CTEK SMARTPASS 120S and 250SE DC to DC charger basic features and install information

About the CTEK 120S and the 250SE
The CTEK SMARTPASS 120S is the charger installed in the INEOS Grenadier if you choose the aux power option. The full CTEK Manual can be downloaded here. It has lots of information about installation. In the first half of 2024 there are reports of an unbranded version of the CTEK 120S being installed into the Grenadier. It is not known how it differs (if at all) from the branded version of the CTEK120S.

You can buy and install a CTEK 250SE, which is a DC to DC charger which mates with the CTEK 120S. The combination has 140 amps of charging power and a solar input.

The CTEK SMARTPASS 120S is the Lithium version (plus other chemistries) installed on the INEOS. The CTEK SMARTPASS 120 (no S) is the non-lithium version. Add S for Lithium.

The CTEK 250SE is the Lithium version (plus other chemistries) of the DC to DC charger, the non-Lithium version being the 250SA. Yep, only the last letter changes A or E.

The CTEK 250SE also gives you a solar input.

Important warnings from the CTEK Manual

The INEOS Grenadier’s aux battery chemistry is EFB not lithium
The INEOS Grenadier’s aux battery is not lithium, but with the 120S and the 250SE you can install a Lithium battery later and not have to buy new chargers (you do need to make some minor wiring changes).

So the best combo, in terms of features and battery chemistry, is the 120S with the 250SE (although the image below shows the 120). The combination looks like this:


Dual mounting bracket
At present, only Black Sheep Innovations has a bracket for sale allowing you to mount the CTEK 120S and 250SE together in the INEOS' battery compartment. Other brackets are under development. Warning: at least one owner of a 2 seater version has reported an issue with fitting the Black Sheep Bracket, he managed to install the bracket by reversing it on his 2 seater.

Bell Auto Services has generously made these diagrams available of their dual mounting bracket for others to freely use.

The CTEK Manual says to secure the connector plates between the two units first. Then secure both units to the Dual Mounting Bracket (see page 6 of the CTEK Manual).

So, secure the connector plates and torque the nuts on the terminal post with a 5mm Allen Key to 8 Nm/71 lb-in of torque (see Figure 2 on page 6 of the CTEK Manual).

Then secure both units to the Dual Mounting Bracket using M4 or ST4.2 screws/bolts, in each of the four corners. Each screw/bolt is torqued to 2 Nm/18 lb-in (see Figure 1 on page 6 of the CTEK Manual). I would use bolts, not screws, to secure both units to the Dual Mounting Bracket.

Tip: once both units are fixed to the Dual Mounting Bracket and the bracket is installed into your INEOS, I would re-torque all the nuts and bolts.

Looking at the Figures below should clear up any misunderstanding.


Connector plates (aka busbars, cables with lugs, etc.)
The connector plates are the two black plates (sometime grey) connecting the two units together in the above images.

The connector plates come in the retail packet of the CTEK 120S, but not the “retail box” that comes with the INEOS Grenadier. CTEK does not sell the connector plates as a separate item. You will need to make you own or buy a pre-made set - someone stuffed up there!

Page 5 of the CTEK Manual gives the requirements for the connector plates, basically a 4mm2 cable (or 12 AWG) and a lug with an M8 size hole, if they are mated next to each other.


Making your own connector plates (or busbar)
I made some connector plates based on @bakepl measurements here. Here they are:


My steps:

1. I used tin plated copper lugs, metric size 10-8 (meaning 10mm2 wire size and 8mm hole size). The lug fits onto the CTEK 250SE terminal, as I checked;
2. I used 8B&S wire cut to 7cm in length (with the lugs I used);
3. I crimped the lugs onto the wire, remembering to have the clear shrink tube on the wire for both ends, before crimping the second lug on. After I crimped the second lug I heat treated the dual wall tubing to each end.
4. I made it slightly bigger than 98mm (100mm), as the wires can flex and being too short is a problem but being a little longer is not.
5. The length measures correctly, but I cannot be 100% sure until I mate the two units together on the bracket, and I need my car for that.
6. I wrapped the red wire using black automotive tape, after taking the photo.

I made a test connector plate first, to work out what I would do wrong and then fix it for the next two.

Using both the CTEK 120S and the 250SE together
This following summerises additional key information from this CTEK instructional video. It is not a substitute for watching the video and reading the manual. It merely summerises key information to help an install.

Fuses
Two 300 amp fuses are needed (but one or both may already be installed on your INEOS).

One 300 amp between the Start Battery (aka main battery) and the CTEK 120S. I believe this is done via a battery fuse on one of the INEOS busbars, known as a MEGA range ZCASE® fuse.

