What is DM-i and how does it work

DM-i is a terminology used by BYD to describe a hybrid car and in the case of the company it means Dual Model intelligent. So, as any other plug-in hybrid on the market, it can drive in pure electric mode, as well as a combination between electric and petrol, when needed. Theoretically, there's no difference between BYD's plug-in hybrid system and others on the market, such as Toyota or Volkswagen, for example.

When there's enough juice in the battery, the car can drive in electric mode, but when it's nearly empty, it will work as a regular hybrid car. This means that it will turn on the petrol engine briefly to charge the batteries, as well as when you press the accelerator harder, to offer better power ratios.

Still, every manufacturer optimizes this system in order to offer a different experience. In the case of Renault cars, they drive in pure electric mode up to 50 km/h, regardless of how hard you accelerate, if the battery isn't nearly depleted. In the case of Toyota cars, if you want nippier accelerations, they will combine the output from both trains to offer the most amount of power.

How is it in the case of BYD cars? Just like for Toyotas, if you press the accelerator harder, it will instantly use the electric motor, followed by the petrol engine just a second or two later, to add more power. Still, I don't know how important this is in the case of BYD cars, as the total system power isn't too different from the one delivered by the electric motors alone.

BYD Seal U DM-i is available in 3 different motor versions, Boost, Comfort and Design. I had the Boost model for testing, which uses an electric motor in the front, 197 horsepower and an 18kWh battery, as well as a petrol engine, 1.5 liter with 4 cylinders that produces 98 horsepower. The system's total power output is 218 horsepower, which is why I said that the ICE engine doesn't add too much; furthermore, it is naturally aspirated, which on a car that weighs almost 2 tons isn't too much of a difference during an acceleration.

The Comfort version keeps the electric motor and the petrol one, while boosting the battery capacity to 26kWh, so there's quite a bit more range for driving in pure electric mode. On the Design trim, you get two electric motors and a turbocharged petrol one, 1.5 liter in 4 cylinders that outputs 120 horsepower and the system's output grows to 324 HP, much better for nippier accelerations. One minus in this case is that the battery used in this version is the 18kWh one, instead of the 26kWh, so the range will technically be the lowest out of the bunch.

Seal U DM-i can be decently efficient in pure electric mode

Being a plug-in hybrid car, you can choose to drive the Seal U DM-i in pure electric mode, if the battery level is above 25%. You can set the percentage on which the car will deactivate the electric mode according to your preferences, but it can't be lower than 25%. In HEV mode, the vehicle will work as a full hybrid, meaning that it will rely on the electric motor for as long as possible, while utilizing the petrol engine to charge up the batteries occasionally, without necessarily using it to move the wheels.

This is where BYD's optimization comes into play. They developed this hybrid system to rely mostly on electric mode and only when you need the most amount of power it will engage the petrol engine to power the wheels. Thus, the company manages to better optimize fuel usage, which is decent for a plug-in hybrid, but not necessarily great.

It heavily depends on how you as a driver manage your trips and how heavy you are on the gas pedal, generally. To protect the petrol engine, BYD made it so that it will turn on every now and then, even if it doesn't need to, but if you're on the EV mode and have plenty of battery, the car will respect that and won't run on gasoline just because it can.

The fuel economy I got when cruising around the city and low to medium speeds was 6-6.5 liters per 100 kilometers, pretty decent for a hefty plug-in hybrid. On the motorway, the fuel consumption rose to around 7.5/100 km, not very surprising for a heavy car and with a fairly poor coefficient drag of 0.34.

Fast charging on the Seal U plug-in hybrid

As any other plug-in hybrid, this car is most efficient when charging it up and driving it in pure electric mode. BYD says that the electric only range is about 100 kilometers and the results I got are not far away from this, but they're not impressive, either, giving the charging times. I drove in pure electric mode for around 15 kilometers around the city on an early Saturday morning and the speed was a bit higher, given there was virtually no traffic. I used 10% of the battery, a little more than I hoped I would, but this is where the fairly small 20kWh battery came into play.

The charging power on this model is 11 kW on AC power and 18 kW on DC. I expected it to charge quicker and I would like to see some improvements in this area, in the future. From 21%, the car charged up to 44% in 15 minutes. Chery offers 40 kW DC charging for its plug-in hybrids and Mercedes, up to 60 kW on some. It's true that even a slower DC charging is better than not having it at all, but even so I would like to see more in this aspect.

Regenerative braking is another subject I want to talk about, because I'm not happy with how it works. Just as it was the case with the Dolphin Surf, Seal U DM-i does a little coasting once you let go of the accelerator, before going into power recuperation, while the braking force isn't too great. From my tests, it goes up to around 50 kW when the speed is 70-90 km/h or higher, and if you press on the brakes yourself, it can go up to some 80 kW. It wouldn't bother me too much if this was the standard regeneration setting.

It bothers me because this is with the strong recuperation turned on, where I expect a stronger braking from the car, as well as the process starting as soon as I release the gas pedal, as it happens on most hybrids and electric cars that I've tested so far.

BYD Seal U DM-i, "the black sheep" when it comes to the driving experience

I admit that I don't normally do this, but before taking the car for a test drive, I've read about it for a bit, figuring out what others think of it. I was a bit surprised that they weren't happy with how the car performs on the road and generally, when it comes to the driving experience. When I drove the Dolphin Surf, I was very pleasantly surprised by how good that car's driving experience was, even on lower quality roads.

