People on forums and Facebook groups ask about battery upgrades for the L300 all the time. The factory battery is quite small, especially if the van has extra accessories like additional lights, audio equipment or a winch.

After a few different setups, I finally ended up with a solution that works really well for me.
I managed to fit an 80Ah battery in the factory location and still make room for a relay module and an additional fuse/distribution box mounted directly on the battery terminal.

The main goals were simple:

• fit a bigger battery in the stock location,
• keep the original fusible links,
• add extra fused power outputs,
• make a proper starter connection,
• and keep the whole thing simple to build.

Final result:

• 80Ah battery fits in the factory place,
• original fusible links stay untouched,
• 3 additional fused power outputs,
• starter connected directly to the battery terminal,
• if you keep the stock battery mounting style, the whole job is actually pretty quick and easy.

If you want to copy this setup, the full parts list is included near the end of the article.

Battery tray modification

There are many ways to mount a battery in an L300.
You can keep the factory-style mounting with two threaded rods over the top of the battery. Or use a strap or other custom solution.

I decided to modify the tray and mount the battery by its base, like in modern cars. There were three reasons for that:

• more free space above the battery for the fuse box,
• ability to move the battery as far back as possible to free space for the relay module,
• and I already planned to make a mounting plate for the relays anyway.

To hold the battery at the rear side, I welded a small piece onto the tray that locks the battery foot in place.

The front mount was made from 3mm steel plate.
At the same time it also works as the mounting plate for the relay module, so one part does two jobs.

If you are interested in the relay module used in this setup, check out the separate article where I describe it in more detail.

I installed four M6 rivet nuts into the battery tray to bolt everything down.
Once assembled, the battery sits very solid and stable.

Electrical connections

This is not completely plug & play.
To make the MTA box fit properly, three small modifications are needed. Luckily all of them are simple.

1. Cutting the MTA box housing

To keep the factory fusible links, a small section of the MTA box housing needs to be trimmed.

Without this cut there is simply no proper space to connect them.

After trimming, you get perfect access to the M8 stud, making the fusible link installation clean and easy.

2. Rotating the terminal clamp

The MTA box comes with the battery clamp mounted using three M6 bolts.

In the factory position, space is very tight and access to the terminal bolt on the battery post is not great.

The solution is simple — rotate the clamp 180°.

This gives more room and makes installation easier while still keeping good access to the mounting bolt.

The whole process takes only a few minutes:

• remove three bolts,
• rotate the clamp,
• bolt it back together.
  
  

  

3. Extending the starter cable

Because the battery is moved further back compared to the factory position, the original starter cable becomes too short.

You can make a completely new cable, but mine was still in very good condition, so I decided to extend it.

For this I used:

• a hydraulic crimp sleeve,
• an M6 cable lug for 25mm² cable,
• quality adhesive heat shrink tubing.

To join two 25mm² cables together, I used a 50mm² crimp sleeve.
After hydraulic crimping, the connection becomes very solid and reliable.

Then everything was sealed with adhesive heat shrink tubing. 

Current connections

Through the MTA box:

• AUX1 — relay module, 60A fuse,
• AUX2 — currently empty,
• AUX3 — car audio amplifier.

The amplifier will probably move to AUX2 later to free up space for a bigger cable for a future winch power supply.

I also connected a battery maintainer charger for longer parking periods.

Parts used

• 80D26L battery — Yuasa Epsilon 80Ah 650A (left positive)
• MTA CDB 0300839 fuse/distribution box
• Triple ground terminal
• Some 25mm² cable
• Cable lugs, crimp sleeves, heat shrink tubing and all the usual electrical supplies

Summary

This setup turned out to be a very practical upgrade for the L300.
The bigger battery gives more reserve power, the additional fused outputs make future accessories much easier to connect, and keeping the factory fusible links means the whole system still looks clean and close to OEM.

The battery tray modification takes some extra work, but it makes the whole layout much cleaner and creates enough space for both the relay module and the MTA distribution box.

For anyone planning additional electrical accessories in the future — lights, compressor, audio system, inverter or winch — this kind of setup makes the electrical system much easier to organize from the start.

And most importantly, everything still fits in the original battery location without turning the engine bay into a custom fabrication project.

Factory headlights in the L300

Depending on the model year, the Mitsubishi L300 came with two different front headlight designs. Early versions used simple square headlights with regular bulbs, while later models got a more modern combined headlight with a projector lens for low beam and a separate reflector for high beam.

What’s interesting is that even after more than 30 years, the factory headlights are still surprisingly well made. Real glass lenses, solid metal reflectors and decent projector housings — back then things were built properly. Even today the original lights still perform reasonably well. But lighting technology has moved forward massively, and modern LED projectors are simply on another level.

If you want to copy this setup, the full parts list is included near the end of the article.