A second 300 amp fuse between the CTEK 120S and the Service Battery (aka auxiliary battery). If you have selected the INEOS aux power pack INEOS uses an inline MEGA fuse in the Midi style (which are not MEGA range ZCASE fuses). I believe, but cannot be certain, this is the Littelfuse fuse holder used in the INEOS.

Warning: you must look at your car’s set up is before doing work, because set ups may vary between countries and models. Do not make assumptions! You may already have one or both fuses already installed.

Fuses used and cable length
Page 5 of the CTEK Manual lists the fuse ratings and cable requirements for your install (see extract above). Cable size can vary depending on the length of a cable run. What cables to use may vary between the CTEK 250SE and 120S. The CTEK supplied Table, extracted above, tells you both. So use it.

More fuse information
This thread has more detailed information on the fuses used in the INEOS.

Terminal screws/nuts on units
Use a 5mm Allen Key on the terminal screws (nuts) and tighten to 8 Nm/71 lb-in of torque (see Figure 2 on page 6 of the CTEK Manual). Tightening by hand is not good enough, as the connector plates and cables will come loose.

The unit itself can be secured using M4 or ST4.2 screws or bolts, in each of the four corners. The screw or bolt is torqued to 2 Nm/18 lb-in (see Figure 1 on page 6 of the CTEK Manual).

Solar panel for the CTEK 250SE
The CTEK 250SE charger is designed for unregulated solar panels:

• between 50 and 300 watts;
• with a maximum open circuit output value of 23 volts;
• using a 6mm cable from the solar panel to the CTEK 250SE.

Use an M8 ring terminal/lug (I suggest a tin-plated copper lug) crimped to the solar panel cable and attach the cables to the solar input on the CTEK 250SE. Tighten terminal screws to 8 Nm/71 lb-in of torque.

Installing lithium batteries – cabling changes required
If you install an auxiliary Lithium battery consult the CTEK Manual because you need to make some minor cabling changes. See page 7 of the CTEK Manual. Note: you need to have the CTEK 120S and 250SE to install an auxiliary Lithium battery.

Additional resources
CTEK Support pages with Guides and Videos here.
Full CTEK Manual attached to post here.

View: https://youtu.be/kTRiqyzK9zA

TheDocAUS said:

About the CTEK 120S and the 250SE
The CTEK SMARTPASS 120S is the charger installed in the INEOS Grenadier if you choose the aux power option.

You can buy and install a CTEK 250SE, which is a DC to DC charger which mates with the CTEK 120S. The combination has 140 amps of charging power and a solar input.

The CTEK SMARTPASS 120S is the Lithium version (plus other chemistries) installed on the INEOS. The CTEK SMARTPASS 120 (no S) is the non-lithium version. Add S for Lithium.

The CTEK 250SE is the Lithium version (plus other chemistries) of the DC to DC charger, the non-Lithium version being the 250SA. Yep, only the last letter changes A or E.

The CTEK 250SE also gives you a solar input.

The INEOS Grenadier’s aux battery chemistry is EFB not lithium
The INEOS Grenadier’s aux battery is not lithium, but with the 120S and the 250SE you can install a Lithium battery later and not have to buy new chargers (you do need to make some minor wiring changes).

So the best combo, in terms of features and battery chemistry, is the 120S with the 250SE (although the image below shows the 120). The combination looks like this:

View attachment 7822390
View attachment 7822392

Mounting bracket
At present only Black Sheep Innovations has a bracket for sale allowing you to mount the CTEK 120S and 250SE in the battery compartment. Other brackets are under development.

Connector plates (aka busbars)
The connector plates are the two black plates (sometime grey) connecting the two units together in the above images.

The connector plates come in the retail packet of the CTEK 120S, but not the “retail box” that comes with the INEOS Grenadier. CTEK does not sell the connector plates as a separate item. You will need to make you own or buy a pre-made set.

Page 5 of the CTEK Manual gives the requirements for the connector plates, basically a 4mm2 (or 12 AWG) cable and a lug with an M8 size hole, if they are mated next to each other.
View attachment 7822384

Making your own connector plates (or busbar)
I made some connector plates based on @bakepl measurements here. Here they are:
View attachment 7822385

My steps:

1. I used tin plated copper lugs, metric size 10-8 (meaning 10mm2 wire size and 8mm hole size). The lug fits onto the CTEK 250SE terminal, as I checked;
2. I used 8B&S wire cut to 7cm in length (with the lugs I used);
3. I crimped the lugs onto the wire, remembering to have the clear shrink tube on the wire for both ends, before crimping the second lug on. After I crimped the second lug I heat treated the dual wall tubing to each end.
4. I made it slightly bigger than 98mm (100mm), as the wires can flex and being too short is a problem but being a little longer is not.
5. The length measures correctly, but I cannot be 100% sure until I mate the two units together on the bracket, and I need my car for that.
6. I might yet wrap the red wire using black or a neutral coloured electrical/automotive tape.

