Cooling system design final and developing radiators

The cooling system design pops up every now and then and is subject to mant changes and different versions. Initially I thought about using a heat exchanger and a mixing valve and the latest idea was to use a 4-way valve just like Tesla does. So I got my hands on one of these valves and worked on controlling it.

Tesla kleppen en pompen

It turned out to be a challenge to use them in the car. There just was not enough space and the orientation of the inlet and outlets was inconvenient. So I decided to skip the 4-way valve and thus drop the possibility of heating the batteries into their ideal temperature range while driving using waste heat from the motor. Back to the drawing board.

koelen back to the drawing board

I do not have much room at all. I could position the electrical battery heater next to the motor. That would allow me to plug the wiring that is attached to the beter into the contactor box. The outlet hose does need to go over te motor in that case though.

battery heater naast motor


Another important aspect of the cooling system are the radiators. When I first discussed my project with Chris from Hartgers Radiateuren he mentioned fans are a good starting point for developing radiators. So I started checking how much room I have. Between the front battery box and the radiator support it’s only 160 mm.

160mm hoogte onder bak

And between the battery box and the airconditioning condenser about 60 mm.

60mm tussen bak en condensor

That’s not a lot so I started searching for a flat suction fan that fits underneath the box. I found a nice one from Spal.

SPAL fan klein

The motor needs the biggest radiator since the efficiency is around 80 to 85% and as EVTV writes “It withstands great abuse to the degree you cool it.”. So the right most corner is for that one since it is the largest space I have plus a bigger fan can be used. The battery radiator will be in the middle and the one for the controller and DC/DC converter to the left. I made some wooden mockups.

mockups radiatoren

That also gave me an idea of how and where to position the cooling pumps. The one for the motor is on the right on top of the chassis beam.

motor pomp

The one for the DC/DC and controller somewhere in the middle.

controller pomp

And the one for the batteries on the left just in front of the steering box.

batterijen pomp

To add some more cooling capacity I developed a V2 mockup for the controller. Partially it sits in front of the battery box, but in the end it has an overall increased cooling surface.

controller radiator groter

With those dummy radiators I went to Chris from Hartgers Radiateuren to discuss them and do a feasibility check whether my thickness assumptions were OK and if he could make them.

check Hartgers

He did not see any issues so I could continue and get down to the details. First step was cutting the side panel.

zijpanelen weggezaagd

That allowed me to easier mount the pump.

pomp rubbers

As close to the battery box support as possible to maximize clearance for the fan.

pomp motor op zn plek

Finding valves

Not only did I buy a Tesla 4-way valve, I also had a Tesla 3-way valve laying around. Tesla used two of those for bypassing the radiator and chiller respectively. The orientation of the outlets was very inconvenient for me so I did a search on alternatives. For example from a Ford Fiesta.

Ford Fiesta bypass

Advantage is that is is a bypass valve and thus easy to control. Disadvantage is that the hose connections turned out to be 17mm and the hose barbs in my system are 19mm. Another option was a 3-way valve from a Golf GTE E-Golf.

Golf GTE klep

That turned out not to be a OR/OR valve so not very handy. Is was nice and compact though. Another option was a GM 3-way valve.

Opel 3 weg

That needs to be controlled using a mircocontroller but did get it working in the end. Another option was a GM 4-way valve. Advantage of that one is that with one valve I could switch between three options:

  1. through radiator
  2. through heater
  3. bypass all

Opel 4 weg

Disadvantage turned out to be that to control it a feedback loop was needed. Got it to work in the end but was a bit more complicated in the end.

My shortlist was GM 3-way (left) or GM 4-way (right).

Opel 4 weg of 3 weg

Battery pump

The pump for the battery cooling loop will be on the left hand side just behing the controller radiator.

Controllers radiator LV

Creating a support turned out to be a challenge. The connector was interfering with it since I want the outlet to point upwards.

Batterijen pomp LV

In the end it worked out nicely together with the 3-way valve.

Batterijen pomp geplaatst

However unfortunately I did not take into account the space needed for the controller fan.

Te krap bij fan

So I modified the support and moved the pump a bit towards the steering box.

Batterijen pomp verplaatst

Controller pump and 4-way valve

The pump for the cooling loop of the DC/DC converter and controller will be somewhere in the middle so I made a temporary mount.

Controller pomp midden

And checked whether using the 4-way valve was an option.

4 weg klep proberen

I could in the end find a way to squeeze it in but it wasn’t ideal. So I decided to move forward using the 3-way valve.

To the drawing board!

The pumps were in place and the dummy radiators are ready.

klaar voor tekenen

So I could continue designing the whole thing in detail. The hose connection for the pump needs to point upwards a bit.

radiators design onshape

The batteries and controller loop each get their own swirl pot to easily get the air out of the system and at the same time have an expansion vessel. The motor cooling loop will just have a traditional expansion vessel and a cap. The latter needs to be a bit to the front to clear the hood support.


And as soon as it all fits in 3D generating drawings is easy in Onshape.

technische tekeningen

And after a lot of fine tuning and tweaking the designs are ready.

Which I used to write a briefing for Chris to build the radiators.

So I took the whole lot to Hartgers Radiateuren and even made some small changes that crossed my mind.

The result

Three wonderful radiators according to my design specs.

Radiateuren gereed

Great job by Chris from Hartgers Radiateuren! Respect and big thanks.

Chris van Hartgers Radiateuren

The good news is that not only was it build according to the specs, my designs were also OK.

Radiateuren passen perfect

They perfectly fit in the car! Perhaps the batteries cooling pump needs to be moved a bit more.

Leave a Comment


OldVolvo is a classic Volvo hobby blog by Lars Rengersen.

Also electric?

Do you also want to convert your car (Volvo or another brand) to full electric? As a spin-off of my own EV conversion project I started EVcreate for 'enabling EV conversions'

More info