CTEK D250SE Review (DC DC Charger/B2B/Battery To Battery)

Our deep dive into off grid power today is DC to DC chargers (aka B2B or battery to battery chargers). Specifically we’re doing a CTEK D250SE Review.

CTEK are certainly the big dog of the battery charging world. Their products have a good reputation for their build quality, technology and long lifespan.

So what we’ll be uncovering is whether the D250SE lives up to that reputation or whether it’s a letdown.

We’ll let you know what we liked, what we didn’t like, who needs this and if you do, how will it meet your needs.

Let’s get cracking, then!

CTEK D250SE Review (DC DC Charger)

Introducing our CTEK D250SE Review

Let’s talk about the D250SE. So what is it? It’s CTEK’s DC DC charger.

It’s not just a charger, though. It has a built in MPPT solar charge controller as well.

CTEK DC DC Charger & MPPT Solar Charge Controller)

You can check it out here.

A DC DC charger (also called battery to battery charger or B2B charger) allows you to provide a safe, stable and powerful charge from your vehicle alternator (or from solar) to your auxiliary/leisure battery. Here’s more info on what a DC to DC charger is.)

The D250SE is CTEK’s DC DC charger.

It also includes an MPPT solar charge controller. That means it maximises and makes best use of all the solar energy collected from your solar panels to best charge your battery.

Hooking unregulated solar panels directly to a battery is a recipe for a disaster, since batteries like stable charge that isn’t constantly changing from very to very low. That can damage your battery. The MPPT solar charge controller provides the solution.

What We Liked About The CTEK D250SE

You can charge from BOTH alternator and solar panels, at the same time.

This is called “Dual Input”.

We said the input charge can come from either your starter battery or from solar panels, but actually you don’t need to choose. You can have both.

The D250SE will take the charge from both inputs and use the power to charge your leisure battery.

It does so cleverly – it’ll prioritise the solar input, which maximises efficiency.

It’s built to last you a really long time

This is one of the key facets you get with CTEK products: long lifespan. They’re well-made, CTEK’s attention to detail is renowned, their manufacturing processes are solid, and all the internal electrical components are of the highest quality. The casing, cables, connectors too.

They’re genuinely built to last, and everything is made to withstand all weather conditions and temperatures. It has IP65 level protection. In other words, they’re durable and hard-wearing.

The D250SE isn’t cheap, being built to this high spec and lasting you for a long time is one of the main reasons why, even apart from its functionality.

It’s smart alternator friendly

If you’ve got a smart alternator (eg. a Euro 5/6, ECU-controlled alternator), you may or may not know that even though it’s an advantage to have one, it can cause problems and even damage your battery if you were to try and directly charge your leisure battery from your starter battery.

That’s one of the issues the D250SE is made to solve. It works perfectly with a smart alternator, allowing you to charge your leisure battery safely and with best efficiency.

The cleverness of the technology to troubleshoot

At Off Grid Power Geek, we judge products not by how the product performs when everything is smooth and conditions are ideal, but rather how it performs when things are changeable, volatile, and deviated from the norm.

That’s where sheer technical knowhow and the depth of technology comes in.

It’s here where the CTEK DC DC charger shines – it’ll solve problems and come up with solutions without you even knowing, where other DC DC chargers, may give you a few problems.

And this leads us to…

It gives you reliably stable output

In this case, no matter how volatile or changeable the inputs are, in what context, we’ve noticed that the D250SE has the ability to always provide a stable output.

And this stable output is crucial for 1) battery health and longevity 2) the power received by your devices being stable and reliable.

You’ll get the most powerful, quickest charging you’ve ever experienced

The 20 Amp charging is powerful.

One of the main things we’ve heard from D250SE users is how completely and how fast it’ll charge your battery.

Efficiency is extremely important to any starter/leisure battery system or solar system. This CTEK battery to battery charger provides exceptionally high efficiency, making the most of all your inputs.

It’s this kind of efficiency that can be the difference between being able to live completely off-grid or needing quite regular hookup charge. Of course, that is also highly dependent on the size of your battery bank.

The biggest advantage of all – it’ll make your batteries last longer and work better (CTEK are the only ones with Desulfation!)

There’s one HUGE advantage of the CTEK D250SE over any other battery to battery charger, and it’s something most people aren’t even aware of. Yet it’s something that can save you a ton of money and hassle with your batteries.