I made a test connector plate first, to work out what I would do wrong and then fix it for the next two.

Using both the CTEK 120S and the 250SE together
This following summerises additional key information from this CTEK instructional video. It is not a substitute for watching the video. It merely summerises key information to help an install.

Fuses
Two 300 amp fuses are needed (but one or both may already be installed on your INEOS).

One 300 amp between the Start Battery (aka main battery) and the CTEK 120S SMARTPASS. I believe this is done via a battery fuse on one of the INEOS busbars, known as a MEGA range ZCASE® fuse.

A second 300 amp fuse between the CTEK 120S and the Serve Battery (aka auxiliary battery). If you have selected the INEOS aux power pack INEOS uses an inline MEGA fuse in the Midi style (which are not MEGA range ZCASE fuses). I believe, but cannot be certain, this is the Littelfuse fuse holder used in the INEOS.

Warning: you must look at your car’s set up is before doing work, because set ups may vary between countries and models. Do not make assumptions! You may already have one or both fuses already installed.

Fuses used and cable length
Page 5 of the CTEK Manual lists the fuse ratings and cable requirements for your install. Cable size can vary depending on the length of a cable run. What cables to use may vary between the CTEK 250SE and 120S. The CTEK supplied Table tells you both, use it.

More fuse information
This thread has more detailed information on the fuses used in the INEOS.

Terminal screws/nuts on units
Use an Allen Key on the terminal screws (nuts) and tighten to 7 N-m of torque (Newton meters). Tightening by hand is not good enough.

Solar panel for the CTEK 250SE
The CTEK 250SE charger is designed for solar panels:

• between 50 and 300 watts;
• with a maximum open circuit output value of 23 volts;
• using a 6mm cable from the solar panel to the charger.

Use an M8 ring terminal/lug (I suggest a tin-plated copper lug) crimped to the solar panel cable and attach the cables to the solar input on the CTEK 250SE. Tighten to 7 N-m of torque.

View: https://youtu.be/kTRiqyzK9zA

Click to expand...

Nice work Doc, thanks for sharing!

Thanks. I still have some proofreading to do.

Thanks @TheDocAUS for all the effort in this research.

TheDocAUS said:

Thanks. I still have some proofreading to do.

Click to expand...

Thanks Doc. Just bought a 250se on the basis above. Appreciate the time and effort you put in. ️

Excellent thank you. Look forward to hearing from someone who has completed the work. Have ordered the plack from Black Sheep, although no evidence it has been dispatched as yet. I have the D250SE and connector bars and all cables plugs and connections required

AnD3rew said:

Excellent thank you. Look forward to hearing from someone who has completed the work. Have ordered the plack from Black Sheep, although no evidence it has been dispatched as yet. I have the D250SE and connector bars and all cables plugs and connections required

Click to expand...

Where/what are the bars/plugs/connections? Just trying to get to the same stage. Tks

ECrider said:

Where/what are the bars/plugs/connections? Just trying to get to the same stage. Tks

Click to expand...

The bars are the one’s supposed ro he supplied by CTEK with the 120s but INEOS aren’t including them. I contacted CTEK and they sent me some. But many have been told they aren’t available, they don’t normally supply them separately. @TheDocAUS has provided information on making up cables to use instead. By cables and plugs I mean I will
be attaching a cable to the D250SE to connect solar inputs and will put an Anderson plug on those because my solar panel’s already have Anderson plugs on them.

AnD3rew said:

The bars are the one’s supposed ro he supplied by CTEK with the 120s but INEOS aren’t including them. I contacted CTEK and they sent me some. But many have been told they aren’t available, they don’t normally supply them separately. @TheDocAUS has provided information on making up cables to use instead. By cables and plugs I mean I will
be attaching a cable to the D250SE to connect solar inputs and will put an Anderson plug on those because my solar panel’s already have Anderson plugs on them.
View attachment 7822401

Click to expand...

Perfect. Tks explanation.

AnD3rew said:

By cables and plugs I mean I will
be attaching a cable to the D250SE to connect solar inputs and will put an Anderson plug on those because my solar panel’s already have Anderson plugs on them.

Click to expand...

My plan is to draw a second pair of wires through one of the standard outlets on the roof. But I think space is too limited to add a second Deutsch plug. Are those available with four connectors. So on two connectors I could use as the normal power supply an the others for the solar input.
What does the community think?