I expected this SUV to be not very dynamic, but to at least compensate with regards to a better comfort on a longer trip and on a lower quality asphalt. But unfortunately, the BYD Seal U DM-i is the kind of car that leaves a lot to be desired when it comes to the driving experience. I've tested enough cars by now to figure out the strong suits and the weak points of every car.

I don't have a lot of good things to say about this model, except for the fact that it is very easy to maneuver at lower speeds and when parking it. The steering is very soft and the car has an impressively tight turning radius, which for an SUV is a pleasant surprise.

This is where the good news ends; When it comes to bumps and potholes, even the smallest ones, the car will let you know about all of them. The vehicle tends to be a bit jumpy over "wavy" roads, so the suspension is soft, but something still doesn't add up; either the wheels are too small or the wheelbase (the distance between the front and rear axle) is a bit too short. The chassis isn't very stable when going over a tram line and turning and those speed limiters that we have in the city can make the car "bouncy", which is especially unpleasant for those in the back.

It's possible that the 19 inch rims don't help a lot when it comes to the comfort, either, but the Seal and the Sealion 7 I heard are much better when it comes to this and they use a similar setup; I will get an idea after I'll try them personally.

Around corners, the car is obviously not dynamic at all, but it's not a complete disaster; you can drive it normally, just don't push its limits, as you will discover them quickly. On the motorway, the Seal U DM-i is stable, but noisy at speeds in excess of 100 km/h, and at higher speeds, the steering doesn't just become more precise, it's kind of stiffer, too. When adjusting the steering, you have to put in more effort to move the wheel, not exactly ideal, especially on a longer trip.

Technologies and comfort BYD Seal U DM-i

The good news for this car is that, in Romania, there are no trim levels. So, between the 3 available versions, Boost, Comfort and Design, the only difference is the engine and battery options. When it comes to features, Seal U DM-i is identical, and this makes me very happy. Often times it can be difficult to estimate the price of a car according to its features and trim levels.

In this case, the base model starts at 38.600 euros, followed by the Comfort level, at 41.100 euros and finally, the Design version, which will set you back 45.700 euros and that's before talking about dealer discounts and such. You can add 1.000 euros if you pick a different color rather than the basic grey one, but that's it. The interior is available in two colors, but there's no extra charge if you pick one over the other. This is very simple and something I would like to see at other manufacturers, as well.

Let's talk about the technologies for a bit; Seal U DM-i offers a bit for everyone: a large tablet in the center is where every bit of the infotainment and adjusting various safety and comfort settings happens. The front seats are fairly comfortable, offering complete electric adjustments for the height, backrest, depth and even an electric leg rest. The seats are heated and ventilated on multiple levels, a good thing, and the material seems to be decent for hot summer days, as well, but I can't be sure (yes, I have PTSD from the Dolphin Surf drive).

There's climate control for two zones in the front and you have a ventilation passage in the back, as well, the car has a heat pump and an air purifier, which can be turned on manually or automatically. The steering wheel is heated, as well, and it's from a material that imitates leather. In the back, there's more than enough room for passengers, even if the driver is taller and if he's a bit shorter, like me, then you can really lay back and relax in the back over a longer trip.

The car uses parking sensors and 360 degree cameras that look very good, a lesson for traditional carmakers which use poor quality units in many cases, while the Seal U DM-i will approximate the distance from an obstacle in centimeters, as well. The driving assistance features are doing an OK job, but you can see that they are not very refined, as they come into effect pretty brutally, such as the lane keep assistant or the adaptive cruise control, which accelerates a bit too powerful.

The audio system is a 10-speaker Infinity by Harman/Kardon unit and it sounds decent, but the 12-speaker Dynaudio one from the Seal or the Sealion 7 should be even better. Listening to music is a pleasure here, as well, but it's not quite among the best sound systems out there, I would say better than the Arkamys one in the Dacia Bigster.

The boot is only 425 liters in volume, pretty mediocre for the car's size, but not small enough to disqualify it altogether. From what I've tested so far, Renault's Austral E-Tech 2025 and the Dacia Bigster, in all its engine versions, offer more space for luggage, with an even more compact chassis.

Conclusions BYD Seal U DM-i

BYD's proposition for a nearly D Segment plug-in hybrid SUV is a very interesting one and it will definitely have its adopters, because it offers quite a lot in an attractive price to features package. Even if it doesn't offer the most refined driving experience, Seal U DM-i comes in a single, top of the line trim level, with hard-to-ignore optionals, such as multi-level climate system with an air purifier, plenty of space and driving assistance or comfort features that you don't find very easily under 40.000 euros.

Plus, the fact that it is a plug-in hybrid that offers DC fast charging can be an advantage for drivers that are always on the move.

From what I've tested so far, I don't have an alternative that's plug-in hybrid, except for the Suzuki Across, which is basically a Toyota RAV4, more expensive, but definitely higher quality than the BYD. That one doesn't feature fast charging capabilities, but the engine option is significantly more balanced, more powerful and possibly, even more economical, even if on the feature side, it lacks compared to the BYD.

For about the same money as the Seal U DM-i, I could recommend the Dacia Bigster or the Renault Austral E-Tech, which are not plug-in hybrid, so they don't charge from an outlet and can't drive for as long in electric only mode. But, when it comes to the engine options, they offer more reliable units, with a similar or even lower fuel economy compared to the BYD's Seal U DM-i.