What are we talking about? We’re talking about CTEK’s charging and one specific stage of their charging – Desulfation stage.

All lead-acid batteries suffer from sulfation, which is the build-up of lead sulfate on your battery plates. Left unchecked it’ll grow, until your battery can no longer store charge or deliver power. And it’s worsened whenever the battery is left in a state of partial discharge.

Many batteries (as many as 84%, in fact) die much earlier than they should due to sulfation. But it’s reversible.

And that’s exactly what CTEK’s desulfation step does. It removes the sulfation from the battery plates.

The result? It revives your battery’s ability to store charge. Which means it delivers smoother, stronger power – closer to how it was when the battery was new.

And this means batteries can last 2 or 3 times longer than they otherwise would. (Here’s more information on leisure battery lifespan)

This is where CTEK’s technology as the world-leading battery charger company comes in. Other DC to DC chargers cannot offer this kind of technology.

The CTEK D250SE can charge all batteries, including AGM and Lithium batteries

It charges Flooded (Wet) (here’s the best lead-acid leisure battery, Superbatt), Gel (here’s the best Gel batteries, UK), AGM, Calcium (Ca-Ca), EFB and Lithium batteries.

AGM batteries need special charging, a particular type of charge that is different from other lead-acid batteries.

This CTEK B2B charger can provide the right type of charge. AGM batteries need 14.7V, which is higher than for ‘traditional’ lead acid batteries.

You will need to wire the device differently for AGM batteries, it tells you how in the user manual.

The D250SE also charges Lithium batteries. That’s crucial. Even if you don’t have one at the moment, you’ll want to know that when you upgrade (and with the best Lithium batteries recent decrease in price, you should consider it, they offer massive benefits compared to lead acid ones!), you can keep using the D250SE with no problems and for many years in the future.

The MPPT is high-quality

The built-in MPPT functionality of the D250SE is a significant advantage over other battery to battery chargers.

The MPPT is what takes the solar energy received, and provides the stable charge to your auxuliary battery, maximising the energy provided.

In terms of safety and the health of your leisure battery, as well as making the most of whatever solar energy is received by your system, the MPPT is a crucial component of this unit.

No power is wasted with the D250SE

Hopefully, this CTEK D250SE review has made it clear to you how efficiently this device uses power.

When your leisure battery is fully charged from the solar input, the D250SE will then start charging your starter battery.

It’ll act as a trickle charger, making sure your starter battery is maintained.

That’s clever, and again it’s maximising the power received, ensuring minimal wastage.

Another key advantage of the CTEK D250SE for saving power and preventing unnecessary battery discharge is that it’ll isolate the starter battery from your leisure/auxiliary battery when the alternator is not in operation.

That’s a great feature. Otherwise, one may discharge the other.

What We Didn’t Like About This CTEK Battery to Battery Charger

Rewiring for AGM

If you change to an AGM battery, you’ll need to do some rewiring. It’s minor and the instructions cover how to do it quite well.

Just a little inconvenient!

It’s not exactly low cost

This CTEK battery to battery charger is not cheap.

It is an investment that’s worth it, though. It’ll easily pay for itself, given how much more efficient your energy usage is when you have it.

Then consider that CTEK’s excellent desulfation charging will make your batteries last much longer, and deliver more power during that time. That’s a big cost saving too.

Anything else I need to know about the B2B charger?


Yes, 2 years.

User Manual any good?

It’s a good ‘un.

Simple descriptions, good English, how to set up the many different types of systems you can have.

Summing Up Our CTEK D250SE Review

What’s left to say then, except the CTEK D250SE is a cracking piece of technology.

If you’re looking to get the most efficient charge to your leisure or auxiliary battery, this is how you’ll get it. It’ll make the most of your alternator (smart or otherside) charge coming in, giving the best possible output charge. And the MPPT technology makes the most of any solar input, at the same time.

Take the time to set it up exactly as the user manual describes and you’ll be good to go.

If you, we believe you can expect it to deliver everything you need it for.


If so, check it out here.

CTEK D250SE DC DC Charger b2b

That’s us calling it a day on our CTEK D250SE Review.

If it’s for you…

Here’s the best place to buy it, on Amazon.