Main goals of the conversion

Like with most modifications on this build, the main goal was to keep everything fully reversible and avoid destroying original parts.

The priorities were simple:

• fully reversible modification,
• keep all factory functions,
• retain both manual and electric headlight adjustment,
• keep the original factory look from the outside,
• projector stays in exactly the same position as the factory lens.

From the outside, it’s honestly very difficult to notice that anything has been modified. The whole thing still looks almost factory unless you know exactly what to look for.

Opening the headlights

The original headlights had to be completely disassembled first. Since the lenses are real glass and the housings are properly sealed, opening them without damage takes some patience.

Once everything was apart, I could finally take measurements and compare the original projector assembly with the new bi-LED unit. Seeing them side by side really shows how much lighting technology has changed over the years. The factory projector is huge and heavy, while the modern bi-LED is much more compact but produces dramatically more usable light.

Designing the adapter

After measuring all the important dimensions, I designed a custom adapter that mounts directly in place of the factory projector and reflector assembly. This allowed me to install the bi-LED projector without cutting or permanently modifying the headlight housing.

The adapter itself was 3D printed from PACF and then annealed in the oven after printing to improve its temperature resistance and long-term stability. At this point my wife is already used to seeing random car parts and 3D prints inside the kitchen oven, so nobody even questions it anymore.

Technically the adapter could also be CNC machined from aluminum, but honestly there’s just no real reason for it. Modern engineering-grade 3D printing materials are more than strong enough for this type of application, both mechanically and thermally.

The finished part feels properly solid, and because everything bolts into factory mounting points, the whole setup can still be returned back to completely stock at any time.

Test fitting and assembly

Before sealing the headlights back together, I spent quite a bit of time test fitting everything and making sure the projector sat perfectly centered behind the original lens opening.

This part was important because I wanted the final result to look as factory as possible. The projector had to sit in exactly the same position as the original one so the outside appearance stayed clean and OEM-like.

Once assembled, the headlights honestly look like something Mitsubishi themselves could have made if the L300 stayed in production a bit longer.

Beam pattern and legality

It’s worth mentioning that modifications like this are technically not road legal in many countries. Even so, I made sure the beam pattern and cutoff line were adjusted properly because I absolutely hate badly aimed headlights myself.

The cutoff is sharp, clean and sits slightly lower than before the conversion, so the lights don’t blind oncoming traffic.

Looking at the beam pattern against a wall, you can immediately see the difference compared to the original setup. The light distribution is much wider, brighter and more controlled instead of just throwing weak light everywhere.

Side-by-side comparison

At one point I actually tested the difference side by side. I left one headlight completely stock and converted only the other side to bi-LED.

The comparison was honestly ridiculous. Next to the bi-LED projector, the original headlight looked more like a parking light than a proper low beam. The photos still don’t fully capture it, but in real life the difference is almost hard to believe.

The amount of light on the road is on a completely different level. The beam spread is smooth and even, visibility at night improved massively, and at the same time the sharp cutoff keeps the light exactly where it should be.

Parts used

• OEM headlights MB831282 and MB831281
• 3.0" Bi-LED projectors
• custom designed adapter plate available in our shop

Driving at night

The biggest difference is noticeable on dark roads outside the city. You spot obstacles, animals or pedestrians much earlier, and night driving becomes way less tiring.

On snowy roads especially, the wider and more even beam pattern makes a huge difference because you can actually see the edges of the road properly instead of driving into a dark tunnel.

Personally, I think upgrades like this genuinely improve safety in older vehicles, especially cars designed back when lighting technology was nowhere near today’s standards.

It’s just a shame that, at least where I live, regulations still don’t really allow modifications like this — even when they’re done properly and responsibly.

Every modern car comes with proper child seat mounting points — so obviously the Mitsubishi L300 doesn’t.

After finishing the restoration, I wanted to start taking my son on trips. That’s when I realized the so-called “universal” Isofix adapters on the market are pretty flimsy and don’t allow for a truly safe installation of a child seat in this vehicle.

So I designed and built my own ISOFIX adapter dedicated specifically to the L300.

Main features:

• Safe and solid mounting of an ISOFIX-compatible child seat

• Use of the factory mounting points (no drilling or sketchy mods wherever possible)

• Ability to install it on either the left or right seat of the second-row bench

The bracket was designed so that it can be installed on the right-hand seat of the second row without any drilling. For the left-hand side, only a single additional hole needs to be made.

It mounts directly to the factory seat belt mounting points on the seat frame, ensuring a firm and solid attachment.

The design was done in Fusion 360 using the sheet metal workspace. I prepared a proper workshop drawing with a flat pattern, so the part can be accurately manufactured on a CNC press brake.

Disclaimer: This adapter has not undergone any official testing, certification, homologation, or crash validation. It has no approvals or safety ratings of any kind. I’m using it entirely at my own risk and responsibility.