansion battery supplies just under 3,000 watt-hours per charge and can be recharged up to 6,000 times, that means each expansion battery can supply you with up to 18 million watt-hours of capacity over its useful life. That’s a LOT of battery power!

So, once you install these into your DIY conversion or RV, you will likely never even think about electric power again unless something fails or if you sell your rig.  However, if you sell your rig, you may decide to take this setup with you to use in your new rig.

The optional plug-and-play DC distribution box is a must for DIY converters.  Not only does it provide several standard DC power receptacles, but it also features a 50-amp 12V DC Anderson plug port, allowing you to provide power directly to your 12V DC power distribution panel by simply running two wires from this box to it.  It couldn’t be any simpler.  

Also important in my mind is the optional Bluetti automatic alternator charging module.  Just use the included high-quality cable set to connect the input side to your existing chassis 12VDC lead acid starter battery, run the output cables to one of two DC input ports on the side of the Apex 300 and it, and any expansion batteries, will be recharged at a 580 watt per hour rate while you drive.  You don’t need to do anything.  It is fully automatic and fully integrated with the rest of the system.  It won’t overheat or damage your alternator.

If you have an alternator rated for 150 amps or more, you can install two Bluetti alternator chargers in parallel to recharge your batteries while driving, at a rate of up to 1,160 watts per hour. If you buy a Bluetti optional adapter, you can even recharge the Apex 300 from standard electric vehicle charging stations or at a pedestal at an RV park.  Again, nice!

Physical size is another important consideration.  This Apex 300 unit is about 21” long, 13” high, and 12” front to back, so it will easily fit into the bays of most DIY conversions and many conventional RVs, whether trailers, vans, fifth wheels, trucks, or motorhomes.  It weighs approximately 80 lbs., so it's not easy to move around. However, with the built-in handles, it can be quickly and easily installed or removed from your vehicle.  

The add-on expansion batteries are the same length and width front to back as the main unit, about 8” tall, and weigh around 60 lbs. each.   They are designed to stack on top of each other and nest securely with the Apex 300.  In addition to the sleek, tight-fitting stacked unit with interconnecting cables, Bluetti also offers longer cables to connect them side by side or front to back, if stacking height is limited in your specific implementation.

Implementation is simple, as most of the electronics in your house battery system are bypassed while your RV is running on shore or generator power.  You can either run a 30-amp or 50-amp shore power RV extension cord from your existing shore power cable over to the Bluetti Apex 300, or you can install a simple A/B switch to allow you to select shore or generator power, just like you do now, or draw power directly from the Bluetti unit.  

Just remove the wires from the output side of your auto transfer switch and attach them to the output side of the A/B switch.  Then run wires from the output side of your auto transfer switch to the input-A side of the A/B switch, and wires from the input-B side of the A/B switch over to the 30-amp or 50-amp output on the Bluetti Apex 300.  When the switch is in the A position, your RV will function just as it does today, drawing power from either shore or generator sources.  When the switch is in the B position, power will be supplied by the Bluetti unit.  Slick!  

If you want to recharge the Bluetti unit from a generator, you may need to have an electrician install an RV-style receptacle on your generator, since most built-in RV generators do not have one.  You can then use one of the Bluetti optional charge cables (20, 30, or 50 amps) to connect the generator output plug to the Bluetti AC charge port.  The Bluetti Apex 300 unit can charge from any source and discharge power to your RV simultaneously.

Many of you will want to know if you can run multiple RV air conditioners on larger RVs or bus conversions for boondocking in the hot, dry, desert southwest or the hot, humid southeast off one of these Bluetti Apex 300 units.  The answer is “Yes” in the sense that three Apex 300 main units connected in parallel will provide inverter output of just under 12,000 watts (about the same 100 amps as if you were plugged into 50-amp shore power), but “No” in the sense of the amount of battery power required to do so for very long, not making it very practical.

That being said, current generation RV air conditioners are very inefficient, as they have a single large electric motor powering the compressor that is either on (at very high amp draws) or off.  The inside and outside air blowers are also single-speed on/off units.  They will consume between 500 and 1,000 watts per hour of operation EACH for every hour they are running.  

Outside temperature and humidity, the amount of insulation in your RV, the number and size of your windows, and the interior temperature setting are just some of the variables that will affect the actual wattage draw over time. However, 500 watts per hour per unit is a reasonable low-end estimate.  That means you would need 12,000 watts of battery capacity to run each one for 24 hours, if you needed to run your A/C units continuously day and night, which is not typical.  

That would be a Bluetti Apex 300 main unit and at least three expansion batteries just for ONE air conditioner running 24 hours.  And, once you depleted those batteries, you would have to run your generator to recharge them anyway, so why not just run the generator to run these inefficient RV air conditioners in the first place? The only time you may want to run your A/C unit off the Bluetti unit is if you only need to run it for a short time to lower the temperature slightly before going to bed.

New and far more efficient RV air conditioners and heat pumps are on the way, which will utilize variable-speed compressors and air handler motors.  Maybe when those are commonplace, running air conditioners off batteries will make more sense.  But not now, in my opinion.  Big solar arrays would help the situation, but not likely enough to make them practical for everyday use on a mobile RV.

As a final note, currently, US customers are eligible for a 30% tax credit on purchases of home power backup equipment through the US government.  So, if you implement these Bluetti units in a way that allows them to be easily removed from your bus or RV and used for home power backup, they may be eligible for the 30% tax credit.  Do your own research to ensure how you implement it to qualify in your situation, as I am not a tax expert and do not provide legal advice.  But, if you are eligible, you can take 30% off the already aggressively priced power system.

While this may sound like a sales pitch for the Bluetti Apex 300 system, that is not my intent.  I have been looking for a long time for a perfect all-in-one, plug-and-play electric power system for DIY conversions and conventional RVs.  One that meets all my needs, and maybe yours, has finally arrived!  Even better, in a highly competitive field like this, I don’t think it will be long before the other players (big and small) will also bring out their version of a power system idealized for bus conversion and RV adaptation. Enjoy!