Great stuff @TheDocAUS - Thanks a lot!
D250SE already waiting in the workshop, 240Wp foldable solar panels as well, cables (missing bus bars) crimped last night.
Ready to go at my end, just need the car for installation ;-)

Added new heading for installing an auxiliary Lithium battery. Modest cabling changes are required.

Pat-Ard said:

My plan is to draw a second pair of wires through one of the standard outlets on the roof. But I think space is too limited to add a second Deutsch plug. Are those available with four connectors. So on two connectors I could use as the normal power supply an the others for the solar input.
What does the community think?

Click to expand...

Roof mounted unregulated solar panel
I buy 6mm2 cable for solar panels, with a MC4 plug one end into the solar panel on the roof rack, then cut off any MC4 plug on the other end. Feed the cable down into the battery compartment, then crimp a M8 lug onto the positive and negative cables and attach each lug to the CTEK250SE as per the instructions below. Tighten to 8 Nm/71 lb-in of torque.

I would try and find a 6-8 plug (for 6mm2 cable and an M8 hole size or something close) and make sure my solar panel complied with the specs quoted in the first post (50 to 300 watts and a maximum open circuit value of 23 volts).

Max open circuit value of 23 volts for solar panels
After looking at several solar panel brands, you are must be careful about this figure, as quite a few brands exceeded 23 volts. The Redarc fixed solar panels seem to be a reasonable choice for Australian users, but you pay the Redarc premium, but only 2 year warranty.

Portable unregulated solar panels
If you are going to plug portable solar panels into the CTEK 250SE make sure they comply with the specs. The CTEK 250SE charger is designed for unregulated solar panels:

• between 50 and 300 watts;
• with a maximum open circuit output value of 23 volts;
• using a 6mm cable from the solar panel to the CTEK 250SE.

If you need/want more solar capacity, you will need to wire up a separate solar controller.

Max open circuit value of 23 volts for solar panels
After looking at several solar panel brands, you are must be careful about this figure, as quite a few brands, in Australia, exceeded 23 volts.

I have made a major revision to the first post. It fixed some typos but also added more information and links.

Plus I have added the solar data in the two posts above.

Michael-

Thanks so much for your explaination.

I am a little confused (yes, stumbled at the first hurdle!) when you say......"At present only Black Sheep Innovations has a bracket for sale allowing you to mount the CTEK 120S and 250SE in the battery compartment. Other brackets are under development.

Each unit can be secured using M4 or ST4.2 screws or bolts, in each of the corners. The screw or bolt is torqued to 2 Nm/18 lb-in (see Figure 1 on page 6 of the CTEK Manual)"

Can you clarify what is the difference between "MOUNTING" the CTEK 120S and 250SE and "SECURING" the CTEK 120S and 250SE?

Is it one or the other but not both?
cheers
mark

I will make some changes, once I work them out.

The bracket allows the the two units to be mounted together. The bracket is then attached inside the INEOS' battery compartment.

Each unit needs to be attached to the bracket by 4 bolts or screws on the four corners of each unit.

EDIT: wording revised and Figures added. @grenadierboy let me know if that fixes up the confusion.

Understood, many thanks

Torquing terminal nuts to 8 Nm
I set my torque screwdriver to 8 Nm of torque tonight and that is a lot of torque. I doubt I can tighten the terminal nut up to 8 Nm on either unit with the screwdriver. My torque wrench would give me the leverage I need but it is too big.

I can think of two other options. First, do not torque to 8 Nm but place a Nord-Lock washer on each terminal post. The nut will not come loose with less torque because of the Nord-Lock washer.

Second, add some clear Marine Goop on the top of the terminal post before tightening the nut. This has worked well over the years because Marine Goop is still flexible when dry and it stops the nut coming off, but it is still easy to remove the nut if you wish. It works much better than Loctite if there are corrugations. Avoid placing any Goop between the lugs and the bottom of the terminal post.

After reading this thread and the Das mo's dead battery thread, I have decided that the factory dual battery setup does suit my use. It is still useful with a maintenance charge on start batteruly, and back up and I believe it connects batteries under winch loads (correct me if I am wrong)

In my fit out I now think I will install the 250se and the just leave it all alone.

Then go the typical (dual battery) route and add a third lithium battery connected to a Redarc BCDC and power a new rear fuse box and switch panel for all the accessories, fridges, lights, pumps, charging, camping stuff, etc.

Question. I'm thinking I would just run this BCDC straight off the starter battery as is typical. Can anyone see a problem with this? Is the output terminal on the smartpass an alternative and is there any benefits to this? I think it would just complicate it?